Spindle Motor Position Adjustment for Accurate Back-EMF Measurement
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Solution Overview
Problem
In magnetic disk devices, repeatable run-out (RRO) causes positional deviations of the magnetic head due to variations in the motor position where counter electromotive voltage is measured during learning and correction, leading to reduced positioning accuracy.
Innovation Solution
The magnetic disk device adjusts the motor position where counter electromotive voltage is measured to a set target position, ensuring consistent measurement points between learning and correction phases, thereby improving the positioning accuracy of the magnetic head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If counter electromotive voltage is measured without adjusting motor position, then measurement process is simple, but positioning accuracy of magnetic head deteriorates due to variations in motor position between learning and correction phases
Solution Approach 1:
The patent adjusts the motor position parameter to a predetermined position before measuring counter electromotive voltage. This parameter change ensures consistent measurement conditions between learning and correction phases, eliminating positioning errors caused by motor position variations while maintaining measurement accuracy.
Solution Approach 2:
The patent performs preliminary adjustment of the motor position to a predetermined position before the measurement process. This preliminary action ensures that the motor is always at the correct position when measurement begins, preventing positioning errors without requiring complex real-time adjustments during measurement.
2Measurement precision
If motor position is adjusted to predetermined position before measurement, then positioning accuracy is improved, but measurement process becomes more complex
Solution Approach 1:
The motor position is adjusted to the predetermined position as a preliminary step before measurement begins. This advance preparation eliminates the need for complex real-time position corrections during measurement, improving accuracy while minimizing time loss through efficient pre-positioning.
Solution Approach 2:
The patent replaces complex mechanical position tracking and correction mechanisms with a simpler electronic control system that automatically adjusts motor position based on predetermined values, reducing both mechanical complexity and measurement time.
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 adjustment allows for accurate correction of positional deviations, enhancing the magnetic head's positioning accuracy by maintaining consistent measurement conditions, which was previously compromised by differing motor positions during learning and usage.
Implementation Method 1
a motor driver integrated circuit (IC) 21 that measures a counter electromotive voltage of the spindle motor 12
Data Source
AI summary
According to an embodiment, a magnetic disk device includes a magnetic disk, a spindle motor that rotates the magnetic disk, a motor driver, and a controller. The motor driver supplies a motor current to the spindle motor and measures a counter electromotive voltage of the spindle motor every time the spindle motor makes one rotation. After the rotation of the magnetic disk starts, the controller adjusts a motor position where the counter electromotive voltage is measured to a set first position.