Z1 Arm Controller

A ROS interface for controlling the Unitree Z1 robot arm.

Overview

This package provides a ROS node for controlling the Unitree Z1 robotic arm. It offers two primary control interfaces:

1. Joint Control: Direct control of the 6 arm joints using position commands
2. End Effector Pose Control: Control of the end effector position and orientation using inverse kinematics

The controller handles the communication with the Z1 arm hardware through the Unitree SDK and exposes simple ROS interfaces for commanding the arm.

Prerequisites

• ROS (tested on ROS Noetic)
• Python 3
• NumPy
• SciPy
• Unitree Z1 SDK (included in /libs/z1_sdk)

Installation

1. Clone this repository into your catkin workspace: bash cd ~/catkin_ws/src git clone https://github.com/your-username/umi_robots.git

2. Build the package: bash cd ~/catkin_ws catkin_make

3. Source the workspace: bash source ~/catkin_ws/devel/setup.bash

4. Build Z1 SDK `bash cd src/umi_robots/libs/z1_sdk mkdir build cd build && rm -r ./* cmake .. make -j

   Usage

Launching the Controller

Start the Z1 arm controller node:

bash rosrun umi_robots z1_arm_controller.py

Controlling the Arm

Joint Control

Send joint position commands to the /joint_commands topic:

```bash

Example: Send joint positions using rostopic

rostopic pub /jointcommands stdmsgs/Float64MultiArray "data: [0.0, 0.5, -0.5, 0.0, 0.0, 0.0]" ```

The message should contain 6 values corresponding to the 6 joints of the Z1 arm (in radians). The controller ensures that joint limits are respected.

End Effector Pose Control

Send end effector pose commands to the /endpose_command topic:

```bash

Example: Send end effector pose

rostopic pub /endposecommand geometrymsgs/Pose "position: x: 0.3 y: 0.0 z: 0.4 orientation: x: 0.0 y: 0.0 z: 0.0 w: 1.0" ```

The controller uses inverse kinematics to calculate the required joint positions to achieve the desired end effector pose.

Features

• Robust quaternion to Euler angle conversion using SciPy's Rotation class
• Joint limit enforcement
• Inverse kinematics support for end effector pose control
• Clean shutdown procedure that sets the arm to a safe "PASSIVE" mode
• Logging of current state and commanded positions

Notes

• The arm is initialized in "JOINTCTRL" mode
• Default joint speed is set to 0.5 rad/s
• Default cartesian speed is set to 0.1 m/s
• When using inverse kinematics, the controller warns if a requested pose is unreachable

Troubleshooting

If the arm does not respond to commands, check: 1. The robot is powered on and properly connected 2. The controller node is running and not reporting errors 3. The commanded positions are within the joint limits 4. For pose commands, verify that the requested pose is within the reachable workspace