| Note: This tutorial assumes that you have completed the previous tutorials: connecting to Dynamixel bus. |
 Please ask about problems and questions regarding this tutorial on answers.ros.org. Don't forget to include in your question the link to this page, the versions of your OS & ROS, and also add appropriate tags. |
Creating a dynamixel action client controller
Description: This tutorial describes how to create a joint controller with one or more Robotis Dynamixel motors.Tutorial Level:
All files that are created in this tutorial should be saved into my_dynamixel_tutorial package which we have created in previous tutorial.
roscd my_dynamixel_tutorial
Step1: Create a client
1 #!/usr/bin/env python
2 import roslib
3 roslib.load_manifest('my_dynamixel_tutorial')
4
5 import rospy
6 import actionlib
7 from std_msgs.msg import Float64
8 import trajectory_msgs.msg
9 import control_msgs.msg
10 from trajectory_msgs.msg import JointTrajectoryPoint
11 from control_msgs.msg import JointTrajectoryAction, JointTrajectoryGoal, FollowJointTrajectoryAction, FollowJointTrajectoryGoal
12
13
14
15 class Joint:
16 def __init__(self, motor_name):
17 #arm_name should be b_arm or f_arm
18 self.name = motor_name
19 self.jta = actionlib.SimpleActionClient('/'+self.name+'_controller/follow_joint_trajectory', FollowJointTrajectoryAction)
20 rospy.loginfo('Waiting for joint trajectory action')
21 self.jta.wait_for_server()
22 rospy.loginfo('Found joint trajectory action!')
23
24
25 def move_joint(self, angles):
26 goal = FollowJointTrajectoryGoal()
27 char = self.name[0] #either 'f' or 'b'
28 goal.trajectory.joint_names = ['joint_1'+char, 'joint_2'+char,'joint_3'+char]
29 point = JointTrajectoryPoint()
30 point.positions = angles
31 point.time_from_start = rospy.Duration(3)
32 goal.trajectory.points.append(point)
33 self.jta.send_goal_and_wait(goal)
34
35
36 def main():
37 arm = Joint('f_arm')
38 arm.move_joint([0.5,1.5,1.0])
39 arm.move_joint([6.28,3.14,6.28])
40
41
42 if __name__ == '__main__':
43 rospy.init_node('joint_position_tester')
44 main()
The Code Explained
Now, let's break down the code piece by piece.
Error: No code_block found Library used for send a trajectory point
Error: No code_block found Remember to add the dependecies to your manifest
Error: No code_block found Library with action messages
Error: No code_block found Create a client through the topic namespace/name_of_server.In this case the namespace is self.name wich would be b_arm f_arm depends on witch arm do you wanna move, so remember to create a meta controller for b_arms and for f_arms, you can check this at previous tutorial.
Error: No code_block found Get the namespace first character that should be b or f and then add this to the trajectory joint names, that should match with joint names in your configuration file (config.yaml), you can review at previous tutorial.
Error: No code_block found send 0.5,1.5,1.0 positions for respectives joints joint_1x, joint_2x, joint_3x
Step2: Executing a client
After you create the client you should launch the controllers and spawners created in previous tutorial.
roslaunch my_dynamixel_tutorial start_meta_controller.launch
and then execute the client
roscd my_dynamixel_tutorial python trajectory_client.py
now see motors move in a trajectory!!
