Design of a Biomimetic BLDC Driven Robotic Arm for Teleoperation & Biomedical Applications

Abstract

For many years, robotics research and development has been held back from the high-power AC motors of industrial automation, locked to low-power, bulky Stepper motors and simple DC Servos. As of a few years ago, Brushless DC motors started seeing use in high-end quadrupedal designs such as Boston Dynamics Cheetah, and Spot. Whilst these used expensive, proprietary control systems that were closed source and out of the reach of many small-scale researchers, developers, and hobbyists, they did demonstrate the potential of a motor-class previously only commonly thought suitable for high-RPM applications like drones and quadcopters. In 2016, an open-source custom driver platform named ODrive was started, which is now in its 3rd iteration. As of 2021, it provides all of the basic hardware and software needed to control 2 closed loop Brushless DC motors per board, using off the shelf encoders and at a reasonable, hobbyist level price point. This technology is, on paper, a huge development for plenty of low-budget robotics research applications. In this project, we design, build, and evaluate a 4 DOF robotic arm using 4 BLDC motors with ODrive control, using 3D printed parts and other components available at a low price point. This arm will be used in the future for testing tele-operative control and so it is designed to be biomimetic, modelled at 2/3 scale with similar proportions and motion capabilities to a real human arm to the elbow. The extremely small, cheap, and lightweight motors selected for this project are shown to output superior speed and torque to stepper motors multiple times their size and weight, albeit at a very significant power draw requirement. The speed and power of a BLDC through a high reduction gearbox allows extremely fast and responsive movement such that it can easily execute complex movements easily in pace with a human arm. Doi: 10.28991/HEF-2021-02-04-03 Full Text: PDF