PC-INTERFACED GONIOMETER FOR
KNEE AND ELBOW JOINT ANGULAR
MEASUREMENTS USING
ACCELEROMETER AND
ZIGBEE TECHNOLOGY
by
Miguel Carlo P. Ang
Anthony Joe P. Melgarejo
Nikko L. Tamaña
A Design Report Submitted to the School of Electrical Engineering,
Electronics Engineering, and Computer Engineering in Partial
Fulfillment of the Requirements for the Degree
Bachelor of Science in Computer Engineering
Mapua Institute of Technology
September 2011
ii
ACKNOWLEDGEMENT
Hardships, trials, failures and obstacles, the group won‟t be able to make
this design a success without the help of these persons who gave us support,
advices and courage to make it to the end.
Our deepest thanks to our professor, Engr. Noel B. Linsangan for giving us
chances in finishing this design and to our adviser, Engr. Analyn N. Yumang for
supporting and believing in us and for guiding us to take the right path. These
two people have been with us in the beginning and until the end of this design.
To our beloved parents, who supported us all the way financially and
emotionally. They encourage us that being competitive is an asset for success.
To our friends, classmates, teachers, and panels, thank you for trusting
and helping us to complete all of the learning materials that we needed as we
went along this the design.
To the persons behind this project, thanks for the camaraderie, unity and
cooperation. Thanks for the time spent and sacrificed. This experience shaped us
to be better individuals.
And lastly, to God Almighty, for making everything possible and for
keeping us strong when we thought of giving up.
Miguel Carlo P. Ang
Anthony Joe P. Melgarejo
Nikko L. Tamaña
iii
TABLE OF CONTENTS
TITLE PAGE
i
APPROVAL SHEET
ii
ACKNOWLEDGEMENT
iii
TABLE OF CONTENTS
iv
LIST OF TABLES
vi
LIST OF FIGURES
vii
ABSTRACT
Chapter 1:
viii
DESIGN BACKGROUND AND INTRODUCTION
Background
Statement of the Problem
Objectives of the Design
Impact of the Design
Design Constraints
Definition of Terms
Chapter 2:
REVIEW OF RELATED DESIGN LITERATURES AND STUDIES
Chapter 3:
DESIGN PROCEDURES
Hardware Development
Software Development
Prototype Development
Bill of Materials
Chapter 4:
TESTING, PRESENTATION, AND INTERPRETATION OF DATA
Wireless Technology Using ZigBee Signal Range Test
Accelerometer Output Scale Test
Precision Test
Output Test
1
1
3
3
4
4
5
8
16
16
21
30
33
34
34
36
42
44
iv
Chapter 5:
CONCLUSION AND RECOMMENDATION
Conclusion
Recommendation
46
46
47
REFERENCES
48
APPENDIX
49
Appendix A: Operation‟s Manual
Appendix B: Pictures of Prototype
Appendix C: Program Listing (in BASIC)
Appendix D: Data Sheets
 PIC16F877A Data Sheet
 ADXL335 Data Sheet
 ZigBee Module Data Sheet
 MAX232 Data Sheet
 L1682 Hitachi LCD Data Sheet
 LM7805 Data Sheet
 SPX2815 Data Sheet
Appendix E: IEEE Format Document
49
54
58
84
85
97
108
110
116
125
152
162
v
LIST OF TABLES
Table 3.1 Bill of Materials
33
Table 4.1 Wireless Data Transmission Proximity Test
35
Table 4.2 Distal Scaling (Positive)
37
Table 4.3 Distal Scaling (Negative)
38
Table 4.4 Proximal Scaling (Negative)
40
Table 4.5 Proximal Scaling (Positive)
41
Table 4.6 Elbow Joint Angle Precision Test
43
Table 4.7 Knee Joint Angle Precision Test
43
Table 4.8 Sent Data Output Test
45
vi
List of Figures
Figure 3.1 System Block Diagram of PC-Interfaced Goniometer for Knee
and Elbow Angular Measurements using Accelerometer
and ZigBee Technology
16
Figure 3.2 Schematic Diagram of the Transmitter with the Accelerometer,
Microcontroller and Zigbee Module
18
Figure 3.3 ZigBee Module Schematic Diagram (Receiver Side)
20
Figure 3.4 Transmitter-side Program Flowchart
21
Figure 3.5 Receiver-side Program Flowchart
23
Figure 3.6 Database Schema
24
Figure 3.7 General Information - Findings Relationship
25
Figure 3.8 General Information – Past Medical History Relationship
26
Figure 3.9 Wireless Goniometer Use Case
27
Figure 3.10 Activity Diagram
28
Figure B.1 Invalid Port Number Error
52
Figure B.2 Receiver Connected to the Laptop via USB and RS232
54
Figure B.3 Accelerometers Attached to Goniometer and Transmitter Device
54
Figure B.4 Transmitter Device with Arm and Leg Straps
55
Figure B.5 Sample Picture of Whole Design
55
Figure B.6 Sample Output of Angle Reading in LCD Display
56
Figure B.7 Output Interface of the Design (Patient Information Database)
56
Figure B.8 Patient Information Database Software
57
vii
ABSTRACT
The main goal of the group is to design a device that addresses the
drawbacks of using a common goniometer. The group presents in this
documentation an alternative method for measuring human joint angles,
specifically knee and elbow joint angles. The digital goniometer consists of two
accelerometers, a digital signal processing element, and a wireless
communication component. Accelerometers are commonly used to sense leg or
arm movement for monitoring the progress of the patient during rehabilitation.
Joint angles are directly calibrated using the output of the accelerometers;
therefore, angles displayed is similar to the common goniometer. The angles
measured are then stored into the patient information database for ease of
evaluation by the rehabilitation doctor.
Keyword: Goniometer, accelerometer, ZigBee technology, wireless transmission
viii
CHAPTER 1
DESIGN BACKGROUND AND INTRODUCTION
Background
Measuring the range of motion (ROM) is vital
in rehabilitation medicine.
Each specific joint has a normal range of motion that is expressed in degrees.
Limited range of motion refers to a joint that has a reduction in its ability to
move, caused by injury, operation, or diseases such as osteoarthritis, rheumatoid
arthritis, or other types of arthritis. Pain, swelling, and stiffness associated with
the injury, operation, and said diseases can limit the range of motion of a
particular joint and impair function and the ability to perform usual daily
activities.
Devices used to measure the ROM of various joints in the human body are
the goniometer and inclinometer. Both devices use a stationary arm, protractor,
fulcrum, and movement arm to measure angle from axis of the joint. The
goniometer is used by rehabilitation doctors to measure ROM as a way to
monitor a patient‟s progress while undergoing physical therapy.
This device aims to address the health and safety of a patient. In physical
therapy and occupational therapy, a goniometer is an instrument which
measures an axis and range of motion. If a patient experiences decreased range
of motion in a joint (e.g a knee or elbow) caused by an operation or fracture, for
example, the therapist can use a goniometer to assess what the range of motion
is prior to intervention. Using the information produced by the goniometer, the
1
therapist can monitor the range of motion after every therapy session. From this
range of motion, the therapist is able to plan the appropriate exercise to achieve
the target joint range of motion suitable for the mobility of the patient. It focuses
on measuring the ROM of the elbow and knee joints.
The angle measured using the device is displayed using a desktop
computer or a laptop. The use of a computer also allows an adequate recording
of the data for each patient using the device, which may be later analyzed with
ease, precision and readability as compared to the conventional method. It is
also much smaller in size compared to the electrogoniometer since it would only
be attached to the patient‟s leg or arm using straps. Due to its smaller size, it is
easier for the physical therapist to set up the device, and the patient is more
comfortable during the measurement process.
The device consists of two dual axis accelerometers, a digital signal
processing
element,
and
a
wireless
communication
component.
The
accelerometers are used to determine the angular position of the knee or elbow
joint. The digital signal processing element calculates the joint angle. This
information is then sent by ZigBee communication to a PC which displays the
joint angle.
2
Statement of the Problem
As the patient flexes, for example, his elbow, the movable arm is moved
by the physician with the forearm of the patient while the stationary arm is held
still. This procedure and the conventional protractor goniometer have the
following disadvantages: 1) the mechanical goniometer is a bulky apparatus; 2)
patients with severe joint dislocation will find the conventional procedure very
painful; 3) measuring the angle while holding the protractor in position
throughout the measurement is a difficult task for the examiner; 4) and holding
the arm/limb in one position for the entire time of procedure is a problem for the
patient too.
Objectives of the Design
The group aims to design a device that addresses the said drawbacks of
using a common goniometer.
The group also considered the following to be able to implement the
device:
1. to interface ZigBee to the PC-Interfaced Goniometer;
2. to display the angular measurements of the knee or elbow with the LCD
display in the device; and
3. to record the angular joint measurement in a database with the same
reading displayed in the device.
3
Impact of the Design
The PC-Interfaced Goniometer for Knee and Elbow Joint Angular
Measurements Using Accelerometer and ZigBee Technology synchronizes with
the trend of swift development of technology in the medical field. The design‟s
significance directly applies to rehabilitation medicine practitioners such as
rehabilitation doctors and physical therapists as it helps them to come up with a
more accurate way of getting the knee and elbow angular joint measurements.
Since it is wirelessly connected to a computer, it allows an adequate recording of
data for each patient, which may be later analyzed with ease, precision and
readability as compared to the conventional method.
The PC-Interfaced Goniometer for Knee and Elbow Joint Angular
Measurements Using Accelerometer and ZigBee Technology‟s major impact can
be seen in the health and safety of patients specifically in the field of physical
therapy and occupational therapy. With its added ease of use and functionalities,
it is a better replacement of the common goniometer used by rehabilitation
doctors in clinics in the Philippines, and all over the world.
Design Constraints
Health expenditures continue to grow very rapidly as technology plays a
big part in improving the delivery of medical care. But the benefits technology
brings outweigh the additional expenses as it significantly improves medical and
surgical procedures (e.g. CT scanners, implantable defibrillators) and new
4
support systems (e.g. electronic medical records and transmission of information,
telemedicine).
The same concept applies in the group‟s design. The PC-Interfaced
Goniometer will be more expensive than the common goniometer because of the
materials used. Therefore, mass manufacturing of the device will be difficult as
the prices of the materials remain expensive, most especially the accelerometers
and ZigBee modules. Also, in the Philippines, not many hospitals have the budget
for newer devices due to their budget restraints. If the economy in the
Philippines does not improve, the purchasing power of the potential buyers of
the device (e.g. hospitals, physical therapists) will be low.
The device can only be used for measuring the angle of the knee and
elbow joints as the title of the design implies due to the design by which it is
manufactured.
Definition of Terms
1. Goniometer – an instrument that either measures an angle or allows an
object to be rotated to a precise angular precision (Encarta World English
Dictionary).
2. Accelerometer – an instrument or device for measuring acceleration,
especially one in which a sensor converts acceleration into an electrical
signal (Encarta World English Dictionary).
5
3. Range of motion (ROM) – The range through which a joint can be
moved, usually its range of flexion and extension. Due to an injury, the
knee may for example lack 10 degrees of full extension (Webster‟s New
World Medical Dictionary).
4. Physical medicine and rehabilitation (Rehabilitation medicine) –
a branch of medicine which aims to enhance and restore functional ability
and quality of life to those with physical impairments or disabilities.
Practitioners of this field are called rehabilitation doctors (Webster‟s New
World Medical Dictionary).
