scripts/move_base.py

   1 #!/usr/bin/env python
   2 # -*- coding: iso-8859-15 -*-
   3
   4 import rospy
   5 import tf
   6 import struct
   7 from i2c import *
   8 from math import *
   9 from geometry_msgs.msg import Twist
  10 from nav_msgs.msg import Odometry
  11
  12 WHEEL_DIST = 0.248
  13
  14 class MoveBase:
  15         def __init__(self):
  16                 rospy.init_node('wild_thumper_move_base')
  17                 rospy.Subscriber("cmd_vel", Twist, self.cmdVelReceived)
  18                 self.tf_broadcaster = tf.broadcaster.TransformBroadcaster()
  19                 self.pub_odom = rospy.Publisher("odom", Odometry, queue_size=16)
  20                 self.set_speed(0, 0)
  21                 rospy.loginfo("Init done")
  22                 i2c_write_reg(0x50, 0x90, struct.pack("BB", 1, 1)) # switch direction
  23                 self.run()
  24
  25         def run(self):
  26                 rate = rospy.Rate(20.0)
  27                 while not rospy.is_shutdown():
  28                         #self.get_odom()
  29                         #self.get_dist_forward()
  30                         #self.get_dist_backward()
  31                         #self.get_dist_left()
  32                         #self.get_dist_right()
  33                         rate.sleep()
  34
  35         def get_odom(self):
  36                 posx, posy, angle = struct.unpack(">fff", i2c_read_reg(0x50, 0x40, 12))
  37                 speed_trans, speed_rot = struct.unpack(">ff", i2c_read_reg(0x50, 0x38, 8))
  38                 current_time = rospy.Time.now()
  39
  40                 # since all odometry is 6DOF we'll need a quaternion created from yaw
  41                 odom_quat = tf.transformations.quaternion_from_euler(0, 0, angle)
  42
  43                 # first, we'll publish the transform over tf
  44                 self.tf_broadcaster.sendTransform((posx, posy, 0.0), odom_quat, current_time, "base_link", "odom")
  45
  46                 # next, we'll publish the odometry message over ROS
  47                 odom = Odometry()
  48                 odom.header.stamp = current_time
  49                 odom.header.frame_id = "/odom"
  50
  51                 # set the position
  52                 odom.pose.pose.position.x = posx
  53                 odom.pose.pose.position.y = posy
  54                 odom.pose.pose.position.z = 0.0
  55                 odom.pose.pose.orientation.x = odom_quat[0]
  56                 odom.pose.pose.orientation.y = odom_quat[1]
  57                 odom.pose.pose.orientation.z = odom_quat[2]
  58                 odom.pose.pose.orientation.w = odom_quat[3]
  59
  60                 # set the velocity
  61                 odom.child_frame_id = "base_link"
  62                 odom.twist.twist.linear.x = speed_trans
  63                 odom.twist.twist.linear.y = 0.0
  64                 odom.twist.twist.angular.z = speed_rot
  65
  66                 # publish the message
  67                 self.pub_odom.publish(odom)
  68
  69
  70         def set_speed(self, trans, rot):
  71                 i2c_write_reg(0x50, 0x50, struct.pack(">ff", trans, rot))
  72
  73         def cmdVelReceived(self, msg):
  74                 trans = msg.linear.x
  75                 rot = msg.angular.z # rad/s
  76                 self.set_speed(trans, rot)
  77
  78         # http://rn-wissen.de/wiki/index.php/Sensorarten#Sharp_GP2D12
  79         def get_dist_ir(self, num):
  80                 dev = i2c(0x52)
  81                 s = struct.pack("B", num)
  82                 dev.write(s)
  83                 dev.close()
  84
  85                 sleep(2e-6)
  86
  87                 dev = i2c(0x52)
  88                 s = dev.read(2)
  89                 dev.close()
  90
  91                 val = struct.unpack(">H", s)[0]
  92                 return 15221/(val - -276.42)/100;
  93
  94         def get_dist_srf(self, num):
  95                 dev = i2c(0x52)
  96                 s = struct.pack("B", num)
  97                 dev.write(s)
  98                 dev.close()
  99
 100                 sleep(50e-3)
 101
 102                 dev = i2c(0x52)
 103                 s = dev.read(2)
 104                 dev.close()
 105
 106                 return struct.unpack(">H", s)[0]/1000.0
 107
 108         def get_dist_left(self):
 109                 dist = self.get_dist_ir(0x1)
 110
 111         def get_dist_right(self):
 112                  dist = self.get_dist_ir(0x3)
 113
 114         def get_dist_forward(self):
 115                 dist = self.get_dist_srf(0x5)
 116
 117         def get_dist_backward(self):
 118                 dist = self.get_dist_srf(0x7)
 119
 120
 121 if __name__ == "__main__":
 122         MoveBase()