Contactless Torque/Speed Sensing Module with Digital Signal Processing Circuit

Abstract

A contactless torque/speed sensing module with digital signal processing circuit is designed and studied. To enhance more sensitivity with respect to the exerted torque, the cross-section of the mechanical structure is designed to be orange-slice-like and two links are connected to the both sides of the flexible orange-slice-like body. To realize this novel torque sensor applied to high-speed shafts, a couple of photo interrupters are equipped. In addition, there are numerous reflective strips attached to the links to cooperate with photo interrupters. Once the flexible body is deformed by an external torque, a relative angle between the two links is induced. Therefore, the two pulses sequences, out of the two corresponding photo detectors, would present a certain degree of time delay. By conversion of this time delay between the two pulse sequences, the exerted torque can be quantified. A set of digital signal processing circuit, which mainly consists of counter ICs, is incorporated to convert the time delay and time period (i.e., inverse of the shaft speed) into digital data in terms of torque and rotational speed of shaft so that almost no signal interference is involved. One of merits of the proposed torque sensor is: real-time measurement on torque applied becomes feasible even if the shaft is rotating at high speed. Another advantage of the fully-digital signal processing circuit is: no need to conduct A/D conversion and free of noise, cross-talk and EMI.