SALUKI ENGINEERING COMPANY
Literature Review
Team 76 - MOWR
Team Members
Project Manager: Brittany Murphy
Dylan Hartman
Rachel Parth
Nathaniel Sparks
Zachary Tennessen
Christopher Tyra
Brittany
10/6/2011
The objective of this project is to create a fully autonomous lawnmower. Upon
completion, it will be able to mow a 10 by 15 meter yard, and avoid stationary and moving
obstacles.
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Literature Review
Table of Contents
Table of Figures ............................................................................................................................................ 3
Tables ............................................................................................................................................................ 4
T94-GPS Lawnmower-Design.................................................................... Error! Bookmark not defined.
Case Western Reserve University CWRU Cutter C design review ............ Error! Bookmark not defined.
Batteries ...................................................................................................... Error! Bookmark not defined.
Robotics ........................................................................................................................................................ 6
Platform: ....................................................................................................................................................... 7
Actuator: ....................................................................................................................................................... 8
Microcontroller: ............................................................................................................................................ 9
Motor controller: ........................................................................................................................................... 9
Sensors: ....................................................................................................................................................... 10
GPS ............................................................................................................................................................. 12
Lawnmower ................................................................................................................................................ 12
Motors ......................................................................................................................................................... 13
Wheels ........................................................................................................................................................ 12
Works Cited ................................................................................................................................................ 16
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Table of Figures
Figure 1: CWRU Cutter 2 Isometric View ................................................. Error! Bookmark not defined.
Figure 3: Tracked Robot
Figure 4: Wheeled Robot............... Error! Bookmark not defined.
Figure 5: Cytron Gear Motor with Encoder .................................................................................................. 8
Figure 6: Parallax BASIC Stamp 2p 40-pin Microcontroller ....................................................................... 9
Figure 7: Vex Bumper Switch .................................................................................................................... 11
Figure 8: Cytron Incremental Rotary Encoder ............................................................................................ 11
Figure 9: Ultrasonic Range Finder .............................................................................................................. 11
Figure 10: RXM-SG GPS module with External Antenna ......................... Error! Bookmark not defined.
Figure 11: GPS Receiver Module ............................................................................................................... 12
Figure 12: PBM 648 SiRF Internal Antenna .............................................. Error! Bookmark not defined.
Figure 13: Yardworks 18” 12A electric lawnmower .................................................................................. 13
Figure 14: Marathon Electric Brake Motor................................................................................................. 14
Figure 15: Acquired Spindle Wheel............................................................................................................ 14
Figure 16: Motorized Wheels ..................................................................................................................... 15
Figure 17: Battery hookup (top) Control Box hookup (bottom) ................................................................. 15
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Tables
Table 1 .......................................................................................................................................................... 5
Table 2 .......................................................................................................................................................... 7
Table 3 .......................................................................................................................................................... 8
Table 4 .......................................................................................................................................................... 9
Table 5 .......................................................................................................................................................... 9
Table 6 ........................................................................................................................................................ 12
Table 7 ........................................................................................................................................................ 12
Table 8 ........................................................................................................................................................ 12
Table 9 ........................................................................................................................................................ 14
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Literature Review
Autonomous objects are created to make tasks simpler. One task that can be tedious is mowing
the lawn. The Institute of Navigation is holding a competition to see who can build the best
autonomous lawnmower. Team 76 will be entering this competition. This lawnmower will
consist of seven subsystems:







Frame Subsystem
Battery/Power Subsystem
Robotics Subsystem
GPS Subsystem
Computer Subsystem
Mower Subsystem
Wheels Subsystem
Each of these subsystems will require a different kind of technology to function and
communicate with each other in order to perform tasks required of the finished lawnmower, such
as moving in different directions and avoiding obstacles. Each of these subsystems have
individual components that have been researched and analyzed so that it can be determined what
the
most
efficient
way
to
implement
them
may
be.
Previous Design Review
Case Western Reserve University CWRU Cutter C Design:
Case Western Reserve University was the 1st place winners of the 2010 ION Robotic Lawn
Mower Completion. Their design also distinguished itself as the only mower to cut over 50% of
Table 1: CWRU Material List
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the required field in the allotted 20 minutes. The other participating teams failed to cut over 50%
due to poor programming and path finding.
Team 94-GPS Lawnmower-Design
The previous time that SIUC had a senior design project based around the Autonomous
Lawnmower Completion was during the Fall 2009 semester. There was no final working
product.
