Submitted To: Dr. Stefan Andrei · (VCR), cars use embedded systems. Lynxmotion Aluminum 4WD1 v2 Robot Kit by RobotShop Distribution Inc. The Lynxmotion Aluminum 4WD1 Robot Kit by

Submitted To:

Dr. Stefan Andrei

Lamar University

Department of Computer Science

08/12/2014

Group Members:

Garrett Bourque

Kanchandeep Kaur

Pooja Aryal

Pedro Velez

Pranay Reddy Peddireddy

Russell Alphin

Sagar Bonthu

Saya Reddy Bijjur

Shaomin Zhang

Shireesh Babu Doosa

Yingho Xu

Yu Wu

1

Abstract

This paper describes how we implemented and examined the development of an embedded

system, namely the A4WD1 v2 Rover. It is a robot manufactured by RobotShop Distribution Inc.

which acquired Lynxmotion, Inc. in 2012. RobotShop Distribution Inc. is a U.S. company

specialized in designing a great variety of programmable embedded systems, especially robots.

The main objective of the project is to implement an autonomous A4WD1 v2 Rover, from

assembling, programming and testing. During the testing, the rover moves forward, backward,

left or right. It also can avoid obstacles which are detected by the sensors. We divided our team

into four groups. Some students were responsible for the assembly of the rover, which was the

initial phase of our project. After the rover was assembled, the software was implemented to

enabled the robot to perform the desired operations. At the same time, some students designed

the project's website, others were involved in programming the rover's code, and the remaining

students wrote the final report. While working on this project, our team experienced certain

challenges during implementation phase that delayed testing of the rover's functionalities. But at

the end, we overcame those challenges by working together while gaining knowledge about how

to implement an embedded system.

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Acknowledgement:

We would like to express our deep gratitude and appreciation to our instructor, Dr. Stefan Andrei,

for his guidance and support throughout the project. The project would not have been successful

without his motivation, support, and expertise. We would like to express our deepest appreciation

to all who provided us the opportunity to complete this report. This project has helped us gain

knowledge about embedded systems, and it helped further develop our programming skills.

3

T a b l e Of Con t e n t

S.no TOPIC PAGE No.

1. Introduction.........................................................................5

2. Hardware Implementation...................................................7

2.1 Hardware Specification......................................................7

2.2 Assembly.............................................................................9

3. Source code............................................................................17

4. Conclusion and future works...............................................29

5. References............................................................................30

4

1. INTRODUCTION:

An embedded system is a system that has software (firmware) embedded into computer-

hardware. An embedded system can be a dedicated system or application, or it can be part of an

application or of a larger system. It has a dedicated function within a larger mechanical or

electrical system, often with real-time computing constraints. Some embedded systems use a real

time operating system which supervises the application software tasks running on the hardware

and organizes the accesses to system resources according to priorities and timing constraints of

tasks in the system. Many appliances likes watches, microwaves, Video Camera Recording

(VCR), cars use embedded systems.

Lynxmotion Aluminum 4WD1 v2 Robot Kit by RobotShop Distribution Inc.

The Lynxmotion Aluminum 4WD1 Robot Kit by RobotShop Distribution Inc. is a robust,

modifiable, and expandable chassis for remote control or autonomous robot experimentation.

The robot chassis is made from heavy-duty anodized aluminum structural brackets and ultra-

tough laser-cut Lexan panels. It includes four 12.0vdc 30:1 gear head motors and four 4.75inches

tires and wheels.

The robot has excellent traction by utilizing popular remote controlled (R/C) truck tires and

wheels. It uses two small NiMH battery packs and a Sabertooth 2x12.00 R/C motor controller.

There are additional decks available that can be added to expand it's functionality. The decks can

5

http://en.wikipedia.org/wiki/Real-time_computing

be stacked on top of each other, so we can add as many as the application require. The robot is

capable of carrying up to a 5lb payload. This version of the robot uses a Bot Board II, a Basic

Atom Pro and three GP2D12 distance sensors for obstacle detection and avoidance.

The robot is compatible with the following batteries and chargers.

