BiQu Arm

Git repository for the BiQu MQP 23-24, containing documentation for the Arduino, CAD, and URDF files for the custom robot arm.

Table of Contents

• Arduino Library
• SolidWorks CAD
• BiQu Go1 URDF

Arduino Library

This folder contains Arduino libraries for controlling a robotic arm via different communication interfaces. Currently, two communication methods are supported: serial USB connection and ROS (Robot Operating System) messages.

Robot_Arm_Serial

This library enables users to command the robotic arm to move to a desired position using a serial USB connection. Commands are sent via the "Serial Monitor" in the Arduino IDE. The command format consists of joint positions in the following order: "[J1 Pos], [J2 Pos], [J3 Pos], [Gripper Pos]". The gripper position is optional.

For example, to move the arm to the joint configuration of 100, -90, and 45 without the gripper moving, the command should be sent as follows:

"100, -90, 45, "

Robot_Arm_ROS

This library facilitates controlling the robotic arm using ROS messages. Users can send ROS messages to command the arm to move to a desired position. This enables integration with ROS-based robotic systems and frameworks.

To enable communication between ROS and Arduino, follow these steps:

1. On the Arduino end, download the Rosserial library from the official Arduino website: Rosserial Arduino Library.

2. On the ROS end, download the rosserial for Arduino by running the following command in the terminal:

   sudo apt-get install ros-${ROS_DISTRO}-rosserial-arduino
   sudo apt-get install ros-${ROS_DISTRO}-rosserial
   

3. Once the ROS device is connected via USB, run the following command in a terminal of the ROS device:

   rosrun rosserial_python serial_node.py /dev/ttyUSB0
   

   Note: the USB port is typically /dev/ttyUSBx or /dev/ttyACMx, but you may need to list out the ports to find it. Also, to enable permission to access the USB port, you may need to use

   sudo chmod a+rw /dev/ttyUSB0
   

To command the arm to move to a desired position. Send a Twist message on the /arm_command topic. The linear field stands for the joint positions and the angular field specifies the joint velocities. For example to move the arm to the joint configuration of [100, -90, 45] with joint velocites of 500 for all three joints. Send the following in the terminal:

```
rostopic pub -1 /arm_command geometry_msgs/Twist  '{linear:  {x: 100.0, y: -90.0, z: 45.0}, angular: {x: 500.0,y: 500.0,z: 500.0}}'
```

SolidWorks CAD

This directory contains the SolidWorks CAD files for the custom robot arm. It includes two assembly files:

• Arm_Gripper_Assem.SLDASM: This file represents the assembly of the arm itself, including the gripper mechanism.

• Whole_Assem.SLDASM: This file represents the assembly of the entire system, including the arm, controller box, onboard Intel NUC, and the rails designed for connection to the Unitree Go1 robot.

Note: The gripper design is sourced from an open-source gripper available on GrabCAD.

BiQu Go1 URDF

To visualize the URDF in Rviz, follow these steps:

1. Clone the repository into your catkin_ws/src directory and navigate to your catkin_ws directory and build the workspace using catkin_make:

2. Open a terminal and enter the following command to visualize the URDF in Rviz:

   roslaunch urdf_tutorial display.launch model:='$(find Arm_URDF)/biqu_go1.urdf'
   

   This command launches Rviz with the specified URDF model. You may need to adjust the fixed_frame parameter in Rviz from base to base_link for correct frame transformation.