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 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.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                 # fake laser scan with ultra sonic range finder
  28                 self.enable_ultrasonic_laser = bool(rospy.get_param('~ultrasonic_laser', "True"))
  29                 # Distance between both wheels in meter (18.55cm)
  30                 self.wheel_dist = float(rospy.get_param('~wheel_dist', "0.1855"))
  31                 # Size of wheel Diameter in meter (5.15cm) * gear ratio (0.5) = 2.575cm
  32                 self.wheel_size = float(rospy.get_param('~wheel_size', "0.02575"))
  33                 # Speed to PWM equation gradiant (The m in pwm = speed*m+b)
  34                 self.speed_gradiant = float(rospy.get_param('~speed_gradiant', "64.3"))
  35                 # Speed to PWM equation constant (The b in pwm = speed*m+b)
  36                 self.speed_constant = float(rospy.get_param('~speed_constant', "-1.7"))
  37
  38                 self.pub_motor = rospy.Publisher("ft/set_motor", Motor, queue_size=16)
  39                 if self.enable_ultrasonic_laser:
  40                         self.pub_scan = rospy.Publisher("scan", LaserScan, queue_size=16)
  41                 self.pub_odom = rospy.Publisher("odom", Odometry, queue_size=16)
  42
  43                 rospy.Subscriber("cmd_vel", Twist, self.cmdVelReceived)
  44                 rospy.Subscriber("ft/get_inputs", Inputs, self.inputsReceived)
  45                 rospy.Subscriber("initialpose", PoseWithCovarianceStamped, self.posReceived)
  46
  47                 rospy.spin()
  48
  49         def posReceived(self, msg):
  50                 self.x = msg.pose.pose.position.x
  51                 self.y = msg.pose.pose.position.y
  52                 orientation = msg.pose.pose.orientation
  53                 angles = tf.transformations.euler_from_quaternion([orientation.x, orientation.y, orientation.z, orientation.w])
  54                 self.alpha = angles[2]
  55
  56         def inputsReceived(self, msg):
  57                 current_time = rospy.Time.now()
  58
  59                 self.update_odometry(msg, current_time)
  60                 if (current_time - self.last_time).to_nsec() > 100e6: # send every 100ms
  61                         self.send_odometry(msg, current_time)
  62                         if self.enable_ultrasonic_laser:
  63                                 self.send_laser_scan(msg, current_time)
  64                         self.last_time = current_time
  65
  66         def update_odometry(self, msg, current_time):
  67                 in_now = msg.input[:2]
  68                 if self.last_in is not None:
  69                         in_diff = [abs(a - b) for a, b in zip(in_now, self.last_in)] # get changed inputs
  70                         # fix in_diff from actual motor direction
  71                         if msg.output[1] > 0: # left reverse
  72                                 in_diff[0] = -in_diff[0]
  73                         elif msg.output[0] == 0 and msg.output[1] == 0: # left stop
  74                                 in_diff[0] = 0
  75                         if msg.output[3] > 0: # right reverse
  76                                 in_diff[1] = -in_diff[1]
  77                         elif msg.output[2] == 0 and msg.output[3] == 0: # right stop
  78                                 in_diff[1] = 0
  79
  80                         dist_dir = (in_diff[1] - in_diff[0]) * self.wheel_size*pi/8 # steps_changed in different direction => m
  81                         delta_alpha = dist_dir/self.wheel_dist
  82
  83                         dist = (in_diff[0] + in_diff[1])/2.0 * self.wheel_size*pi/8 # steps_changed same direction => m
  84
  85                         delta_x = cos(self.alpha + delta_alpha/2)*dist
  86                         delta_y = sin(self.alpha + delta_alpha/2)*dist
  87
  88                         self.alpha += delta_alpha
  89                         if self.alpha > 2*pi:
  90                                 self.alpha -= 2*pi
  91                         elif self.alpha < -2*pi:
  92                                 self.alpha += 2*pi
  93                         self.x += delta_x
  94                         self.y += delta_y
  95
  96                 self.last_in = in_now
  97
  98         def send_odometry(self, msg, current_time):
  99                 # speeds
 100                 dt = (current_time - self.last_time).to_sec()
 101                 vx = sqrt((self.x - self.x_last)**2 + (self.y - self.y_last)**2) / dt
 102                 if (msg.output[0]-msg.output[1] + msg.output[2]-msg.output[3]) < 0:
