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Dynamixel workbench velocity controller with wheel command
Description: This tutorial describes how to running velocity controllerKeywords: robotis, dynamixel, velocity, wheel
Tutorial Level: BEGINNER
Next Tutorial: Dynamixel workbench torque controller
Contents
IF YOU ALREADY CREATE my_dynamixel_workbench_tutorial PACKAGE, THEN YOU JUMP TO STEP 2.
Step 1: Create a package
$ cd ~/catkin_ws/src $ catkin_create_pkg my_dynamixel_workbench_tutorial std_msgs roscpp
Step 2: Prepare two Dynamixels
We need two Dynamixels which are assembled common mobile platform.
Step 3: Create a launch file for the velocity control node
First we need a launch file in launch folder in my_dynamixel_workbench_tutorial package. This launch file connects to the dynamixel_workbench_controller package and sets device name and baudrate of a Dynamixel. We assume that the Dynamixel is connected to /dev/ttyUSB0 and baudrate 57600. If not, make sure you set your device name and baudrate correctly. NOTE: IN THIS TUTORIAL, WE USE XM430-W210
1. Make a launch file in ros package which we created
$ cd my_dynamixel_workbench_tutorial $ mkdir launch $ cd launch $ gedit velocity_control.launch
2. Type or copy&paste code below to connect dynamixel_workbench_controllers packages and set parameters
<launch> <arg name="device_name" default="/dev/ttyUSB0"/> <arg name="baud_rate" default="57600"/> <arg name="left_wheel" default="1"/> <arg name="right_wheel" default="2"/> <arg name="profile_velocity" default="200"/> <arg name="profile_acceleration" default="50"/> <param name="device_name" value="$(arg device_name)"/> <param name="baud_rate" value="$(arg baud_rate)"/> <param name="left_wheel" value="$(arg left_wheel)"/> <param name="right_wheel" value="$(arg right_wheel)"/> <param name="profile_velocity" value="$(arg profile_velocity)"/> <param name="profile_acceleration" value="$(arg profile_acceleration)"/> <node name="velocity_control" pkg="dynamixel_workbench_controllers" type="velocity_control" required="true" output="screen"/> </launch>
3. Before we operating this package, we need to access permission for USB device
$ sudo chmod a+rw /dev/ttyUSB0
4. Now we can run tutorial package:
$ cd ~/catkin_ws && catkin_make $ roslaunch my_dynamixel_workbench_tutorial velocity_control.launch
If velocity_controllers find linked Dynamixels, we could show state of it and command list and set torque on:
----------------------------------------------------------------------- dynamixel_workbench controller; velocity control example ----------------------------------------------------------------------- MODEL : XM430-W350 ID : 1 MODEL : XM430-W350 ID : 2 -----------------------------------------------------------------------
Step 4: Check state of Dynamixel
Now, we can check a state of linked Dynamixels through /dynamixel_state topic:
$ rostopic echo /dynamixel_state
For example:
dynamixel_state:
-
model_name: "XM430-W350"
id: 1
torque_enable: 1
goal_current: 0
goal_velocity: 0
goal_position: 2050
present_current: 0
present_velocity: 0
present_position: 2049
moving: 0
-
model_name: "XM430-W350"
id: 2
torque_enable: 1
goal_current: 0
goal_velocity: 0
goal_position: 1969
present_current: 0
present_velocity: 0
present_position: 1967
moving: 0
Step 5: Run mobile platform
We run the two linked Dynamixels using rosservice call or dynamixel_workbench_operators [unit : rad/sec].
$ rosrun dynamixel_workbench_operators wheel_operator
Then, we can set velocity using keyboard.
[ INFO] [1498123238.521332487]: Set angular velocity(+-0.2 rad/sec) to your Dynamixel!! by using keyboard [ INFO] [1498123238.521369361]: w : Forward [ INFO] [1498123238.521380496]: x : Backward [ INFO] [1498123238.521389146]: a : Left [ INFO] [1498123238.521397016]: d : Right [ INFO] [1498123238.521404724]: s : STOPS [ INFO] [1498123238.521414139]: ESC : exit
Press 'w' then the mobile plaform is running!! or
$ rosservice call /wheel_command -- [right_vel] [left_vel]
The mobile plaform is running!!
If you have a question about running velocity_controller, please make anew issue.
