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 LaserScan
   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                 self.wheel_dist = 0.188 # 18.8cm
  18                 self.wheel_size = 0.052*0.5 # 5.2cm; gear ration=0.5
  19                 self.speed = (0, 0)
  20                 self.x = 0
  21                 self.y = 0
  22                 self.alpha = 0
  23                 self.last_in = None
  24                 self.tf_broadcaster = tf.TransformBroadcaster()
  25                 self.last_time = rospy.Time.now()
  26                 self.input_count = 0
  27                 self.x_last = 0
  28                 self.y_last = 0
  29                 self.alpha_last = 0
  30
  31                 self.pub_motor = rospy.Publisher("ft/set_motor", Motor)
  32                 self.pub_scan = rospy.Publisher("scan", LaserScan)
  33                 self.pub_odom = rospy.Publisher("odom", Odometry)
  34
  35                 rospy.Subscriber("cmd_vel", Twist, self.cmdVelReceived)
  36                 rospy.Subscriber("ft/get_inputs", Inputs, self.inputsReceived)
  37
  38                 rospy.spin()
  39
  40         def inputsReceived(self, msg):
  41                 current_time = rospy.Time.now()
  42                 self.input_count+=1
  43
  44                 self.update_odometry(msg, current_time)
  45                 if self.input_count >= 10:
  46                         self.input_count = 0
  47                         self.tf_broadcaster.sendTransform((0.0, 0.0, 0.0), (0.0, 0.0, 0.0, 1.0), current_time, "odom", "map");
  48                         self.send_odometry(msg, current_time)
  49                         self.send_laser_scan(msg, current_time)
  50
  51         def update_odometry(self, msg, current_time):
  52                 in_now = msg.input[1:3]
  53                 if self.last_in is not None:
  54                         in_diff = [abs(a - b) for a, b in zip(in_now, self.last_in)] # get changed inputs
  55                         # fix in_diff from actual motor direction
  56                         if self.speed[0] < 0:
  57                                 in_diff[0] = -in_diff[0]
  58                         elif self.speed[0] == 0:
  59                                 in_diff[0] = 0
  60                         if self.speed[1] < 0:
  61                                 in_diff[1] = -in_diff[1]
  62                         elif self.speed[1] == 0:
  63                                 in_diff[1] = 0
  64
  65                         dist_dir = (in_diff[1] - in_diff[0])*self.wheel_size*pi/8 # steps_changed in different direction => m
  66                         delta_alpha = dist_dir/self.wheel_dist
  67
  68                         dist = (in_diff[0] + in_diff[1])/2.0*self.wheel_size*pi/8 # steps_changed same direction => m
  69
  70                         delta_x = cos(self.alpha + delta_alpha/2)*dist
  71                         delta_y = sin(self.alpha + delta_alpha/2)*dist
  72
  73                         self.alpha += delta_alpha
  74                         if self.alpha > 2*pi:
  75                                 self.alpha -= 2*pi
  76                         elif self.alpha < -2*pi:
  77                                 self.alpha += 2*pi
  78                         self.x += delta_x
  79                         self.y += delta_y
  80
  81                 self.last_in = in_now
  82
  83         def send_odometry(self, msg, current_time):
  84                 # speeds
  85                 dt = (current_time - self.last_time).to_sec()
  86                 vx = (self.x - self.x_last) / dt
  87                 vy = (self.y - self.y_last) / dt
  88                 valpha = (self.alpha - self.alpha_last) / dt
  89                 self.last_time = current_time
  90                 self.x_last = self.x
  91                 self.y_last = self.y
  92                 self.alpha_last = self.alpha
  93
  94                 # since all odometry is 6DOF we'll need a quaternion created from yaw
  95                 odom_quat = tf.transformations.quaternion_from_euler(0, 0, self.alpha)
  96
  97                 # first, we'll publish the transform over tf
  98                 self.tf_broadcaster.sendTransform((self.x, self.y, 0.0), odom_quat, current_time, "base_link", "odom");
  99
 100                 # next, we'll publish the odometry message over ROS
 101                 odom = Odometry()
 102                 odom.header.stamp = current_time
 103                 odom.header.frame_id = "/odom"
 104
 105                 # set the position
 106                 odom.pose.pose.position.x = self.x
 107                 odom.pose.pose.position.y = self.y
 108                 odom.pose.pose.position.z = 0.0
 109                 odom.pose.pose.orientation.x = odom_quat[0]
 110                 odom.pose.pose.orientation.y = odom_quat[1]
 111                 odom.pose.pose.orientation.z = odom_quat[2]
 112                 odom.pose.pose.orientation.w = odom_quat[3]
 113
 114                 # set the velocity
 115                 odom.child_frame_id = "base_link";
 116                 odom.twist.twist.linear.x = vx
 117                 odom.twist.twist.linear.y = vy
 118                 odom.twist.twist.angular.z = valpha
 119
 120                 # publish the message
 121                 self.pub_odom.publish(odom)
 122
 123         def send_laser_scan(self, msg, current_time):
 124                 # first, we'll publish the transform over tf
 125                 self.tf_broadcaster.sendTransform((0.06, 0.0, 0.0), (0.0, 0.0, 0.0, 1.0), current_time, "scan", "base_link");
 126
 127                 # actually ultra sonic range finder
 128                 scan = LaserScan()
 129                 scan.header.stamp = current_time
 130                 scan.header.frame_id = "/scan"
 131                 scan.angle_min = -pi/4;
 132                 scan.angle_max = pi/4;
 133                 scan.angle_increment = pi/4;
 134                 scan.time_increment = 0.1;
 135                 scan.range_min = 0.0;
 136                 scan.range_max = 4.0;
 137                 for i in range(3):
 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                 outmsg = Motor()
 173                 outmsg.num = 1
 174                 outmsg.speed = round(speed_l)
 175                 self.pub_motor.publish(outmsg)
 176
 177                 outmsg = Motor()
 178                 outmsg.num = 2
 179                 outmsg.speed = round(speed_r)
 180                 self.pub_motor.publish(outmsg)
 181
 182                 self.speed = (speed_l, speed_r)
 183
 184 if __name__ == '__main__':
 185         RoboExplorer()