5. Physical therapy – A branch of rehabilitative health that uses specially
designed exercises and equipment to help patients regain or improve their
physical abilities. Physical therapists work with many types of patients,
from infants born with musculoskeletal birth defects, to adults suffering
from after-effects of injury, to elderly post-stroke patients (Webster‟s New
World Medical Dictionary).
6. Occupational therapy – a profession concerned with promoting health
and well being through occupation. The primary goal of occupational
therapy is to enable people to participate in the activities of everyday life.
Occupational therapists achieve this outcome by enabling people to do
things that will enhance their ability to participate or by modifying the
environment to better support participation.
7. Supine - lying on the back (Webster‟s New World Medical Dictionary).
6
8. Flexion - The act of flexing or bending, bending of a joint to approximate the
parts it connects (Webster‟s New World Medical Dictionary).
9. Axis - A straight line joining two opposing poles of a spheric body, about which
the body may revolve. (Webster‟s New World Medical Dictionary).
10. PCB – Printed Circuit Board, a rigid, flat board that holds chips and other
electronic components. The board is made of layers, typically 2 - 10, that
interconnect
components
via
copper
pathways
(PC
Magazine
Encyclopedia).
11. PIC – Programmable Interrupt Controller, special purpose integrated
circuit that functions as an overall manager in a interrupt driven system
(Webster‟s Encyclopedia).
12. Wireless – using radio signals: using radio signals rather than wire
(Encarta World English Dictionary).
13. ZigBee - A wireless network used for home, building and industrial control. It
conforms to the IEEE 802.15.4 wireless standard for low data rate networks.
With a maximum speed of 250 Kbps at 2.4 GHz, ZigBee is slower than Wi-Fi and
Bluetooth, but is designed for low power so that batteries can last for months
and years. The typical ZigBee transmission range is roughly 50 meters, but that
can vary greatly depending on temperature, humidity and air quality (PC
Magazine Encyclopedia).
7
Chapter 2
REVIEW OF RELATED DESIGN LITERATURES AND STUDIES
This chapter includes compiled research works and studies that are
related to the design. The content of this chapter are used as reference for the
development of the design. The group used the following related articles,
research works, and inventions as reference which will aid in having an in-depth
understanding about the design that the group is working on.
A related article entitled “Goniometer Based to Computer”[1] from the IEEE
issued last April 5, 2004 cited a goniometer that was designed based on the
computer‟s focus on the measurements of angles of the arms. The article cited
that universal goniometers are commonly used during physical assessments of
patients under physiotherapeutic treatments, but the measurement accuracy is
influenced by its own quality and also the differences among articulations being
assessed. In order to ease the specialist‟s work, a goniometer based to a
computer fixed to the patient has been designed to give the angle of the arms,
allowing a faster evaluation of the patient‟s progress. The angle is measured
using an optical encoder and its value is properly interpreted by the PC and
presented on the monitor. The use of a computer also allows an adequate
recording of data which may be analyzed with ease, precision and readability
compared to the conventional method.
8
The group will use their design as guide for the PC-interfacing of the
group‟s design. The article discussed the procedure on how their goniometer is
interfaced but the goniometer is wired into the computer on which the group‟s
design aims to enhance into wireless data communication.
One of the objectives of the design is to display the angular joint
measurement in a PC monitor. The PC-interfacing is discussed in the first article
cited while the angular joint measurements computation is based in the next
article. In the article “A New Flexible Optical Fiber Goniometer for Dynamic
Angular Measurements: Application to Human Joint Movement Monitoring,”
development
of
a
substitute
for
the
common
goniometers
[3]
and
electrogoniometers are implemented. The article discussed the major drawback
in using such devices including the presence of a fixed hinge that imposes a fixed
center of rotation. This causes problems in measuring the bending angle in some
joints like human joints which have a variable rotation center. Instead of using a
fixed center of rotation, they used optical fiber, a sensor measuring the relative
angle in a rotating joint. It makes use of the intensity modulation of a laser beam
propagating in a single-mode optical-fiber, due to the changes of its polarization
status originated by the rotation of contiguous portions of fiber, where controlled
birefringence has been induced by a fixed radius fiber loop. A prototype of this
sensor has been developed with a range of relative angle of 90deg with a
resolution of less than 0.01deg and a standard deviation of 0.1deg. Main
advantages of this innovative sensor are lightness, flexibility, high speed of
9
reaction and high accuracy. This paper describes the implemented sensor, the
equipment implemented for the test, and the results of laboratory activities are
reported and discussed.
This article[3] will serve as the basis for the computation of the angle.
Instead of using optical fibers, the group will use two accelerometers which have
the same advantage as the optical fiber.
How to Measure Range of Motion[5]
The range of motion (ROM) of a joint is an angular measure of that joint's
movement between the fully extended and fully flexed position. The
measurement of a joint's ROM is a common method of assessing a joint's
recovery after an injury or surgery. This procedure requires a goniometer, which
may be any device that measures angles. However, the specific purpose of a
medical goniometer is to measure a joint's ROM.
1) A medical goniometer consists of a central portion that joins two arms
made of a stiff material. One arm is fixed with respect to the central portion, and
the other arm is able to rotate freely about the central portion. The central
portion also has a hole in its center. The central portion of the goniometer
measures the angle of separation between the two arms of the goniometer.
2) In measuring the ROM between the lower and upper arm, the point of
rotation is the elbow.
10
3) The hole should be placed in the central portion of the goniometer
directly over the joint's point of rotation. In the case of the elbow, this is the
point on the elbow where the lower arm joins to the elbow.
4) The goniometer's stationary arm should be aligned along the reference
line for that joint while keeping the goniometer's hole over the joint's point of
rotation. The reference line is the line that will indicate a movement of 0
degrees. In the case of the elbow, the reference line is the upper arm.
5) The subject is instructed to extend the joint as far as he can without
experiencing pain. Align the goniometer's rotating arm with the limb that moved
in this extension. In the case of the elbow, this limb is the lower arm. The central
portion of the goniometer will now show the joint's ROM in degrees.
In the present design, this procedure is followed in order to emulate the
procedure used in clinical situations.
Measuring Tilt with Low-g Accelerometers
This application note[6] describes how accelerometers are used to measure
the tilt of an object. Accelerometers can be used for measuring both dynamic
and static measurements of acceleration. Tilt is a static measurement where
gravity is the acceleration being measured. Therefore, to achieve the highest
degree resolution of a tilt measurement, a low-g, high sensitivity accelerometer
is required. In measuring the angle, the change in degrees of tilt directly
corresponds to a change in the acceleration due to a changing component of
11
gravity acted on the accelerometer. In order to determine the angle of tilt, θ, the
A/D values from the accelerometer are sampled by the ADC channel on the
microcontroller. The acceleration is compared to the zero g offset to determine if
it is a positive or negative acceleration. One solution can measure 0° to 90° of
tilt with a single axis accelerometer, or another solution can measure 360° of tilt
with two axis configuration (XY, X and Z), or a single axis configuration (e.g. X or
Z), where values in two directions are converted to degrees and compared to
determine the quadrant that they are in. A tilt solution can be solved by either
implementing an arccosine function, an arcsine function, or a look-up table
depending on the power of the microcontroller and the accuracy required by the
application.
The group included this paper[6] as a reference in computing for the
angle. The method included in this paper can serve as an alternative solution for
the computation of the angle. Since the concept in computing the angle of tilt is
roughly the same for this method (comparing values in different degree of tilt),
the group considered this article as a related literature. Furthermore, the solution
presented in this article can serve as a backup to ensure that if the solution the
group used does not live up to its expectation or yielded poor test results, the
group can still use the solution in this article to fix the problem.
12
ZigBee Technology
The design will use the analog signals from the movement of the
accelerometers, convert it into digital signal, then transmit it using the ZigBee
wireless technology. According to an article entitled “Networked Wireless Meter
Reading System Based on ZigBee Technology”[4] (Liting Cao, Wei Jiang, Zhaoli
Zhang) from IEEE issued last July 2008 the ZigBee, namely IEEE802.15.4
technology standard is one of the WPAN IEEE802.15 technology standard.
ZigBee bend itself to realize a short distant double direction wireless
communication protocol which is lower in complexity, lower cost and lower
speed. In this article[4] the ZigBee technology was used to solve the problems
existed in meter reading systems. The structure of the system employs
distributed structure the measure meters, sensor nodes, data collectors, server
and wireless communication network. For a short distance transmission the data
collector collects data using ZigBee communication.
Another article supports the use of wireless technology. The article which
is entitled, “5.5mA 2.4-GHz two-point modulation ZigBee transmitter”, by Rui Yu
Theng-Tee, Yeo Kwang-Hung, Tan Shouxian,MouYike, Cui Haifeng, Wang HwaSeng, and Yap Ting from IEEE issued last September 2009 describes a 2.4-GHz
two-point modulation IEEE 802.15.4 (ZigBee) compliant transmitter presented.
The sigma-delta fractional-N PLL based transmitter is optimized for both lowpower and low-cost purposes. A novel closed-loop calibration scheme is
13
proposed to minimize the gain mismatch between two modulation points, which
is the main source of error in two-point modulation.
With these articles, the group concludes that ZigBee wireless Technology
has advantages with the other RF modules with its low power consumption, low
cost, and a wider range.
PIC16F877A Microcontroller
In an article entitled ¨Network model based automation of thermal
processes using an embedded digital controller”, by Ganesh, A.B. Sangeetha,
A.L. Ravi, V.R. issued last Dec. 2009 from IEEE, a microcontroller is used. The
article describes the network architectures of both WAN and LAN based real time
control and monitoring of thermal process station using an embedded digital
controller. The function of the microcontroller in this design is a temperature
controller that communicates directly with the temperature transmitter. The
design uses the PIC16F877A microcontroller.
The group‟s design will use two microcontroller units, one for the
transmitter, and the other is for the receiver part. The article above shows that
microcontrollers can interact with transmitters, thus it can also interact with
receivers.
Microchip Programmable Interface Controller (PIC) are popular with both
industrial developers and designers due to their low cost, wide availability, large
user base, and serial programming (and re-programming with flash memory)
14
capability. Different levels of on-board features are being associated to each type
of microcontrollers. The smallest ones can add some simple automation to a
project, while huge devices have the capabilities of a microprocessor system,
offering much more than simple control.
15
CHAPTER 3
DESIGN PROCEDURES
This chapter discusses the procedures that were followed in the
development of the design.
This also includes the block diagram, schematic
diagram and the system flow chart.
Hardware Development
Block Diagram
TRANSMITTER
Accelerometer
(Upper Limb)
Accelerometer
(Lower Limb)
ZigBee
Technology
MCU/ADC
9V Battery
RECEIVER
ZigBee
Technology
MAX232
COMPUTER
Figure 3.1
System Block Diagram of PC-Interfaced Goniometer for Knee and
Elbow Angular Measurements using Accelerometer and ZigBee
Technology
16
Figure 3.1 shows the basic block diagram of the overall system design.
The system is composed of two divisions: the transmitter and the receiver. The
primary input of the system will be coming from the two accelerometers. From
the figure, the accelerometers are connected to the MCU that interprets the
analog signal, then converts it into digital signal. The ZigBee Module will be
responsible for the wireless transmission.
The main output of the system is the angular measurement reading that is
shown in the LCD attached to the device. The last block in the diagram
represents the Computer to where the angular measurement is stored in the
patient‟s database. That completes the process of the designed system.
