Magnetic Head Positioning With Adaptive Feedforward Vibration Control
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Solution Overview
Problem
Magnetic disk devices face challenges in maintaining accurate positioning of the magnetic head due to disturbances such as vibration, which affect the performance and efficiency of data access operations.
Innovation Solution
Implementing a feedforward control mechanism that adjusts the VCM current instruction value based on sensor feedback from multiple vibration sensors and VCM current detection, using IIR filters to suppress interference and improve positioning accuracy by optimizing the transfer function coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedforward control based on sensor values is executed to suppress disturbance influence, then positioning accuracy of the magnetic head is improved, but device complexity increases due to additional sensors and control mechanisms
Solution Approach 1:
The patent implements feedforward control that uses sensor values (vibration sensors and VCM current detection) to predict and compensate for disturbances before they affect positioning accuracy. The controller adjusts the VCM current instruction value based on detected vibration and current characteristics, enabling proactive disturbance suppression rather than reactive correction.
Solution Approach 2:
The patent introduces intermediate processing through IIR filters that process sensor signals before they reach the control algorithm. The transfer function with adjustable coefficients acts as an intermediary that shapes the control response, allowing complex control behavior to be achieved through structured signal processing rather than direct complex control logic.
2Measurement precision
If IIR filters with adjustable coefficients are used to optimize transfer function for disturbance suppression, then positioning accuracy is improved, but difficulty of detecting and measuring increases due to complex signal processing requirements
Solution Approach 1:
The patent employs dynamic adjustment of IIR filter coefficients based on operating conditions. The transfer function coefficients are not fixed but are adapted according to the detected vibration characteristics and VCM current patterns, allowing the control system to optimize its response for different operating scenarios and disturbance types.
Solution Approach 2:
The patent changes the parameters of the IIR filter (coefficients a1, a2, b1, b2) to optimize the transfer function for different disturbance conditions. By adjusting these parameters based on sensor feedback, the system adapts its frequency response and filtering characteristics to match the actual disturbance spectrum, improving suppression effectiveness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances the positioning accuracy of the magnetic head by effectively mitigating the impact of disturbances, thereby improving the performance and efficiency of data access operations in magnetic disk devices.
Implementation Method 1
a magnetic head is moved in a radial direction of a magnetic disk by a voice coil motor (VCM)
Implementation Method 2
correct the first instruction value by a first feedforward control based on a first detection value obtained by the first sensor
Data Source
AI summary
According to an embodiment, a controller corrects an instruction value of a VCM current by a first feedforward control based on a first detection value obtained by a first sensor. The controller executes a first operation in accordance with occurrence of a set event. In the first operation, the controller acquires a first waveform that is a waveform of a deviation amount of a detection position from a target position of a magnetic head, and acquires from the first waveform a first frequency band that is a frequency band whose amplitude is greater than a first threshold. The controller adjusts a coefficient of a transfer function of the first feedforward control to suppress the first detection value in a second frequency band different from the first frequency band and output a correction amount for a first instruction value based on the first detection value in the first frequency band.