Passive Variable Impedance For Shared Control

2026-04-22

AI Summary

This work addresses the loss of passivity in shared control systems arising from time-varying stiffness impedance control and multi-objective torque arbitration. To resolve this issue, the paper proposes a unified framework that co-designs time-varying stiffness impedance control with a weighted fusion of multiple controller torques, ensuring closed-loop passivity through a passivity-based system reconfiguration. The approach imposes no restrictions on the stiffness matrix or arbitration weights and accommodates time-varying matrices with non-diagonal elements, thereby providing, for the first time, a systematic guarantee of passivity stability for such systems. Simulations and multi-platform experiments demonstrate the effectiveness of the proposed method in achieving stable and flexible shared control.

Technology Category

• Intelligent Robots: Behavior Learning & Control
• Multiagent Systems: Agreement, Argumentation & Negotiation
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Novel mobile and WoT systems, and system-of-systems
• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Economics, Online Markets and Human Computation: The sharing economy

Abstract

Shared Control methods often use impedance control to track target poses in a robotic manipulator. The guidance behavior of such controllers is shaped by the used stiffness gains, which can be varying over time to achieve an adaptive guiding. When multiple target poses are tracked at the same time with varying importance, the corresponding output wrenches have to be arbitrated with weightings changing over time. In this work, we study the stabilization of both variable stiffness in impedance control as well as the arbitration of different controllers through a scaled addition of their output wrenches, reformulating both into a holistic framework. We identify passivity violations in the closed loop system and provide methods to passivate the system. The resulting approach can be used to stabilize standard impedance controllers, allowing for the development of novel and flexible shared control methods. We do not constrain the design of stiffness matrices or arbitration factors; both can be matrix-valued including off-diagonal elements and change arbitrarily over time. The proposed methods are furthermore validated in simulation as well as in real robot experiments on different systems, proving their effectiveness and showcasing different behaviors which can be utilized depending on the requirements of the shared control approach.

Problem

• Shared Control
• Variable Impedance
• Passivity
• Impedance Control
• Wrench Arbitration

Innovation

• variable impedance control
• shared control
• passivity
• wrench arbitration
• adaptive stiffness