A Stability Analysis for the Acceleration-based Robust Position Control of Robot Manipulators via Disturbance Observer

TL;DR

This paper introduces a nonlinear stability analysis for acceleration-based robust position control of robot manipulators using Disturbance Observer, highlighting how tuning parameters affect stability, robustness, and noise sensitivity.

Contribution

It provides a new theoretical stability analysis and practical insights into tuning disturbance observer parameters for improved robot manipulator control.

Findings

Proper tuning of nominal inertia matrix enhances stability.

Increasing DOb bandwidth reduces position error bounds.

Non-diagonal inertia elements improve stability and robustness.

Abstract

This paper proposes a new nonlinear stability analysis for the acceleration-based robust position control of robot manipulators by using Disturbance Observer (DOb). It is shown that if the nominal inertia matrix is properly tuned in the design of DOb, then the position error asymptotically goes to zero in regulation control and is uniformly ultimately bounded in trajectory tracking control. As the bandwidth of DOb and the nominal inertia matrix are increased, the bound of error shrinks, i.e., the robust stability and performance of the position control system are improved. However, neither the bandwidth of DOb nor the nominal inertia matrix can be freely increased due to practical design constraints, e.g., the robust position controller becomes more noise sensitive when they are increased. The proposed stability analysis provides insights regarding the dynamic behavior of DOb-based robust motion control systems. It is theoretically and experimentally proved that non-diagonal elements of the nominal inertia matrix are useful to improve the stability and adjust the trade-off between the robustness and noise sensitivity. The validity of the proposal is verified by simulation and experimental results.