Chargers & Accessories

6.0 - 12vdc Ni-CD & Ni-MH Universal Smart Charger (USC-02)

Batteries

12.0 Volt Ni-MH 1600mAh Battery Pack (BAT-01)




2. H ARDWARE IMPLEMENTATION

2.1SPECIFICATIONS:

The A4WD1 v2 Rover consists of following hardware.

a) A4WD1 v2 Rover Body Kit

The A4WD1 v2 Rover chassis is made from heavy-duty anodized aluminum structural brackets and ultra-tough laser-cut Lexan panels. The chassis of the robot is expandable. The body's rectangular shape allows us to mount the four servo motors on its four corners, the servo controller on the bottom, and Bot Board II on the top side of the Body Kit.

b) Bot Board II

The Bot Board II is the best carrier board for the Basic Atom, or any other 24 or 28 pinmicrocontrollers. It has an onboard speaker, three buttons and three LEDs, a Sony PS2controller port, a reset button, logic and servo power inputs, an I/O bus with power andground, and a 5vdc 250mA regulator. Up to 20 servos can be plugged in directly.

Figure: The Bot Board II Circuit Board

6

http://www.lynxmotion.com/p-426-60-volt-ni-mh-2800mah-battery-pack.aspx




http://www.lynxmotion.com/showproduct.aspx?ProductID=602&CategoryID=48

c) The BASIC Atom 28 Pin

The powerful Basic Atom is faster and has more memory than a BS2. This chip is easy to program and reliable to use. It can be plugged into the Bot Board for complete access to all of the I/O pins. It is BS2 Pin Compatible and includes O'Scope and In Circuit Debugger (ICD).

d) Sabertooth 2X12.00(SSC-32 Servo Controller)

The Sabertooth 2X12.00 has 32 channels of 1uS resolution servo control. The Sabertooth 2X12.00 supports bidirectional communication with Query commands, Synchronized or "Group"moves and 12 built in Servo Hexapod Gait Sequencer, MiniSSC-II emulation.

Figure: Sabertooth 2X12.00 Circuit Board

e) The DB9 Serial Data Cable - 6'

The DB9 Serial Data Cable is used to connect to a Bot Board II or SSC-32 servo controller with the computer in order to configure the A4WD1 v2 Rover.

f) Servo Motors

The motors are efficient and reliable. They have neutral time for robotics use. The electric motors need 12Vdc to operate and have a speed of 200 RPM (revolutions per minute). The motors also have a 30:1 gear reduction ratio.

g) Off Road Robot Tire

The A4WD1 v2 Rover tires are Traxxas Stampede Tera (Model Number: TRC-01). The tire's diameter is 4.75 inches and the width is 2.375 inches. The hubs accept any 6mm output shaft. The total weight of the tires is 0.75 oz.

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Figure: AW4D1 wheels and tires.

h) 12mm Hex Mounting Hub

In order to mount the four TRC-01 Off Road tires, we used the 12mm hex pattern RC truck hubs.The hubs are compatible with any electric motor that has a 6mm shaft. The hub's model number is HUB-12, and their weight is 0.07 oz each. i) 12.0 Volt Ni-MH 2800mAh Battery Pack

The rover uses a 2800mAh Ni-MH 12Vdc battery pack to reduce the total weight compared to a similar Ni-Cad battery pack. The installed battery pack is the BAT-06.

The specification of the A4WD1 Rover is as follows. Overall Length: 12.00" Overall Width: 13.50" Tire Height: 4.75" Chassis Length: 9.75" Chassis Width: 8.00" Chassis Height: 4.00" Ground Clearance: 1.63" Weight: 4lbs 6 oz. Speed: 36" per second.

2.2 ASSEMBLY

For the rover to function well, it is very important to implement the hardware properly. We followed various steps to assemble the hardware components. They are as follows:

Step 1:

Mounting the motor: In order to connect the motor, the red wire is connected to the positive battery terminal (+) and the yellow wire is connected to the negative terminal(-). We used two 3X6 mm screws to mount the motor to the chassis.

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Step 2:We connected the chassis end brackets using 3mm x 6mm screws.

Step 3: We used four of the 3mm x 6mm screws to attach the bottom lexan panel.

Step 4:We removed the tire-connection screws, and attach the tires as instructed. We verified that the tires treads were aligned properly.

Step 5: We installed the motor controller. We consulted the given instructions when connecting the wiresto the terminals.

