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 *
   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.x = 0
  20                 self.y = 0
  21                 self.alpha = 0
  22                 self.last_in = None
  23                 self.tf_broadcaster = tf.broadcaster.TransformBroadcaster()
  24                 self.last_time = rospy.Time.now()
  25                 self.x_last = 0
  26                 self.y_last = 0
  27                 self.alpha_last = 0
  28
  29                 # fake laser scan with ultra sonic range finder
  30                 self.enable_ultrasonic_laser = bool(rospy.get_param('~ultrasonic_laser', "True"))
  31                 # Distance between both wheels in meter (18.55cm)
  32                 self.wheel_dist = float(rospy.get_param('~wheel_dist', "0.1855"))
  33                 # Size of wheel Diameter in meter (5.15cm) * gear ratio (0.5) = 2.575cm
  34                 self.wheel_size = float(rospy.get_param('~wheel_size', "0.02575"))
  35                 # Speed to PWM equation gradiant (The m in pwm = speed*m+b)
  36                 self.speed_gradiant = float(rospy.get_param('~speed_gradiant', "64.3"))
  37                 # Speed to PWM equation constant (The b in pwm = speed*m+b)
  38                 self.speed_constant = float(rospy.get_param('~speed_constant', "-1.7"))
  39
  40                 self.pub_motor = rospy.Publisher("ft/set_motor", Motor)
  41                 if self.enable_ultrasonic_laser:
  42                         self.pub_scan = rospy.Publisher("scan", LaserScan)
  43                 self.pub_odom = rospy.Publisher("odom", Odometry)
  44
  45                 rospy.Subscriber("cmd_vel", Twist, self.cmdVelReceived)
  46                 rospy.Subscriber("ft/get_inputs", Inputs, self.inputsReceived)
  47
  48                 rospy.spin()
  49
  50         def inputsReceived(self, msg):
  51                 current_time = rospy.Time.now()
  52
  53                 self.update_odometry(msg, current_time)
  54                 if (current_time - self.last_time).to_nsec() > 100e6: # send every 100ms
  55                         self.send_odometry(msg, current_time)
  56                         if self.enable_ultrasonic_laser:
  57                                 self.send_laser_scan(msg, current_time)
  58                         self.last_time = current_time
  59
  60         def update_odometry(self, msg, current_time):
  61                 in_now = msg.input[:2]
  62                 if self.last_in is not None:
  63                         in_diff = [abs(a - b) for a, b in zip(in_now, self.last_in)] # get changed inputs
  64                         # fix in_diff from actual motor direction
  65                         if msg.output[1] > 0: # left reverse
  66                                 in_diff[0] = -in_diff[0]
  67                         elif msg.output[0] == 0 and msg.output[1] == 0: # left stop
  68                                 in_diff[0] = 0
  69                         if msg.output[3] > 0: # right reverse
  70                                 in_diff[1] = -in_diff[1]
  71                         elif msg.output[2] == 0 and msg.output[3] == 0: # right stop
  72                                 in_diff[1] = 0
  73
  74                         dist_dir = (in_diff[1] - in_diff[0])*self.wheel_size*pi/8 # steps_changed in different direction => m
  75                         delta_alpha = dist_dir/self.wheel_dist
  76
  77                         dist = (in_diff[0] + in_diff[1])/2.0*self.wheel_size*pi/8 # steps_changed same direction => m
  78
  79                         delta_x = cos(self.alpha + delta_alpha/2)*dist
  80                         delta_y = sin(self.alpha + delta_alpha/2)*dist
  81
  82                         self.alpha += delta_alpha
  83                         if self.alpha > 2*pi:
  84                                 self.alpha -= 2*pi
  85                         elif self.alpha < -2*pi:
  86                                 self.alpha += 2*pi
  87                         self.x += delta_x
  88                         self.y += delta_y
  89
  90                 self.last_in = in_now
  91
  92         def send_odometry(self, msg, current_time):
  93                 # speeds
  94                 dt = (current_time - self.last_time).to_sec()
  95                 vx = sqrt((self.x - self.x_last)**2 + (self.y - self.y_last)**2) / dt
  96                 vy = 0.0
  97                 valpha = (self.alpha - self.alpha_last) / dt
  98                 self.x_last = self.x
  99                 self.y_last = self.y
 100                 self.alpha_last = self.alpha
