Design of a large-range torque sensor with variable resolutions

Traditional force/torque sensors usually have a constant resolution over the whole range. High resolution and large measuring range cannot be well balanced in the sensor design. To address this problem, this paper presents a design method for a large-range torque sensor with variable resolutions based on the principle of variable stiffness. The sensor is constructed by multiple radial flexures with different stiffness in series. The torque applied on the flexure center is measured by gauging the strains of radial flexures. Thanks to the behaviors of compound motions of the flexural structure, the sensor can therefore provide variable resolutions in the different ranges. A passive eddy current damper is designed to suppress mechanical vibration of the flexural structure induced by external disturbances. Analytical models are established and validated through finite element simulations to evaluate the sensor characteristics. A sensor prototype is finally fabricated and tested to verify the feasibility of the proposed method of changing resolution. Experimental results show that the torque sensor can provide variable resolutions of 0.2948 mN⋅m and 1.6272 mN⋅m in the small and large ranges of [0, 0.19 N⋅m] and [0.19 N⋅m, 2.3 N⋅m], respectively. In addition, the sensor possesses excellent vibration suppression performance even under an external shock applied to it.