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 *
   6 from geometry_msgs.msg import Twist, TransformStamped, Point32, PoseWithCovarianceStamped
   7 from sensor_msgs.msg import Range
   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.x = 0
  18                 self.y = 0
  19                 self.alpha = 0
  20                 self.last_in = None
  21                 self.tf_broadcaster = tf.broadcaster.TransformBroadcaster()
  22                 self.last_time = rospy.Time.now()
  23                 self.x_last = 0
  24                 self.y_last = 0
  25                 self.alpha_last = 0
  26
  27                 # Distance between both wheels in meter (18.55cm)
  28                 self.wheel_dist = float(rospy.get_param('~wheel_dist', "0.1855"))
  29                 # Size of wheel Diameter in meter (5.15cm) * gear ratio (0.5) = 2.575cm
  30                 self.wheel_size = float(rospy.get_param('~wheel_size', "0.02575"))
  31                 # Speed to PWM equation gradiant (The m in pwm = speed*m+b)
  32                 self.speed_gradiant = float(rospy.get_param('~speed_gradiant', "64.3"))
  33                 # Speed to PWM equation constant (The b in pwm = speed*m+b)
  34                 self.speed_constant = float(rospy.get_param('~speed_constant', "-1.7"))
  35
  36                 self.pub_motor = rospy.Publisher("ft/set_motor", Motor, queue_size=16)
  37                 self.pub_sonar = rospy.Publisher("sonar", Range, queue_size=16)
  38                 self.pub_odom = rospy.Publisher("odom", Odometry, queue_size=16)
  39
  40                 rospy.Subscriber("cmd_vel", Twist, self.cmdVelReceived)
  41                 rospy.Subscriber("ft/get_inputs", Inputs, self.inputsReceived)
  42                 rospy.Subscriber("initialpose", PoseWithCovarianceStamped, self.posReceived)
  43
  44                 rospy.spin()
  45
  46         def posReceived(self, msg):
  47                 self.x = msg.pose.pose.position.x
  48                 self.y = msg.pose.pose.position.y
  49                 orientation = msg.pose.pose.orientation
  50                 angles = tf.transformations.euler_from_quaternion([orientation.x, orientation.y, orientation.z, orientation.w])
  51                 self.alpha = angles[2]
  52
  53         def inputsReceived(self, msg):
  54                 current_time = rospy.Time.now()
  55
  56                 self.update_odometry(msg, current_time)
  57                 if (current_time - self.last_time).to_nsec() > 100e6: # send every 100ms
  58                         self.send_odometry(msg, current_time)
  59                         self.send_range(msg, current_time)
  60                         self.last_time = current_time
  61
  62         def update_odometry(self, msg, current_time):
  63                 in_now = msg.input[:2]
  64                 if self.last_in is not None:
  65                         in_diff = [abs(a - b) for a, b in zip(in_now, self.last_in)] # get changed inputs
  66                         # fix in_diff from actual motor direction
  67                         if msg.output[1] > 0: # left reverse
  68                                 in_diff[0] = -in_diff[0]
  69                         elif msg.output[0] == 0 and msg.output[1] == 0: # left stop
  70                                 in_diff[0] = 0
  71                         if msg.output[3] > 0: # right reverse
  72                                 in_diff[1] = -in_diff[1]
  73                         elif msg.output[2] == 0 and msg.output[3] == 0: # right stop
  74                                 in_diff[1] = 0
  75
  76                         dist_dir = (in_diff[1] - in_diff[0]) * self.wheel_size*pi/8 # steps_changed in different direction => m
  77                         delta_alpha = dist_dir/self.wheel_dist
  78
  79                         dist = (in_diff[0] + in_diff[1])/2.0 * self.wheel_size*pi/8 # steps_changed same direction => m
  80
  81                         delta_x = cos(self.alpha + delta_alpha/2)*dist
  82                         delta_y = sin(self.alpha + delta_alpha/2)*dist
  83
  84                         self.alpha += delta_alpha
  85                         if self.alpha > 2*pi:
  86                                 self.alpha -= 2*pi
  87                         elif self.alpha < -2*pi:
  88                                 self.alpha += 2*pi
  89                         self.x += delta_x
  90                         self.y += delta_y
  91
  92                 self.last_in = in_now
