This paper presents a new rotary position-control system using a color sensor. The angle sensing mechanism is based on the working principle of a red-green-blue (RGB) sensor that measures the radiant-intensity variation of the light reflected on the color surface. The optical-power propagation mechanism from a light-emitting diode (LED) source to the RGB sensor’s voltage is investigated using the light reflected on the designated-RGB codes of the cylindrical color-track surface. The nonlinearity due to a color printer and a paper roughness is compensated for through iterative comparisons with the reference angle achieved from a precision potentiometer. The performance of this new absolute angle sensor is validated using a rotary mechanical system with a cylindrical inertia controlled by a lead compensator. The stability of the positioning system is also investigated with the frequency response. Eventually, the feasibility of this new rotary angle sensor with the cost-effective and non-contact sensing mechanism is demonstrated.

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