Dynamic information storage or retrieval – With servo positioning of transducer assembly over track...
Patent
1988-09-26
1990-04-03
Richardson, Robert L.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
360 7809, 360 7804, G11B 2108, G11B 2110, G11B 555
Patent
active
049146440
ABSTRACT:
A disk file digital servo control system utilizes a state estimator wherein the voice coil motor (VCM) current is modeled, rather than measured, thereby eliminating the need for analog-to-digital conversion of the actual VCM current. The VCM current is fed back directly to the input to the power amplifier where it is summed with the control signal output. This effectively changes the integrating power amplifier into a low pass filtering power amplifier, with linear input-output characteristics. Thus, during track following or short seeks, the VCM current is estimated based on this linear model. During long seeks, when the power amplifier is saturated, the VCM current is modeled based upon the known VCM characteristics during saturation, which include the effects of the back electromotive force and the coil current rise time. The microprocessor in the digital servo control system determines which VCM current model to use by a determination of when the power amplifier is in saturation. In the preferred embodiment, the microprocessor determines power amplifier saturation based upon a value of the head velocity error, which is the difference between the commanded velocity and the estimated velocity.
REFERENCES:
patent: 4133011 (1979-01-01), Kurzweil, Jr.
patent: 4297734 (1981-10-01), Laishley et al.
patent: 4412161 (1983-10-01), Cornaby
patent: 4679103 (1987-07-01), Workman
patent: 4835632 (1989-05-01), Shih et al.
Digital Control of Dynamic Systems, Franklin and Powell, Addison-Wesley Publishing Co. (1983), Chapter 6, pp. 131-139.
Chen James C.
Shih Shih-Ming
Yu Mantle M.
Berthold Thomas R.
International Business Machines - Corporation
Richardson Robert L.
Robertson David L.
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