Contact Sensing via Joint Torque Sensors and a Force/Torque Sensor for Legged Robots

2025-10-12

AI Summary

This work addresses the challenge of detecting and precisely localizing foot-ground contact points for quadrupedal robots. We propose a contact perception method integrating distributed joint strain-based torque sensors with hip-mounted six-axis force/torque sensors. Leveraging a generalized momentum observer framework, our approach achieves real-time estimation of contact forces and positions via multi-sensor fusion, high-accuracy calibration, and a physics-driven estimation strategy that obviates motor current modeling and friction compensation. Key contributions include: (i) the design of low-cost, highly linear distributed strain-based torque sensors; and (ii) a lightweight perception architecture that requires no dynamics modeling or parameter identification. Simulation and experimental results demonstrate a contact force estimation error below 0.2 N, sub-centimeter contact point localization accuracy (mean error: 0.8 cm), and sensor measurement accuracy of 96.4%.

Technology Category

• Intelligent Robots: Multimodal Perception & Sensor Fusion
• Computer Vision: Low Level & Physics-based Vision
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Responsible Web: Human-perceived consequences of algorithmic deployment on the web

Abstract

This paper presents a method for detecting and localizing contact along robot legs using distributed joint torque sensors and a single hip-mounted force-torque (FT) sensor using a generalized momentum-based observer framework. We designed a low-cost strain-gauge-based joint torque sensor that can be installed on every joint to provide direct torque measurements, eliminating the need for complex friction models and providing more accurate torque readings than estimation based on motor current. Simulation studies on a floating-based 2-DoF robot leg verified that the proposed framework accurately recovers contact force and location along the thigh and shin links. Through a calibration procedure, our torque sensor achieved an average 96.4% accuracy relative to ground truth measurements. Building upon the torque sensor, we performed hardware experiments on a 2-DoF manipulator, which showed sub-centimeter contact localization accuracy and force errors below 0.2 N.

Problem

• Detecting and localizing contact along robot legs using joint torque sensors
• Developing low-cost strain-gauge torque sensors for direct torque measurements
• Achieving accurate contact force recovery and localization for legged robots

Innovation

• Joint torque sensors detect contact using momentum observer
• Low-cost strain-gauge sensors eliminate friction modeling needs
• System achieves sub-centimeter contact localization accuracy