  93
  94         def send_odometry(self, msg, current_time):
  95                 # speeds
  96                 dt = (current_time - self.last_time).to_sec()
  97                 vx = sqrt((self.x - self.x_last)**2 + (self.y - self.y_last)**2) / dt
  98                 if (msg.output[0]-msg.output[1] + msg.output[2]-msg.output[3]) < 0:
  99                         # moving backward
 100                         vx*=-1
 101                 valpha = (self.alpha - self.alpha_last) / dt
 102                 self.x_last = self.x
 103                 self.y_last = self.y
 104                 self.alpha_last = self.alpha
 105
 106                 # since all odometry is 6DOF we'll need a quaternion created from yaw
 107                 odom_quat = tf.transformations.quaternion_from_euler(0, 0, self.alpha)
 108
 109                 # first, we'll publish the transform over tf
 110                 self.tf_broadcaster.sendTransform((self.x, self.y, 0.0), odom_quat, current_time, "base_link", "odom")
 111
 112                 # next, we'll publish the odometry message over ROS
 113                 odom = Odometry()
 114                 odom.header.stamp = current_time
 115                 odom.header.frame_id = "/odom"
 116
 117                 # set the position
 118                 odom.pose.pose.position.x = self.x
 119                 odom.pose.pose.position.y = self.y
 120                 odom.pose.pose.position.z = 0.0
 121                 odom.pose.pose.orientation.x = odom_quat[0]
 122                 odom.pose.pose.orientation.y = odom_quat[1]
 123                 odom.pose.pose.orientation.z = odom_quat[2]
 124                 odom.pose.pose.orientation.w = odom_quat[3]
 125
 126                 # set the velocity
 127                 odom.child_frame_id = "base_link"
 128                 odom.twist.twist.linear.x = vx
 129                 odom.twist.twist.linear.y = 0.0
 130                 odom.twist.twist.angular.z = valpha
 131
 132                 # publish the message
 133                 self.pub_odom.publish(odom)
 134
 135         def send_range(self, msg, current_time):
 136                 # ultra sonic range finder
 137                 scan = Range()
 138                 scan.header.stamp = current_time
 139                 scan.header.frame_id = "forward_sensor"
 140                 scan.radiation_type = 0
 141                 scan.field_of_view = 60*pi/180
 142                 scan.min_range = 0.0
 143                 scan.max_range = 4.0
 144                 scan.range = msg.d1/100.0
 145                 self.pub_sonar.publish(scan)
 146
 147         # test with rostopic pub -1 cmd_vel geometry_msgs/Twist '[0, 0, 0]' '[0, 0, 0]'
 148         def cmdVelReceived(self, msg):
 149                 trans = msg.linear.x
 150                 rot = msg.angular.z # rad/s
 151
 152                 # handle rotation as offset to speeds
 153                 speed_offset = (rot * self.wheel_dist)/2.0 # m/s
 154
 155                 # handle translation
 156                 speed_l = 0
 157                 wish_speed_left = trans - speed_offset
 158                 if abs(wish_speed_left) > 0:
 159                         speed_l = self.speed_gradiant*abs(wish_speed_left) + self.speed_constant
 160                         if wish_speed_left < 0:
 161                                 speed_l*=-1
 162                 speed_r = 0
 163                 wish_speed_right = trans + speed_offset
 164                 if abs(wish_speed_right) > 0:
 165                         speed_r = self.speed_gradiant*abs(wish_speed_right) + self.speed_constant
 166                         if wish_speed_right < 0:
 167                                 speed_r*=-1
 168
 169                 # check limits
 170                 if speed_l < -7: speed_l = -7
 171                 elif speed_l > 7: speed_l = 7
 172                 if speed_r < -7: speed_r = -7
 173                 elif speed_r > 7: speed_r = 7
 174
 175                 #print "Speed wanted: %.2f m/s %.2f rad/s, set: %d %d" % (trans, rot, round(speed_l), round(speed_r))
 176
 177                 outmsg = Motor()
 178                 outmsg.num = 0
 179                 outmsg.speed = round(speed_l)
 180                 self.pub_motor.publish(outmsg)
 181
 182                 outmsg = Motor()
 183                 outmsg.num = 1
 184                 outmsg.speed = round(speed_r)
 185                 self.pub_motor.publish(outmsg)
 186
 187 if __name__ == '__main__':
 188         RoboExplorer()