17
Schematic Diagram
Figure 3.2
Schematic Diagram of the Transmitter with the Accelerometer,
Microcontroller and Zigbee Module
18
Figure 3.1 shows the schematic diagram of the device. Power is supplied
by the 9v battery which is controlled by a switch. It passes through a diode
which serves as a protection in case the battery is improperly connected. Opamp then regulates the voltage to 3.3V which is to be used by the
accelerometers. In parallel, another voltage regulator gives the 5V which the
microcontroller and the LCD need. The accelerometer outputs analog voltage
which is connected to a debouncer circuit, seen as a collection of capacitors to
keep the voltage stable. The debouncer circuit stabilizes the voltage to be passed
into the microcontroller, since the accelerometer output is analog. The voltage
then passes through a precision resistor, which is like a potentiometer that sets
the reference voltage to be used by the ADC in the conversion from analog
signal to digital. The conversion of the voltage and calculation of the angle is
done inside the microcontroller. The output is passed to the LCD, which displays
the output into readable text, and to the ZigBee, for transmission. Before the
signal reaches the ZigBee, it passes through a voltage divider. Since the input
voltage of the microcontroller is 5v, the output can reach 5V, which is a problem
to the ZigBee. The ZigBee can only accommodate 3.3V, which explains the need
for a voltage divider.
19
Figure 3.3
Zigbee Module Schematic Diagram (Receiver Side)
Figure 3.2 shows the receiver side of the device. The signal is received by
ZigBee. The signal is digital when it leaves the module. It then passes through
MAX232 which amplifies the signal so no loss is incurred due to line resistance.
The capacitors are needed as stated in its datasheet. The 5V supply came from
the 1st USB connection and is then regulated down to 3.3V which the IC needs.
The signal is then passed through the serial-to-USB cable to send the data.
20
Software Development
System Flowchart
Start
Initialize values
Get analog signal
from
accelerometer
End
No
Convert analog
signal to digital
Scale values
Trim values for
distal and proximal
Perform addition/
subtraction of
proximal and distal
values
Send button
pressed
Yes
Pass data to
zigbee(transmitter)
Send data to
zigbee(receiver)
Figure 3.4
Transmitter-side Program Flowchart
21
Figure 3.4 illustrates how the device works. First, the values are initiated
when the device is turned on. These initiations cover the initial values of the
registers like the TRIS, necessary control bits of the ADC, and initialization of the
values that will be used. When done initiating, the analog signal that the
accelerometers
generate
is
being
taken
by
the
microcontroller.
The
microcontroller has a built-in ADC that converts analog signals to digital. The
resulting digital signal will be in the form of numbers usually in the range of
hundreds. These values are then scaled because the values that the
accelerometers produce are too unstable because of sensitivity. Scaling will
provide a much more workable set of values that the designers need in the
conversion of the angles. After scaling the values, the designers subtract a
certain number to the value to produce the angle. This is based on the value that
the designers get when they put the accelerometer perfectly flat so that it
produces a 0 angle and that the value that makes it zero is the one subtracted to
get the angles. Since the designers are using 2 accelerometers to compensate
for the angle of the other, they are either added or subtracted to one another
depending on the orientation to get the final angle. The result is then passed to
the receiver side when the button is pressed.
22
Start
Receive Data from
transmitter
Convert to Digital
Signal (ZigBee
module)
Signal
Amplification by
MAX232
Data is read by the
PC-side software
End
Figure 3.5
Receiver-side Program Flowchart
Figure 3.5 shows that after receiving the signal, an IC converts the signal
to RS232, which is the standard when using serial cable. This is then converted
to USB so that the signal can be transferred to the PC to be used by the
program.
23
Database Schema
Figure 3.6
Database Schema
Figure 3.6 shows that the database relationship used is one to many, as
ID from General Information table, can have multiple links to other tables. This
relationship is applied because the database was made to record the details of
the patient and the results of the test only. A simple database design means less
work for the program. This relationship ensures that the program will run
efficiently and ensures that the data will be stored correctly.
24
Entity Relationship Diagram
ID
Referring
Doctor
Patient Name
Date of
Referral
General
Information
Date of
Evaluation
Age
Gender
Patients
have
Address
Religion
ID
Ocular
Findings
Range of
Motion (Arm)
Palpatation
Range of
Motion (Leg)
Figure 3.7
General Information-Findings Relationship
25
ID
Referring
Doctor
Date of
Referral
Patient Name
General
Age
Date of
Evaluation
Gender
Patients
have
Address
Religion
ID
Operation
Past Medical History
Medication
Figure 3.8
General Information-Past Medical History Relationship
Figures 3.7 and 3.8 shows the relationship between the tables in the
database. The general information table stores the basic information needed to
identify the patient. This is where all data from the patient‟s identity is being
stored. A patient may have past medical history like operations and medications.
This is why there is a relationship between the tables. The link that binds the two
tables is the ID from the general information table. In every consultation, there
will be findings or results. The relationship of the two tables can be seen in
figure 3.6, where the linking element is also the ID from the general information
table.
26
Use Case
Wireless Goniometer Software
Add Record
Delete Record
Edit Record
User
Get
measurements
Figure 3.9
Wireless Goniometer Use Case
Figure 3.9 illustrates the use case of the software. The software is
designed to record the measurements that the device will pass to it. The
software does not need any more users since it will be only be used by doctors
and in order to simplify the use of the device. This results to a single user as can
be seen in the use case.
27
Activity Diagram
Start
Select Record
Edit Record
Add Record
Delete Record
Get Measurements
End
Select Mode
Leg
Arm
Record Angle
Figure 3.10
Activity Diagram
28
Figure 3.10 shows the activity diagram of the program. This basically
shows the flow of all options that the user will face when using the program.
First, since there are no other accounts to log in, the user is faced with options
to add, delete, or make an examination. The process of adding and deleting
records are straight forward; the user enters the name of the patient to be
deleted and the program deletes it from the database. In adding, the user inputs
the necessary information and adds it to the database. In selecting a patient, the
user may opt to edit the record or make an examination. In editing, the user
simply adds or deletes information from the patient in the database. In making
an examination, the user is free to choose which mode to use. If it is an arm
examination, the user simply clicks record button on the section that is labelled
“arm.” The user clicks record on the leg section otherwise. The program
automatically receives the data from the device and records the angle. This angle
is then recorded in the database.
29
Prototype Development
The design procedure will show the step-by-step procedure on how the
design was built. It will describe the detailed information about the
conceptualization of the design project.
1. Conceptualization
After
knowing
how
the
design
will
work
as
a
whole,
the
conceptualization of the transmitter and receiver part must be equated to
simplify the design hardware and software.
2. Simplified design requirement
It is also important to create an initial drafting of materials required as the
development of the project proceeds. This will give the researchers an
overview of the project.
3. Illustrate the block diagram
This defines the major composition of the design and shows how each
block is related with each other. The block diagram for the transmitter
consists of the Microcontroller Unit (MCU), Accelerometer for Upper Limb,
Accelerometer for Lower Limb, Wireless technology using ZigBee, and 9V
Battery. The block diagram of the receiver consists of the ZigBee technology,
MAX232, and Computer.
30
4. Draw schematic diagram
Schematic diagram of this design shows how each device was
interconnected. It contains major components such as the Microcontroller
Unit (MCU), Accelerometer for Upper Limb, Accelerometer for Lower Limb,
Wireless technology using ZigBee, and 9V Battery for the transmitter. On the
other hand, the receiver of the system uses components such as the wireless
technology using ZigBee Module and the Computer.
In developing the design, the following materials were used each, with a
brief discussion:
PIC16F877A
This type of microcontroller was used in the design primarily because of
its many inputs. PIC16F877A has a maximum of 40 I/O pins which is very much
suitable for the design. It has a maximum of 256 bytes for its register which is
also much appropriate for the design to be possible. It also has built – in UART
(Universal Asynchronous Receiver Transmitter) that can communicate with
peripheral devices such as personal computers or laptops.
31
ZigBee Wireless Technology
The ZigBee technology was used because it has greater range and is
widely used in today‟s wireless technology. The group used this because of its
low consumption of power and wide range of transmission.
MAX232
The MAX232 is a dual driver/receiver that converts signals from an RS-232
serial port to signals suitable for use in TTL compatible digital logic circuits and
vice versa. MAX232 operates at 5V DC input voltage and connected to V s pin of
the IC. The MAX232 IC is used to interface the central computer and the Zigbee
module in the receiver side.
HD44780U (LCD)
The HD44780U dot-matrix liquid crystal display controller and driver LSI
displays alphanumeric, Japanese characters, and symbols. It can be configured
to drive a dot-matrix liquid crystal display under the control of a 4- or 8-bit
microprocessor. The HD44780U character generator Rom is extended to
generate 208 5x8 dot character fonts and 32 5x10 character fonts for a total of
240 different character fonts. The low power supply (2.7V to 5.5V) of the
HD44780U is suitable for any portable battery-driven product requiring low
power dissipation.
32
ADXL335 (3-axis Accelerometer)
The ADXL335 is a small, thin, low power, complete 3-axis accelerometer
with signal conditioned voltage outputs. ADXL335 measures acceleration with a
minimum full-scale range of
g. It can measure the static acceleration of
gravity in tilt-sensing applications, as well as dynamic acceleration resulting from
motion, shock, or vibration. In the design, it is used as a motion sensor.
Bill of Materials
QTY
1
1
1
1
1
2
2
1
1
1
1
1
1
1
2
1
3
1
1
1
1
1
2
2
1
-
MATERIALS
ACRYLIC SENSOR CASING
WOODEN STAND
CONTROLLER CASING
RECEIVER CASING
MCU PIC16F877
ACCELEROMETER
ZIGBEE
PUSH BUTTON
LCD 2X16
MULTI-TURN TRIMMER RESISTOR
MAX232 DRIVER
USB TO RS232 CABLE
9PIN RS232 CONNECTOR RA
USB CABLE
33PG9 3.3V VOLTAGE REGULATOR
LM7805
CAPACITORS
9V BATTTERY
9V BATTTERY HOLDER
9V BATTERY CLIP
TOGGLE SWITCH
PCB
ARM STRAPS
LEG STRAPS
VELCRO TAPE
MISCELLANEOUS
TOTAL
PRICE
170
300
300
100
300
1,800
3,800
15
1,400
75
150
200
65
50
70
16
75
135
18
13
25
200
400
400
50
2150
12,277
Table 3.10
Bill of Materials
33
Chapter 4
TESTING, PRESENTATION AND INTERPRETATION OF DATA
This chapter presents various tests performed by the designers to
determine the effectiveness of the design. The tests are conducted with
relevance to the design objectives.
Wireless Technology using ZigBee Signal Range Test
The researchers conducted a signal range test to determine the capability
of the wireless technology. Goniometers are intended for clinical use in very
close proximity which commonly has an area of 5 sq. m but still, the designers
decided to test the full capability of the ZigBee in case it is necessary to be used
in larger proximity. Here are the procedures in conducting this test:
1.
Set-up and turn on the apparatus and run the software.
2.
Separate the transmitter and receiver side 10m – 50m away from
each other with 10m intervals after every 5 trials. Make sure they are in
line of sight.
3.
While in the 'Edit' menu, click the 'Record' button in either arm or
leg measurements. This signifies that the software is ready to receive and
add the data in the database.
4.
While the 'Record' button is active, push the 'Send' button in the
34
transmitter side. Take note of the angle reading sent.
5.
Observe the angle reading received and added in the database
displayed in the PC interface. Also, take note of the speed of data
transmission.
