Hitachi, Ltd.

Masato Soma

Yoshinori Ishikawa

Yukinobu Tada

Atsushi Okuyama

Dan Aoki

Shinya Imura

Takashi Yoshida

Fujio Tajima

Norihisa Yanagihara

Masamichi Ito

Hidehito Yamada

Yasuhiro Mii

In a control apparatus for operating with program data, it is possible to alter the operation of a control circuit by rewriting the data of the program memory built in an LSI, with ease and at a low cost independently of the operation of the control circuit. For that purpose, the control apparatus includes a ROM, a SRAM, a means for writing data in the SRAM, a selection means for selecting the output from the ROM or the SRAM in accordance with the addresses supplied to the ROM and the SRAM, and a control means for outputting the addresses to the ROM and the SRAM and operating with the output from the selection means as program data.

Control apparatus for selectively operating with program data from two memories and having a system controller supplying program data and address for writing the data to the second memory

An actuator control device is provided for performing some modifications such as making the output of a disturbance observer zero for quickly restoring the proper tracking control if the out-of-track state takes place and if the outside force exceeding the maximum force generated by an actuator is applied to the device itself. In the actuator control device, a disturbance observer estimates disturbance added to the actuator. The second control signal corresponding to the estimated disturbance is added to the first control signal. The added signal is made to be a third control signal. Further, the second control signal is stored in a storage unit. The stored value is further added to the third control signal as the fifth control signal. By performing some modifications such as making the second control signal zero according to the abnormal state, this arrangement makes it possible to quickly restore the proper tracking control even if the out-of-track state takes place.

Actuator control device

Control apparatus and optical disc apparatus using it

A positioning system of an optical disc apparatus includes focus error detecting part for detecting a focus error signal as a focal shift of a light spot related to an information recording surface of an optical disc, light spot moving part in the direction intersecting substantially perpendicularly to the optical disc surface, first digital arithmetic part for receiving the focus error signal and outputting a first control signal, second digital arithmetic part for receiving the focus error signal and a specified third control signal, performing arithmetic operations of a disturbance observer and outputting a second control signal, adding circuit for adding the first control signal and the second control signal and outputting the third control signal, drive circuit for driving the light spot moving part in a direction intersecting perpendicularly to the disc surface by the third control signal, wherein the first and the second digital arithmetic circuit perform arithmetic operations at different sampling periods.

Positioning device for optical disc apparatus

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Yokohama, Japan

Masato Soma