Figure 1: CWRU First Place Winner in 2010
Batteries
In order to run the push mower deck, the corded push mower deck must be converted to
run off of DC power from batteries. It is required to calculate out how much power is needed in
order to run the push mower. The mower deck requires 120V and 12A to run.
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𝑃𝑜𝑤𝑒𝑟(𝑊𝑎𝑡𝑡 𝐻𝑜𝑢𝑟𝑠) = 𝑉𝑜𝑙𝑡𝑠 ∗ 𝐴𝑚𝑝𝑠 → 𝑃𝑜𝑤𝑒𝑟 = 120𝑉 ∗ 12Ah
The calculations show that 1440 Watts of power is needed to run the mower. The two main
choices of battery are described in Table 4.
Type
Starting
Lighting
and
Igniting
Deep Cell
(Deep
Cycle)
Purpose
Large amount
of
instantaneous
power to start
object
Small/medium
amounts of
continuously
available
power to draw
upon
Plate Type
Thinner,
porous plates
made to
increase
surface area
Thicker, solid
plates made
to allow
longer current
draws
Power output
Recommended
for vehicle
starting
Recommended
for continuous
amounts of
power
consumptions
Table 2: Battery Specifications
Due to the continuous power requirements, the best choice of a battery would be one or
two Deep cell batteries that can provide the amount of energy required for the autonomous
lawnmower to operate. The autonomous lawnmower will need to be able to operate off of the
battery for no less than 20 minutes. That is the maximum amount of time allotted to a team to
mow the given yard.
Robotics
In order to create an automated lawnmower it is necessary to create a version of an artificial
intelligent lawnmower. This requires a version of a robot lawn motor to be built, and that in turn
involves many different components. Parts of a robot consist of:





Platform
Actuator
Microcontroller
Motor controller
Sensors
Provided are brief explanations of what each part will do in the overall system of a robot and
offers possible choices for each part including specifications and cost of each component.
Platform:
Platforms are the type of robots that will be built. They range from land (wheeled, legged or
tracked), to aerial to aquatic and finally to stationary robots.
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Figure 2: Wheeled Robot
Figure 3: Tracked Robot
Actuator:
An actuator is a device that will change energy to physical motion. For robots, it is to change
electrical energy into physical motion. Physical motion can contain of rotational or linear
motion. This will allow the robot to move in any direction on the ground. The actuator is also
known as a motor. There are several kinds of actuators; rotational actuators are AC, DC, geared
DC, R/C servo, industrial servo and stepper motors. Linear actuators are DC linear, solenoids,
muscle wire, pneumatic, and hydraulic.
Name
Cytron 12V,
1140rpm,
6.37oz-in
Gear Motor
with Encoder
Tamiya
Worm Gear
Box
Gear Ratio
Voltage
Torque
Speed
Current
Price/unit
5:1
12 V
45mN.m
1140 rpm
0.9 A
$50.00
216:1,
336:1
3V
70 g-cm
9400 rpm
2.7 A
$13.97
Table 3: Actuator Comparison
Figure 4: Cytron Gear Motor with Encoder
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Microcontroller:
The microcontroller may be the most important part of the robot; it is in many cases considered
the ‘brain’ of the robots. The microcontroller is the device that will execute a program in order
to make the robot perform its task. This is also the device where outputs from various sensors
used by the robot will feed into, to complete different requirements as stated in the program.
Name
Parallax BASIC Stamp 1
Microcontroller Module
Processor Speed
# of I/O pins
Price/unit
4 MHz turbo
8
$29.00
NanoCore12MAXC128
Module
Parallax BASIC Stamp 2p
40- Pin Microcontroller
Module
8 MHz
40
$35.70
20 MHz turbo
32 and 2 dedicated
serial
$89.00
Table 4:Microcontroller Comparison
Figure 5: Parallax BASIC Stamp 2p 40-pin Microcontroller
Motor controller:
The motor controller assists in controlling the motor. The microcontroller has the program in its
memory, and is capable of directing the robot where to go and how fast to travel in that direction;
however it usually does not have enough power to power itself as well drive the motor. Thus the
microcontroller and the motor controller work in tandem – with the microcontroller reading its
program and the inputs from the sensor and directing the motor control to power the motor with
‘x’ amount of power. There are different types of motor controllers; some of these types are DC
motor control, servo motor control, stepper motor control, and linear actuator control.
