Abstract: A system for reducing written-in high-frequency repeatable run-out track mis-registration occurring during writing of servo information onto a hard disk implementable in a hard disk drive is described. The system includes an excitation frequency adjuster enabled to adjust excitation frequencies away from mechanical modes to provide desired rotation speed of a servo track writer. The mechanical modes are present in said hard disk drive. The system also includes an excitation level adjuster enabled to adjust excitation level to provide a desired DC gain level associated with a motor controller of the servo track writer. The system further includes an excitation frequency content adjuster enabled to adjust excitation frequency content to provide desired current profile of the motor controller, such that a reduction of written-in high frequency repeatable run-out track mis-registration is realized.

Abstract: A method for reducing written-in high frequency repeatable run out track mis-registration of a hard disk is described. The method includes adjusting the excitation frequencies away from mechanical modes to provide desired rotating speed of a servo track writer. The mechanical modes are relative to said hard disk drive. The method further includes adjusting excitation levels to provide desired DC gain level associated with a motor controller of the servo track writer, wherein instances of the written-in high frequency repeatable run out track mis-registration are reduced.

Abstract: The position and motion of a rotating element is determined by using a two-grating moire pattern. Movement of the element causes a projected scale image representing radiation reflected from the element to shift relative to a fixed grating thereby generating moire fringes. The accumulated fringes serve to measure absolute position and motion of the element.

Abstract: The position of a rotating element is controlled by a galvanometer and a servo system. The position of the rotating element is determined by using a two-grating moire pattern. Movement of the element causes a projected scale image representing radiation reflected from the element to shift relative to a fixed grating thereby generating moire fringes. The accumulated fringes serve to measure absolute position and motion of the element. The servo digitally processes the measured position to generate several force components which are then combined to control the amount of force applied by the galvanometer to rotate the element.

Abstract: A control circuit generates a variable analog output voltage in response to momentary closure of touch control means by an operator. The control level selected via the touch control means is sampled, digitized, digitally stored and reconverted to the analog output voltage for driving a motor at a commensurate speed. Selection of a different control level generates a correspondingly different digital value and thus a different analog output voltage. The selected control level and the corresponding analog output voltage may be maintained for an extended period of time until a new selection is made, or a different operating mode is entered. A mode change causes an automatic reset to a neutral operating condition (e.g., zero analog output voltage).

Abstract: A professional audio tape transport capstan control system includes a single capstan continuously engaging a length of tape to provide bidirectional motion control in all modes of operation. A D.C. capstan drive motor is directly coupled to the capstan and energized for precise control over tape motion. A hybrid servo switches between digital position phase lock velocity control and analog constant acceleration control to provide both precise control over play speed and rapid acceleration. With acceleration to a stabilized play speed occurring in less than 0.5 sec an operator may treat the acceleration time as instantaneous for most applications.

Abstract: A switching motor control system that is particularly well suited for the reel motor of a tape transport system includes an energization command system commanding motor energization in response to tape buffer loop length, a feedback system indicating buffer loop length and actual motor current and a feedforward system energizing the motor to reduce the difference between commanded motor energization and actual energization as indicated by motor current. An integrator which sums the command and feedback signals with an AC reference signal outputs a triangle wave signal that is readily converted to a digital command signal by a simple transistor detector. An economical digital control circuit delays and selectively inhibits the digital command signal to control a motor drive amplifier in a switching mode which avoids power dissipation in the motor drive amplifier.

Abstract: A dynamic brake for the supply reel motor of a tape transport. Upon power failure, the motor is coupled as a generator to supply current to a lamp, which functions as a substantially constant current load, and produces a substantially constant braking torque upon the supply reel.