Joint Position Example

Running Example Joint Position Program:

Summary

The Joint Position Control Examples demonstrate how to use position control to move and sense the arm based on joint angles. Examples include keyboard or joystick based user control of arm angles, along with complementary example programs to record and playback poses.

• Overview
• Running the Example:
  • Keyboard Control
  • Joystick Control
    • (Alternative) Manual Start
• Recording Joint Positions
• Playback Recordings

Overview

The joint pose example uses joint position control of Baxter's arms. Either the keyboard or a joystick can be used as a controller. Joint names are labeled below.

Note: For control of Head Joints, see the Head Wobbler Example.

Keyboard Control

Start the example joint pose program using the keyboard to control Baxter:

$ rosrun joint_position keyboard.py

    hit ? for help commands
    esc to exit example and disable the robot

Joystick Control

To use the example joint pose program using a joystick game controller to control the joints:

First ensure that joy drivers are installed.

$ rospack find joy

If not run:

$ sudo apt-get install ros-electric-joystick-drivers

To run the example:

$ roslaunch joint_position joystick.launch joystick:=logitech

Note: This method uses an included ROS launch file to start both joint pose example and joy_node using the roslaunch tool. You can exit the joint_position example by hitting any keyboard key, however you will have to ctrl-c to also cleanup the joy_node.

Joystick Button Mappings

NOTE: Don't forget to calibrate each gripper before using gripper open/close.

(And no, the 'joystick left <-> robot right' mappings are not typos; they assume the user is in front of the robot when using the joystick.)

Buttons	Action	Buttons	Action
Function 1 or 2 (e.g. Select/Select)	Help	<Any Keyboard key>	Quit
Left Button (X)	right: gripper calibrate	Right Button (B)	left: gripper calibrate
Top Button (Y)		Bottom Button (A)
Left Trigger [PRESS]	right: gripper close	Right Trigger [PRESS]	left: gripper close
Left Trigger [RELEASE]	right: gripper open	Right Trigger [RELEASE]	left: gripper open
Left Bumper	right: cycle <current joints> +1	Right Bumper	left: cycle <current joints> +1

Stick Axes	Action
Left Stick Horizontal	right: increase/decrease <current joint 1> (s0)
Left Stick Vertical	right: increase/decrease <current joint 2> (s1)
Right Stick Horizontal	left: increase/decrease <current joint 1> (s0)
Right Stick Vertical	left: increase/decrease <current joint 2> (s1)

Press any keyboard key to quit.

Note: The left and right bumper buttons will cycle through the joints that are controlled with the left and right stick (<current joint 1> and <current joint 2>). The order the joints are cycled through is S0-S1-E0-E1-W0-W1-W2.

Alternative Manual Start

Alternatively, you can run the joint pose example and the joy_node (joystick driver) independently in their own shells:

1. Initialize an environment and run the joy_node:

$ cd ~/sdk-examples
$ ./init <robot_hostname>
$ export ROS_IP=<xxx.xxx.xxx.xxx>

$ rosrun joy joy_node

2. From another shell, repeat the initialization and run the example program:

# repeat lines 1-3 above
$ rosrun joint_position joystick.py logitech

For the joystick examples to work, the joy_node driver must be running at the same time as the example. Using any of the other one-line launch commands to start the joystick examples is really just using a short-cut to start two programs at once.

Recording Joint Positions

You can start recording the joint positions at any time using:

$ rosrun joint_position recorder.py <filename>

After you have finished recording, stop the joint_position program using <Ctrl-C> or hit one of the function 1 or 2 buttons on the game controller.

Playback Recordings

You can now playback the recording using:

$ rosrun joint_position file_playback.py <filename>