Dual-VCM Seek Profile Current Limiting
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Solution Overview
Problem
Existing data storage devices face challenges in managing peak current consumption and preventing head damage during emergency unloads, particularly when using voice coil motors (VCMs) to position heads over disk surfaces, as they often exceed current limits and may result in head contact with ramps during power failures.
Innovation Solution
Implementing a dual-priority seek profile system for VCMs, where one VCM operates with a high performance seek profile and the other with a reduced performance seek profile, allowing for concurrent seeking while limiting total current consumption and ensuring sufficient braking power during emergencies by assigning high and low priority based on seek direction and proximity to disk edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If both VCMs use high performance seek profile concurrently, then seek speed is improved, but current consumption exceeds limits
Solution Approach 1:
The patent applies different seek profiles to different VCMs based on their specific situations. One VCM uses a high performance seek profile while the other uses a reduced performance seek profile, allowing each to operate according to its local needs rather than applying a uniform approach to all VCMs
Solution Approach 2:
The patent implements partial high performance action by allowing only one VCM to use the high performance seek profile at a time, while the other uses a reduced performance profile. This partial application of high performance seeking prevents current limits from being exceeded while still maintaining good overall performance
2Reliability
If VCMs use high performance seek profile during emergency unload, then braking power is sufficient, but current limits are exceeded
Solution Approach 1:
During emergency unload, the patent assigns high priority (and thus high performance seek profile) specifically to the VCM that requires sufficient braking power, while the other VCM uses reduced performance profile. This local differentiation ensures safety where needed while managing overall current consumption
Solution Approach 2:
The patent applies high performance seeking partially during emergency unload, only to the VCM that needs it for safe operation. This partial application provides sufficient braking power where critical while keeping total current consumption within limits
3Use of energy by moving object
If one VCM is delayed to limit current, then current limits are maintained, but seek time increases
Solution Approach 1:
The patent changes the performance parameter of the seek profile from high to reduced performance for one VCM, which directly controls current consumption but results in increased seek time. This parameter change allows the system to operate within current limits
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 effectively prevents current limits from being exceeded and ensures safe emergency unloads by adjusting seek profiles to manage power distribution, reducing the risk of head damage and optimizing seek times while maintaining performance.
Implementation Method 1
a head actuator such as a voice coil motor (VCM) to position the head radially over the disk
Data Source
AI summary
A data storage device is disclosed comprising a first voice coil motor (VCM) configured to actuate a first head, and a second VCM configured to actuate a second head. A high priority is assigned to the first VCM and a low priority to the second VCM. A first access command is serviced using the first head by seeking the first VCM using a first high performance seek profile. When seeking the second VCM without seeking the first VCM, a second access command is serviced using the second head using a second high performance seek profile. When concurrently seeking the first VCM and the second VCM, the seeking of the second VCM is with a reduced performance seek profile, wherein the second high performance seek profile decreases a seek time of the second VCM compared to the reduced performance seek profile.