scripts/robo_explorer.py

   1 #!/usr/bin/env python
   2 import roslib; roslib.load_manifest('roboint')
   3 import rospy
   4 import tf
   5 import tf.broadcaster
   6 import tf.transformations
   7 from math import sin, cos, pi
   8 from geometry_msgs.msg import Twist, TransformStamped, Point32
   9 from sensor_msgs.msg import LaserScan
  10 from nav_msgs.msg import Odometry
  11 from roboint.msg import Motor
  12 from roboint.msg import Inputs
  13
  14
  15 class RoboExplorer:
  16         def __init__(self):
  17                 rospy.init_node('robo_explorer')
  18
  19                 self.wheel_dist = 0.188 # 18.8cm
  20                 self.wheel_size = 0.051*0.5 # 5.1cm; gear ration=0.5
  21                 self.speed = (0, 0)
  22                 self.x = 0
  23                 self.y = 0
  24                 self.alpha = 0
  25                 self.last_in = None
  26                 self.tf_broadcaster = tf.broadcaster.TransformBroadcaster()
  27                 self.last_time = rospy.Time.now()
  28                 self.x_last = 0
  29                 self.y_last = 0
  30                 self.alpha_last = 0
  31
  32                 self.pub_motor = rospy.Publisher("ft/set_motor", Motor)
  33                 self.pub_scan = rospy.Publisher("scan", LaserScan)
  34                 self.pub_odom = rospy.Publisher("odom", Odometry)
  35
  36                 rospy.Subscriber("cmd_vel", Twist, self.cmdVelReceived)
  37                 rospy.Subscriber("ft/get_inputs", Inputs, self.inputsReceived)
  38
  39                 rospy.spin()
  40
  41         def inputsReceived(self, msg):
  42                 current_time = rospy.Time.now()
  43
  44                 self.update_odometry(msg, current_time)
  45                 if (current_time - self.last_time).to_nsec() > 100e6: # send every 100ms
  46                         self.send_odometry(msg, current_time)
  47                         self.send_laser_scan(msg, current_time)
  48                         self.last_time = current_time
  49
  50         def update_odometry(self, msg, current_time):
  51                 in_now = msg.input[:2]
  52                 if self.last_in is not None:
  53                         in_diff = [abs(a - b) for a, b in zip(in_now, self.last_in)] # get changed inputs
  54                         # fix in_diff from actual motor direction
  55                         if self.speed[0] < 0:
  56                                 in_diff[0] = -in_diff[0]
  57                         elif self.speed[0] == 0:
  58                                 in_diff[0] = 0
  59                         if self.speed[1] < 0:
  60                                 in_diff[1] = -in_diff[1]
  61                         elif self.speed[1] == 0:
  62                                 in_diff[1] = 0
  63
  64                         dist_dir = (in_diff[1] - in_diff[0])*self.wheel_size*pi/8 # steps_changed in different direction => m
  65                         delta_alpha = dist_dir/self.wheel_dist
  66
  67                         dist = (in_diff[0] + in_diff[1])/2.0*self.wheel_size*pi/8 # steps_changed same direction => m
  68
  69                         delta_x = cos(self.alpha + delta_alpha/2)*dist
  70                         delta_y = sin(self.alpha + delta_alpha/2)*dist
  71
  72                         self.alpha += delta_alpha
  73                         if self.alpha > 2*pi:
  74                                 self.alpha -= 2*pi
  75                         elif self.alpha < -2*pi:
  76                                 self.alpha += 2*pi
  77                         self.x += delta_x
  78                         self.y += delta_y
  79
  80                 self.last_in = in_now
  81
  82         def send_odometry(self, msg, current_time):
  83                 # speeds
  84                 dt = (current_time - self.last_time).to_sec()
  85                 vx = (self.x - self.x_last) / dt
  86                 vy = (self.y - self.y_last) / dt
  87                 valpha = (self.alpha - self.alpha_last) / dt
  88                 self.x_last = self.x
  89                 self.y_last = self.y
  90                 self.alpha_last = self.alpha
  91
  92                 # since all odometry is 6DOF we'll need a quaternion created from yaw
  93                 odom_quat = tf.transformations.quaternion_from_euler(0, 0, self.alpha)
  94