The following table shows the results gathered based on the signal range test.
TRIAL
1
2
3
4
5
10m
Good
Good
Good
Good
Good
20m
Good
Good
Good
Good
Good
30m
Good
Good
Good
Good
Good
40m
Good
Good
Good
Good
Good
50m
Poor
Poor
Poor
Poor
Poor
Table 4.1
Wireless Data Transmission Proximity Test
The designers tested the wireless proximity within a 10m – 40m range.
The testing was done in an area wherein the receiver is in line of sight and a few
meters away from the transmitter. An angle reading will be sent to the database
by pushing the „Send‟ button in the apparatus and clicking the „Record‟ button in
the PC interface.
The results show that within 40m, the data transmission is „Good‟ which
means that there is no delay and the sent data is correct. In a distance of 50m,
the data transmission is „Poor‟ meaning that there is no received data.
35
Accelerometer Output Scale Test
In this test, there will be four tables presented. These are for the positive
and negative distal, and positive and negative proximal scaling. The values
presented in these tables are analog to digital conversions which are outputs
from the accelerometers with corresponding angle measurements from the
goniometer. The following are steps to scale the digital output:
Distal Accelerometer Test:
1. Attach the two accelerometers in a conventional goniometer. It is
recommended to use a stand for support and stability to be able to put
one accelerometer in 0° position.
2. Modify the code in the microcontroller so that the actual digital decimal
output of the accelerometer will be displayed in the LCD.
3. While one accelerometer is in 0° position, tilt the other accelerometer
slowly and record the digital output every 5° interval for 5 trials.
4. The direction in which the distal arm is moving will determine the sign
of the angle.
5. Record output.
36
TRIAL
1
2
3
4
5
5°
362 362 362
362
362
10°
363 363 363
364
364
15°
364 364 365
365
365
20°
366 366 366
366
368
25°
370 370 370
370
371
30°
372 372 372
372
376
35°
377 377 378
378
380
40°
381 381 381
381
383
45°
384 386 386
386
389
50°
390 391 392
393
395
55°
396 397 397
398
402
60°
403 404 405
405
408
65°
409 410 411
412
415
70°
416 417 419
419
422
75°
423 423 425
426
429
80°
430 430 432
433
436
85°
437 438 440
441
444
90°
445 446 448
448
451
95°
452 453 455
457
459
100°
460 461 463
465
467
105°
468 469 471
472
475
110°
476 477 479
481
484
115°
485 486 487
488
491
120°
492 493 495
495
498
125°
499 500 501
502
505
130°
506 507 509
509
512
135°
513 514 514
515
518
140°
519 519 524
532
538
Table 4.2
Distal Scaling (Positive)
37
The values presented in the preceding table are analog to digital
conversions which are outputs from the accelerometer with corresponding angle
measurements from the goniometer. These values are the direct result of analog
to digital conversion done inside the PIC. These numbers represents the tilt of
the accelerometers that is used to get the angle of the device. The numbers that
is shown in the table is the output from the Y-axis of the accelerometer.
TRIAL
1
2
3
4
5
5°
2
2
2
2
2
10°
3
3
3
3
3
15°
4
4
4
4
4
20°
5
5
5
6
6
25°
7
7
7
7
9
30°
10
10
10
11
12
35°
13
13
14
14
16
40°
17
17
18
18
20
45°
21
21
22
23
25
50°
26
27
28
29
31
55°
32
33
33
35
38
60°
39
40
42
42
44
65°
45
46
48
50
52
70°
53
54
56
56
58
75°
59
60
62
65
67
80°
68
69
71
72
74
85°
75
76
78
80
82
90°
83
84
86
88
90
Table 4.3
Distal Scaling (Negative)
38
The values presented in the preceding table are analog to digital
conversions which are outputs from the same accelerometer with corresponding
angle measurements from the goniometer. These values are the direct result of
analog to digital conversion done inside the PIC and are the same in the way
that the values are being fetched as the positive distal scaling test. The reason
for the difference in value despite the same concept in producing the result is in
the way it is programmed. The process of producing these results is simply
subtracting 360 (which is the ADC value at 0 degree) from the ADC value of the
negative distal scaling. This is to avoid confusion with positive distal scaling
which can cause confusion in programming and testing.
Proximal Accelerometer Test:
1. Attach the two accelerometers in a conventional goniometer. It is
recommended to use a stand for support and stability to be able to put
one accelerometer in 0° position.
2. Modify the code in the microcontroller so that the actual digital decimal
output of the accelerometer will be displayed in the LCD.
3. While one accelerometer is in 0° position, tilt the other accelerometer
slowly and record the digital output every 5° interval for 5 trials.
4. The direction in which the proximal arm is moving will determine the
sign of the angle.
5. Record output.
39
TRIAL
1
2
3
4
5
80
451
451
451
451
451
75°
450
450
450
449
449
70°
448
446
446
445
445
65°
444
443
442
442
442
60°
441
439
438
438
437
55°
436
435
432
432
430
50°
431
429
429
428
427
45°
426
423
422
421
421
40°
420
420
417
415
415
35°
414
410
409
408
408
30°
407
405
404
401
401
25°
400
395
394
393
393
20°
392
390
388
386
386
15°
385
381
379
378
377
10°
376
374
373
371
371
5°
370
367
365
362
361
Table 4.4
Proximal Scaling (Negative)
The values presented in the preceding table are analog to digital
conversions which are outputs from the accelerometer with corresponding angle
measurements from the goniometer. These values show the proximal scaling that
is needed in the determination of the angle. The different values at different
trials show that the in a certain angle, there can be different values
corresponding to it. These values can have a range of up to 9 or 10. This is
important to know since less sensitivity in the measurement means that there
will be more workable data to be processed.
40
TRIAL
1
2
3
4
5
5°
359
358
356
354
352
10°
350
349
347
345
343
15°
342
341
340
338
336
20°
334
334
332
330
328
25°
325
323
322
322
320
30°
318
316
315
314
314
35°
310
309
308
307
305
40°
304
303
302
301
299
45°
298
297
296
295
293
50°
292
292
291
389
387
55°
286
286
285
285
283
60°
282
282
281
280
278
65°
277
277
277
276
275
70°
274
274
273
271
271
75°
270
270
270
269
269
80°
268
268
268
268
268
85°
267
267
267
267
267
90°
266
266
266
266
266
Table 4.5
Proximal Scaling (Positive)
The values presented in the preceding table are analog to digital
conversions which are outputs from the accelerometer with corresponding angle
measurements from the goniometer. The values in this test, like in the distal
scaling test, are similar in the way it is being produced. The values between the
angles of both positive and negative scaling are just separated with a small
margin, showing that the procedure is the same.
41
Precision Test
Precision Testing was conducted by the designers to verify the reliability of
the design's angle measurements. It is not necessary to have an accuracy of
100% with the angle measurement. Since, it is only intended for monitoring the
improvement of the range of motion of the patients‟ joints. A very close reading
to the actual angle measurement is needed, nonetheless.
To conduct the test, the following steps are used:
1. Attach the two accelerometers in a conventional goniometer. It is
recommended to use a stand for support and stability to be able to put
one accelerometer in 0° position.
2. Turn on the transmitter side of the device.
3. For the arm measurement, tilt the Distal in 10° interval starting from 0°.
For the leg measurement, tilt both the Distal and Proximal until they meet
just like an actual leg with the same interval and starting point.
4. Record the result from the LCD display 5 trials each interval.
42
TRIAL
1
2
3
4
5
0°
0°
0°
2°
0°
1°
10°
0°
7°
0°
10°
15°
20°
18°
20°
21°
20°
18°
30°
30°
31°
29°
30°
30°
40°
39°
40°
40°
41°
39°
50°
51°
52°
50°
49°
50°
60°
59°
61°
61°
60°
60°
70°
71°
70°
70°
70°
69°
80°
82°
79°
81°
80°
79°
90°
90°
89°
90°
91°
91°
100°
101°
101°
100°
100°
101°
110°
109°
111°
110°
110°
110°
120°
120°
120°
120°
120°
120°
130°
129°
130°
130°
131°
130°
140°
140°
140°
140°
139°
140°
Table 4.6
Elbow Joint Angle Precision Test
TRIAL
1
2
3
4
5
0°
2°
0°
0°
0°
1°
10°
12°
7°
8°
10°
9°
20°
20°
20°
21°
20°
21°
30°
30°
31°
30°
30°
30°
40°
40°
41°
40°
40°
39°
50°
50°
50°
49°
50°
49°
60°
60°
60°
61°
61°
60°
70°
70°
69°
70°
70°
70°
80°
81°
79°
80°
80°
80°
90°
89°
90°
91°
91°
90°
100°
99°
100°
100°
101°
100°
110°
110°
110°
110°
110°
110°
120°
120°
120°
120°
120°
120°
130°
131°
130°
130°
131°
130°
140°
140°
139°
140°
139°
140°
Table 4.7
Knee Joint Angle Precision Test
43
As seen from Tables 4.6 and 4.7 and in reflection to the Accelerometer
Output Scale Test, small angles from 0° to 20° have discrepancies but as stated
earlier, these are negligible. There is also a ± 3 tolerance in the angle
measurements but these are not a problem because the purpose of the design is
to monitor the improvement of the patients' joints' range of motion, not the
accuracy of measurements. Overall, the design's measurements are precise,
nonetheless.
Output Test
Output Testing is conducted to determine if the sent data from the
apparatus is received successfully by the database.
Procedure for Output Test:
1.
Set-up and turn on the apparatus and run the software. Make sure
the transmitter and receiver side are in close proximity.
2.
While in the 'Edit' menu, click the 'Record' button in either arm or
leg measurements. This signifies that the software is ready to receive and
add the data in the database.
3.
Tilt the Distal upward starting from 0° to 140° with 10° interval.
4.
While the 'Record' button is active, push the 'Send' button in the
transmitter side. Make sure the angle is correct in every trial.
5.
Record the data received in the database and displayed in the PC
interface. Do 5 trials each interval.
44
TRIAL
1
2
3
4
5
0°
0°
0°
0°
0°
0°
10°
10°
10°
10°
10°
10°
20°
20°
20°
20°
20°
20°
30°
30°
30°
30°
30°
30°
40°
40°
40°
40°
40°
40°
50°
50°
50°
50°
50°
50°
60°
60°
60°
60°
60°
60°
70°
70°
70°
70°
70°
70°
80°
80°
80°
80°
80°
80°
90°
90°
90°
90°
90°
90°
100°
100°
100°
100°
100°
100°
110°
110°
110°
110°
110°
110°
120°
120°
120°
120°
120°
120°
130°
130°
130°
130°
130°
130°
140°
140°
140°
140°
140°
140°
Table 4.8
Sent Data Output Test
The „Send‟ button in the apparatus is to be pushed and the „Record‟
button in the PC interface should be pressed to successfully send and receive
data. The sent data displayed in the apparatus should be equal to the received
data displayed in the PC interface.
The results in Table 4.8 show that the data transmission is perfect given
that the transmission range is within 40m. Whatever the reading is in the
goniometer when the 'Send' button is pressed, the ZigBee will send and receive
the correct data. Then, the PC interface will output the transmitted data if the
'Record' button is clicked.
45
Chapter 5
CONCLUSION AND RECOMMENDATION
This chapter contains the general conclusion of the development of the
design in relation to its objectives. The results of the various tests performed
should also be clearly defined in this chapter. Recommendation for the
improvement of the design is also stated in this chapter.