Step 6 :

We connected the board and the chip in order to assemble the Botboard II and the SSC -32 processor. When installing the board to rover's chasis we use four .250” 4-40 screws. Once the Botboard II was attached to the chasis, we proceded to install the Atom Pro chip.

3. SOURCE CODE

The language used is BASIC, and the software package has compiler and a linker associated withit. We wrote the firmware using the provided IDE, and after the software being compiled, it wastransferred (loaded) to the rover using the same IDE. The IDE also allowed the team to verify thesensor's detection and range of detection.

Below are the two source codes used for the AW4D1 v2 Rover.

Source code 1: 4WD1AUTO.BAS

This code is used for setting up all the parameters for servos, setting up min, max speed,direction of movement when faced with obstacle, servo pulse out, and basic robot movementloops.

'Program name: 4WD1AUTO.BAS

'Connections

'Pin 16 Jumper to battery (VS)

'Pin 17 Left GP2D12 Sensor (Right facing sensor)

'Pin 18 Right GP2D12 Sensor (Left facing sensor)

'Pin 19 Rear GP2D12 Sensor

'Pin 0 Left Sabertooth channel.

9

'Pin 1 Right Sabertooth channel.

'Pin 12 A Button.

'Pin 13 B Button.

'Pin 14 C Button.

'Pin 9 Speaker.

temp var byte

filter var word(10)

ir_right var word

ir_left var word

ir_rear var word

LSpeed var word

RSpeed var word

minspeed con 1750

maxspeed con 1250

LSpeed = 1500

RSpeed = 1500

low p0

low p1

sound 9, [100\880, 100\988, 100\1046, 100\1175]

main

gosub sensor_check

; Numbers lower than 1500 result in forward direction.

; Numbers higher than 1500 result in reverse direction.

LSpeed = (LSpeed - 10) min maxspeed ;accelerates the motors

RSpeed = (RSpeed - 10) min maxspeed

;

; For testing should include sound when the sensors detect anything

; Need to take a look to see what happens if we change (LSpeed + ir_right)

10

; Added the if endif statements and the sound

if(ir_left > 15) then

sound 9, [100\880, 100\988, 100\1046, 100\1175]

LSpeed = (LSpeed + ir_left) max minspeed ; when something is detected, this decelerates the opposite side

endif

;


; Need to take a look to see what happens if we change (RSpeed + ir_left)

if(ir_right > 15) then

sound 9, [100\880, 100\988, 100\1046, 100\1175]

RSpeed = (RSpeed + ir_right) max minspeed

endif

; if both front sensors are detected

if(ir_left > 15) then

if(ir_right > 15 ) then

sound 9, [100\880, 100\988, 100\1046, 100\1175]

LSpeed = (LSpeed + ir_left) min maxspeed

RSpeed = (Rspeed + ir_right) min maxspeed

endif

endif

;

;


if (ir_rear > 15) then

; included what I believe is sound

sound 9, [100\880, 100\988, 100\1046, 100\1175]

LSpeed = (LSpeed - ir_rear) min maxspeed ;if something is detected behind the robot, accelerates both sides

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RSpeed = (RSpeed - ir_rear) min maxspeed

endif

; Send out the servo pulses

pulsout 0,(LSpeed*2) ; Left Sabertooth channel.

pulsout 1,(RSpeed*2) ; Right Sabertooth channel.

pause 20

goto main

sensor_check

for temp = 0 to 9

adin 17, filter(temp)

next

ir_right = 0

for temp = 0 to 9

ir_right = ir_right + filter(temp)

next

ir_right = ir_right / 85

for temp = 0 to 9


next

ir_left = 0

for temp = 0 to 9

ir_left = ir_left + filter(temp)

next

ir_left = ir_left / 85

for temp = 0 to 9


next

ir_rear = 0

12

for temp = 0 to 9

ir_rear = ir_rear + filter(temp)

next

ir_rear = ir_rear / 85

serout s_out,i38400,["ir_right - ", dec ir_right, " ir_left - ", dec ir_left, " ir_rear - ", dec ir_rear, "LSpeed - ", dec LSpeed, " RSpeed - ", dec RSpeed, 13]

return

Source code 2: 2_ZigZag.BAS

This code is used for testing the ZigZag movement of robot and the ability to avoid the obstacle.