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Name
2A 5V-16V Dual
Serial Motor
Controller
Pololu DC Motor
Driver 3A, 5V28V- MC33926
Current
Operating
Voltage
Price/unit
2 A per motor,
total of 4 A
5V-16V
$19.95
3A
5V-28V
$23.95
Table 5: Motor Controller Comparison
Figure 6: Pololu DC Motor Driver
Sensors:
Sensors will allow the robot to explore and understand the environment it is in. There are many
different types of sensors out there, and they can be used alone or in combinations with others.
The outputs of these sensors will feed into the microcontroller, as before stated, to complete
various parameters that may be needed in the program. The different categories of sensors that
are being considered are:

Contact: An example of a contact sensor would be Vex Bumper Switch. This costs
$12.99/unit. It requires 5.06 ounces to trigger.
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Literature Review
Figure 7: Vex Bumper Switch

Distance: An example of this would be an encoder such as the Cytron Incremental Rotary
Encoder. This costs $135.48/unit, requires an input of 5 V – 24 V and consumes
approximately 120mA. This sensor also fulfills the requirement for positioning.
Figure 8: Cytron Incremental Rotary Encoder

Positioning: An example of this would be an ultrasonic sensor such as the Maxbotix LVMaxSonar-WR1 Weather Resistant Ultrasonic Range Finder. This costs $99.95/unit,
detection ranges from 12” to 254” and has a 42KHz ultrasonic ping.
Figure 9: Ultrasonic Range Finder
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Global Positioning System
The GPS lawnmower has a lot of different types of GPS to choose from, but the main
choice of GPS chips are from the company Parallax. The GPS use satellites orbiting Earth to
receive a signal from the GPS chip and use it to pinpoint the location. It records the time the
signal was sent and received by the satellite and sends information to other satellites to get their
information. The more satellites being used, the more accurate the location will be. A minimum
of three satellites must be used to calculate the two dimensional location for most GPS. More
satellites must be used to be able to calculate the three dimensional location. The GPS chip in
order to be effective must have a Wide Area Augmented System (WAAS). Another important
part of the GPS chip is the NMEAD0183 which is the language the chip uses to produce the
coordinates.
Chip Name
RXM-SG GPS
Module
GPS Receiver
Module
PBM 648
SiRF
Number of Voltage
Satellites
20
5V
Accuracy
NMEAD0183 WAAS
Price
±20 yards
Version 1
Yes
$79.99
12
5V
±5 meters
Version 1
Yes
$79.99
20
3.3 – 5V
±5 meters
Version 2.2
Yes
$34.99
Table 6: GPS Chip Comparison
Languages
In order to properly integrate everything together and to get everything be automated,
there will have to be a program to make it move, run the GPS chip, collect inputs from sensors,
run the mower deck, and digitally map out the mowing area. Some possible programming
languages that might be used are C, C++, Java, and Basic.
Programming
Language
C
C++
Java
Basic
Developer
Microsoft
Microsoft
Sun
John George Kemeny and Thomas
Eugene Kurtz
Programming
Difficulty
5
2
2
5
Operating
System
Windows
Windows
Windows/Sun
Any
Table 72: Language Comparison
Lawnmower
The lawnmower is one of the most important components to the autonomous lawnmower
project. Not only does it provide a basic framework for the computer components and electric
motors to be placed on but it also provides parts that would normally not be available by
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Literature Review
themselves. Electric push lawnmowers are among the most commonly used mowers,
information about these mowers are found in table 8.
Types of Electric Push
Lawnmowers
Range
Operation Time
Lawn Size
Corded
Cordless
Fixed (150-250 ft.)
Unlimited
≈3000 square ft.
Unlimited
Battery Dependant
≈5000 square ft.
Table 83: Electric Push Lawnmower Comparison
Figure 10: Yardworks 18” 12A electric lawnmower
Motors
The motor, while part of the lawnmower, is crucial to power the blades under the mower
deck. Like the lawnmower there is a choice between two types of motors: internal combustion
and electric. The internal combustion engine is more common but electric motors are slowly
gaining popularity. The electric motors for lawnmowers are typically 12V brushless motors
weighing about 15-20 lbs. The benefits of the electric motors are that they run very quietly and
they do not take up too much space on the mower chassis. The one drawback to electric motors
is the power. Usually the more power needed out of the motor, the larger and heavier it gets.