CONCLUSION
In the design PC-Interfaced Goniometer for Knee and Elbow Joint Angular
Measurements Using Accelerometer and ZigBee Technology, the designers were
able to develop a device that addresses the drawbacks of using a conventional
goniometer. The designers were able to design a functional goniometer that is
less bulky and more portable than conventional goniometers such as
electrogoniometers and mechanical goniometers by using accelerometers and
straps instead of the hinged protractor and arms. The design of the device
enables the examiner to freely guide the patient‟s limbs since he does not need
to hold the goniometer and keep it in place during the procedure, making it
easier for the examiner. Since the procedure will be much easier and faster, the
patient will be more comfortable during the procedure.
The design is incorporated with ZigBee Technology in transmitting the
captured data from the accelerometers and receiving the data to be stored in the
46
Patient Information database. The software serves as the database where the
patient‟s information and angle measurements are stored.
RECOMMENDATION
The researchers suggest replacing ZigBee with other wireless technology
that offers more features such as lower power consumption and wider range of
data communication.
It is also suggested to add further enhancements to the software where
implementation of the accelerometer will enable the user to achieve more
accurate readings in any orientation possible. Also, it is suggested to make it the
device flexible in terms of functionality by making it possible for the device to
measure other human joints as well.
Other than using the computer desktop or laptop as the information
storage, it is suggested to use a Personal Digital Assistant (PDA) or other
handheld devices such as iPad and iTouch to make the device more portable.
The researchers also recommend performing further research to make the
application run on other operating systems other than the Windows platform
such as Linux to provide software portability.
47
REFERENCES
1. Barreiro, M.S. Frere, A.F. Theodorio, N.E.M. Amate, F.C. (2004). Goniometer
Based to Computer, Engineering in Medicine and Biology Society Journal, IEEE
2. Jeong-Whan, Lee Lee-Yon, Hong Jae-Hoon (2007). A Simple Optical Angular
Sensors to Measure the Human Joint Angle, SICE-ICASE, IEEE
3. Donno, M. Palange, E. Di Nicola, F. Bucci, G. Ciancetta, F. (2008). A New
Flexible Optical Fiber Goniometer for Dynamic Angular Measurements:
Application to Human Joint Movement Monitoring, Instrumentation and
Measurement, IEEE Transactions
4. Liting C., Wei J., Zhaoli Z. (2008). Networked Wireless Meter Reading
System Based on Zigbee Technology. Wireless Technology, IEEE, page(s):
3455
5. Rui Yu Theng-Tee, Yeo Kwang-Hung, Tan Shouxian,MouYike, Cui Haifeng,
Wang Hwa-Seng, and Yap Ting (2009). 5.5mA 2.4-GHz two-point
modulation ZigBee transmitter. Wireless Technology, IEEE
6. Ganesh, A.B. Sangeetha, A.L. Ravi, V.R. (2009). Network Model Based
Automation of Thermal Processes Using an Embedded Digital Controller.
IEEE
7. C. C. Norkin, D.J. White (2003). Measurement of Joint Motion: A Guide to
Goniometry, 3rd Edition, F.A. Davis Company, Philadelphia
8. Michelle Clifford, Leticia Gomez (2005) Freescale Semiconductor:
Measuring Tilt with low-g Accelerometers, Sensor Products, Temple, AZ
48
APPENDIX A
Operation’s Manual
1. System Requirement
a. Windows XP or higher version of OS
b. 9V Battery
c. RS232 to USB port cable
2. Installation Procedures
a. Provide a 9V Battery for the transmitter device
b. Flick the switch to ON to enable transmitter device.
c. Connect the receiver device to a computer using a RS232 to USB
port cable.
d. Install the driver for the RS232 to USB port.
e. Fit straps onto the patient.
f. Attach accelerometers to the straps.
3. User’s Manual
Preparing the Device
Before starting, it is better to be familiar with the device. The device has
two parts, one is the transmitter and the other is the receiver. The transmitter is
incorporated with two accelerometers which are attached to the straps fitted to
the upper and lower limb of the patient. The receiver has a USB power source
supply that directly gets its power source to the computer.
49
After distinguishing the devices we now proceed with fitting the
accelerometers. Straps are fitted to the upper and lower limb of the patient‟s leg
or arm. After securing the straps, the accelerometers are attached to the straps
using Velcro.
a.) Press the switch located at the side to enable the device and make sure
that the initial reading on the device is 0 degrees.
b.) Connect the receiver to the USB port of the computer to access its power
source. Using a RS232 to USB port cable, connect the device to the
computer.
Measurement Procedure (Elbow)
1) Fit the straps onto the patient‟s arm.
2) Position the patient in supine position and the arm is close to the side
of the body.
3) Attach the accelerometers into each strap.
4) Set the accelerometer so that the reading in the LCD display is 0
degrees.
5) Flex the elbow by moving the hand toward the shoulder. Maintain the
forearm supination during the motion.
6) The end of flexion ROM occurs when resistance to further motion is felt
and attempts to overcome the resistance cause flexion of the shoulder.
7) Press the SEND button to record the reading into the patient
information database.
50
Measurement Procedure (Knee)
1) Fit the straps onto the patient‟s leg.
2) Position the patient in supine position with the knee in extension.
3) Attach the accelerometers into each strap.
4) Set the accelerometer so that the reading in the LCD display is 0
degrees.
5) Hold the patient‟s ankle in one hand and move the thigh with the other
hand.
6) The end of flexion ROM occurs when resistance to further motion is felt
and attempts to overcome the resistance cause additional hip flexion.
7) Press the SEND button to record the reading into the patient
information database.
Using the Software
Before using the application make sure that the driver for the RS232 USBto-Serial Port Cable is installed.
a.) Open “Digital_Goniometer.exe”.
b.) The user will be prompted to the main page.
c.) The user can opt to add New Patient Information or Open Patient
Information.
51
d.) To add/edit Patient Information including the joint angular measurements,
click Edit.
e.) To close the program, press the File from the Menu bar and click Exit.
4. Troubleshooting Guides and Procedures
Scenario: Invalid Port Number
Figure B.1
Invalid Port Number Error
Solution A.
Check if Port Number in the program is correct.
-
The port number corresponds to the port where the receiver
device should be attached.
52
Solution B.
Check if receiver is connected.
-
The receiver is connected via a RS232 serial to USB port. Check
if the connection is proper. The receiver‟s power is also supplied
via USB port. Check also if it is connected.
53
APPENDIX B
Pictures of Prototype
RECEIVER
RS232 Serial-to-USB Cable
Figure B.2
Receiver Connected to the Laptop via USB and RS232
ACCELEROMETERS
LCD DISPLAY
SEND BUTTON
Figure B.3
Accelerometers Attached to Goniometer and Transmitter Device
54
ARM & LEG STRAPS
Figure B.4
Transmitter Device with Arm and Leg Straps
Figure B.5
Sample Picture of Whole Design
55
Figure B.6
Sample Output of Angle Reading in LCD Display
Figure B.7
Output Interface of the Design (Patient Information Database)
56
Figure B.8
Patient Information Database Software
57
APPENDIX C
Program Listing (in BASIC)
' 4 LINER LCD
' XYZ MONITOR
' Y and Z-axis
Device = 16F877A ' Were using 8bitmicro PIC16F877
XTAL = 4
' 4mhz resonator/crystal is used.
DelayMS 500
Declare ADIN_RES 10
' Set the resolution to 10 bit
Declare ADIN_TAD FRC
' Choose the RC osc for ADC samples
Declare ADIN_STIME 150
' Allow 150us for charge time
UNSIGNED_DWORDS = On
' remove negative values
LCD_DTPIN = PORTB.0
' Used for 4 data line interface.
LCD_RSPIN = PORTB.4
line will attach to.
' Assigns the Port and Pins that the LCD's RS
LCD_ENPIN = PORTB.5
line will attach to.
' Assigns the Port and Pin that the LCD's EN
LCD_INTERFACE = 4
required by the LCD.
' Inform the compiler 4-line interface is
LCD_LINES = 2
has.
' Inform the compiler how many lines the LCD
LCD_TYPE = 0
alphaNUMERIC.
