Smart Crutch
The 6th arm
ENSC440 Group #5
Tues, April 14, 2009
Story Time !
Why do we want to make
the Smart Crutch!!!
Presentation Outline :









System Overview
Team Dynamics
Research Background
System Input/Output
Friction Sensor
Motion Sensor
Experiment Result
Prevention Mechanism
Hardware Design







RF Alarm System
Software
Timeline
Finances
Business Opportunities
Future Work
Acknowledgments
System Overview




User Interface
Warning Stage
Prevention Stage
Transmission Stage
Team Dynamic
Research Background
Two-Point Gait
Three-Point Gait
Research Background
Four-Point Gait
Research Background
- Free Body Diagram
System Inputs/Outputs
Friction Sensor
Friction Sensor
Activation Switch
Motion Sensor



Triple Axis
Accelerometer
Output Voltage
with Respect to
Gravity
Output Voltage
Between 1.3V-2V
Experiment Results
Warning Activation
Motion Sensor
Friction Sensor
Prevention Activation
Conditions to Activate
Prevention:
• Activation Switch is On
• Happens After Warning
• Decreasing Angle
(10 Degrees/0.07 (v))
Alarm Activation


When User Falls
Less than 30 Degrees or More than
160 Degrees in X-Axis or Y-Axis
Activation Algorithm
Prevention mechanism
What does it do?




Arm extends
outwards
Extra Support
One-way Gear
prevents
backsliding
Pull-back
mechanism
Hardware Design
1.
2.
3.
What are on the Board?
Detailed hardware description for
certain parts on the board
RF remote alarm system
What are on the board?
Atmel Atmega16A 8 bits microcontroller
32 programmable IO pins
16K bytes in system programming flash
We use ISP interface to program the
microcontroller
What are on the board?
2 lines x 16 character LCD
- Display the user response
What are on the board?
5 user buttons interface
- For user to enter their User ID and weight
What are on the board?
Accelerometer ADXL330
- Used for measuring the angular position
of the crutch
RF transmitter (ASK scheme)
- Used for sending the help message to
the remote receiver during emergency
situation
What are on the board?
Friction sensing circuitry
Fall-prevention mechanism control circuitry
On board Buzzer
- Will sound when the user has the tendency
to slip
What are on the board?
5V regulator circuitry
- The power source is a 8.4V Ni-Cd
battery with 1800mA-hour
- The total current draw for the
overall system is around 200mA
PCB layout
2X16 Characters
Black/White LCD
On/Off
Switch
5V regulator Power
Circuitry
Warning DC
Buzzer
434MHz
RF transmitter
Reset
Button
Friction Sensing
Circuitry
Microcontroller
Power Indication
LED
10 Pin
ISP
Interface
Fall Prevention
Motor Circuitry
Accelerometer
User Interface
Buttons
Enter
Button Control Circuitry
6 pin Motor
Connector
The built PCB image
Detailed hardware description
Detailed hardware description
RF alarm system
-
-
The remote alarm system will generate
a series of beeping sound when
crutches fall
Transmission range within 100m
RF alarm system
Detailed Schematic
Software Design
Microcontroller resources
 16 bit timer – warning and alarm
 512 B EEPROM – user info database
 External interrupt 0 – push buttons
 8 bit processor
 1 MHz internal clock
 AREF ~ 2.56V; 2.65 used
Software Design
IDLE
STATE
Enter ID
Enter Weight
Recognize?
NO
Show Weight
YES
Fall
Prevention
Alarm
ALARM Detected
10x
ALARM not
detected
10x
Warning not
detected 30x
Fall detected 1x
Warning
Sampling
Warning detected
30x
Software
ADC calculation
 single ended connection
 Aref = 2.65 V
Vin = (ADC * Aref) / 1024
Software - Testing





Use 512 B eeprom for dumping sensor
values
Extract values from txt file and convert
to Matlab
Plot values in matlab
Plot values in pyLab
72 kg
Software - Testing
Color Scheme
 Green – Friction Sensor Voltage
 Red – Required Angle Voltage
 Blue – Y-Axis Voltage
 Light Blue – X-Axis Voltage
Software - Testing
Crutch 1 – Cemented Floor
3
2.5
Volts
2
1.5
1
0.5
0
0
2
4
6
Time (sec)
8
10
12
4
x 10
Software - Testing
Crutch 2 – Cemented Floor
3
2.5
Volts
2
1.5
1
0.5
0
0
2
4
6
8
Time (usec)
10
12
14
4
x 10
Software - Testing
Crutch 1 – Carpeted Floor
3
2.5
2
Volts

1.5
1
0.5
0
0
2
4
6
8
Time (usec)
10
12
14
4
x 10
Software - Testing
Crutch 2 – Carpeted Floor
3
2.5
2
Volts

1.5
1
0.5
0
0
5
10
Time (usec)
15
4
x 10
Software – Testing
Crutch 1 – water/slippery
2.5
2
1.5
Volts

1
0.5
0
0
2
4
6
Time (usec)
8
10
12
4
x 10
Software - testing
Crutch 2 – water/slippery
1.8
1.6
1.4
1.2
Volts

1
0.8
0.6
0.4
0.2
0
0
2
4
6
Time (usec)
8
10
12
4
x 10
Timeline
Finances
Description
Total Prize
2 lines* 16 LCD module
$
60.00
Circuit components
$
70.00
434MHz RF transmitter/receiver
$
8.00
2 Battery, Battery Charger
$ 135.00
Triple Axis Accelerometer
$
Microcontroller
$
30.00
DC Motor
$
80.00
Atmel Microcontroller development board
$ 150.00
Underarm Crutch
$
70.00
Mechanical components
$
65.50
Total Cost
$ 668.50
-
Finances
Additional Costs



spare/extra parts
travel
tools/equipment
Person
Amir
James
Stan
Ben
Kyle
Total
Expenditure
Spent
$
$
$
$
$
$
200.00
200.00
300.00
200.00
-
900.00
Business Opportunity



Hospital: The patient with
temporary or permanent disability
with their lower body
Senior’s home: The senior people
who has difficulty walking or weak
vision.
Home: For family member with
disability
Future Work





Sensors
Hardware
Software
Prevention
Summary
Future Sensors



Bearing System for
Suspended Friction
Sensor
Optical Motion Slip
Sensor
Water Sensor
Future Hardware

Reduce Space
• Less Amplifiers
• Surface Mount
• Smaller Battery

Reduce Cost
• New MC
• Machine
Manufacturing
• Smaller Battery
Future Software




Communication
between crutches
and nurse
Communication
between left and
right crutches
New Interface
GUI
Future Fall Prevention


Larger Range of Fall
Prevention
Closed Body
• Water Resistant
• No Catching of Clothing

Lighter
• Less Stress on Body

Adaptable/ Reusable
• Connect to different
crutch styles
Summary



Conceal to 1 ½ “
Diameter
Reusable
Surface-mount
Electronic
Components, and
reduce cost
What We Learned





Out of the box thinking
Cooperative teamwork is an absolute
necessity
Resourcefulness
How to work in stressful situations
How to fill the gap between theory and
practice
Acknowledgement
ASA Concepts would like to thank:
Patrick Leung
Steve Whitmore
Dr. Andrew Rawicz
Fred Heep
Jason Lee
Jamie Westell
Questions?