HDD Voice Coil Control for Adaptive Seek Deceleration
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Solution Overview
Problem
Existing magnetic disk drives face challenges in maximizing seek performance due to limitations in deceleration current saturation, which is influenced by the fluctuating coil resistance of the voice coil motor, making it difficult to optimize the deceleration drive current for precise stopping at target positions.
Innovation Solution
A method to estimate the coil resistance of the voice coil motor by calculating the inductance voltage during seek acceleration, using a conversion table to adjust the deceleration drive current based on the estimated resistance, ensuring it does not saturate and optimizing the seek operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the drive current for deceleration is increased to saturation to maximize deceleration, then the seek performance is improved, but the magnetic head cannot stop accurately at the target position due to current saturation
Solution Approach 1:
The patent applies dynamics by making the deceleration drive current adaptive rather than fixed. The controller dynamically adjusts the deceleration drive current based on real-time coil resistance measurements, allowing the current to be optimized for each specific seek operation. This resolves the contradiction by enabling high deceleration when conditions permit while preventing saturation that would compromise positioning accuracy.
Solution Approach 2:
The patent changes the parameter of drive current based on coil resistance measurements. By measuring the actual coil resistance and using it to calculate an optimal deceleration drive current, the system adapts the electrical parameter to match the physical state of the voice coil motor. This allows maximizing deceleration without entering the saturation region, thereby maintaining positioning accuracy.
2Manufacturing precision
If the deceleration drive current is limited to prevent saturation, then positioning accuracy is maintained, but the deceleration performance is reduced
Solution Approach 1:
The patent implements feedback by measuring the coil resistance and using this information to adjust the deceleration drive current. The controller continuously monitors the electrical characteristics of the voice coil motor and feeds this information back into the control algorithm. This feedback mechanism enables the system to determine the optimal current level that maintains positioning accuracy while maximizing deceleration performance.
Solution Approach 2:
The patent applies preliminary action by measuring the coil resistance before executing the deceleration phase. This pre-measurement allows the controller to pre-calculate the optimal deceleration drive current based on the actual coil resistance, ensuring that the current is set correctly before the deceleration begins. This prevents both saturation and underutilization of the voice coil motor's capability.
3Device complexity
If a fixed deceleration drive current is used, then the control is simple, but the seek performance cannot be optimized due to coil resistance fluctuations
Solution Approach 1:
The patent applies self-service by enabling the voice coil motor system to self-diagnose and self-adjust. The controller measures the coil resistance itself and uses this self-obtained information to optimize the deceleration drive current. This eliminates the need for external calibration or complex lookup tables, achieving performance optimization through a relatively simple self-measuring and self-adjusting mechanism.
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 approach enhances seek performance by allowing for higher deceleration currents, improving the magnetic head's ability to stop accurately at target positions, thereby increasing access performance.
Implementation Method 1
a voice coil motor including a magnet and a coil, which moves the magnetic head in a radial direction of the magnetic disk
Implementation Method 2
a back electromotive voltage estimation section which estimates a back electromotive voltage induced in the coil of the voice coil motor based on the velocity calculated in the velocity calculation section and the position of the magnetic head during acceleration of the seek operation
Data Source
AI summary
According to one embodiment, a magnetic disk drive comprising, a magnetic disk, a magnetic head, a voice coil motor, and a controller. The controller includes a seek control section, a velocity calculation section, a back electromotive voltage estimation section, and a coil resistance estimation section.