Low-Cost Robotic Actuator

Project Goals

The goal of this project is to develop a 6-axis arm using hobby-grade equipment, with industry-grade design principles.

In principle, the design targets low-cost BLDC motors with Field-Oriented Control (FOC), drivers, and encoders, back-driveable cycloidal reducers, and 3D printable components.

Out of practicality, I am prioritising the lowest cost of hardware, then I will attempt to assess how good (or bad) we can make a robot arm using these components.

Regardless, this is intended as a learning exercise for my spare time, and should be a good project to get me up to speed at a practical level quite quickly.

Progress

This project is currently on hold while I establish myself in Zürich and purchase in some electronics equipment.

For a bit of fun, I threw the current 19:1 gearbox reducer model I developed in FreeCAD into my CAD-Blender rendering pipeline to get this result.

Development Log

Mechanical Development

1. [COMPLETE] Develop a back-driveable, 3D-printed gearbox proof of concept.

• Cycloidal drive selected for promising backlash/precision capabilities in 3D prints.
• 19:1 cycloidal gearbox designed in FreeCAD.
• Reducer design printed and tested as a standalone unit. Passes back-driveability requirement.

2. [IN PROGRESS] Gearbox Optimization & Testing

• Optimise cycloid geometry parameters for strength, smoothness, backlash, and friction.

3. [PENDING] Integrate and Test with Electronic Hardware

• Design mountings for electronics hardware.
• Evaluate precision, repeatability with motors at different loads.

4. [IN PROGRESS] Develop modular drive unit, and variants for different joints.

• Develop a design for a modular joint-linkage system for ease of development.

Control and Drive Development

1. [COMPLETE] Specify and Purchase BLDC Motors and Control Hardware

• 4010, and 2208 BLDC motors purchased (Cheapest motors on AliExpress)
• MKS Dual FOC v3.2, ESP32 based controllers purchased (Cheapest control hardware on AliExpress)
• 12-bit AS5048 and another type of 14-bit encoder purchased.

1. [IN PROGRESS] Evaluate Motor and Control Hardware

• Motors, drivers and encoders running
• Further testing of FOC algorithms required - yet to get smooth motion out of the current setup.
• Progress waiting on purchasing a benchtop power supply.

Software Development

1. [PENDING] Select control system software stacks.

2. [PENDING] Attempt to implement inverse kinematics from scratch in Python as learning exercise.