' Inform the compiler that the type of LCD is
58
HSERIAL_BAUD = 9600
' Baud rate (transmission speed)
HSERIAL_RCSTA = %10010000
' Enable serial port and continuous receive
HSERIAL_TXSTA = %00100100
' Enable transmit and asynchronous mode
HSERIAL_CLEAR = On
PORTB_PULLUPS = On
ADCON1 = %10001010
result
' Enable Internal pullup resistor
' Set PORTA.0,1,2 to 4 analog and right justify
TRISA = %111111
' Set PortA as analog Input
TRISB = %01000000
' Set PortB as all bits Output (LCD)
TRISC = %00000000
(ACCELEROMETERS)
' Set PortC as all bits Output (ZIGBEE)
Dim Z_axis_U As Word ' Declare variable "Z_axis_U / Proximal"
Dim Y_axis_U As Word ' Declare variable "y_axis_U / Proximal"
Dim Z_axis_L As Word ' Declare variable "Z_axis_L / Distal"
Dim Y_axis_L As Word ' Declare variable "Y_axis_L / Distal"
Dim angle As Word
Dim var1 As Word
Dim neg_distal As Bit
Dim neg_proximal As Bit
Clear PORTA
' Clear portA
Clear PORTB
' Clear portB
Clear PORTC
' Clear portC
Clear PORTE
' Clear portC
Clear Y_axis_U
' Clear Variable
59
Clear Z_axis_U
' Clear Variable
Clear Y_axis_L
' Clear Variable
Clear Z_axis_L
' Clear Variable
BEGIN:
Cls
' CLEAR SCREEN
DelayMS 500
Print At 1,1," GONIOMETER "
Print At 2,1,"
2011
"
DelayMS 3000
DISPLAY:
Cls
Loop:
Clear neg_proximal
Y_axis_L = ADIn 0
'Place the conversion into variable "Y_axis_Lower"
DelayMS 15
Y_axis_U = ADIn 1 „Place the conversion into variable "Y_axis_Upper"
DelayMS 15
Z_axis_U = ADIn 2 'Place the conversion into variable "Z_axis_Lower"
DelayMS 15
Z_axis_L = ADIn 4
'Place the conversion into variable "Z_axis_Upper"
DelayMS 15
60
Y_axis_U = Y_axis_U - 93
' compensation
'-------------------------------------'
(+) DISTAL SCALING
'-------------------------------------Clear neg_distal
If Z_axis_L > 454 Then
Select Y_axis_L
Case 362
Y_axis_L = 365
'5
Case 363 To 364
Y_axis_L = 370
' 10
Case 364 To 365
Y_axis_L = 375
' 15
Case 366
Y_axis_L = 378
Case 367 To 368
Y_axis_L = 380
' 20
Case 369
Y_axis_L = 383
Case 370 To 371
Y_axis_L = 385
' 25
Case 372
Y_axis_L = 387
61
Case 373 To 376
Y_axis_L = 390
' 30
Case 377
Y_axis_L = 392
Case 378
Y_axis_L = 394
Case 379 To 380
Y_axis_L = 395
' 35
Case 381
Y_axis_L = 397
Case 382 To 383
Y_axis_L = 400
' 40
Case 384 To 385
Y_axis_L = 402
Case 386
Y_axis_L = 404
Case 387 To 389
Y_axis_L = 405
' 45
Case 390 To 391
Y_axis_L = 407
Case 392 To 393
Y_axis_L = 408
Case 394 To 395
Y_axis_L = 410
' 50
62
Case 396 To 397
Y_axis_L = 412
Case 398
Y_axis_L = 414
Case 399 To 402
Y_axis_L = 415
' 55
Case 403 To 404
Y_axis_L = 417
Case 405
Y_axis_L = 418
Case 406 To 408
Y_axis_L = 420
' 60
Case 409 To 410
Y_axis_L = 422
Case 411 To 412
Y_axis_L = 424
Case 413 To 415
Y_axis_L = 425
' 65
Case 416 To 417
Y_axis_L = 427
Case 418 To 419
Y_axis_L = 428
Case 420 To 422
Y_axis_L = 430
' 70
63
Case 423
Y_axis_L = 432
Case 424 To 425
Y_axis_L = 433
Case 426
Y_axis_L = 434
Case 427 To 429
Y_axis_L = 435
' 75
Case 430
Y_axis_L = 437
Case 431 To 432
Y_axis_L = 438
Case 433
Y_axis_L = 439
Case 434 To 436
Y_axis_L = 440
' 80
Case 437 To 438
Y_axis_L = 442
Case 439 To 440
Y_axis_L = 443
Case 441
Y_axis_L = 444
Case 442 To 444
Y_axis_L = 445
' 85
64
Case 445 To 446
Y_axis_L = 447
Case 447 To 448
Y_axis_L = 448
Case 449 To 451
Y_axis_L = 450
' 90
Case 452 To 453
Y_axis_L = 452
Case 454 To 455
Y_axis_L = 453
Case 456 To 457
Y_axis_L = 454
Case 458 To 459
Y_axis_L = 455
' 95
Case 460 To 461
Y_axis_L = 457
Case 462 To 463
Y_axis_L = 458
Case 464 To 465
Y_axis_L = 459
Case 466 To 467
Y_axis_L = 460
' 100
Case 468 To 469
Y_axis_L = 462
65
Case 470 To 471
Y_axis_L = 463
Case 472
Y_axis_L = 464
Case 473 To 475
Y_axis_L = 465
' 105
Case 476 To 477
Y_axis_L = 467
Case 478 To 479
Y_axis_L = 468
Case 480 To 481
Y_axis_L = 469
Case 482 To 484
Y_axis_L = 470
' 110
Case 485 To 486
Y_axis_L = 472
Case 487 To 488
Y_axis_L = 474
Case 489 To 491
Y_axis_L = 475
' 115
Case 492 To 493
Y_axis_L = 477
Case 494 To 495
Y_axis_L = 478
66
Case 496 To 498
Y_axis_L = 480
' 120
Case 499 To 500
Y_axis_L = 482
Case 501 To 502
Y_axis_L = 484
Case 503 To 505
Y_axis_L = 485
' 125
Case 506 To 507
Y_axis_L = 487
Case 508 To 509
Y_axis_L = 488
Case 510 To 512
Y_axis_L = 490
' 130
Case 513 To 514
Y_axis_L = 492
Case 515
Y_axis_L = 494
Case 516 To 518
Y_axis_L = 495
' 135
Case 519
Y_axis_L = 497
Case 520 To 550 '522
Y_axis_L = 500
' 140
67
EndSelect
EndIf
Y_axis_L = Y_axis_L - 360 ' ZERO POINT
'-------------------------------------'
(-) DISTAL SCALING
'-------------------------------------If Z_axis_L < 454 Then
' NEGATIVE DISTAL CONVERSION
neg_distal = 1
Select Y_axis_L
Case 2
Y_axis_L = 5
Case 3
Y_axis_L = 10
Case 4
Y_axis_L = 15
Case 5 To 6
Y_axis_L = 20
Case 7
Y_axis_L = 23
Case 8 To 9
Y_axis_L = 25
Case 10
68
Y_axis_L = 27
Case 11 To 12
Y_axis_L = 30
Case 13
Y_axis_L = 32
Case 14
Y_axis_L = 34
Case 15 To 16
Y_axis_L = 35
Case 17
Y_axis_L = 37
Case 18
Y_axis_L = 38
Case 19 To 20
Y_axis_L = 40
Case 21
Y_axis_L = 42
Case 22
Y_axis_L = 43
Case 23
Y_axis_L = 44
Case 24 To 25
Y_axis_L = 45
Case 26 To 27
69
Y_axis_L = 47
Case 28
Y_axis_L = 48
Case 29
Y_axis_L = 49
Case 30 To 31
Y_axis_L = 50
Case 32 To 33
Y_axis_L = 52
Case 34 To 35
Y_axis_L = 54
Case 36 To 38
Y_axis_L = 55
Case 39 To 40
Y_axis_L = 57
Case 41 To 42
Y_axis_L = 58
Case 43 To 44
Y_axis_L = 60
Case 45 To 46
Y_axis_L = 62
Case 47 To 48
Y_axis_L = 63
Case 49 To 50
70
Y_axis_L = 64
Case 51 To 52
Y_axis_L = 65
Case 53 To 54
Y_axis_L = 67
Case 55 To 56
Y_axis_L = 68
Case 57 To 58
Y_axis_L = 70
Case 59 To 60
Y_axis_L = 72
Case 61 To 62
Y_axis_L = 73
Case 63 To 65
Y_axis_L = 74
Case 66 To 67
Y_axis_L = 75
Case 68 To 69
Y_axis_L = 77
Case 70 To 71
Y_axis_L = 78
Case 72
Y_axis_L = 79
Case 73 To 74
71
Y_axis_L = 80
Case 75 To 76
Y_axis_L = 82
Case 77 To 78
Y_axis_L = 83
Case 79 To 80
Y_axis_L = 84
Case 81 To 82
Y_axis_L = 85
Case 83 To 84
Y_axis_L = 87
Case 85 To 86
Y_axis_L = 88
Case 87 To 88
Y_axis_L = 89
Case 89 To 120 '90
Y_axis_L = 90
EndSelect
EndIf
'-------------------------------------'
(-) PROXIMAL SCALING
'-------------------------------------If Y_axis_U > 360 Then neg_proximal = 1
Select Y_axis_U
72
Case 451
' 80
Y_axis_U = 80
Case 449 To 450
' 75
Y_axis_U = 75
Case 446 To 448
' 70
Y_axis_U = 70
Case 445
Y_axis_U = 67
Case 443 To 444
' 65
Y_axis_U = 65
Case 442
Y_axis_U = 63
Case 439 To 441
' 60
Y_axis_U = 60
Case 437 To 438
' 57
Y_axis_U = 55
Case 435 To 436
' 55
Y_axis_U = 55
Case 433 To 434
Y_axis_U = 54
Case 432
Y_axis_U = 52
Case 430 To 431
' 50
Y_axis_U = 50
73
Case 429
Y_axis_U = 48
Case 427 To 428
Y_axis_U = 47
Case 425 To 426
' 45
Y_axis_U = 45
Case 423 To 424
Y_axis_U = 44
Case 421 To 422
Y_axis_U = 42
Case 419 To 420
' 40
Y_axis_U = 40
Case 417 To 418
Y_axis_U = 38
Case 415 To 416
Y_axis_U = 37
Case 412 To 414
' 35
Y_axis_U = 35
Case 410 To 411
Y_axis_U = 34
Case 408 To 409
Y_axis_U = 32
Case 405 To 407
' 30
Y_axis_U = 30
74
Case 403 To 404
Y_axis_U = 28
Case 401 To 402
Y_axis_U = 27
Case 398 To 400
' 25
Y_axis_U = 25
Case 395 To 397
Y_axis_U = 24
Case 393 To 394
Y_axis_U = 22
Case 390 To 392
' 20
Y_axis_U = 20
Case 388 To 389
Y_axis_U = 18
Case 386 To 387
Y_axis_U = 17
Case 383 To 385
' 15
Y_axis_U = 15
Case 381 To 382
Y_axis_U = 14
Case 379 To 380
Y_axis_U = 13
Case 377 To 378
Y_axis_U = 12
75
Case 374 To 376
' 10
Y_axis_U = 10
Case 373
Y_axis_U = 8
Case 371 To 372
Y_axis_U = 7
Case 369 To 370
Y_axis_U = 5
'5
Case 367 To 368
Y_axis_U = 4
Case 365 To 366
Y_axis_U = 3
Case 362 To 364
Y_axis_U = 2
Case 361
Y_axis_U = 1
'-------------------------------------'
(+) PROXIMAL SCALING
'-------------------------------------Case 360
Y_axis_U = 0
Case 359
Y_axis_U = 1
Case 357 To 358
76
Y_axis_U = 2
Case 355 To 356
Y_axis_U = 3
Case 353 To 354
Y_axis_U = 4
Case 351 To 352
Y_axis_U = 5
'5
Case 350
Y_axis_U = 6
Case 348 To 349
Y_axis_U = 7
Case 346 To 347
Y_axis_U = 8
Case 344 To 345
Y_axis_U = 9
Case 342 To 343
Y_axis_U = 10
' 10
Case 341
Y_axis_U = 12
Case 339 To 340
Y_axis_U = 13
Case 337 To 338
Y_axis_U = 14
Case 335 To 336
77
Y_axis_U = 15
' 15
Case 333 To 334
Y_axis_U = 17
Case 331 To 332
Y_axis_U = 18
Case 329 To 330
Y_axis_U = 19
Case 326 To 328
Y_axis_U = 20
' 20
Case 323 To 325
Y_axis_U = 22
Case 321 To 322
Y_axis_U = 24
Case 319 To 320
Y_axis_U = 25
' 25
Case 316 To 318
Y_axis_U = 27
Case 314 To 315
Y_axis_U = 28
Case 311 To 313
Y_axis_U = 30
' 30
Case 309 To 310
Y_axis_U = 32
Case 307 To 308
78
Y_axis_U = 34
Case 305 To 306
Y_axis_U = 35
' 35
Case 303 To 304
Y_axis_U = 37
Case 301 To 302
Y_axis_U = 38
Case 299 To 300
Y_axis_U = 40
' 40
Case 297 To 298
Y_axis_U = 42
Case 295 To 296
Y_axis_U = 44
Case 293 To 294
Y_axis_U = 45
' 45
Case 292
Y_axis_U = 47
Case 290 To 291
Y_axis_U = 48
Case 287 To 289
Y_axis_U = 50
' 50
Case 286
Y_axis_U = 52
Case 285
79
Y_axis_U = 54
Case 283 To 284
Y_axis_U = 55
' 55
Case 282
Y_axis_U = 57
Case 281
Y_axis_U = 58
Case 278 To 280
Y_axis_U = 60
' 60
Case 277
Y_axis_U = 63
Case 275 To 276
Y_axis_U = 65
' 65
Case 274
Y_axis_U = 67
Case 271 To 273
Y_axis_U = 70
' 70
Case 269 To 270
Y_axis_U = 75
' 75
Case 268
Y_axis_U = 80
' 80
Case 267
Y_axis_U = 85
' 85
Case 266
80
Y_axis_U = 90
' 90
Case Else
Y_axis_U = 0
EndSelect
Print At 1,1,"D=",DEC4 Y_axis_L," P=",DEC4 Y_axis_U," "
If neg_distal = 0 And neg_proximal = 0 Then
angle = Y_axis_L + Y_axis_U
ElseIf neg_distal = 1 And neg_proximal = 0 Then
If Y_axis_L > Y_axis_U Then
angle = Y_axis_L - Y_axis_U
Else
angle = Y_axis_U - Y_axis_L
EndIf
ElseIf neg_distal = 0 And neg_proximal = 1 Then
If Y_axis_L > Y_axis_U Then
angle = Y_axis_L - Y_axis_U
Else
angle = Y_axis_U - Y_axis_L
EndIf
Else
angle = Y_axis_L + Y_axis_U
81
EndIf
If angle > 360 Then Clear angle
' angle = 0
Print At 2,1,"Angle= ",Dec angle,"'Deg.