 101
 102                 # since all odometry is 6DOF we'll need a quaternion created from yaw
 103                 odom_quat = tf.transformations.quaternion_from_euler(0, 0, self.alpha)
 104
 105                 # first, we'll publish the transform over tf
 106                 self.tf_broadcaster.sendTransform((self.x, self.y, 0.0), odom_quat, current_time, "base_link", "odom")
 107
 108                 # next, we'll publish the odometry message over ROS
 109                 odom = Odometry()
 110                 odom.header.stamp = current_time
 111                 odom.header.frame_id = "/odom"
 112
 113                 # set the position
 114                 odom.pose.pose.position.x = self.x
 115                 odom.pose.pose.position.y = self.y
 116                 odom.pose.pose.position.z = 0.0
 117                 odom.pose.pose.orientation.x = odom_quat[0]
 118                 odom.pose.pose.orientation.y = odom_quat[1]
 119                 odom.pose.pose.orientation.z = odom_quat[2]
 120                 odom.pose.pose.orientation.w = odom_quat[3]
 121
 122                 # set the velocity
 123                 odom.child_frame_id = "base_link"
 124                 odom.twist.twist.linear.x = vx
 125                 odom.twist.twist.linear.y = vy
 126                 odom.twist.twist.angular.z = valpha
 127
 128                 # publish the message
 129                 self.pub_odom.publish(odom)
 130
 131         def send_laser_scan(self, msg, current_time):
 132                 # first, we'll publish the transform over tf
 133                 self.tf_broadcaster.sendTransform((0.06, 0.0, 0.0), (0.0, 0.0, 0.0, 1.0), current_time, "scan", "base_link")
 134
 135                 # actually ultra sonic range finder
 136                 num_points = 60 # The base planner needs at least 30 points to work in the default config
 137                 opening_angle = 30*pi/180 # each side
 138                 scan = LaserScan()
 139                 scan.header.stamp = current_time
 140                 scan.header.frame_id = "/scan"
 141                 scan.angle_min = -opening_angle
 142                 scan.angle_max = opening_angle
 143                 scan.angle_increment = (2*opening_angle)/num_points
 144                 scan.time_increment = 0.0
 145                 scan.range_min = 0.0
 146                 scan.range_max = 4.0
 147                 for i in range(num_points):
 148                         scan.ranges.append(msg.d1/100.0)
 149                 #scan.intensities.append(0.5)
 150                 #scan.intensities.append(1.0)
 151                 #scan.intensities.append(0.5)
 152                 self.pub_scan.publish(scan)
 153
 154         # test with rostopic pub -1 cmd_vel geometry_msgs/Twist '[0, 0, 0]' '[0, 0, 0]'
 155         def cmdVelReceived(self, msg):
 156                 trans = msg.linear.x
 157                 rot = msg.angular.z # rad/s
 158
 159                 # handle rotation as offset to speeds
 160                 speed_offset = (rot * self.wheel_dist)/2.0 # m/s
 161
 162                 # handle translation
 163                 speed_l = 0
 164                 wish_speed_left = trans - speed_offset
 165                 if abs(wish_speed_left) > 0:
 166                         speed_l = self.speed_gradiant*abs(wish_speed_left) + self.speed_constant
 167                         if wish_speed_left < 0:
 168                                 speed_l*=-1
 169                 speed_r = 0
 170                 wish_speed_right = trans + speed_offset
 171                 if abs(wish_speed_right) > 0:
 172                         speed_r = self.speed_gradiant*abs(wish_speed_right) + self.speed_constant
 173                         if wish_speed_right < 0:
 174                                 speed_r*=-1
 175
 176                 # check limits
 177                 if speed_l < -7: speed_l = -7
 178                 elif speed_l > 7: speed_l = 7
 179                 if speed_r < -7: speed_r = -7
 180                 elif speed_r > 7: speed_r = 7
 181
 182                 #print "Speed wanted: %.2f m/s %.2f rad/s, set: %d %d" % (trans, rot, round(speed_l), round(speed_r))
 183
 184                 outmsg = Motor()
 185                 outmsg.num = 0
 186                 outmsg.speed = round(speed_l)
 187                 self.pub_motor.publish(outmsg)
 188
 189                 outmsg = Motor()
 190                 outmsg.num = 1
 191                 outmsg.speed = round(speed_r)
 192                 self.pub_motor.publish(outmsg)
 193
 194 if __name__ == '__main__':
 195         RoboExplorer()