Disturbance Compensation for Safe Kinematic Control of Robotic Systems with Closed Architecture

TL;DR

This paper presents a robust disturbance compensation method for safe and precise kinematic control of industrial robots with closed inner-loop controllers, combining disturbance rejection and control barrier functions.

Contribution

It introduces an easily integrated outer-loop add-on that enhances robustness and safety without modifying the inner-loop controller, validated through theoretical analysis and hardware experiments.

Findings

Superior tracking accuracy demonstrated on a PUMA robot

Enhanced safety guarantees via formal proof

Robust performance under uncertain inner-loop dynamics

Abstract

In commercial robotic systems, it is common to encounter a closed inner-loop torque controller that is not user-modifiable. However, the outer-loop controller, which sends kinematic commands such as position or velocity for the inner-loop controller to track, is typically exposed to users. In this work, we focus on the development of an easily integrated add-on at the outer-loop layer by combining disturbance rejection control and robust control barrier function for high-performance tracking and safe control of the whole dynamic system of an industrial manipulator. This is particularly beneficial when 1) the inner-loop controller is imperfect, unmodifiable, and uncertain; and 2) the dynamic model exhibits significant uncertainty. Stability analysis, formal safety guarantee proof, and hardware experiments with a PUMA robotic manipulator are presented. Our solution demonstrates superior performance in terms of simplicity of implementation, robustness, tracking precision, and safety compared to the state of the art. Video: https://youtu.be/zw1tanvrV8Q