A Unified Robust Motion Controller Synthesis for Compliant Robots Driven by Series Elastic Actuators

TL;DR

This paper introduces a unified robust motion control approach for compliant robots with Series Elastic Actuators, effectively handling both matched and mismatched disturbances through advanced disturbance estimation and system transformation techniques.

Contribution

It presents a novel controller design using a second-order Disturbance Observer and system transformation to address complex disturbance scenarios in compliant robot control.

Findings

Effective disturbance estimation and compensation demonstrated in simulations

Unified control approach improves robustness for position and force control

System transformation simplifies disturbance handling in compliant robots

Abstract

This paper proposes a unified robust motion controller for the position and force control problems of compliant robot manipulators driven by Series Elastic Actuators (SEAs). It is shown that the dynamic model of the compliant robot includes not only matched but also mismatched disturbances that act on the system through a different channel from the control input. To tackle this complex robust control problem, the unified robust motion controller is synthesised by employing a second-order Disturbance Observer (DOb), which allows us to estimate not only disturbances but also their first and second order derivatives, and a novel controller design approach in state space. By using the Brunovsky canonical form transformation and the estimations of disturbances and their first and second order derivatives, the dynamic model of the robot is reconstructed so that a new system model that includes only matched disturbances is obtained for compliant robots driven by SEAs. The robust position and force controllers are simply designed by eliminating the matched disturbances of the reconstructed system model via the conventional DOb-based robust control method. The stability and performance of the proposed robust motion controllers are verified by simulations.