However, to turn the blades on a mower the power requirement is not high. Using a brushless
motor also adds to the safety of the motor because it does not create sparks, like the brushed
motor does, and it can be precisely controlled.
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Figure 11: Marathon Electric Brake Motor
Wheels
The wheels and motors that have been acquired for the autonomous lawnmower are from
the company Sunrise Medical. These were given to Southern Illinois University Carbondale by
Adam Sims’ senior design team. Below is a table of the wheel specifications for the acquired
wheels.
Wheel type
Motor
Diameter
Width
Control box
Volts
RPM
Spindle
None
8 inches
2 inches
None
None
Unknown
Electric wheel
Fracmo,
brushed motor
12.5
inches
2.5
inches
VSI joystick
–
Discontinued
22.5 min. or
24 max.
114
Table 9: Wheel Specifications
There are two spindle, or free moving, wheels that are going to be used for the front of
the design. The spindle wheels will be attached to the front of the lawnmower frame by using a
three hundred and sixty degree spinning attachment that came attached to the wheels. A type of
suspension system might be used in the final design to compensate for the irregularities of the
ground.
Figure 12: Acquired Spindle Wheel
At the end of the project, the electric powered wheels will be the drive system for the
machine. The same process as a zero turn riding lawnmower will be applied to make the turning
radius of the machine as minimal as possible. They will be attached to the rear of the
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lawnmowers’ frame to get the full effect of the zero turn process. The zero turn lawnmower
spins the wheels in opposite directions to turn effectively left or right. These wheels will be
attached securely to the frame to insure that they do not come off in the process of turning or
moving. Due to the specifications in table 14, the autonomous lawnmower will need to have two
12 Volt batteries attached in series for a single motor to run.
Figure 13: Motorized Wheels
The motor should be wired to a control box that connects to a Voltage Source Inverter
joystick. The joystick is the steering mechanism that would allow the lawnmower to turn in a
circle or away from an obstacle. The VSI joystick that is needed is now no longer available to
the general public. Also, it cannot be tampered with or worked on due to magnetic sensitive
components. The VSI joystick was the only item that could not be found in the machine shop on
campus. Since the VSI joystick cannot be found or replaced in the foreseeable future, two
options are available: get a new set of electric motors and wheels, or splice the wires that would
go to a control box and try to manipulate the motors by changing the polarity of the batteries by
using a mechanical and electrical system coupled with a computer program.
Figure 14: Battery hookup (top)
Figure 15: Control Box hookup (bottom)
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Works Cited
Purdie, Tom. Interview. Rachel Parth. 5 October 2011.
Team 94 Saluki Engineering Company Lawnmower-Design Report : 2009. Trevor Parnell, Adam Sims,
Krishna Patel
CWRU Cutter C Technical Report: 2010. Case Western Reserve University, 10900 Euclid Avenue,
Cleveland, Ohio, 44106, USA
http://alternatives.rzero.com/lang.html
Java information. http://en.wikipedia.org/wiki/Java_(programming_language)
C. http://www.eskimo.com/~scs/cclass/notes/sx1.html
C++. http://www.cprogramming.com/begin.html
Visual Basic. http://en.wikipedia.org/wiki/Microsoft_Visual_Studio
GPS Receiver Module.
http://www.parallax.com/Portals/0/Downloads/docs/prod/acc/GPSManualV2.0.pdf
RXM-SG GPS Module w/Ext Antenna.
http://www.parallax.com/Portals/0/Downloads/docs/prod/acc/28505-RXM-SG-GPSModulev1.0.pdf
Northern Arizona wind and sun. http://www.windsun.com/Batteries/Battery_FAQ.htm
http://www.wind-sun.com/ForumVB/showthread.php?t=8228
Wheeled Robot picture: http://news.cnet.com/8301-17938_105-10378593-1.html
Tracked Robot picture: http://defenseupdate.com/features/2008/november/11208_minirobotugv_urbancombatindoor.html
“The AC’s and DC’s of Electric Motors”, A.O. Smith, Retrieved 2009/12/07
http://www.aosmithmotors.com/uploadedFiles/AC-DC%20manual.pdf
http://thelawnmower.info/history.php
“Push for more Efficient Mowers”, Published May 05, 2008.
http://www.metronews.ca/vancouver/live/article/48994