'Pins: (pin spec is coming from samples)

'Pin 16 Jumper to battery (VS)

'Pin 17 Left GP2D12 Sensor (Right facing sensor)

'Pin 18 Right GP2D12 Sensor (Left facing sensor)

'Pin 19 Rear GP2D12 Sensor

'Pin 0 Left Sabertooth channel.

'Pin 1 Right Sabertooth channel.

'Pin 12 A Button.

'Pin 13 B Button.

'Pin 14 C Button.

'Pin 9 Speaker.

PIN0 con p0

PIN1 con p1

PIN9 con p9

PIN17 con p17

PIN18 con p18

PIN19 con p19

; hi, this is an array.

13

TIMES con 10

ii var word

array var word(TIMES)

; this value is determined by field test and debug prints

; rather than reading the data sheet. so, it might be not

; very accurately correct but it should work well.

THRESHOLD_SENSDIST con 180

sensor_left var word

sensor_right var word

sensor_rear var word

; the speed thresholds are from sample code, and i cannot

; guarantee its correctness. let's see the test results.

;SPEED_MIN con 1250; 1750 ' min speed

SPEED_MAX con 1750; 1250 ' max speed

SPEED_FORWARD con 1550 ;[1500, 1250]

SPEED_FORWDACC con 1700 ;[1500, 1250]

SPEED_BACKWARD con 200 ;[1750, 1500]

SPEED_TURNMAX con 1200;1600 ;1450

SPEED_TURNMIN con 700;1250 ;==ZERO speed.

speed_left var word

speed_right var word

; timer used during turning.

CYCLE con 100 ; supposed to be unit as mili-sec

TIMER_TURN con 10 ; if yes, that is 1 sec

timer var word

14

; a very simple state machine

STATE_INIT con 0

STATE_FORWARD con 1

STATE_TURNLEFT con 2

STATE_TURNRIGHT con 3

STATE_BACKWARD con 4

STATE_FORWDACC con 5

state var word

; here the program executes

; first, init of course

low PIN0

low PIN1

sound PIN9, [100\880, 100\988, 100\1046, 100\1175]

; and now, start the state machine

state = STATE_INIT;

; main() of this program, based on the state machine

main ;()

if (state = STATE_INIT) then

; just go straight forward

state = STATE_FORWARD;

endif

; check the sensors

gosub sensor_check

15

if (state <> STATE_BACKWARD) then

if ((sensor_left > THRESHOLD_SENSDIST) AND (sensor_right > THRESHOLD_SENSDIST)) then

; there is an obstacle infront of me

; so, try to back up.

state = STATE_BACKWARD;

timer = 0;

endif

endif

if (state = STATE_FORWARD) then

; now do something according to the sensors

if (sensor_rear > THRESHOLD_SENSDIST) then

state = STATE_FORWDACC;

timer = 0;

else

if (sensor_left > THRESHOLD_SENSDIST) then

; there is an obstacle at my left hand

state = STATE_TURNRIGHT;

timer = 0;

else

if (sensor_right > THRESHOLD_SENSDIST) then

; there is an obstacle my right hand

state = STATE_TURNLEFT;

timer = 0;

else

; nothing happens, so keep going forward.

speed_left = SPEED_FORWARD;

speed_right = SPEED_FORWARD;

16

endif

endif

endif

endif

if (state = STATE_TURNLEFT) then

speed_left = SPEED_TURNMIN;

speed_right = SPEED_TURNMAX;

if (timer > TIMER_TURN) then

; turning finished, now go forward


timer = 0;

serout s_out,i38400, [" --LEFT TURN END, FORWARD...-- ", 13];

else

timer = timer + 1;

serout s_out,i38400, [" -<-LEFT-<- ", 13];

endif

endif

if (state = STATE_TURNRIGHT) then

speed_left = SPEED_TURNMAX;

speed_right = SPEED_TURNMIN;


; turning finished, now go forward


timer = 0;

serout s_out,i38400, [" --RIGHT TURN END, FORWARD...-- ", 13];

else

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timer = timer + 1;

serout s_out,i38400, [" ->-RIGHT->- ", 13];

endif

endif

if (state = STATE_BACKWARD) then

speed_left = SPEED_BACKWARD;

speed_right = SPEED_BACKWARD;


