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 i2c
   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                 self.run()
  19
  20         def run(self):
  21                 rate = rospy.Rate(10.0)
  22                 while not rospy.is_shutdown():
  23                         #self.get_dist_forward()
  24                         #self.get_dist_backward()
  25                         #self.get_dist_left()
  26                         #self.get_dist_right()
  27                         rate.sleep()
  28
  29         def set_speed(self, left, right):
  30                 if left > 0: left+=80
  31                 elif left < 0: left-=80
  32                 if right > 0: right+=80
  33                 elif right < 0: right-=80
  34
  35                 if left > 255: left=255
  36                 elif left < -255: left=-255
  37                 if right > 255: right=255
  38                 elif right < -255: right=-255
  39
  40                 dev = i2c(0x56)
  41                 s = struct.pack(">Bhh", 0x1, left, right)
  42                 dev.write(s)
  43                 dev.close()
  44
  45         def cmdVelReceived(self, msg):
  46                 trans = msg.linear.x
  47                 rot = msg.angular.z # rad/s
  48
  49                 right = rot*pi*WHEEL_DIST + trans
  50                 left = trans*2-right
  51                 self.set_speed(left, right)
  52
  53         # http://rn-wissen.de/wiki/index.php/Sensorarten#Sharp_GP2D12
  54         def get_dist_ir(self, num):
  55                 dev = i2c(0x52)
  56                 s = struct.pack("B", num)
  57                 dev.write(s)
  58                 dev.close()
  59
  60                 sleep(2e-6)
  61
  62                 dev = i2c(0x52)
  63                 s = dev.read(2)
  64                 dev.close()
  65
  66                 val = struct.unpack(">H", s)[0]
  67                 return 15221/(val - -276.42)/100;
  68
  69         def get_dist_srf(self, num):
  70                 dev = i2c(0x52)
  71                 s = struct.pack("B", num)
  72                 dev.write(s)
  73                 dev.close()
  74
  75                 sleep(50e-3)
  76
  77                 dev = i2c(0x52)
  78                 s = dev.read(2)
  79                 dev.close()
  80
  81                 return struct.unpack(">H", s)[0]/1000.0
  82
  83         def get_dist_left(self):
  84                 dist = self.get_dist_ir(0x1)
  85
  86         def get_dist_right(self):
  87                  dist = self.get_dist_ir(0x3)
  88
  89         def get_dist_forward(self):
  90                 dist = self.get_dist_srf(0x5)
  91
  92         def get_dist_backward(self):
  93                 dist = self.get_dist_srf(0x7)
  94
  95
  96 if __name__ == "__main__":
  97         MoveBase()