Improving playability of Blu-ray disc drives by using adaptive suppression of repetitive disturbances

This paper deals with the problem of adaptive suppression of disturbances on Blu-ray disc drives servo-mechanisms. The proposed methodology is intended for enhancing playability of low quality media at higher rotational speeds. One of the main problems in controlling an optical disc drive concerns the control of the radial lens position which assures the disc playback. However, due to the rotary nature of the Blu-ray disc the most important sources of disturbances concern those that present periodic behaviour. The frequency of such disturbances is proportional to the disc speed and inversely depends on the radial lens position, making more difficult the task of the tracking-controller when a high speed playback is required. Here, a new parametric adaptation algorithm is proposed to reject the main narrow-band disturbances without increasing the controller bandwidth. The proposed scheme makes use of the internal model principle and the Youla–Kucera parameterization. The parametric adaptation algorithm together with the robust stability and performance analysis are part of the main contribution of this paper. An experimental-data study illustrates the behaviour of the high speed tracking control.