Modeling and Control of a DC Motor Coupled to a Non-Rigid Joint

Vítor Pinto,Paulo Costa,José Gonçalves

doi:10.3390/asi3020024

Abstract

Throughout this paper, the model, its parameter estimation and a controller for a solution using a DC motor with a gearbox worm, coupled to a non-rigid joint, will be presented. First, the modeling of a non-linear system based on a DC Motor with Worm Gearbox coupled to a non-rigid joint is presented. The full system was modeled based on the modeling of two sub-systems that compose it—a non-rigid joint configuration and the DC motor with the worm gearbox configuration. Despite the subsystems are interdependent, its modelling can be performed independently trough a carefully chosen set of experiments. Modeling accurately the system is crucial in order to simulate and know the expected performance. The estimation process and the proposed experimental setup are presented. This setup collects data from an absolute encoder, a load cell, voltage and current sensors. The data obtained from these sensors is presented and used to obtaining some physical parameters from both systems. Finally, through an optimization process, the remaining parameters are estimated, thus obtaining a realistic model of the complete system. Finally, the controller setup is presented and the results obtained are also presented.

Highlights

DC motors are widely used components as electrical actuators, in cars, trains and driving high power hoisting machines, milling machines, among others
Whether using these to change the angle of a joint of a robotic manipulator, to drive a vehicle’s traction system, or even to rotate the sensor of a LiDAR (Light Detection and Ranging), there are numerous uses for these in robotics. Another example are the legged-robotic vehicles that can be found in [1]. They have a non-linear behavior that results from the fact that they cannot rotate at any supply voltage, always having a minimum rotation torque that prevents rotation until a when a certain voltage is reached, which is commonly denominated by the motor dead zone
Taking into account the above mentioned considerations, the motor model is further described using the equations associated with it. These are present all over the literature associated with DC motors, so no references will be presented to specific publications

Summary

Introduction

DC (direct current) motors are widely used components as electrical actuators, in cars, trains and driving high power hoisting machines, milling machines, among others. The Quasi-Direct Drive is an example of the technology applied to actuate an non-rigid joint, as presented in [10] for a quadruped As it can be understood, all the mentioned research has a same primary step—the modeling phase—applied to mathematically translate the behavior of the system. Robotic systems often include DC motors and having a realistic model is crucial to improve the control performance This is required to be able to design suitable controllers, test them in simulation and obtain relevant results. 2020, 3, 24 essential characteristics of the non-rigid joint developed for this work are not expected to suffer structural changes, the estimation of its dynamic parameters will be carried out with offline techniques, performed through real hardware tests.

Proposed Models

DC Motor and Worm Gearbox Model

Non-Rigid Joint Model

DC Motor with Worm Gearbox

Conclusions and Future Work