Design of a High-Resolution Instantaneous Torque Sensor Based on the Double-Eccentric Modulation Principle

Abstract

A novel non-contact instantaneous torque sensor is proposed in this paper. The mechanical structure of the torque sensor mainly consists of two eccentric sleeves rotating about an elastic shaft. The measurement of torque is transformed into the measurement of the phase difference between the eccentric sleeves. Eddy current sensors are used to measure distance changes between their probes and the eccentric sleeves. The phase is modulated by the distance changes when any torque applied to the elastic shaft the demodulation principle of the phase relies on solving simple trigonometric functions without any complex signal processing methods. Therefore, the acquisition of torque can be performed instantaneously without any accumulation of time or integer-period sampling. The proposed sensor has a simple structure with no electrical components within the rotational parts. Additionally, the proposed sensor facilitates the measurement of static torque, dynamic torque, and even reciprocating torque over a wide range of angular speeds. The sensor was calibrated by a torsion-testing setup and experimental results indicate that the sensitivity of the sensor is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${23.05N\centerdot }{m}/ ^\circ $ </tex-math></inline-formula> , the sum of squares due to error is 0.09449, and the root-mean-squared error is 0.1375. The non-linearity is 0.914%. The proposed sensor accuracy is 0.06%.