Showing papers by "M Maarten Steinbuch published in 1995"

Adaptive repetitive control of a compact disc mechanism

Abstract: Radial track following of a compact disc player servo mechanism is severely exposed to periodic disturbances, induced by the eccentric rotation of the disc. The period of this disturbance is not available for measurement and varies slowly in time. Periodic disturbances can be adequately attenuated using the concept of repetitive control, provided the period is known. To deal with time varying periodic disturbances, a repetitive controller is tuned based on a simple though inaccurate physical model of the time varying character of the period. The model is tuned based on an estimate of the period, obtained through recursive identification. Experimental results show that the proposed scheme enables a significant improvement of the tracking accuracy of the radial servo mechanism.

Filter, repetitive control system and learning control system both provided with such filter

Abstract: Repetitive control systems and learning control systems using filters composed of delay circuits and having parameters resulting in a very high loop gain for only specific frequencies. The result of this is a substantial reduction of periodic disturbances with frequencies corresponding to the specific frequencies. The parameters of the filters are selected such that the robustness for frequency-variations in the periodic disturbances is improved.

Robust control of a compact disc mechanism

Abstract: A compact disc (CD) player is an optical decoding device that reproduces high-quality audio from a digitally coded signal recorded as a spiral-shaped track on a reflective disc. Apart from the audio application, other optical data systems (CD-ROM, optical data drive) and combined audio/video applications (CD-interactive, CD-video) have emerged. An important research area for these applications is the possibility of increasing the rotational frequency of the disc to obtain faster data readout and shorter access time. For higher rotational speeds, however, a higher servo bandwidth is required that approaches the res onance frequencies of bending and torsional modes of the CD mechanism. Moreover, the system behavior varies from player to player because of manufacturing tolerances of CD players in mass production, which explains the need for robustness of the controller. Further, an increasing percentage of all CD-based applications is for portable use. Thus, additionally, power consumption and shock sensitivity play a decisive role in the performance assessment of controller design for CD systems. In this chapter we concentrate on the possible improvements of both the track-following and focusing behavior of a CD player, using robust control design techniques.

Control system for a process that exhibits periodic disturbances

Abstract: In a control system a characteristic quantity of a process (1) exhibits a periodic disturbance. A measuring system (2) generates a measuring signal (Vm) which represents the characteristic quantity. A control device controls the process in response to the measuring signal (Vm). To reduce the periodic disturbance, the control device (3) comprises a delay circuit (4) which delays an input signal (Vin) related to the measuring signal (Vm) by a time interval (T) having the length of a period (Tp) of the periodic disturbance. The control device (3) comprises an analysis circuit (6) for deriving an analysis signal (Va) which is indicative of a deviation between the period of the periodic disturbance and the delay time. By means of a control circuit (13) and an adapter circuit (7), the delay time (T) is set in dependence on the analysis signal (Va) to a value for which the analysis signal (Va) indicates that the delay time (T) is equal to the period (Tp). A correlation system can be used for deriving the analysis signal (Va).

Recording and/or reproducing apparatus including a servo control loop

Abstract: A recording and/or reproducing apparatus for recording/reproducing an information signal in a track on a longitudinal record carrier (2), comprises reel driving means including a motor (11) for driving a reel (9) to rotate to effect a feeding operation of the record carrier in its longitudinal direction. Record carrier speed detection means (20, 21, 56) are present for generating a first detection signal in relation to the speed of the record carrier during said feeding operation. Second detection means (18, 60) are present, adapted to generate a second detection signal having a relation to the radius of the amount of record carrier being wound on said reel. Further, signal combination means (58, 64) are present for combining said first and second detection signal and a predetermined signal which is representative of a predetermined speed of the record carrier so as to obtain a servo control signal, such that the feeding speed of the record carrier may be equal to the predetermined speed. The signal combination means are adapted to generate said servo control signal such that it is equivalent to calculating a deviation between said predetermined signal and said first detection signal, and non-linearly combining said deviation with said second detection signal.

Control system and control means for controlling a quantity of such a control system

Abstract: In a control system a characteristic quantity of a process (1) exhibits a periodic disturbance. A measuring system (2) generates a measuring signal (Vm) which represents the characteristic quantity. A control device controls the process in response to the measuring signal (Vm). To reduce the periodic disturbance, the control device (3) comprises a delay circuit (4) which delays an input signal (Vin) related to the measuring signal (Vm) by a time interval (T) having the length of a period (Tp) of the periodic disturbance. The control device (3) comprises an analysis circuit (6) for deriving an analysis signal (Va) which is indicative of a deviation between the period of the periodic disturbance and the delay time. By means of a control circuit (13) and an adapter circuit (7), the delay time (T) is set in dependence on the analysis signal (Va) to a value for which the analysis signal (Va) indicates that the delay time (T) is equal to the period (Tp). A correlation system can be used for deriving the analysis signal (Va).

Control system and control means to be used in such a control system, and a correlation system

Abstract: In a control system a characteristic quantity of a process (1) exhibits a periodic disturbance. A measuring system (2) generates a measuring signal (Vm) which represents the characteristic quantity. A control device controls the process in response to the measuring signal (Vm). To reduce the periodic disturbance, the control device (3) comprises a delay circuit (4) which delays an input signal (Vin) related to the measuring signal (Vm) by a time interval (T) having the length of a period (Tp) of the periodic disturbance. The control device (3) comprises an analysis circuit (6) for deriving an analysis signal (Va) which is indicative of a deviation between the period of the periodic disturbance and the delay time. By means of a control circuit (13) and an adapter circuit (7), the delay time (T) is set in dependence on the analysis signal (Va) to a value for which the analysis signal (Va) indicates that the delay time (T) is equal to the period (Tp). A correlation system can be used for deriving the analysis signal (Va).