 103                         # moving backward
 104                         vx*=-1
 105                 valpha = (self.alpha - self.alpha_last) / dt
 106                 self.x_last = self.x
 107                 self.y_last = self.y
 108                 self.alpha_last = self.alpha
 109
 110                 # since all odometry is 6DOF we'll need a quaternion created from yaw
 111                 odom_quat = tf.transformations.quaternion_from_euler(0, 0, self.alpha)
 112
 113                 # first, we'll publish the transform over tf
 114                 self.tf_broadcaster.sendTransform((self.x, self.y, 0.0), odom_quat, current_time, "base_link", "odom")
 115
 116                 # next, we'll publish the odometry message over ROS
 117                 odom = Odometry()
 118                 odom.header.stamp = current_time
 119                 odom.header.frame_id = "/odom"
 120
 121                 # set the position
 122                 odom.pose.pose.position.x = self.x
 123                 odom.pose.pose.position.y = self.y
 124                 odom.pose.pose.position.z = 0.0
 125                 odom.pose.pose.orientation.x = odom_quat[0]
 126                 odom.pose.pose.orientation.y = odom_quat[1]
 127                 odom.pose.pose.orientation.z = odom_quat[2]
 128                 odom.pose.pose.orientation.w = odom_quat[3]
 129
 130                 # set the velocity
 131                 odom.child_frame_id = "base_link"
 132                 odom.twist.twist.linear.x = vx
 133                 odom.twist.twist.linear.y = 0.0
 134                 odom.twist.twist.angular.z = valpha
 135
 136                 # publish the message
 137                 self.pub_odom.publish(odom)
 138
 139         def send_laser_scan(self, msg, current_time):
 140                 # actually ultra sonic range finder
 141                 num_points = 60 # The base planner needs at least 30 points to work in the default config
 142                 opening_angle = 30*pi/180 # each side
 143                 scan = LaserScan()
 144                 scan.header.stamp = current_time
 145                 scan.header.frame_id = "forward_sensor"
 146                 scan.angle_min = -opening_angle
 147                 scan.angle_max = opening_angle
 148                 scan.angle_increment = (2*opening_angle)/num_points
 149                 scan.time_increment = 0.0
 150                 scan.range_min = 0.0
 151                 scan.range_max = 4.0
 152                 for i in range(num_points):
 153                         scan.ranges.append(msg.d1/100.0)
 154                 #scan.intensities.append(0.5)
 155                 #scan.intensities.append(1.0)
 156                 #scan.intensities.append(0.5)
 157                 self.pub_scan.publish(scan)
 158
 159         # test with rostopic pub -1 cmd_vel geometry_msgs/Twist '[0, 0, 0]' '[0, 0, 0]'
 160         def cmdVelReceived(self, msg):
 161                 trans = msg.linear.x
 162                 rot = msg.angular.z # rad/s
 163
 164                 # handle rotation as offset to speeds
 165                 speed_offset = (rot * self.wheel_dist)/2.0 # m/s
 166
 167                 # handle translation
 168                 speed_l = 0
 169                 wish_speed_left = trans - speed_offset
 170                 if abs(wish_speed_left) > 0:
 171                         speed_l = self.speed_gradiant*abs(wish_speed_left) + self.speed_constant
 172                         if wish_speed_left < 0:
 173                                 speed_l*=-1
 174                 speed_r = 0
 175                 wish_speed_right = trans + speed_offset
 176                 if abs(wish_speed_right) > 0:
 177                         speed_r = self.speed_gradiant*abs(wish_speed_right) + self.speed_constant
 178                         if wish_speed_right < 0:
 179                                 speed_r*=-1
 180
 181                 # check limits
 182                 if speed_l < -7: speed_l = -7
 183                 elif speed_l > 7: speed_l = 7
 184                 if speed_r < -7: speed_r = -7
 185                 elif speed_r > 7: speed_r = 7
 186
 187                 #print "Speed wanted: %.2f m/s %.2f rad/s, set: %d %d" % (trans, rot, round(speed_l), round(speed_r))
 188
 189                 outmsg = Motor()
 190                 outmsg.num = 0
 191                 outmsg.speed = round(speed_l)
 192                 self.pub_motor.publish(outmsg)
 193
 194                 outmsg = Motor()
 195                 outmsg.num = 1
 196                 outmsg.speed = round(speed_r)
 197                 self.pub_motor.publish(outmsg)
 198
 199 if __name__ == '__main__':
 200         RoboExplorer()