"
DelayMS 310
If PORTB.6 = 0 Then SEND
GoTo Loop
SEND:
DelayMS 1100
HSerOut [Dec angle]
' SEND ANGLE VALUE TO PC
Print At 1,1," Data Sent! "
Clear PORTA
' Clear portA
Clear PORTC
' Clear portC
DelayMS 1000
While PORTB.6 = 0
DelayMS 50
Wend
Clear PORTA
' Clear portA
Clear PORTB
' Clear portB
Clear PORTC
' Clear portC
Clear PORTE
' Clear portC
82
DelayMS 50
'
EndIf
GoTo DISPLAY
End
83
APPENDIX D
(Datasheets)
84
PIC16F877A Data Sheet
85
86
87
88
89
90
91
92
93
94
95
96
ADXL335 Datasheet
97
98
99
100
101
102
103
104
105
106
107
ZigBee Module Datasheet
108
109
MAX232 Datasheet
110
111
112
113
114
115
L1682 Hitachi LCD Datasheet
116
117
118
119
120
121
122
123
124
LM7805 Datasheet
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
SPX2815 Datasheet
152
153
154
155
156
157
158
159
160
161
PC-Interfaced Goniometer for Knee and Elbow
Joint Angular Measurements Using
Accelerometer and ZigBee Technology
Miguel Carlo P. Ang, Anthony Joe P. Melgarejo, Nikko L. Tamaña
Analyn N. Yumang, Adviser
BS in Computer Engineering – School of EECE, Mapua Institute of Technology
Abstract— The main goal of the group is to design a device that
addresses the drawbacks of using a common goniometer. The
group presents in this documentation an alternative method for
measuring human joint angles, specifically knee and elbow joint
angles. The digital goniometer consists of two accelerometers, a
digital signal processing element and a wireless communication
component. Accelerometers are commonly used to sense leg or
arm movement for monitoring the progress of the patient during
rehabilitation. Joint angles are directly calibrated using the
output of the accelerometers therefore angles displayed is similar
to the common goniometer. The angles measured are then stored
into the patient information database for ease of evaluation of the
rehabilitation doctor.
Index Terms— Goniometer, accelerometer, ZigBee Technology,
wireless transmission
I. INTRODUCTION
Measuring the range of motion (ROM) is vital
in rehabilitation medicine. Each specific joint has a normal
range of motion that is expressed in degrees. Limited range of
motion compared to the normal refers to a joint that has a
reduction in its ability to move caused by injury, operation or
diseases such as osteoarthritis, rheumatoid arthritis, or other
types of arthritis. Pain, swelling and stiffness associated with
the injury, operation and said diseases can limit the range of
motion of a particular joint and impair function and the ability
to perform usual daily activities.
Devices used to measure the ROM of various joints
in the human body are the goniometer and inclinometer. Both
devices use a stationary arm, protractor, fulcrum and
movement arm to measure angle from axis of the joint. The
goniometer is used by rehabilitation doctors to measure ROM
as a way to monitor a patient’s progress while undergoing
physical therapy.
This device aims to address the health and safety of a
patient. In physical therapy and occupational therapy, a
goniometer is an instrument which measures an axis and range
of motion. If a patient experiences decreased range of motion
in a joint (e.g a knee or elbow) caused by an operation or
fracture, for example, the therapist can use a goniometer to
assess what the range of motion is prior to intervention. Using
the information produced by the goniometer, the therapist can
monitor the range of motion after every therapy session. From
this range of motion, the therapist is able to plan the
appropriate exercise to achieve the target joint range of motion
suitable for the mobility of the patient. It focuses on measuring
the ROM of the elbow and knee joints.
The angle measured using the device is displayed
using a desktop computer or a laptop. The use of a computer
also allows an adequate recording of the data for each patient
using the device, which may be later analyzed with ease,
precision and readability as compared to the conventional
method. It is also much smaller in size compared to the
electrogoniometer since it would only be attached to the
patient’s leg or arm using straps. Due to its smaller size, it is
easier for the physical therapist to set up the device and the
patient is more comfortable during the measurement process.
The device consists of two dual axis accelerometers,
a digital signal processing element and a wireless
communication component. The accelerometers are used to
determine the angular position of the knee or elbow joint. The
digital signal processing element calculates the joint angle.
This information is then sent by ZigBee communication to a
PC which displays the joint angle.
II. REVIEW OF RELATED DESIGN LITERATURE AND STUDIES
A related article entitled “Goniometer Based to
Computer” from IEEE issued last April 5, 2004 designed a
goniometer based to computer focused on the measurements
of angles of the arms. The article discussed that universal
goniometers are commonly used during physical assessments
of patients under physiotherapeutical treatments, but the
measurement accuracy is influenced by its own quality and
also the differences among articulations being assessed. In
order to ease the specialist’s work, a goniometer based to
162
computer fixed to the patient has been designed to give the
angle of the arms, allowing a faster evaluation of the patient’s
progress. The angle is measured using an optical encoder and
its value is properly interpreted by the PC and presented on the
monitor. The use of a computer also allows an adequate
recording of data which may be analyzed with ease, precision
and readability compared to the conventional method.
Measuring Tilt with Low-g Accelerometers
This application note describes how accelerometers
are used to measure the tilt of an object. Accelerometers can
be used for measuring both dynamic and static measurements
of acceleration. Tilt is a static measurement where gravity is
the acceleration being measured. Therefore, to achieve the
highest degree resolution of a tilt measurement, a low-g, high
sensitivity accelerometer is required. In measuring the angle,
the change in degrees of tilt directly corresponds to a change
in the acceleration due to a changing component of gravity
acted on the accelerometer. In order to determine the angle of
tilt, θ, the A/D values from the accelerometer are sampled by
the ADC channel on the microcontroller. The acceleration is
compared to the zero g offset to determine if it is a positive or
negative acceleration. One solution can measure 0° to 90° of
tilt with a single axis accelerometer, or another solution can
measure 360° of tilt with two axis configuration (XY, X and
Z), or a single axis configuration (e.g. X or Z), where values in
two directions are converted to degrees and compared to
determine the quadrant that they are in. . A tilt solution can be
solved by either implementing an arccosine function, an
arcsine function, or a look-up table depending on the power of
the microcontroller and the accuracy required by the
application.
We included this paper as a reference in computing
for the angle. The method included in this paper can serve as
an alternative solution for the computation of the angle. Since
the concept in computing the angle of tilt is roughly the same
for our method (comparing values in different degree of tilt),
we considered this article as a related literature. Furthermore,
the solution presented in this article can serve as a backup to
ensure that if the solution we used does not live up to its
expectation or yielded poor test results, we can still use the
solution in this article to fix the problem.
ZigBee Technology
The design will use the analog signals from the
movement of the accelerometers and convert it into digital
signal then transmit it using the ZigBee wireless technology.
According to an article entitled “Networked Wireless Meter
Reading System Based on ZigBee Technology” (Liting Cao,
Wei Jiang, Zhaoli Zhang) from IEEE issued last July 2008 the
ZigBee, namely IEEE802.15.4 technology standard is one of
WPAN IEEE802.15 technology standard. ZigBee bend itself
to realize a short distant double direction wireless
communication protocol which is lower complexity, lower
cost and lower speed. In this article the ZigBee technology
was used to solve the problems existed in meter reading
systems. The structure of the system employs distributed
structure the measure meters, sensor nodes, data collectors,
server and wireless communication network. For a short
distance transmission the data collector collects data using
ZigBee communication.
Another article supports the use of wireless
technology, the article which is entitled, “5.5mA 2.4-GHz
two-point modulation ZigBee transmitter”, by Rui Yu ThengTee, Yeo Kwang-Hung, Tan Shouxian,MouYike, Cui Haifeng,
Wang Hwa-Seng, and Yap Ting from IEEE issued last
September 2009 describes that a 2.4-GHz two-point
modulation IEEE 802.15.4 (ZigBee) compliant transmitter is
presented. The sigma-delta fractional-N PLL based transmitter
is optimized for both low-power and low-cost purposes. A
novel closed-loop calibration scheme is proposed to minimize
the gain mismatch between two modulation points, which is
the main source of error in two-point modulation.
With these articles, the group can say that ZigBee
wireless Technology has advantages with the other RF
modules with its low power consumption, low cost and has a
wider range.
PIC16F877A Microcontroller
In an article entitled ¨Network model based
automation of thermal processes using an embedded digital
controller”, by Ganesh, A.B. Sangeetha, A.L. Ravi, V.R.
issued last Dec. 2009 from IEEE, a microcontroller is used.
The article describes the network architectures of both WAN
and LAN based real time control and monitoring of thermal
process station using an embedded digital controller. The
function of the microcontroller in this design is a temperature
controller that communicates directly with the temperature
transmitter. The design uses the PIC16F877A microcontroller.
The group’s design will use two microcontroller
units, one for the transmitter and the other is for the receiver
part. The article above shows that microcontrollers can
interact with transmitters, thus it can also interact with
receivers.
Microchip Programmable Interface Controller (PIC)
are popular with both industrial developers and designers due
to their low cost, wide availability, large user base, and serial
163
programming (and re-programming with flash memory)
capability. Different levels of on-board features are being
associated to each type of microcontrollers. The smallest ones
can add some simple automation to a project, while the huge
devices have the capabilities of a microprocessor system,
offering much more than simple control.
III. DESIGN PROCEDURES
This chapter discusses the procedures that were
followed in the development of the design. This also includes
the block diagram, schematic diagram and the system flow
chart.
Hardware Development
Block Diagram
TRANSMITTER
Accelerometer
Accelerometer
(Upper Limb)
(Lower Limb)
MCU/ADC
ZigBee
Technology
Schematic Diagram of the Transmitter with the
Accelerometer, Microcontroller and Zigbee Module
(See last page)
Power is supplied by the 9v battery which is
controlled by a switch. It passes through a diode which serves
as a protection in case the battery is improperly connected.
Then an op-amp then regulates the voltage to 3.3V which is to
be used by the accelerometers. In parallel, another voltage
regulator gives the 5V which the microcontroller and the LCD
needs. The accelerometer outputs analog voltage which is
connected to a debouncer circuit seen as a collection of
capacitors to keep the voltage stable. The debouncer circuit
stabilizes the voltage to be passed into the microcontroller
since the accelerometer output is analog. The voltage then
passes through a precision resistor, which is like a
potentiometer that sets the reference voltage to be used by the
ADC in the conversion from analog signal to digital. The
conversion of the voltage and calculation of the angle is done
inside the microcontroller. The output is passed to the LCD,
which displays the output into readable text, and to the
ZigBee, to be transmitted. Before the signal reaches the
ZigBee, it passes through a voltage divider. Since the input
voltage of the microcontroller is 5v, the output can reach 5V,
which is a problem to the ZigBee. The ZigBee can only
accommodate 3.3V, which explains the need for a voltage
divider.
