controller_turtlebot.py

#!/usr/bin/env python

# ROS imports
import roslib; roslib.load_manifest('control_turtlebot')
import rospy
import tf
import math

#ROS messages
from geometry_msgs.msg import Twist
from nav_msgs.msg import Odometry
from control_turtlebot.srv import GotoWaypoint, GotoWaypointResponse, FindPathToGoal, FindPathToGoalResponse, FindPathToGoalRequest

#Numpy
import numpy as np

class Controller(object):

    def __init__(self):
        self.odometry_sub_ = rospy.Subscriber("/odom", Odometry, self.odomCallback, queue_size = 1)
        self.control_input_pub_ = rospy.Publisher("/mobile_base/commands/velocity", Twist, queue_size = 1)
        
        self.serv_ = rospy.Service('/controller_turtlebot/goto', 
                                  GotoWaypoint, 
                                  self.calculateControlInput)
        
        self.current_position_ = np.zeros(2)
        self.current_orientation_ = 0.0
        
        self.desired_position_ = np.zeros(2)
        self.desired_orientation_ = 0.0
        
        
        rospy.wait_for_service('/controller_turtlebot/find_path_to_goal')
        try:
            self.find_path_to_goal_serv_ = rospy.ServiceProxy('/controller_turtlebot/find_path_to_goal', FindPathToGoal)
        except rospy.ServiceException, e:
            print "Service call failed: %s"%e
        
        return
    
    def calculateControlInput(self, req):
        
        planner_request = FindPathToGoalRequest()
        planner_request.goal_state_x = req.goal_state_x
        planner_request.goal_state_y = req.goal_state_y
        #planner_request.goal_state_z = req.goal_state_z
        
        planner_response = self.find_path_to_goal_serv_(planner_request)
        
        for pose in planner_response.poses:
            #print pose
            control_input = Twist()
            self.desired_position_[0] = pose.position.x
            self.desired_position_[1] = pose.position.y
            #self.desired_position_[2] = pose.position.z
            
            loop_rate = rospy.Rate(100) # 10Hz
            orientation_approach = False
            while not rospy.is_shutdown():
                inc_x = self.desired_position_[0] - self.current_position_[0]
                inc_y = self.desired_position_[1] - self.current_position_[1]
                
                self.desired_orientation_ = wrapAngle(math.atan2(inc_y, inc_x))
                yaw_error = wrapAngle(self.desired_orientation_ - self.current_orientation_)
                distance_to_goal = math.sqrt(math.pow(inc_x, 2.0) + math.pow(inc_y, 2.0))
                
                if abs(yaw_error) > 0.04 and not orientation_approach:
                    control_input.angular.x = 0.0
                    control_input.angular.y = 0.0
                    control_input.angular.z = yaw_error * 1.0
                
                    control_input.linear.x = 0.08
                    control_input.linear.y = 0.0
                    control_input.linear.z = 0.0
                else:
                    control_input.angular.x = 0.0
                    control_input.angular.y = 0.0
                    control_input.angular.z = 0.0
                    
                    orientation_approach = True
                    liner_speed = abs(distance_to_goal) * 0.5
                    
                    if liner_speed < 0.1:
                        control_input.linear.x = 0.1
                    elif liner_speed > 0.2:
                        control_input.linear.x = 0.2
                    else:
                        control_input.linear.x = liner_speed
                    
                    control_input.linear.y = 0.0
                    control_input.linear.z = 0.0
                    
                self.control_input_pub_.publish(control_input)
                
                rospy.logdebug("%s: current position: [%f, %f]\n", rospy.get_name(), self.current_position_[0], self.current_position_[1])
                rospy.logdebug("%s: desired position: [%f, %f]\n", rospy.get_name(), self.desired_position_[0], self.desired_position_[1])
                rospy.logdebug("%s: yaw_error: %f\n", rospy.get_name(), yaw_error)
                rospy.logdebug("%s: current orientation: %f\n", rospy.get_name(), self.current_orientation_)
                rospy.logdebug("%s: desired orientation: %f\n", rospy.get_name(), self.desired_orientation_)
                rospy.logdebug("%s: distance_to_goal: %f\n", rospy.get_name(), distance_to_goal)
                rospy.logdebug("%s: control_input.linear.x %f\n", rospy.get_name(), control_input.linear.x)
                rospy.logdebug("%s: control_input.angular.z %f\n", rospy.get_name(), control_input.angular.z)
                
                if distance_to_goal <= 0.2:
                    break
                loop_rate.sleep()
        
        return GotoWaypointResponse()

    def odomCallback(self, odometry_msg):
        self.current_position_[0] = odometry_msg.pose.pose.position.x
        self.current_position_[1] = odometry_msg.pose.pose.position.y
        (r, p, y) = tf.transformations.euler_from_quaternion([odometry_msg.pose.pose.orientation.x, odometry_msg.pose.pose.orientation.y, odometry_msg.pose.pose.orientation.z, odometry_msg.pose.pose.orientation.w])
        self.current_orientation_ = wrapAngle(y)
        return

def wrapAngle(angle):
    """wrapAngle
    
    Calculates angles values between 0 and 2pi"""
    return (angle + ( 2.0 * math.pi * math.floor( ( math.pi - angle ) / ( 2.0 * math.pi ) ) ) )

if __name__ == '__main__':
    rospy.init_node('control_turtlebot', log_level=rospy.INFO)
    rospy.loginfo("%s: starting turtlebot controller", rospy.get_name())

    controller = Controller()
    rospy.spin()