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

Remember Where Are We Going? Sumo-Bot competitions

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

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

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

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

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 5 ' trigger pulse = 10 uS ToCm CON 30 ' conversion factor to cm

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

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 5 ' take five samples PULSOUT Trigger, Trig10 ' 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

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

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

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

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

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

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

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

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

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

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

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