VCM Current Feedback Control for Reliable HDD Seek Operations
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Solution Overview
Problem
In magnetic disk devices, insufficient voltage drop margins in voice coil motors (VCM) due to current supply issues can lead to failed seek operations, deteriorating performance.
Innovation Solution
A controller in the magnetic disk device estimates seek voltage margins and controls VCM current using both estimated and actual values, incorporating VCM current deviation amounts to maintain a sufficient margin, thereby preventing seek operation failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the amount of current supplied to the VCM is increased to improve seek operation speed, then the moving speed of the magnetic head increases and seek time is shortened, but the voltage drop margin becomes insufficient and seek operation may fail
Solution Approach 1:
The patent applies dynamics by making the VCM current control adaptive and variable rather than fixed. The controller dynamically adjusts the VCM current based on real-time feedback from the current detection circuit, allowing the system to optimize seek speed while preventing voltage drop margin insufficiency. This dynamic control enables the current to be increased when margin is sufficient and reduced when margin becomes critical, resolving the contradiction between speed and reliability.
Solution Approach 2:
The patent implements feedback control by using the current detection circuit to continuously monitor the actual VCM current and comparing it with the commanded current. The controller uses this feedback information to adjust the VCM current in real-time, ensuring that the voltage drop margin remains sufficient while maximizing seek operation speed. This closed-loop feedback mechanism directly addresses the contradiction by allowing adaptive current adjustment based on actual system conditions.
2Productivity
If the VCM current is increased to reduce seek time, then productivity is improved, but the voltage drop margin becomes insufficient causing seek operation failures
Solution Approach 1:
The system dynamically adjusts VCM current based on real-time monitoring of voltage drop margins. During seek operations, the controller increases current to maximize speed when margin is sufficient, and reduces current when margin becomes critical, thereby maintaining high productivity while preventing seek operation failures.
Solution Approach 2:
The current detection circuit provides continuous feedback on actual VCM current consumption. The controller uses this feedback to adjust current supply dynamically, ensuring that productivity is maximized within the safe operating margin, thus resolving the contradiction between seek operation efficiency and success rate.
3Reliability
If the VCM current is precisely controlled to maintain sufficient voltage drop margin, then reliability is improved, but the seek operation speed may decrease
Solution Approach 1:
Rather than using a fixed conservative current limit that would reduce speed, the system dynamically adjusts the current based on real-time conditions. This allows the system to maintain reliability by preventing margin insufficiency while maximizing speed when conditions permit, thus resolving the contradiction between reliability and speed.
Solution Approach 2:
The feedback mechanism allows the controller to precisely control VCM current based on actual consumption patterns. This precise control ensures reliability is maintained by preventing voltage drop margin insufficiency, while still allowing high current (and thus high speed) when the margin is sufficient, resolving the trade-off between reliability and speed.
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
The solution ensures accurate and real-time control of VCM current, maintaining a small seek voltage margin to prevent insufficiency, thus improving performance and reducing seek operation failures.
Implementation Method 1
a magnetic head is moved in a radial direction of a magnetic disk by a voice coil motor (VCM)
Data Source
AI summary
According to an embodiment, in a magnetic disk device, a current detection circuit detects an amount of a first current that is generated by a drive circuit and drives a motor. In a seek operation, a controller acquires a commanded value based on a deviation amount of the amount of the first current detected by the current detection circuit from the commanded value. Then, the controller inputs the acquired commanded value to the drive circuit.