A new digital demodulation of sinusoidal encoder signal for positioning control of spiral servo track writing

Abstract

An adaptive digital demodulation method for a sinusoidal encoder signal is proposed for fast and accurate analysis of spiral servo track writing (SSTW). The proposed methods combine adaptive signal correction and digital interpolation. In addition, digital phase-shifted sinusoid (PSS) interpolation is proposed in order to acquire precise position information. The adaptive signal correction method compensates for a fast-motion non-ideal encoder signal. The digital PSS can be simply implemented and can resolve the switching noise of conventional analog methods. The proposed adaptive digital demodulation scheme can be simply digitalized and can improve the position control in SSTW. From the simulation and experimental results, we have validated the proposed methods, which show noticeable improvement in terms of the Lissajous error and the position error signal.