1. Some Material taken from RobotSubsumption.pdf
Control
Some Material taken from RobotSubsumption.pdf

2. Remember Where Are We Going?
Sumo-Bot competitions

3. Controlling Robot Movement Based on Photo-Resistor Readings
' -----[ Constants ]
LeftDark CON 108
RightDark CON 114
LeftWhite CON 20
RightWhite CON 22
' Average light sensor value
LeftThreshold CON LeftWhite + LeftDark / 2
RightThreshold CON RightWhite + RightDark / 2
' -----[ Variables ]
timeLeft VAR Word
timeRight VAR Word
' -----[ Main Routine ] DO
GOSUB Test_Photoresistors
GOSUB Navigate
LOOP

4. Code ' -----[ Subroutine - Test_Photoresistors ]--------------
HIGH 6 ' Left RC time measurement.
PAUSE 5
RCTIME 6, 1, timeLeft
HIGH 3 ' Right RC time measurement.
RCTIME 3, 1, timeRight
RETURN

5. Code ' -----[ Subroutine - Navigate to avoid light ]-------------
IF (timeLeft < LeftThreshold) AND (timeRight < RightThreshold) THEN
PULSOUT 13, ‘ go backwards
PULSOUT 12, 850
ELSEIF (timeLeft < LeftThreshold) THEN
PULSOUT 13, ‘ go right
PULSOUT 12, 600
ELSEIF (timeRight < RightThreshold) THEN
PULSOUT 13, ‘ go left
PULSOUT 12, 800
ELSE
PULSOUT 13, ‘ go forwards
PULSOUT 12, 650
ENDIF
PAUSE 20
RETURN

6. Finite State Machine (FSM) Representation
both high
left low
right low
both low
Read photo-
resistors
backup
turn right
turn left
go forward

7. Controlling Robot Movement Based on Proximity Measurement
' {$STAMP BS2}
' {$PBASIC 2.5}
' -----[ Pins ]
Trigger PIN 0
Echo PIN 1
' -----[ Variables ]
samples VAR Nib ' loop counter
pWidth VAR Word ' pulse width sonic sensor
rawDist VAR Word ' filtered distance
cm VAR Word
inches VAR Word
irDetectLeft VAR Bit
irDetectRight VAR Bit
pulseCount VAR Byte
' -----[ Constants ]
Trig10 CON ' trigger pulse = 10 uS
ToCm CON ' conversion factor to cm

8. Code ' -----[ Main Routine ]----------------------------------- DO
GOSUB Read_IR
GOSUB Read_Sonar
IF (sonarForward = 0) THEN
GOSUB Forward_Pulse
ELSEIF (irDetectLeft = 0) THEN
GOSUB Turn_Left
ELSEIF (irDetectRight = 0) THEN
GOSUB Turn_Right
ELSE
ENDIF
LOOP

9. Code ' -----[ Subroutines ]-------------------------------------
Read_IR:
FREQOUT 8, 1, 38500
irDetectLeft = IN9
FREQOUT 2, 1, 38500
irDetectRight = IN3
RETURN
Read_Sonar:
rawDist = 0
FOR samples = 1 TO ' take five samples
PULSOUT Trigger, Trig ' 10 uS trigger pulse
PULSIN Echo, 1, pWidth ' measure pulse
rawDist = rawDist + (pWidth / 5)
PAUSE 10
NEXT
IF ( ((rawDist / ToCm) */ $03EF) ) < 36 THEN
sonarForward = 0
ELSE sonarForward = 1 ENDIF

10. Code ' -----[ Subroutines ]--------------------------------------
Forward_Pulse:
PULSOUT 13, 850
PULSOUT 12, 650
RETURN
Turn_Left:
PULSOUT 13, 650

11. Code ' -----[ Subroutines ]--------------------------------------
Turn_Right:
PULSOUT 13, 850
PULSOUT 12, 850
RETURN
Back_Up:
PULSOUT 13, 650

12. Finite State Machine (FSM) Representation
Read IR
& Sonar
Go forward
turn left
turn right
go forward
Obj forward
Obj right
Obj left
No Obj

13. How to Put It Together? Read IR & sonar Go forward turn right
No Obj
Obj left
Obj right
Obj forward
Read IR
& sonar
Go forward
turn right
turn left
go forward
both high
left low
right low
both low
Read photo-
resistors
backup
turn right
turn left
go forward

14. Possible Problems Jerky or halting movement Chase object over boundary
Never detect opponent
More?

15. Possible Solution Subsumption Architecture
A programming process by which one behavior subsumes, or over-rides another based on an explicit priority that we have defined. First described by Dr. Rodney Brooks in "A robust layered control system for a mobile robot,” IEEE Journal of Robotics and Automation., RA-2, April, 14-23, 1986.
FSM with exit conditions

16. FSM Go forward Go backwards read IR & sonar and set nextState variable
Photoresistors
and set nextState
variable
check nextState
variable and
branch
turn
teft
turn
right

17. Alternative FSM read Photoresistors and set nextState variable backup
turn left
turn right
go forward
check nextState
variable and
branch
Read IR
Go forward
turn right
turn left
go forward

18. Program High-Level Outline
Declare pin assignments, constants and variables
Initialize thresholds
Wait the required start delay
Read boundary line sensors and move accordingly
If the boundary line is not detected, read proximity sensors and move accordingly
Repeat steps 4 and 5 until completion

19. Main Loop Do GOSUB Read_Line_Sensors
IF (lightLeft < leftThresh) AND (lightRight < rightThresh) THEN
GOSUB About_Face ' boundary ahead
ELSEIF (lightLeft < leftThresh) THEN
GOSUB Spin_Right ' boundary to left
ELSEIF (lightRight < rightThresh) THEN
GOSUB Spin_Left ' boundary to right
ELSE
PULSOUT LMotor, LFwdFast
PULSOUT RMotor, RFwdFast
GOSUB Search_For_Opponent
ENDIF
Loop

20. Possible Enhancements
Optimize the position of the sensors
Optimize your mechanical design for fighting
Consider using lego components including motors
Design against being pushed out of the ring
Optimize the code to maximize bot performance
Evaluate tradeoffs in movement choices and sensor reading
Optimize the programming constructs that you use to increase processing speed
BRANCH value, (Case_0, Case_1, Case_2)
LOOKUP Index, (Value0, Value1, ...ValueN), Variable
LOOKDOWN Target, {ComparisonOp} [Value0, Value1, ...ValueN], Variable