  95                 # first, we'll publish the transform over tf
  96                 self.tf_broadcaster.sendTransform((self.x, self.y, 0.0), odom_quat, current_time, "base_link", "odom")
  97
  98                 # next, we'll publish the odometry message over ROS
  99                 odom = Odometry()
 100                 odom.header.stamp = current_time
 101                 odom.header.frame_id = "/odom"
 102
 103                 # set the position
 104                 odom.pose.pose.position.x = self.x
 105                 odom.pose.pose.position.y = self.y
 106                 odom.pose.pose.position.z = 0.0
 107                 odom.pose.pose.orientation.x = odom_quat[0]
 108                 odom.pose.pose.orientation.y = odom_quat[1]
 109                 odom.pose.pose.orientation.z = odom_quat[2]
 110                 odom.pose.pose.orientation.w = odom_quat[3]
 111
 112                 # set the velocity
 113                 odom.child_frame_id = "base_link"
 114                 odom.twist.twist.linear.x = vx
 115                 odom.twist.twist.linear.y = vy
 116                 odom.twist.twist.angular.z = valpha
 117
 118                 # publish the message
 119                 self.pub_odom.publish(odom)
 120
 121         def send_laser_scan(self, msg, current_time):
 122                 # first, we'll publish the transform over tf
 123                 self.tf_broadcaster.sendTransform((0.06, 0.0, 0.0), (0.0, 0.0, 0.0, 1.0), current_time, "scan", "base_link")
 124
 125                 # actually ultra sonic range finder
 126                 num_points = 60 # The base planner needs at least 30 points to work in the default config
 127                 opening_angle = 30*pi/180 # each side
 128                 scan = LaserScan()
 129                 scan.header.stamp = current_time
 130                 scan.header.frame_id = "/scan"
 131                 scan.angle_min = -opening_angle
 132                 scan.angle_max = opening_angle
 133                 scan.angle_increment = (2*opening_angle)/num_points
 134                 scan.time_increment = 0.001/num_points
 135                 scan.range_min = 0.0
 136                 scan.range_max = 4.0
 137                 for i in range(num_points):
 138                         scan.ranges.append(msg.d1/100.0)
 139                 #scan.intensities.append(0.5)
 140                 #scan.intensities.append(1.0)
 141                 #scan.intensities.append(0.5)
 142                 self.pub_scan.publish(scan)
 143
 144         # test with rostopic pub -1 cmd_vel geometry_msgs/Twist '[0, 0, 0]' '[0, 0, 0]'
 145         def cmdVelReceived(self, msg):
 146                 trans = msg.linear.x
 147                 rot = msg.angular.z # rad/s
 148
 149                 # handle rotation as offset to speeds
 150                 speed_offset = (rot * self.wheel_dist)/2.0 # m/s
 151
 152                 # handle translation
 153                 speed_l = 0
 154                 wish_speed_left = trans - speed_offset
 155                 if abs(wish_speed_left) > 1.7/64.3:
 156                         speed_l = 64.3*abs(wish_speed_left) - 1.7
 157                         if wish_speed_left < 0:
 158                                 speed_l*=-1
 159                 speed_r = 0
 160                 wish_speed_right = trans + speed_offset
 161                 if abs(wish_speed_right) > 1.7/64.3:
 162                         speed_r = 64.3*abs(wish_speed_right) - 1.7
 163                         if wish_speed_right < 0:
 164                                 speed_r*=-1
 165
 166                 # check limits
 167                 if speed_l < -7: speed_l = -7
 168                 elif speed_l > 7: speed_l = 7
 169                 if speed_r < -7: speed_r = -7
 170                 elif speed_r > 7: speed_r = 7
 171
 172                 #print "Speed wanted: %.2f %.2f, set: %d %d" % (trans, rot*180/pi, round(speed_l), round(speed_r))
 173
 174                 outmsg = Motor()
 175                 outmsg.num = 1
 176                 outmsg.speed = round(speed_l)
 177                 self.pub_motor.publish(outmsg)
 178
 179                 outmsg = Motor()
 180                 outmsg.num = 2
 181                 outmsg.speed = round(speed_r)
 182                 self.pub_motor.publish(outmsg)
 183
 184                 self.speed = (speed_l, speed_r)
 185
 186 if __name__ == '__main__':
 187         RoboExplorer()