Variable Impedance Control for Floating-Base Supernumerary Robotic Leg in Walking Assistance

TL;DR

This paper introduces a variable impedance control method for a floating-base supernumerary robotic leg, enhancing safety and adaptability in walking assistance by dynamically adjusting impedance to handle disturbances.

Contribution

It proposes a novel hybrid position/force impedance controller with a real-time impedance parameter network for improved disturbance handling in floating-base robotic systems.

Findings

Enhanced stability and disturbance rejection demonstrated in simulations.

Improved human-robot interaction through dynamic impedance adjustment.

Effective shock mitigation and support force control validated experimentally.

Abstract

In human-robot systems, ensuring safety during force control in the presence of both internal and external disturbances is crucial. As a typical loosely coupled floating-base robot system, the supernumerary robotic leg (SRL) system is particularly susceptible to strong internal disturbances. To address the challenge posed by floating base, we investigated the dynamics model of the loosely coupled SRL and designed a hybrid position/force impedance controller to fit dynamic torque input. An efficient variable impedance control (VIC) method is developed to enhance human-robot interaction, particularly in scenarios involving external force disturbances. By dynamically adjusting impedance parameters, VIC improves the dynamic switching between rigidity and flexibility, so that it can adapt to unknown environmental disturbances in different states. An efficient real-time stability guaranteed impedance parameters generating network is specifically designed for the proposed SRL, to achieve shock mitigation and high rigidity supporting. Simulations and experiments validate the system's effectiveness, demonstrating its ability to maintain smooth signal transitions in flexible states while providing strong support forces in rigid states. This approach provides a practical solution for accommodating individual gait variations in interaction, and significantly advances the safety and adaptability of human-robot systems.