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
  27                 self.pub_motor = rospy.Publisher("ft/set_motor", Motor)
  28                 self.pub_scan = rospy.Publisher("scan", LaserScan)
  29                 self.pub_odom = rospy.Publisher("odom", Odometry)
  30
  31                 rospy.Subscriber("cmd_vel", Twist, self.cmdVelReceived)
  32                 rospy.Subscriber("ft/get_inputs", Inputs, self.inputsReceived)
  33
  34                 rospy.spin()
  35
  36         def inputsReceived(self, msg):
  37                 current_time = rospy.Time.now()
  38
  39                 self.tf_broadcaster.sendTransform((0.0, 0.0, 0.0), (0.0, 0.0, 0.0, 1.0), current_time, "odom", "map");
  40                 self.send_odometry(msg, current_time)
  41                 self.send_laser_scan(msg, current_time)
  42
  43                 self.last_time = current_time
  44
  45         def send_odometry(self, msg, current_time):
  46                 dt = (current_time - self.last_time).to_sec();
  47                 in_now = msg.input[1:3]
  48                 if self.last_in is not None:
  49                         in_diff = [abs(a - b) for a, b in zip(in_now, self.last_in)] # get changed inputs
  50                         if self.speed[0] < 0:
  51                                 in_diff[0] = -in_diff[0]
  52                         if self.speed[1] < 0:
  53                                 in_diff[1] = -in_diff[1]
  54
  55                         dist_dir = (in_diff[1] - in_diff[0])*self.wheel_size*pi/8 # steps_changed in different direction => m
  56                         delta_alpha = dist_dir/self.wheel_dist
  57
  58                         dist = (in_diff[0] + in_diff[1])/2.0*self.wheel_size*pi/8 # steps_changed same direction => m
  59
  60                         delta_x = cos(self.alpha + delta_alpha/2)*dist
  61                         delta_y = sin(self.alpha + delta_alpha/2)*dist
  62
  63                         self.alpha += delta_alpha
  64                         if self.alpha > 2*pi:
  65                                 self.alpha -= 2*pi
  66                         elif self.alpha < -2*pi:
  67                                 self.alpha += 2*pi
  68                         self.x += delta_x
  69                         self.y += delta_y
  70
  71                         # speeds
  72                         vx = delta_x / dt
  73                         vy = delta_y / dt
  74                         valpha = delta_alpha / dt
  75
  76                         # since all odometry is 6DOF we'll need a quaternion created from yaw
  77                         odom_quat = tf.transformations.quaternion_from_euler(0, 0, self.alpha)
  78
  79                         # first, we'll publish the transform over tf
  80                         self.tf_broadcaster.sendTransform((self.x, self.y, 0.0), odom_quat, current_time, "base_link", "odom");
  81
  82                         # next, we'll publish the odometry message over ROS
  83                         odom = Odometry()
  84                         odom.header.stamp = current_time
  85                         odom.header.frame_id = "/odom"
  86
  87                         # set the position
  88                         odom.pose.pose.position.x = self.x
  89                         odom.pose.pose.position.y = self.y
  90                         odom.pose.pose.position.z = 0.0
  91                         odom.pose.pose.orientation.x = odom_quat[0]
  92                         odom.pose.pose.orientation.y = odom_quat[1]
  93                         odom.pose.pose.orientation.z = odom_quat[2]
  94                         odom.pose.pose.orientation.w = odom_quat[3]
  95
  96                         # set the velocity
  97                         odom.child_frame_id = "base_link";
  98                         odom.twist.twist.linear.x = vx
  99                         odom.twist.twist.linear.y = vy
 100                         odom.twist.twist.angular.z = valpha
 101
 102                         # publish the message
 103                         self.pub_odom.publish(odom)
 104                 self.last_in = in_now
 105
 106         def send_laser_scan(self, msg, current_time):
 107                 # first, we'll publish the transform over tf
 108                 self.tf_broadcaster.sendTransform((0.06, 0.0, 0.0), (0.0, 0.0, 0.0, 1.0), current_time, "scan", "base_link");
 109
 110                 # actually ultra sonic range finder
 111                 scan = LaserScan()
 112                 scan.header.stamp = current_time
 113                 scan.header.frame_id = "/scan"
 114                 scan.angle_min = -pi/4;
 115                 scan.angle_max = pi/4;
 116                 scan.angle_increment = pi/4;
 117                 scan.time_increment = 0.01;
 118                 scan.range_min = 0.0;
 119                 scan.range_max = 4.0;
 120                 for i in range(3):
 121                         scan.ranges.append(msg.d1/100.0)
 122                 scan.intensities.append(0.5)
 123                 scan.intensities.append(1.0)
 124                 scan.intensities.append(0.5)
 125                 self.pub_scan.publish(scan)
 126
 127         # test with rostopic pub -1 cmd_vel geometry_msgs/Twist '[0, 0, 0]' '[0, 0, 0]'
 128         def cmdVelReceived(self, msg):
 129                 trans = msg.linear.x
 130                 rot = msg.angular.z # rad/s
 131
 132                 # handle rotation as offset to speeds
 133                 speed_offset = (rot * self.wheel_dist)/2.0 # m/s
 134
 135                 # handle translation
 136                 speed_l = 0
 137                 wish_speed_left = trans - speed_offset
 138                 if abs(wish_speed_left) > 1.7/64.3:
 139                         speed_l = 64.3*abs(wish_speed_left) - 1.7
 140                         if wish_speed_left < 0:
 141                                 speed_l*=-1
 142                 speed_r = 0
 143                 wish_speed_right = trans + speed_offset
 144                 if abs(wish_speed_right) > 1.7/64.3:
 145                         speed_r = 64.3*abs(wish_speed_right) - 1.7
 146                         if wish_speed_right < 0:
 147                                 speed_r*=-1
 148
 149                 # check limits
 150                 if speed_l < -7: speed_l = -7
 151                 elif speed_l > 7: speed_l = 7
 152                 if speed_r < -7: speed_r = -7
 153                 elif speed_r > 7: speed_r = 7
 154
 155                 outmsg = Motor()
 156                 outmsg.num = 1
 157                 outmsg.speed = round(speed_l)
 158                 self.pub_motor.publish(outmsg)
 159
 160                 outmsg = Motor()
 161                 outmsg.num = 2
 162                 outmsg.speed = round(speed_r)
 163                 self.pub_motor.publish(outmsg)
 164
 165                 self.speed = (speed_l, speed_r)
 166
 167 if __name__ == '__main__':
 168         RoboExplorer()