Ultra precise position estimation of servomotor using analog quadrature encoders

This paper describes the ultra precise position estimation of a servomotor using a sinusoidal encoder based on Arcsine Interpolation Method for the cost reduction of circuit design. The amplitude and offset errors of the sinusoidal encoder output signals, from encoder itself and analog signal processing procedures, are effectively compensated and on-line tuned by utilizing a low cost programmable differential amplifier without any special expensive equipments. To theoretically evaluate the practical resolution of this system, the relationship between the amplitude of ADC input signal errors and the anticipated resolution is also dealt with. The performance of the proposed method is verified by comparing it with speed control characteristics of the servomotor driving system using a digital incremental 50,000ppr encoder in the experiments.