Disk Device Head Position Control for Disturbance Suppression
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Solution Overview
Problem
Existing head position control systems for disk devices face challenges in adapting to a wide range of disturbance frequencies without affecting the control characteristics, particularly in suppressing external vibrations and eccentricity, which degrades positioning accuracy as recording density increases and devices are used in mobile equipment.
Innovation Solution
A head positioning control method that computes a position error and generates state information using an estimated gain from a disturbance model defined by a transfer function with a numerator of a filter, allowing for effective disturbance suppression across various frequencies without altering the control characteristics, by adding a disturbance suppression value to the control value and driving the actuator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a compensator for selectively suppressing a specific frequency range is added to handle eccentricity, then positioning accuracy is improved for that specific frequency, but the characteristics of the original control system are affected when the suppression width is set to be wide or high frequency disturbance is suppressed
Solution Approach 1:
The patent divides the control system into two independent parts: the original observer control system for basic positioning, and a separate disturbance observer with compensator for frequency-specific disturbance suppression. This segmentation allows each part to function independently without interfering with the other, enabling wide-range disturbance suppression while preserving original control characteristics.
Solution Approach 2:
The patent introduces a disturbance observer as an intermediary component that estimates disturbance signals and generates compensator outputs. This intermediary process allows disturbance suppression to be achieved without directly modifying the original control system, thereby maintaining its characteristics while adapting to various disturbance frequencies.
2Reliability
If disturbance suppression function is added after observer design, then disturbance suppression capability is improved, but the characteristics of the entire control system shift considerably requiring redesign
Solution Approach 1:
The patent segments the control system design process by first completing the observer design for basic positioning, then separately adding the disturbance suppression function through a disturbance observer. This segmentation allows the disturbance suppression to be added without requiring redesign of the original observer, reducing overall system complexity.
Solution Approach 2:
The patent performs preliminary design of the observer control system before adding disturbance suppression capabilities. By establishing the base observer first, the subsequent addition of disturbance observer and compensator becomes a supplementary enhancement rather than a fundamental redesign, simplifying the overall development process.
Data Source
AI summary
A positioning control device based on an observer control has a disturbance suppression function to which a disturbance suppression function is added without affecting the control characteristics of the observer. Models of an actuator and a disturbance model are separated, and for the disturbance model, state information is generated using an estimated gain determined from a disturbance model defined by a transfer function of which denominator is a numerator of a filter in which degrees of denominator and numerator for shaping a sensitivity function are the same, and the disturbance suppression value of the actuator is computed from the state information. The vibration of the head can be prevented adapting to a wide range of disturbance frequencies without affecting the control characteristics of the observer.