Sonars Theory of operation: The SRF-08 emits an ultrasonic pulse, then waits for an echo to return. Based on the time between the pulse generation and.

Bot Matrix Printer11/21/13

SonarsTheory of operation:

The SRF-08 emits an ultrasonic pulse, then waits for an echo to return.Based on the time between the pulse generation and echo return, the sensor calculates the distance from its rear face to the detected surface,and then reports the distance in centimeters over the i2c interface.

Behavior

Row1

Row0

Row2

Row3

Y target distanceX target distance

Sensor IntegrationThe platform houses an array of sonars. Two sonars are mounted along the right face of the platform, equidistantly ahead of and behind the drive wheels. Another sonar points ahead of the platform.

SRF08SRF08SRF08SRF08

SR

F08

SR

F08

Sensor IntegrationThe array of sonars allows the robot to determine its position in 2D space relative to

two perpendicular vertical surfaces, such as the corner of a room. Having sonars on two perpendicular faces of the platform allows the robot to determine its distance from the two surfaces, while positioning two of the sonars on the same face allows it to determine its relative rotation or parallelism.

SRF08SRF08SRF08SRF08

SR

F08

SR

F08

Distance 1 Distance 2

Distance 3

Sensor Integration

SRF08SRF08SRF08SRF08

Distance 1 = Distance 2

SRF08SRF08

SRF08SRF08

SR

F08

SR

F08

Distance 1 =/= Distance 2

Opposite = Distance2-Distance1

SR

F08 Xdist

Ydist = (Distance 1 + Distance 2)/2

import mathimport smbusimport timeimport servo5import servo8import srf08_1import srf08_2import srf08_3servo5.direction(heading = 'blah')row = 0time.sleep(30)while row < 12: ytarg = 20 + 5*row xtarg = 50 - 30*math.pow(-1, row) print "xtarg is" print xtarg xrng = srf08_3.srf() print "xrng is" print xrng while xrng >= xtarg : rng = srf08_1.srf() rng2 = srf08_2.srf() ydist = (rng+rng2)/2 yerr = (ydist-ytarg) opposite = rng-rng2 servo8.direction("forward", yerr, opposite) time.sleep(.05) xrng = srf08_3.srf() print "xrng" print xrng

servo8.direction("left", yerr, opposite) time.sleep(1.8) servo8.direction("straight", yerr, opposite) time.sleep(.45) servo8.direction("right", yerr, opposite) time.sleep(1.5) row = row+1 print "row" print row ytarg = 20 + 5*row xtarg = 50 - 30*math.pow(-1, row) print "xtarg is" print xtarg xrng = srf08_3.srf() print "xrng is" print xrng while xrng <= xtarg : rng = srf08_1.srf() rng2 = srf08_2.srf() ydist = (rng+rng2)/2 yerr = (ydist-ytarg) opposite = rng-rng2 servo8.direction("backward", yerr, opposite) time.sleep(.05) xrng = srf08_3.srf() print "xrng" print xrng servo8.direction("left", yerr, opposite) time.sleep(1.8) servo8.direction("straight", yerr, opposite) time.sleep(.45) servo8.direction("right", yerr, opposite) time.sleep(1.5) row = row+1 print "row" print rowservo8.direction("x", yerr, opposite)

Navigation Programming

def color( ydist, xdist ): import numpy import servodraw

a = [[1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ], [1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, ], [0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, ], [0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, ], [0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, ], [0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, ], [0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, ], [0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, ], [0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 0, ], [0, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 0, ], [1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, ], [1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, ]]

y = int(ydist) x = int(xdist)

print y print x b = a[y][x] servodraw.direction(b) return b

Print Programming

def direction( heading ):

import Adafruit_BBIO.PWM as PWM

servo_pin = "P8_19" duty_min = 3 duty_max = 14.5 duty_span = duty_max - duty_min

if heading == 'x':

PWM.cleanup()

return

elif heading == '1': angle = 180 elif heading == '0': angle = 0 else: angle = 90

angle_f = float(angle)

duty = ((angle_f / 180) * duty_span + duty_min)

PWM.set_duty_cycle(servo_pin, duty)

return