Fine tracking control system based on double feedforward tracking control considering time delay for optical disc

Abstract

This paper compares performance of a double feedforward control system that considers for time delay. Recently, digital content size continues to increase. In order to cope, manufacturers of digital storage media try to increase capacity by narrowing the track pitch of these digital storage media. This digital controller designs and implements in a Field-Programmable Gate Array (FPGA). However, the control system includes non-integer the time delay. The time delay element exists in its characteristic polynomial. Therefore, the system is possibly destabilized by time delay. In the feedforward system, the feedforward compensation value is delayed by time delay. Considering these factors, a high-precision pickup control system that considering time delay is needed for optical discs. This paper proposes a new double feedforward control system considering time delay. In this paper, the tracking performance of the control system is compared to the conventional feedback control system and the new error based communication disturbance observer. In optical disc systems, the proposed double feedforward control system considering time delay has a good performance.