9V Battery
Zigbee Module Schematic Diagram (Receiver Side)
RECEIVER
ZigBee
Technology
MAX232
COMPUTER
Figure 3.1
System Block Diagram of PC-Interfaced Goniometer for
Knee and Elbow Angular Measurements using
Accelerometer and ZigBee Technology
The system is composed of two divisions the
transmitter and the receiver. The primary input of the system
will be coming from the two accelerometers. From the figure,
the accelerometers are connected to the MCU that interprets
the analog signal then converts it into digital signal. The
ZigBee Module will be responsible for the wireless
transmission.
The main output of the system is the angular
measurement reading that is shown in the LCD attached to the
device. The last block in the diagram represents the Computer
to where the angular measurement is stored in the patient’s
database. That completes the process of the designed system.
(See last page)
The signal is received by the receiver ZigBee. The
signal is digital when it leaves the module. It then passes
through MAX232 which amplifies the signal so no loss is
incurred due to line resistance. The capacitors are needed as
stated by its datasheet. The 5V supply came from the 1 st USB
connection and is then regulated down to 3.3V which the IC
needs. The signal is then passed through the serial-to-USB
cable to send the data.
Prototype Development
The design procedure will show the step-by-step
procedure on how the design was built. It will describe the
detailed information about the conceptualization of the design
project.
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1.
Conceptualization
After knowing the design will work as a whole,
the conceptualization of the transmitter and receiver part
must be equated to simplify the design hardware and
software.
2.
Simplified design requirement
It is also important to create initial drafting of
materials required as the development of the project
proceeds. This will give the researchers an overview of
the project.
3.
Illustrate the block diagram
Defines the major composition of the design and
shows how each block is related with each other. The
block diagram for the transmitter consists of the
Microcontroller Unit (MCU), Accelerometer for Upper
Limb, Accelerometer for Lower Limb, Wireless
technology using ZigBee, and 9V Battery. The block
diagram of the receiver consists of the ZigBee
technology, MAX232 and Computer.
4.
Draw schematic diagram
Schematic diagram of this design shows how each
device was interconnected. It contains major components
such as the Microcontroller Unit (MCU), Accelerometer
for Upper Limb, Accelerometer for Lower Limb,
Wireless technology using ZigBee, and 9V Battery for the
transmitter. On the other hand, the receiver of the system
uses components such as the wireless technology using
ZigBee Module and the Computer.
In developing the design, the following materials are used
each with its brief discussion:
PIC16F877A
This type of microcontroller is used in the design
primarily because of its many inputs. PIC16F877A has a
maximum of 40 I/O pins which is very much suitable for the
design. It has a maximum of 256 bytes for its register which is
also much appropriate for the design to be possible. It also has
built – in UART (Universal Asynchronous Receiver
Transmitter) that can communicate with peripheral devices
such as personal computers or laptops.
Max232
The MAX232 is a dual driver/receiver that converts
signals from an RS-232 serial port to signals suitable for use in
TTL compatible digital logic circuits and vice versa. MAX232
operates at 5V DC input voltage and connected to Vs pin of
the IC. The MAX232 IC is used to interface the central
computer and the Zigbee module in the receiver side.
HD44780U (LCD)
The HD44780U dot-matrix liquid crystal display
controller and driver LSI displays alphanumerics, Japanese
characters, and symbols. It can be configured to drive a dotmatrix liquid crystal display under the control of a 4- or 8-bit
microprocessor. The HD44780U character generator Rom is
extended to generate 208 5x8 dot character fonts and 32 5x10
character fonts for a total of 240 different character fonts. The
low power supply (2.7V to 5.5V) of the HD44780U is suitable
for any portable battery-driven product requiring low power
dissipation.
ADXL335 (3-axis Accelerometer)
The ADXL335 is a small, thin, low power, complete
3-axis accelerometer with signal conditioned voltage outputs.
ADXL335 measures acceleration with a minimum full-scale
range of
g. It can measure the static acceleration of gravity
in tilt-sensing applications, as well as dynamic acceleration
resulting from motion, shock, or vibration. In the design, it is
used as a motion sensor.
IV. TESTING, PRESENTATION AND INTERPRETATION OF DATA
This chapter presents various tests performed by the
designers to determine the effectiveness of the design. The
tests are conducted with relevance to the design objectives.
Wireless Technology using ZigBee Signal Range Test
ZigBee Wireless Technology
The ZigBee technology was used because it has
greater range and it is widely used in today’s wireless
technology. The group used this because of its low
consumption of power and wide range of transmission.
The researchers conducted a signal range test to
determine the capability of the wireless technology. The
testing was done in an area wherein the receiver is in line of
sight and a few meters away from the transmitter. The
following table shows the results gathered based on the signal
range test.
165
TRIAL
1
2
3
4
5
10m
Good
Good
Good
Good
Good
20m
Good
Good
Good
Good
Good
30m
Good
Good
Good
Good
Good
40m
Good
Good
Good
Good
Good
50m
Poor
Poor
Poor
Poor
Poor
The designers tested the wireless proximity within 10m –
40m range. Even if it is only designed for clinical use with
very close proximity which commonly has an area of 5 sq. m,
the designers decided to test the full capability of the Zigbee in
case it is necessary for larger proximity use. The results show
that within 40m, the data transmission is good which means
that there is no delay and the sent data is correct. In a distance
of 50m, the data transmission is poor meaning that there is no
received data.
Accelerometer Output Scale Test
In this test, there will be four tables presented. These
are for the positive and negative distal and positive and
negative proximal scaling. The values presented in these tables
are analog to digital conversions which are outputs from the
accelerometers with corresponding angle measurements from
the goniometer.
TRIAL
1
2
3
4
5
1° - 5°
362
362
362
362
362
6° - 10°
363
363
363
364
364
11° - 15°
364
364
365
365
365
16° - 20°
366
366
366
366
368
21° - 25°
369
369
369
369
371
26° - 30°
372
372
372
372
376
31° - 35°
377
377
378
378
380
36° - 40°
381
381
381
381
383
41° - 45°
384
386
386
386
389
46° - 50°
390
391
392
393
395
51° - 55°
396
397
397
398
402
56° - 60°
403
404
405
405
408
61° - 65°
409
410
411
412
415
66° - 70°
416
417
419
419
422
71° - 75°
423
423
425
426
76° - 80°
430
430
432
433
81° - 85°
437
438
440
86° - 90°
445
446
91° - 95°
452
96° - 100°
Based on the scaling test, the accelerometer's output
is not evenly distributed with every tilt. Small angles from 0°
to 20° in some cases have a few discrepancies but these are
negligible as this range is small for clinical observations.
Precision Test
TRIAL
1
2
3
4
5
0°
0°
0°
2°
0°
1°
10°
0°
7°
0°
10°
15°
20°
18°
20°
21°
20°
18°
30°
30°
31°
29°
30°
30°
40°
39°
40°
40°
41°
39°
50°
51°
52°
50°
49°
50°
60°
59°
61°
61°
60°
60°
70°
71°
70°
70°
70°
69°
80°
82°
79°
81°
80°
79°
90°
90°
89°
90°
91°
91°
100°
101°
101°
100°
100°
101°
110°
109°
111°
110°
110°
110°
120°
120°
120°
120°
120°
120°
130°
129°
130°
130°
131°
130°
140°
140°
140°
140°
139°
140°
Precision Testing was conducted by the designers to
verify the reliability of the design's angle measurements. As
seen from the results and in reflection to the Accelerometer
Output Scale Test, small angles from 0° to 20° have
discrepancies but as stated earlier these are negligible. There is
also a ± 3 tolerance in the angle measurements but these are
not a problem because the purpose of the design is to monitor
the improvement of the patients' joints' range of motion, not
the accuracy of measurements. Overall, the design's
measurements are precise, nonetheless.
Output Test
TRIAL
1
2
3
4
5
0°
0°
0°
0°
0°
0°
10°
10°
10°
10°
10°
10°
429
20°
20°
20°
20°
20°
20°
436
30°
30°
30°
30°
30°
30°
441
444
40°
40°
40°
40°
40°
40°
448
448
451
50°
50°
50°
50°
50°
50°
453
455
457
459
460
461
463
465
467
60°
60°
60°
60°
60°
60°
101° - 105°
468
469
471
472
475
70°
70°
70°
70°
70°
70°
106° - 110°
476
477
479
481
484
80°
80°
80°
80°
80°
80°
111° - 115°
485
486
487
488
491
90°
90°
90°
90°
90°
90°
116° - 120°
492
493
495
495
498
100°
100°
100°
100°
100°
100°
121° - 125°
499
500
501
502
505
126° - 130°
506
507
509
509
512
131° - 135°
513
514
514
515
518
136° - 140°
519
519
524
532
538
110°
110°
110°
110°
110°
110°
120°
120°
120°
120°
120°
120°
130°
130°
130°
130°
130°
130°
140°
140°
140°
140°
140°
140°
166
The results show that the data transmission is perfect
given that the transmission range is within 40m. Whatever the
reading is in the goniometer when the 'Send' button is pressed,
the ZigBee will send and receive the correct data. Then, the
PC interface will output the transmitted data if the 'Record'
button is clicked.
V. CONCLUSION AND RECOMMENDATION
This chapter contains the general conclusion of the
development of the design in relation to its objectives. The
results of the various tests performed should also be clearly
defined in this chapter. Recommendation for the improvement
of the design is also stated in this chapter.
CONCLUSION
In the design PC-Interfaced Goniometer for Knee and
Elbow Joint Angular Measurements Using Accelerometer and
ZigBee Technology, the designers were able to develop a
device that addresses the drawbacks of using a common
goniometer.
The design is incorporated with ZigBee Technology
in transmitting the captured data from the accelerometers and
receiving the data to be stored in the Patient Information
database. The software serves as the database where the
patient’s information and angle measurements are stored.
systems other than the Windows platform such as Linux to
provide software portability.
References
Barreiro, M.S. Frere, A.F. Theodorio, N.E.M. Amate,
F.C. (2004). Goniometer Based to Computer,
Engineering in Medicine and Biology Society
Journal, IEEE
Jeong-Whan, Lee Lee-Yon, Hong Jae-Hoon (2007). A Simple
Optical Angular Sensors to Measure the Human Joint
Angle, SICE-ICASE, IEEE
Donno, M. Palange, E. Di Nicola, F. Bucci, G. Ciancetta,
F. (2008). A New Flexible Optical Fiber Goniometer
for Dynamic Angular Measurements: Application to
Human Joint Movement Monitoring, Instrumentation
and Measurement, IEEE Transactions
Liting C., Wei J., Zhaoli Z. (2008). Networked Wireless Meter
Reading System Based on Zigbee Technology.
Wireless Technology, IEEE, page(s): 3455
C. C. Norkin, D.J. White (2003). Measurement of Joint
Motion: A Guide to Goniometry, 3rd Edition, F.A.
Davis Company, Philadelphia
RECOMMENDATION
The researchers suggests replacing ZigBee with other
wireless technology that offers more features such as lower
power consumption and wider range of data communication.
It is suggested to add further enhancements to the
software where implementation of the accelerometer will
enable the user to achieve more accurate readings in any
orientation possible. Also, it is suggested to make it the device
flexible in terms of functionality by making it possible for the
device to measure other human joints as well.
Other than using the computer desktop or laptop as
the information storage, it is suggested to use a Personal
Digital Assistant (PDA) or other handheld devices such as
iPad and iTouch to make the device more portable.
The researchers also recommend performing further
research to make the application run on other operating
167
Schematic Diagram of the Transmitter with the Accelerometer,
Microcontroller and ZigBee Module
ZigBee Module Schematic Diagram (Receiver Side)
168