Loop Shaping Filters for Magnetic Disk Positioning Accuracy
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Solution Overview
Problem
In magnetic disk devices, the positioning accuracy of the magnetic head is not improved when multiple loop shaping filters are used to suppress NRRO disturbances across various vibration frequencies, as they interfere with each other, failing to effectively cancel out disturbances.
Innovation Solution
The implementation of a magnetic disk device with multiple loop shaping filters, where the coefficients of each filter are determined by considering the frequency response of other filters, allowing them to be set in a way that they collectively suppress disturbances across multiple frequencies, improving the positioning accuracy by canceling out the effects of different disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple loop shaping filters are added to suppress NRRO disturbances of multiple vibration frequencies, then the coverage of disturbance suppression is improved, but the filters mutually interfere with each other and positioning accuracy deteriorates
Solution Approach 1:
Each loop shaping filter is assigned a specific frequency band with localized suppression characteristics. The filters are designed to target specific vibration frequencies (e.g., 3kHz, 3.5kHz, 4kHz) rather than attempting broad-spectrum suppression, thereby reducing mutual interference while maintaining comprehensive coverage across multiple frequencies.
Solution Approach 2:
The system employs feedback mechanisms where the output of each loop shaping filter is fed back to adjust its coefficients based on the actual disturbance characteristics. This allows the filters to adapt to changing vibration conditions and minimize mutual interference through dynamic coefficient adjustment, improving both coverage and positioning accuracy.
2Reliability
If loop shaping filters are designed with high gain to improve disturbance cancellation, then suppression effectiveness is improved, but phase matching becomes difficult and positioning accuracy deteriorates
Solution Approach 1:
The system dynamically adjusts filter parameters including gain, phase, and center frequency to optimize disturbance cancellation. By changing these parameters based on detected vibration characteristics, the system maintains high suppression effectiveness while preserving phase matching between the magnetic head and disk surface, thereby improving positioning accuracy.
Solution Approach 2:
The loop shaping filters are designed with dynamic characteristics that allow real-time adjustment of gain and phase parameters. This dynamic adaptability enables the system to maintain optimal disturbance cancellation across varying operating conditions without sacrificing phase matching accuracy, resolving the contradiction between suppression effectiveness and positioning precision.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a controlled object, a controller which controls a motion of the controlled object, and loop shaping filters each connected in parallel to the controller. During a determination of coefficients of the loop shaping filters using a transfer function from outputs of the loop shaping filters to before an input of a disturbance affecting the controlled object, the first set of coefficients of each the loop shaping filter is determined by reflecting a frequency response of the other loop shaping filters, and the determined first sets of coefficients of the loop shaping filters are set to the loop shaping filters, respectively.