scripts/robo_explorer.py

   1 #!/usr/bin/env python
   2 import roslib; roslib.load_manifest('roboint')
   3 import rospy
   4 import tf
   5 from math import sin, cos, pi
   6 from geometry_msgs.msg import Twist, TransformStamped, Point32
   7 from sensor_msgs.msg import PointCloud
   8 from nav_msgs.msg import Odometry
   9 from roboint.msg import Motor
  10 from roboint.msg import Inputs
  11
  12
  13 class RoboExplorer:
  14         def __init__(self):
  15                 rospy.init_node('robo_explorer')
  16
  17                 rospy.Subscriber("cmd_vel", Twist, self.cmdVelReceived)
  18                 rospy.Subscriber("ft/get_inputs", Inputs, self.inputsReceived)
  19
  20                 self.pub_motor = rospy.Publisher("ft/set_motor", Motor)
  21                 self.pub_cloud = rospy.Publisher("point_cloud", PointCloud)
  22                 self.pub_odom = rospy.Publisher("odom", Odometry)
  23
  24                 self.wheel_dist = 0.188 # 18.8cm
  25                 self.wheel_size = 0.052*0.5 # 5.1cm gear ration=0.5
  26                 self.speed = (0, 0)
  27                 self.x = 0
  28                 self.y = 0
  29                 self.alpha = 0
  30                 self.last_in = [0, 0]
  31                 self.odom_broadcaster = tf.TransformBroadcaster()
  32                 self.last_time = rospy.Time.now()
  33
  34                 rospy.spin()
  35
  36         def inputsReceived(self, msg):
  37                 current_time = rospy.Time.now()
  38
  39                 dt = (current_time - self.last_time).to_sec();
  40                 in_now = msg.input[1:3]
  41                 in_diff = [abs(a - b) for a, b in zip(in_now, self.last_in)] # get changed inputs
  42                 if self.speed[0] < 0:
  43                         in_diff[0] = -in_diff[0]
  44                 if self.speed[1] < 0:
  45                         in_diff[1] = -in_diff[1]
  46
  47                 dist_dir = (in_diff[1] - in_diff[0])*self.wheel_size*pi/8
  48                 delta_alpha = dist_dir/self.wheel_dist
  49
  50                 dist = (in_diff[0] + in_diff[1])/2.0*self.wheel_size*pi/8
  51
  52                 delta_x = cos(self.alpha + delta_alpha/2)*dist
  53                 delta_y = sin(self.alpha + delta_alpha/2)*dist
  54
  55                 self.alpha += delta_alpha
  56                 if self.alpha > 2*pi:
  57                         self.alpha -= 2*pi
  58                 elif self.alpha < -2*pi:
  59                         self.alpha += 2*pi
  60                 self.x += delta_x
  61                 self.y += delta_y
  62
  63                 # speeds
  64                 vx = delta_x / dt
  65                 vy = delta_y / dt
  66                 valpha = delta_alpha / dt
  67
  68                 # since all odometry is 6DOF we'll need a quaternion created from yaw
  69                 odom_quat = tf.transformations.quaternion_from_euler(0, 0, self.alpha)
  70
  71                 # first, we'll publish the transform over tf
  72                 self.odom_broadcaster.sendTransform((0.0, 0.0, 0.0), odom_quat, current_time, "odom", "base_link");
  73
  74                 # next, we'll publish the odometry message over ROS
  75                 odom = Odometry()
  76                 odom.header.stamp = current_time
  77                 odom.header.frame_id = "odom"
  78
  79                 # set the position
  80                 odom.pose.pose.position.x = self.x
  81                 odom.pose.pose.position.y = self.y
  82                 odom.pose.pose.position.z = 0.0
  83                 odom.pose.pose.orientation = odom_quat
  84
  85                 # set the velocity
  86                 odom.child_frame_id = "base_link";
  87                 odom.twist.twist.linear.x = vx
  88                 odom.twist.twist.linear.y = vy
  89                 odom.twist.twist.angular.z = valpha
  90
  91                 # publish the message
  92                 self.pub_odom.publish(odom)
  93
  94                 # sent PointCloud
  95                 cloud = PointCloud()
  96                 cloud.header.stamp = current_time
  97                 cloud.header.frame_id = "sensor_frame"
  98                 cloud.points.append(Point32(msg.d1/10.0, 0, 0))
  99                 self.pub_cloud.publish(cloud)
 100
 101                 self.last_time = current_time
 102                 self.last_in = in_now
 103
 104
 105         def cmdVelReceived(self, msg):
 106                 trans = msg.linear.x
 107                 rot = msg.angular.z
 108
 109                 # speed steps = 7
 110                 # max trans = 0.1m/s
 111                 # max rot = 0.29rad/s
 112
 113                 speed_l = int(trans*7/0.1 - rot*7/0.29)
 114                 speed_r = int(trans*7/0.1 + rot*7/0.29)
 115                 if speed_l < -7: speed_l = -7
 116                 elif speed_l > 7: speed_l = 7
 117                 if speed_r < -7: speed_r = -7
 118                 elif speed_r > 7: speed_r = 7
 119
 120                 outmsg = Motor()
 121                 outmsg.num = 1
 122                 outmsg.speed = speed_l
 123                 self.pub_motor.publish(outmsg)
 124
 125                 outmsg = Motor()
 126                 outmsg.num = 2
 127                 outmsg.speed = speed_r
 128                 self.pub_motor.publish(outmsg)
 129
 130                 self.speed = (speed_l, speed_r)
 131
 132 if __name__ == '__main__':
 133         RoboExplorer()