; backing finished, now go, er, left

state = STATE_TURNLEFT;

timer = 0;

serout s_out,i38400, [" --BACKING END, ER, TURN-LEFT...-- ", 13];

else

timer = timer + 1;

serout s_out,i38400, [" -.-BACKING-.- ", 13];

endif

endif

if (state = STATE_FORWDACC) then

speed_left = SPEED_FORWDACC;

speed_right = SPEED_FORWDACC;


; backing finished, now go, er, left


timer = 0;

serout s_out,i38400, [" --ACCELARATING END, FORWARD...-- ", 13];

else

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timer = timer + 1;

serout s_out,i38400, [" -+-ACCELARATING-+- ", 13];

endif

endif

; in case the speeds are out of limits.

;speed_left = speed_left min SPEED_MIN;

speed_left = speed_left max SPEED_MAX;

;speed_right = speed_right min SPEED_MIN;

speed_right = speed_right max SPEED_MAX;


serout s_out,i38400, [" B-<-<-<- sl=", dec speed_left, " sr=", dec speed_right, 13];

endif


serout s_out,i38400, [" B->->->- sl=", dec speed_left, " sr=", dec speed_right, 13];

endif


serout s_out,i38400, [" B-.-.-.- sl=", dec speed_left, " sr=", dec speed_right, 13];

endif

; finally, send out the servo pulses

pulsout PIN0,(speed_left *2);

pulsout PIN1,(speed_right*2);

; wait, why multiply by 2 ???

; i donnot know, see what happens..


19

serout s_out,i38400, [" E-<-<-<- "];

endif


serout s_out,i38400, [" E->->->- "];

endif


serout s_out,i38400, [" E-.-.-.- "];

endif

pause CYCLE;

goto main

; a subroutine, to read the sensors.

sensor_check ;()

for ii = 0 to (TIMES - 1)

adin PIN18, array(ii);

next

sensor_left = 0;


sensor_left = sensor_left + array(ii);

next

sensor_left = sensor_left / TIMES;



next

sensor_right = 0;


sensor_right = sensor_right + array(ii);

next

20

sensor_right = sensor_right / TIMES;



next

sensor_rear = 0;


sensor_rear = sensor_rear + array(ii);

next

sensor_rear = sensor_rear / TIMES;

4. CONCLUSION

In this project, our team went through the whole process of implementing an autonomousA4WD1 v2 Rover, starting with the assembly, and finishing with the programming and testing ofthe rover. During operation, the rover moves forward, backward, left, and/or right. It is alsocapable of avoiding obstacles detected by the sensors.

During the implementation of the A4WD1 v2 Rover, the team faced with some obstacles thatprevented them from adding all the desired functionality. The first and major obstacle found wasthe incompatibility of the charger with the 12Vdc battery pack. This cause delays in testing sincewe did not have a charged battery to verify the firmware's accuracy. Another limitation found bythe team was that the A4WD1 v2 Rover's sensors are unable to detect some obstacles along it'spath.

Aside from the fairly small obstacles faced by the team, the A4WD1 v2 Rover allowed us to gainexperience implementing an embedded system and gave the students team work experiences thatcan be applied in conjunction with the knowledge gain in the project.

5. REFERENCES

1. Dr. Stefan Andrei: Lectures notes for ‘Embedded Systems’ Class (COSC-430101/COSC-5340-01), Summer of 2014: Embedded Systems. Lamar University, Department of Computer Science, Beaumont, Texas

2. http://en.wikipedia.org/wiki/Rover_%28space_exploration%29

3. http://www.lynxmotion.com/driver.aspx?Topic=assem05

4. http://galaxy.lamar.edu/~sandrei/Johnny5/

5. http://www.superdroidrobots.com/ATR_std2.aspx

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http://www.superdroidrobots.com/ATR_std2.aspx

Documents

Submitted To: Dr. Stefan Andrei · (VCR), cars use embedded systems. Lynxmotion Aluminum 4WD1 v2 Robot Kit by RobotShop Distribution Inc. The Lynxmotion Aluminum 4WD1 Robot Kit by