ROS機器人Diego 1#制作（五）base controller---角速度的标定

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角速度标定，即控制機器人人轉動固定的角度，看機器人是否按照控制指令完成，在這裡我們讓機器人轉360度，代碼如下：

#!/usr/bin/env python
import rospy
from geometry_msgs.msg import Twist, Quaternion
from nav_msgs.msg import Odometry
import tf
from math import radians, copysign
from transform_utils import quat_to_angle, normalize_angle
import PyKDL
from math import pi

class CalibrateAngular():
    def __init__(self):
        # Give the node a name
        rospy.init_node('calibrate_angular', anonymous=False)
        
        # Set rospy to execute a shutdown function when terminating the script
        rospy.on_shutdown(self.shutdown)
        
        # How fast will we check the odometry values?
        self.rate = 10
        r = rospy.Rate(self.rate)
        
        # The test angle is 360 degrees
        self.test_angle = 2*pi #這裡注意，在ROS中使用的弧度，不能直接寫360

        self.speed = 0.1 # radians per second
        self.tolerance = 1 # degrees converted to radians
        self.odom_angular_scale_correction = 1
        self.start_test = True
        
        # Publisher to control the robot's speed
        self.cmd_vel = rospy.Publisher('/cmd_vel', Twist, queue_size=5)
        
        # The base frame is usually base_link or base_footprint
        self.base_frame = rospy.get_param('~base_frame', '/base_link')

        # The odom frame is usually just /odom
        self.odom_frame = rospy.get_param('~odom_frame', '/odom')

        # Initialize the tf listener
        self.tf_listener = tf.TransformListener()
        
        # Give tf some time to fill its buffer
        rospy.sleep(2)
        
        # Make sure we see the odom and base frames
        self.tf_listener.waitForTransform(self.odom_frame, self.base_frame, rospy.Time(), rospy.Duration(60.0))
            
        rospy.loginfo("Bring up rqt_reconfigure to control the test.")
        
        reverse = 1
        
        while not rospy.is_shutdown():
            if self.start_test:
                # Get the current rotation angle from tf
                self.odom_angle = self.get_odom_angle()
                rospy.loginfo("self.odom_angle: "+str(self.odom_angle))
                
                last_angle = self.odom_angle
                turn_angle = 0
                self.test_angle *= reverse
                error = self.test_angle - turn_angle
                rospy.loginfo("errir: "+str(error))
                                
                # Alternate directions between tests
                reverse = -reverse
                
                while abs(error) > self.tolerance and self.start_test:
                    if rospy.is_shutdown():
                        return
                    rospy.loginfo("*************************** ")
                    # Rotate the robot to reduce the error
                    move_cmd = Twist()
                    move_cmd.angular.z = copysign(self.speed, error)
                    rospy.loginfo("move_cmd.angular.z: "+str(move_cmd.angular.z))
                    self.cmd_vel.publish(move_cmd)
                    r.sleep()
                 
                    # Get the current rotation angle from tf                   
                    self.odom_angle = self.get_odom_angle()
                    rospy.loginfo("current rotation angle: "+str(self.odom_angle))
                    
                    # Compute how far we have gone since the last measurement
                    delta_angle = self.odom_angular_scale_correction * normalize_angle(self.odom_angle - last_angle)
                    rospy.loginfo("delta_angle: "+str(delta_angle))
                    
                    # Add to our total angle so far
                    turn_angle += abs(delta_angle)
                    rospy.loginfo("turn_angle: "+str(turn_angle))

                    # Compute the new error
                    error = self.test_angle - turn_angle
                    rospy.loginfo("error: "+str(error))

                    # Store the current angle for the next comparison
                    last_angle = self.odom_angle
                                    
                # Stop the robot
                self.cmd_vel.publish(Twist())
                
                # Update the status flag
                self.start_test = False
                params = {'start_test': False}
                dyn_client.update_configuration(params)
                
            rospy.sleep(0.5)
                    
        # Stop the robot
        self.cmd_vel.publish(Twist())
        
    def get_odom_angle(self):
        # Get the current transform between the odom and base frames
        try:
            (trans, rot)  = self.tf_listener.lookupTransform(self.odom_frame, self.base_frame, rospy.Time(0))
        except (tf.Exception, tf.ConnectivityException, tf.LookupException):
            rospy.loginfo("TF Exception")
            return
        
        # Convert the rotation from a quaternion to an Euler angle

        return quat_to_angle(Quaternion(*rot))
        
    def shutdown(self):
        # Always stop the robot when shutting down the node
        rospy.loginfo("Stopping the robot...")
        self.cmd_vel.publish(Twist())
        rospy.sleep(1)
if __name__ == '__main__':
    try:
        CalibrateAngular()
    except:
        rospy.loginfo("Calibration terminated.")

           

接下來運作如下指令，控制小車旋轉：

rosrun diego_nav calibrate_angular.py
           

影響角速度的主要參數是wheel_track，是以如果發現機器人不能按照要求旋轉固定角度，可以調整此參數。

可以到優酷檢視已經完成線速度和角速度标定的Diego 1#履帶機器人