scripts/move_base.py

   1 #!/usr/bin/env python
   2 # -*- coding: iso-8859-15 -*-
   3
   4 import rospy
   5 import struct
   6 from i2c import *
   7 from math import *
   8 from geometry_msgs.msg import Twist
   9
  10 WHEEL_DIST = 0.248
  11
  12 class MoveBase:
  13         def __init__(self):
  14                 rospy.init_node('wild_thumper_move_base')
  15                 rospy.Subscriber("cmd_vel", Twist, self.cmdVelReceived)
  16                 self.set_speed(0, 0)
  17                 rospy.loginfo("Init done")
  18                 i2c_write_reg(0x50, 0x90, struct.pack("BB", 1, 1)) # switch direction
  19                 self.run()
  20
  21         def run(self):
  22                 rate = rospy.Rate(10.0)
  23                 while not rospy.is_shutdown():
  24                         #self.get_dist_forward()
  25                         #self.get_dist_backward()
  26                         #self.get_dist_left()
  27                         #self.get_dist_right()
  28                         rate.sleep()
  29
  30         def set_speed(self, left, right):
  31                 if left > 0: left+=80
  32                 elif left < 0: left-=80
  33                 if right > 0: right+=80
  34                 elif right < 0: right-=80
  35
  36                 if left > 255: left=255
  37                 elif left < -255: left=-255
  38                 if right > 255: right=255
  39                 elif right < -255: right=-255
  40
  41                 dev = i2c(0x50)
  42                 s = struct.pack(">Bhhhh", 0x1, right, right, left, left)
  43                 dev.write(s)
  44                 dev.close()
  45
  46         def cmdVelReceived(self, msg):
  47                 trans = msg.linear.x
  48                 rot = msg.angular.z # rad/s
  49
  50                 right = rot*pi*WHEEL_DIST + trans
  51                 left = trans*2-right
  52                 self.set_speed(left, right)
  53
  54         # http://rn-wissen.de/wiki/index.php/Sensorarten#Sharp_GP2D12
  55         def get_dist_ir(self, num):
  56                 dev = i2c(0x52)
  57                 s = struct.pack("B", num)
  58                 dev.write(s)
  59                 dev.close()
  60
  61                 sleep(2e-6)
  62
  63                 dev = i2c(0x52)
  64                 s = dev.read(2)
  65                 dev.close()
  66
  67                 val = struct.unpack(">H", s)[0]
  68                 return 15221/(val - -276.42)/100;
  69
  70         def get_dist_srf(self, num):
  71                 dev = i2c(0x52)
  72                 s = struct.pack("B", num)
  73                 dev.write(s)
  74                 dev.close()
  75
  76                 sleep(50e-3)
  77
  78                 dev = i2c(0x52)
  79                 s = dev.read(2)
  80                 dev.close()
  81
  82                 return struct.unpack(">H", s)[0]/1000.0
  83
  84         def get_dist_left(self):
  85                 dist = self.get_dist_ir(0x1)
  86
  87         def get_dist_right(self):
  88                  dist = self.get_dist_ir(0x3)
  89
  90         def get_dist_forward(self):
  91                 dist = self.get_dist_srf(0x5)
  92
  93         def get_dist_backward(self):
  94                 dist = self.get_dist_srf(0x7)
  95
  96
  97 if __name__ == "__main__":
  98         MoveBase()