A Low-Cost Rotary Optical Potentiometer Mechanism Based on Optoelectronics Technique

A novel low-cost high-precision absolute rotary angle-sensing mechanism using optoelectronic components is proposed. Its working principle is based on the change of the optical power reflected off the monotone-colored pattern track from a red light emitting diode (LED) to a red-green-blue (RGB) sensor. The main advantages of this low-cost sensor are its simplicity, high resolution, and non-contacting structure. The propagation mechanism for the output voltage of the RGB sensor from a red LED source is formulated analytically. The stationary rectangular-window mask between the cylindrical black-colored V-shape track and the RGB sensor is also employed to linearize the received optical power with circular beam pattern. The effect from the black-and-white laser-printer resolution is studied with various reference angles using a high-precision potentiometer. The performance of the proposed optical rotary potentiometer mechanism is demonstrated using a rotary position-control test bed. The bandwidth (BW) of 4.42 kHz, resolution of 0.167°, and nonlinearity of 2.8% are achieved.