Self-Adapting Variable Impedance Actuator Control for Precision and Dynamic Tasks

TL;DR

This paper presents a sensorless, self-adapting impedance controller for variable impedance actuators that enhances teleoperation performance across precision and dynamic tasks, reducing system complexity and improving safety.

Contribution

The study introduces a novel impedance control law that automatically adapts without additional sensors, enabling effective teleoperation for both precise and dynamic tasks.

Findings

Controller performs comparably to state-of-the-art stiff teleoperation devices for precision tasks.

System offers increased safety and reduced wear during dynamic tasks.

Self-adapting controller simplifies system design and enhances versatility.

Abstract

Variable impedance actuators (VIAs) as tool devices for teleoperation could extend the range of tasks that humans can perform through a teleoperated robot by mimicking the change of upper limb stiffness that humans perform for different tasks, increasing the dynamic range of the robot. This requires appropriate impedance control. Goal of this study is to show the effectiveness of a controller that does not require additional sensors, reducing system complexity and increasing ease of use. The controller should allow to perform precise positioning tasks and dynamic tasks like hammering through teleoperation with a VIA tool device automatically adapting the impedance setting of the VIA. This is achieved by a control law according to the principle "slow-stiff/fast-soft". The controller was tested in a human user study with 24 participants comparing the human-machine performance with the self-adapting controller in a bilateral telemanipulation experiment with two tasks (precision/dynamic) using three impedance settings (high/low/adaptive impedance). The results indicate that the proposed system performs equally well as state of the art stiff teleoperation devices for precision tasks, while having benefits in terms of increased safety and reduced wear for dynamic tasks. This is a step towards teleoperation with a wide dynamic range.