A Novel 6-axis Force/Torque Sensor Using Inductance Sensors

2025-05-14

AI Summary

Traditional strain-based six-axis force/torque (F/T) sensors suffer from contact-dependent measurement, reliance on external amplifiers and data acquisition (DAQ) systems, and inherent trade-offs between compactness and high accuracy. To address these limitations, this paper proposes a fully integrated, contactless inductive F/T sensor. Force information is acquired via displacement sensing of a conductive target, while a CAN-FD signal processing module is embedded directly onto the PCB, enabling 4 kHz high-speed sampling and on-chip closed-loop processing. We introduce a novel rational function modeling approach to significantly enhance system linearity and calibration accuracy. The sensor achieves crosstalk < 0.5%, force resolution of 0.03 N, and over 55,000 quantization levels. Static evaluation shows superior RMSE and R² compared to state-of-the-art nonlinear models. Overall performance exceeds that of commercial counterparts, fulfilling the stringent requirements of precision robotics for high-accuracy, miniaturized, and minimally intrusive integrated sensing.

Technology Category

• Intelligent Robots: Multimodal Perception & Sensor Fusion
• Application Domains: Internet of Things, Sensor Networks & Smart Cities
• Machine Learning: Calibration & Uncertainty Quantification

Application Category

• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Semantics and Knowledge: Methods, algorithms and applications for the development of semantic models, knowledge graphs and other forms of structured data models with machine-interpretable semantics

Abstract

This paper presents a novel six-axis force/torque (F/T) sensor based on inductive sensing technology. Unlike conventional strain gauge-based sensors that require direct contact and external amplification, the proposed sensor utilizes non-contact inductive measurements to estimate force via displacement of a conductive target. A compact, fully integrated architecture is achieved by incorporating a CAN-FD based signal processing module directly onto the PCB, enabling high-speed data acquisition at up to 4~kHz without external DAQ systems. The sensing mechanism is modeled and calibrated through a rational function fitting approach, which demonstrated superior performance in terms of root mean square error (RMSE), coefficient of determination ($R^2$), and linearity error compared to other nonlinear models. Static and repeatability experiments validate the sensor's accuracy, achieving a resolution of 0.03~N and quantization levels exceeding 55,000 steps, surpassing that of commercial sensors. The sensor also exhibits low crosstalk, high sensitivity, and robust noise characteristics. Its performance and structure make it suitable for precision robotic applications, especially in scenarios where compactness, non-contact operation, and integrated processing are essential.

Problem

• Develops a 6-axis force/torque sensor using non-contact inductive sensing
• Integrates CAN-FD module for compact high-speed data acquisition
• Achieves high accuracy and resolution for precision robotic applications

Innovation

• Non-contact inductive force sensing via displacement
• Integrated CAN-FD module for high-speed data
• Rational function fitting for superior calibration