This repository provides the necessary tools to control and develop libraries to control the Wearable Robotic Third Arm (WRTA). Currently, the code to control the robot is in the form of a ROS package, supporting ROS Noetic. We have plans to add support for ROS 2 (Humble) as well. Launch files are provided to run the robot on hardware or in simulation, as well as optionally with an Optitrack Mo-Cap setup (more details below).
You should have ROS-Noetic installed. Clone the repo into a catkin workspace. PyPot is used to control the Dynamixel Motors.
To install PyPot: python3 -m pip install PyPot
Temporarily set USB port permissions, example for ACM0 usb port using: sudo chmod 0777 /dev/ttyACM0
Alternatively, add the current user to the dialout group: sudo adduser $USER dialout
Build the catkin workspace: catkin_make
Source the workspace: source devel/setup.bash
The five joints are defined in the file urdf/third_arm_5dof.urdf as follows:
| Joint Name | Type | Parent Link | Child Link | Min | Max |
|---|---|---|---|---|---|
| Horizontal Panning | Revolute | Base Link | Base Motor | -3.14 | 3.14 |
| Vertical Pitching | Revolute | Base Motor | Lift Motor | 0.00 | 1.57 |
| Length Extension | Prismatic | Extend Link 1 | Extend Link 2 | 0.00 | 0.12 |
| Wrist Rotation | Revolute | Extend Link 2 | Wrist Rotation Motor | -3.14 | 3.14 |
| Wrist Pitching | Revolute | Wrist Rotation Motor | Wrist Tilt Motor | 0.00 | 3.14 |
To launch an rviz visualization of the robot with GUI controls for those joints, build and source the workspace, then run roslaunch third_arm urdf_5dof.launch
To launch an empty gazebo world with the third arm in it, run:
roslaunch third_arm wrta_gazebo.launch
Position controllers are defined for each joint in config/wrta_controllers.yaml.
You can publish float position messages to the following controller topics, e.g. with a tool like rqt:
- /wrta/horizontal_panning_controller/command
- /wrta/vertical_pitching_controller/command
- /wrta/length_extension_controller/command
- /wrta/wrist_pitching_controller/command
- /wrta/wrist_rotation_controller/command
Note that this will also launch the controller. To launch ros_control and load the controllers separately, run:
roslaunch third_arm wrta_control.launch
once Gazebo is running.
All of the actuators in the third arm are Dynamixel servomotors, (MX-64, MX-64, MX-28, MX-28, and AX-12) respectively. They are daisy-chained on a single serial bus via a USB2AX module and powered with a 12V supply (recommended 10A rating). Note that the USB2AX is no longer produced or avaiable to purchase. However, a very similar setup can be achieved using a U2D2 with the accompanying U2D2 power board.
To control the robot using the provided libraries, do the following:
- Plug the 12V supply in to the USB2AX or U2D2.
- Connect the USB cable fromt he USB2AX or U2D2 to your computer.
- Source your catkin workspace.
- Run
roslaunch third_arm third_arm_noetic.launch.
If you have an optitrack motion-tracking system, you can use our provided code with our experimental "online" controller. This uses a PID loop to update the servo velocities according towards the current location of a tracked object (e.g. a person's hand).
Otherwise, motion-tracking is disabled by default. You can specify a target location and the robot will move to the correct joint angles to realize that pose.
Plug in Power FIRST
Plug in USB
export ROS_MASTER_URI=http://192.168.0.124:11311
export ROS_IP=192.168.0.124
cd third_arm_noetic_ws/
source devel/setup.bash
roslaunch third_arm third_arm_noetic.launch
Switch to HRC2 network
source devel/setup.bash
roslaunch mocap_optitrack mocap.launch
rostopic echo /tf
Port not found:
- Make sure using a port on the back of the PC, 1 from the left looking from behind. There is a USB extension connected to it for convenience.
Error finding Dynamixel Motor:
- Shut down all terminals
- Unplug WRTA from computer and power
- Plug in power
- Plug in USB cable
- Rerun scripts
write a service to use dynamixel command - done
command arm through dynamixel command - done
write a publisher for JointTrajectory - wip
- write a service to use dynamixel execution - wip
Set WRTA dynamixel wrist tilt motor to wheel mode and command a slow velocity to it
https://emanual.robotis.com/docs/en/dxl/protocol2/
Goal_Position range - 0 2048 4095 but depends on motor limits
Motors and their models:
id : 1, model name : MX-64
id : 2, model name : MX-64
id : 3, model name : MX-28
id : 4, model name : AX-12A
id : 5, model name : AX-12A
id : 6, model name : MX-28
this is for the object even though it says robot ('Robot orientation =', [-0.027261753897265567, 0.8300776298749009, 0.29825615225767416, -0.4703947202043823]) ('Robot position =', [0.07514090090990067, 2.003984212875366, 0.14993013441562653]) ('Robot orientation =', [-0.027261753897265567, 0.8300776298749009, 0.29825615225767416, -0.4703947202043823]) ('Robot position =', [0.07478132843971252, 2.0018575191497803, 0.1488160938024521]) ('Robot orientation =', [-0.041804371034848915, 0.8302444516663823, 0.3029710460828637, -0.4659990238992184]) ('Robot position =', [0.07478132843971252, 2.0018575191497803, 0.1488160938024521]) ('Robot orientation =', [-0.041804371034848915, 0.8302444516663823, 0.3029710460828637, -0.4659990238992184]) ('Robot position =', [0.07119814306497574, 2.0003042221069336, 0.1495422124862671]) ('Robot orientation =', [-0.05553610425074222, 0.8342336751606665, 0.30679464169761433, -0.4548043141596291])