Performance Enhancement of Capacitive-type Torque Sensor by using Resonant Circuit

This paper proposes a method for improving the resolution of a capacitive-type (C-type) torque sensor. This method amplifies the output signal variation of a capacitance-to-digital (CDC) chip by designing a series resonant circuit. This study considers the data sampling method of the CDC chip and the effects of the resonant circuit on the output signal. The CDC chip employs a switched-capacitor (SC) integrator for data sampling. The SC integrator was simulated to estimate the amplification of the output signal by the resonant circuit. The inductance and resistance of the resonant circuit are designed to optimize the sensor performance. As the SC integrator is commonly used in CDC chips, the proposed method is adaptable to a majority of existing C-type sensors. When fabricating the sensor, it is important to obtain the designed capacitance for implementing the resonant circuit. We design printed circuit board structures that can accurately obtain the designed gap between sensor electrodes and the ground. Artificial neural network (ANN) was used for the sensor calibration process. To prove the effectiveness of these methods, the performance of a sensor equipped with the resonant circuit was compared to that of a previously developed sensor.