Compliance while resisting: A shear-thickening fluid controller for physical human-robot interaction

2024-03-04

Int. J. Robotics Res.

AI Summary

To address insufficient safety of linear controllers under large-impact conditions in physical human–robot interaction (pHRI), this paper proposes shear-thickening fluid control (SFC). We first model the phase-transition dynamics of shear-thickening fluids as a nonlinear impedance control law, unifying passivity, Lyapunov stability, and robust suppression of mid-to-high-frequency strong impacts. Discrete coupled stability conditions and parameter design guidelines are rigorously derived. Through combined frequency-domain and time-domain analysis, alongside experiments on both fixed-base and mobile robotic platforms, SFC demonstrates significantly enhanced impact resilience compared to conventional linear and nonlinear admittance controllers—eliminating self-excited oscillations while simultaneously improving safety and operational compliance in real-world tasks such as water delivery and factory collaboration.

Technology Category

• Intelligent Robots: Human-Robot Interaction
• Natural Language Processing: Safety and Robustness
• Humans and AI: Human-Aware Planning and Behavior Prediction

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Economics, Online Markets and Human Computation: The sharing economy
• Systems and Infrastructure for Web, Mobile and WoT: Web applications in cross-disciplinary domains and verticals such as mixed reality, smart cities, and digital health

Abstract

Physical human-robot interaction (pHRI) is widely needed in many fields, such as industrial manipulation, home services, and medical rehabilitation, and puts higher demands on the safety of robots. Due to the uncertainty of the working environment, the pHRI may receive unexpected impact interference, which affects the safety and smoothness of the task execution. The commonly used linear admittance control (L-AC) can cope well with high-frequency small-amplitude noise, but for medium-frequency high-intensity impact, the effect is not as good. Inspired by the solid-liquid phase change nature of shear-thickening fluid, we propose a shear-thickening fluid control (SFC) that can achieve both an easy human-robot collaboration and resistance to impact interference. The SFC’s stability, passivity, and phase trajectory are analyzed in detail, the frequency and time domain properties are quantified, and parameter constraints in discrete control and coupled stability conditions are provided. We conducted simulations to compare the frequency and time domain characteristics of L-AC, nonlinear admittance controller (N-AC), and SFC and validated their dynamic properties. In real-world experiments, we compared the performance of L-AC, N-AC, and SFC in both fixed and mobile manipulators. L-AC exhibits weak resistance to impact. N-AC can resist moderate impacts but not high-intensity ones and may exhibit self-excited oscillations. In contrast, SFC demonstrated superior impact resistance and maintained stable collaboration, enhancing comfort in cooperative water delivery tasks. Additionally, a case study was conducted in a factory setting, further affirming the SFC’s capability in facilitating human-robot collaborative manipulation and underscoring its potential in industrial applications.

Problem

• Human-Robot Interaction
• Impact Mitigation
• Linear Control Limitations

Innovation

• Shear Thickening Fluid Control
• Human-Robot Interaction
• Enhanced Safety and Stability