Mini-Arm

The Mini Arm is a miniature version of the Desktop-Arm project, a portable 6DOF 3D-printed open-source robot arm. Plug in a USB cable and immediately enjoy these features:

• Runs on Raspberry Pico 2 microcontroller using CircuitPython
• Internal IK solver to handle joint state calculations on the microcontroller!
• 95% 3D printable components (aside from nuts & bolts)
• Total parts cost <= $100
• Weighs less than 1lb (~0.3kg)

These install instructions were tailored using a Windows 10 OS. There are also setup instructions for Ubuntu and the Raspberry Pi too.

Contents

• Repository Structure
• Installation
  • Software
  • Hardware
• Demos
  • Xbox Teleop
  • Face Detection
• Tests
• Multimodal agentic AI Integration
• AJ GUI
• ROS2 Robot Visualizer
• Acknowledgements

Repository Structure

This GitHub repository contains Installation and Quick Start instructions for the Mni Arm project. Here is a description of the repository structure:

• miniarm_ros - Contains ROS packages for the Mini Arm
• pico - Contains CircuitPython firmware and code for the Mini Arm using a Raspberry Pico microcontroller
• tests - Python test scripts for the package
• XboxClient - Teleop script to run on a PC with a connected Xbox controller

Installation

Software:

1. Choose Pico firmware

   We have provided CircuitPython firmware for both the Pico and Pico2! Choose the right uf2 file for your Pico version, or download the CircuitPython latest firmware for the Pico or Pico 2.

2. Move/drag the uf2 file to the Pico drive.

   • When you plug in the Pico for the first time, you should see a new drive appear on your computer with the Poci in bootloader mode. You can always access this by pressing the BOOTSEL button while plugging in the Pico.
   • Move/drag the uf2 file to the Pico drive. The Pico will automatically reboot and the LED will turn green to indicate successful flashing.

3. Replace the contents of the code.py and lib folder to the Pico drive.

   • The code.py file contains the main code to run the Mini Arm. Open this file to enable/disable certain settings.

Hardware:

1. Building the arm

   • The full list of parts needed to assemble the arm can be found in the B.O.M.
   • Files for 3D printing can be found on HowToMechatronics with assembly instructions

2. Electrical wiring

   

---

Demos

A MiniArmClient class is included to make it easy to communicate and send commands to the Mini Arm. As an example, we can send a help command to give us a list of available commands.

from mini_arm import MiniArmClient
client = MiniArmClient(port='COM3', baudrate=9600, verbose=True) # Windows port example, use '/dev/ttyACM0' for Linux
client.send('help')

The output should return all the supported commands with their descriptions:

================================= List of commands =============================================
 movemotor   |  MOTOR VALUE     | // Moves motor A to absolute position B (deg)
 movemotors  |  VALUES          | // Moves motors absolute position B (deg) assimung VALUES is a list
 info        |                  | // Prints info about robot system (motors, grippers, and sensors)
 set_gripper |  VALUE, STRING   | // Gripper command to set the state (open/close) or position
 set_pose    |  VALUES          | // Updates the end effector pose to an absolute cartesian coordinate pose. Pass a list of values (ex: [X,Y,Z] or [X,Y,Z,R,P,Y])
 get_pose    |                  | // Returns the current position and orientation of the robot end effector
 set_joints  |  (DISABLED)      | // Updates the robot joint state. Pass a list of values (ex: [0,0,0,0,0,0])
 get_joints  |                  | // Returns the current robot joint state
 set_led     |  VALUES          | // Set the RGB LED to a specific color using 0-255 values in a 3-element list
 set_delta   |  VALUES          | // Updates the end effector pose with a delta movement relative to the robot's current pose. Pass a list of values (ex: [X,Y,Z] or [X,Y,Z,R,P,Y])
 posture     |  (DISABLED)      | // Updates the end effector pose with a Cartesian displacement relative to the robot's origin. Pass a list of values (ex: [X,Y,Z] or [X,Y,Z,R,P,Y])
 controller  |  (DISABLED)      | // Controller-specific message as a long ascii string with buttons and joystick data that gets converted into a delta position. Check 'xbox_utils' for message type details
 help        |                  | // Display available commands
 play_music  |  STRING          | // Play a music file 
 debug       |  STRING          | // Pass 'on' or 'off' to enable or disable the verbose output
 set_rate    |  VALUE           | // Update the main loop rate (Hz)
 trajectory  |  STRING [REPEAT] | // Perform a specified trajectory (e.g. 'circle') with optional repeat argument (true/false)
 stop        |                  | // Stop ongoing traetories
 fsr         |                  | // Read the sensor values from the FSRs
 home        |                  | // Set the robot to its home position
 test        |                  | // Test command to verify output from device
 ================================================================================================

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Xbox Teleop

When the arm first turns on, the LED will change to green to indicate successful connection to the network. A blue light indicates a successful connection to the server with a client. Open the xbox-client.py file and set COMM_TYPE to the same type set for Mini Arm in the settings.toml file. Plug in a controller, open a terminal in the directory containing the xbox-client.py file, then run the python file:

python xbox-client.py

Face Detection

TBD

Tests

A variefy of test scripts have been created to validate functionality of a variety of components. These tests can be found in the tests folder, although they are somewhat unorganized...

Multimodal agentic AI Integration

TBD

AJ GUI

Robot control cana also be done through the Unity version of the "AJ" GUI v1 (Link coming soon), or an SSH terminal to the robot. FOR TCP/IP, quickest way using a python terminal:

ROS2 Robot Visualizer

The Mini Arm can be visualized in RViz2 using the included ROS2 packages. Refer to the build instructions for more information.

Feel free to reach out to me in case of any issues.
If you find this repo useful in any way please do star ⭐️ it so that others can reap it's benefits as well!

Acknowledgements

This project is inspired from the work done by:

• Alberto Abarzua
• Mithi Sevilla
• Zenetio
• Ohara124c41.
• NitishPuri

License

Copyright 2022-2023 Jonathan Shulgach

This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, you can obtain one at https://mozilla.org/MPL/2.0/.