Magnetic Disk Device Humidity-Compensated Microactuator Control
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Solution Overview
Problem
The positioning accuracy of magnetic disk devices is degraded due to humidity changes, affecting the performance of the actuator's microcomponents, particularly those using thin film piezoelectric elements, as their mechanical properties are humidity-dependent.
Innovation Solution
A magnetic disk device is designed with a humidity sensor and control circuit that adjusts the voltage applied to the microactuator based on humidity levels, using a control gain calculation to maintain accurate positioning by accounting for changes in the microactuator's displacement amount with relative humidity, thereby compensating for humidity-induced variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a microactuator using thin film piezoelectric elements is used to position the magnetic head, then positioning speed and responsiveness are improved, but positioning accuracy deteriorates due to humidity changes affecting the mechanical properties of the piezoelectric elements
Solution Approach 1:
The patent changes the control parameter from a fixed voltage value to a humidity-dependent voltage value. The control circuit calculates the required voltage based on the measured humidity level and the predetermined relationship between humidity and stroke amount, thereby compensating for the humidity-induced changes in piezoelectric element properties and maintaining positioning accuracy.
Solution Approach 2:
The patent implements a feedback mechanism where the humidity sensor continuously monitors the internal humidity level, and the control circuit uses this feedback information to dynamically adjust the voltage applied to the microactuator. This closed-loop control ensures that positioning accuracy is maintained despite humidity variations.
2Device complexity
If the voltage to the microactuator is kept constant for simple control, then device complexity is reduced, but positioning accuracy deteriorates due to unaccounted humidity variations
Solution Approach 1:
The patent introduces a humidity sensor as an intermediary device that measures the humidity level and provides information to the control circuit. This intermediary enables the system to adapt to humidity changes without requiring a completely complex control architecture, bridging the gap between simple voltage application and accurate positioning.
Solution Approach 2:
The control circuit changes the voltage parameter based on humidity measurements. By calculating the required voltage adjustment according to the predetermined relationship between humidity and stroke amount, the system maintains positioning accuracy while keeping the control logic relatively simple.
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
This solution ensures highly accurate and humidity-independent positioning control by dynamically adjusting the control gain of the microactuator, preventing deterioration in positioning accuracy due to environmental humidity changes.
Implementation Method 1
a humidity sensor positioned within the case to measure a humidity in the case
Implementation Method 2
positioning accuracy of an actuator that moves a magnetic head may be degraded due to humidity... particularly those using thin film piezoelectric elements, as their mechanical properties are humidity-dependent
Data Source
AI summary
A magnetic disk device includes a case including a magnetic disk, a magnetic head configured to read or write data from or to the magnetic disk, an actuator configured to move the magnetic head, and a humidity sensor positioned within the case to measure a humidity in the case and output a measurement value; a control circuit configured to calculate a value of a voltage to be applied to the actuator based on a displacement amount of the magnetic head and the measurement value output from the sensor, and output the calculated value; and a servo controller configured to control the actuator by applying the voltage to the actuator according to the value output by the control circuit.