International Business Machines Corporation

Other

Alps Electric Co., Ltd.

Quantum Corporation

True Position Magnetics, Inc.

Richard K Oswald

Ronald A Smith

Ronald R Moon

Michael G Machado

Avraham Perahia

K C Odencrantz

Donald W Dahlin

Kenny Wong

Louis Hlousek

Philip M Scheinert

Saied Motaei

Paul W Siggins

Magnetic field position transducer for two or more dimensions

An apparatus and method for rotating an optical element, such as a diffraction grating or mirror, utilizes a moving coil actuator and an optical encoder to provide precise element position control. The moving coil actuator, which is coupled to the optical element, is comprised of a coil immersed in a magnetic field created by a pair of magnets. Current flowing in the coil windings causes the coil, and ultimately the optical element, to rotate. An optical encoder monitors the rotation of the element and provides rotation signals representative of the instantaneous element position to an actuator control circuit. The actuator control circuit phase shifts the rotation signals and compares the phase shifted rotation signals to a desired reference signal to generate position and velocity error signals. In a track follow mode, the position error signal is applied to the moving coil actuator via a loop compensator. When the apparatus is operating in an optimal seek mode, a trajectory generator receives the velocity error signals and generates an optimum velocity signal based on a preprogrammed velocity curve. The optimum velocity signal is then applied to the moving coil actuator via the loop compensator.

Apparatus and method for rotating an optical element using a moving coil

A disk file subsystem is disclosed which utilizes a track address decoding circuit which converts the track address which is recorded on the magnetic media in Gray code according to a 1/6 (2,8) run-length-limited recording code to its corresponding binary track address.

Track address detecting means by HDD sector servo method

A digital-analog driver circuit for a plural-phase brushless D.C. motor includes a logic circuit responsive to commutation control signals for generating commutation gating signals, a digital function generation circuit responsive to a commutation signal supplied by the logic circuit and further responsive to a high frequency clocking signal, for generating a pulse width modulated digital function signal having a base period of the high frequency clocking signal and a timed interval synchronized to the commutation signal and for supplying the digital function signal to the logic circuit, the logic circuit including a function signal inversion circuit for generating an inverted digital function signal, and having a gating circuit for selectively putting out the digital function signal and the inverted digital function signal in synchronism with the commutation signal, plural digital to analog converters each for converting the digital function signal and the inverted digital function signal into an analog phase driving signal, and plural phase transistor drivers each being responsive to a said analog phase driving signal, for applying a driving current to a phase winding of the brushless D.C. motor.

Digital-analog driver for brushless D.C. spindle motor

This invention is directed to a system for generating clock signals from a source signal having two harmonically related and phase coherent frequencies such as shown in U.S. Pat. No. 3,534,344 (Santana) and U.S. Pat. No. 3,879,753 (Dunn). The clock system employs a pair of synchronous demodulators for generating a phase error signal to control a voltage controlled oscillator (VCO). The source signal is applied to a pair of synchronous demodulators, each of which is supplied with a different carrier frequency. The output of each demodulator represents the area of the signal being demodulated. The output of each demodulator is zero and a null condition exists when the system is in a phase locked condition. At a non-locked condition, the output of one demodulator has multiple null points. The function of the second demodulator is to resolve the ambiguity between the desired and undesired null points. Carrier signals are generated under control of the VCO by dividing the output of the VCO signal to obtain carrier signals having the appropriate relationship to the source signal.

Clocking system for servo signal having two or more harmonically related

A positioning system for moving a member between positions in time optimal fashion employs concurrent 'feedforward' and 'feedback' control. The feedforward control system provides major control and the feedback control system provides minor control to correct for deviations between the actual and a nominal system. The feedback loop may thus be of low bandwidth permitting desensitization to high frequency disturbances or the employment of inherently low bandwidth controlled variables. The 'feedforward' control function includes successive portions of opposite polarity corresponding to acceleration and deceleration of the member and also includes a subtractive velocity related component. This function represents the approximate current input to an electromagnetic coil actuator of a nominal system required to move such a member between positions in time optimal fashion.

Positioning system employing feedforward and feedback control

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San Jose, CA, United States of America

Richard K Oswald