Method and apparatus to compensate for servo wedge rotational offset after a head switch
AssigneeWestern Digital Corporation
InventorsRichard W. Hull, David B. Joan, Charles R. Patton, III, Vafa James Rakshani, Charles W. Simmons
Life of this patent
Estimating the term…
Abstract
A disk drive controller having a microprocessor and a sampled signal head positioning system measures and stores the relative rotational offsets between heads arranged in a stacked relationship and respective servo wedges on different disk surfaces. The offsets are stored in a table and subsequently applied to a servo wedge detection circuit to ensure that a next sequential wedge is detected after a head switch.
Claims16
A disk drive having a sampled signal head positioning servo system, first and second rotating recording surfaces wherein each recording surface has multiple sequentially-active equally spaced-apart servo wedges, first and second heads mounted in a stacked arrangement and disposed over the first and second recording surfaces respectively, and including a processor for controlling disk operations, the disk drive further comprising:
- the first head having a first position over a first servo wedge;
- the second head having a second position over a second servo wedge;
- a means for providing a value representing a rotational offset between the first position and the second position;
- a means for detecting a servo wedge including a timing means programmable by the processor, to establish a window for reading the servo wedge;
- and
- after a head switch from the first head to the second head the processor applying the rotational offset value to the timing means to establish a window for reading a servo wedge on the second recording surface.
In a disk drive having a sampled signal servo system, first and second recording surfaces, and first and second heads disposed in a stacked arrangement over the recording surfaces, a method for determining a rotational offset between the first and second heads and respective servo wedges on the first recording and second recording surfaces, the method comprising the steps of:
- a) detecting a servo wedge on the first surface using a servo wedge timing mode;
- b) setting a timer to start when the first surface servo wedge is detected;
- c) performing a head switch to the second surface;
- d) detecting a next respective servo wedge on the second surface using a servo wedge timing mode;
- e) stopping the timer when the second surface wedge is detected;
- f) storing the timer value;
- and
- g) converting the timer value to a rotational offset value.
A disk drive having a sampled signal head positioning servo system, first and second rotating recording surfaces wherein each recording surface has multiple sequentially-active equally spaced-apart servo wedges on the corresponding recording surface, first and second heads mounted in a stacked arrangement and disposed over the first and second recording surfaces respectively, the first head having a first position over a first servo wedge, the second head having a second position over a second servo wedge, and including a processor for controlling disk operations, the disk drive further comprising:
- a circuit to measure and store a rotational offset between the first position and the second position;
- and
- a circuit to read the servo wedge after a head switch from the first head to the second head in which the processor applies the measured and stored rotational offset value corresponding to the first position and the second position in order to establish a window for reading a servo wedge on the second recording surface.
In a disk drive having a sampled signal servo system, first and second recording surfaces, and first and second heads disposed in a stacked arrangement over the recording surfaces, a method for determining a rotational offset between the first and second heads and respective servo wedges on the first recording and second recording surfaces, the method comprising:
- detecting a servo wedge on the first surface;
- performing a head switch to the second surface;
- detecting a next respective servo wedge on the second surface;
- generating a rotational positional offset from the detection of the servo wedge on the first surface and the detection of the servo wedge on the second surface;
- and
- storing the rotational positional offset for subsequent use during head switches when reading the first and second surfaces.
Dependencies are inferred from the claim text.