A Novel Proximity Sensor Based on Parallel Plate Capacitance

The proximity sensor plays an important role in recognition, positioning, tracking, and avoiding of obstacles in robot movement. The existing proximity sensors cannot identify the direction and measure the distance of the approaching object simultaneously. In order to solve mentioned problem, this paper presents a novel proximity sensor based on parallel plate capacitance. The proposed proximity sensor adopts the structure wherein driving electrode and sensing electrodes are located on the same plane. The number of driving electrodes differs from the number of sensing electrodes, and sensing electrodes are symmetrically distributed around the driving electrode. In this paper, we developed the circuit model of the proximity sensor based on parallel plate capacitance, and analyzed the influence of the guard ring on sensor sensitivity. We also designed a new sensor structure, which employs four sensing electrodes to identify direction of the approaching object. In addition, the proximity sensor performances in terms of direction identification were verified by experiments, and both sensing errors and sensor repeatability were calculated. The experimental results have shown that proposed proximity sensor can distinguish four different directions and measure the object distance in the range of 1 ~ 40 mm simultaneously. The sensing errors were less than 5% and the repeatability error was 1.05%.