Hard Disk VCM Braking with Variable Duty-Cycle Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional hard disk drives (HDDs) face limitations in braking capability due to fixed duty-cycle operation in discontinuous mode, which restricts maximum seek speed and affects data transfer rates, particularly when quickly slowing down the voice coil motor (VCM) after a fast seek.
Innovation Solution
Implementing a self-adjusting duty-cycle in the VCM operation that varies as a function of the detected speed, allowing higher current during high-speed phases to rapidly decelerate the VCM, thereby improving braking efficiency and reducing the risk of hitting the parking ramp or inner crash stop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed duty-cycle is used in discontinuous mode for VCM braking, then the operating simplicity is maintained, but the braking capability is limited and maximum seek speed must be restricted
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed duty-cycle to a variable duty-cycle that adapts to changing VCM speed conditions. The controller dynamically adjusts the duty-cycle percentage based on detected speed levels, allowing the system to optimize braking performance at different speed ranges while maintaining operational simplicity through automated control.
Solution Approach 2:
The patent implements parameter changes by modifying the duty-cycle parameter from a constant value to a variable value that changes with speed. This allows the braking current to be optimized at different speed levels, improving braking capability without complicating the overall control architecture, as the parameter adjustment is automatically managed by the controller.
2Device complexity
If a fixed duty-cycle is used during braking, then the control system complexity is reduced, but the braking time increases and speed recovery is slower
Solution Approach 1:
The system uses dynamics to adapt the duty-cycle in real-time based on VCM speed feedback. The controller continuously monitors speed and adjusts the duty-cycle accordingly, enabling faster braking without requiring a fundamentally more complex control system architecture.
Solution Approach 2:
The patent implements feedback by using speed detection to inform duty-cycle adjustments. The controller receives feedback about the current VCM speed and automatically adjusts the braking duty-cycle to optimize stopping time, achieving faster speed recovery while keeping the control system relatively simple through automated closed-loop control.
3Productivity
If the VCM is slowed down quickly after fast seek, then the data transfer rate is improved, but the risk of mechanical damage increases with fixed duty-cycle operation
Solution Approach 1:
The patent applies parameter changes by adjusting the duty-cycle based on speed conditions. During fast seeks, the system can tolerate higher speeds for improved data transfer, but automatically reduces the duty-cycle when speed becomes dangerous, thereby preventing mechanical damage while maximizing productivity during normal operation.
Solution Approach 2:
The system applies preliminary anti-action by proactively reducing the duty-cycle before dangerous speeds are reached. The controller detects high speeds and preemptively adjusts the braking parameters to prevent potential mechanical damage, allowing the system to maintain high data transfer rates during fast seeks while protecting against overshoot risks.
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
Enhances HDD reliability and data transfer rates by enabling faster speed recovery and reducing the risk of mechanical damage during head retraction, while maintaining controlled speed regulation.
Implementation Method 1
the VCM power stage (also) is controlled in a discontinuous mode: the current through the VCM is periodically interrupted to facilitate reading the VCM back electromotive force (BEMF) generated in response to motion
Implementation Method 2
the current through the VCM is periodically interrupted to facilitate reading the VCM back electromotive force (BEMF) generated in response to motion
Data Source
AI summary
In accordance with an embodiment a method includes: receiving a slow down command to slow down a speed of a voice coil motor (VCM) in a hard disk drive; in response to receiving the slow down command, operating the VCM in a discontinuous mode by switching on and off a current through the VCM with a duty-cycle, wherein operating the VCM in the discontinuous mode reduces the speed of the VCM; sensing the speed of the VCM while operating the VCM in the discontinuous mode; and varying the duty-cycle of the switching on and off the current through the VCM as a function of the sensed speed of the VCM operated in the discontinuous mode, wherein varying the duty-cycle comprises reducing the duty-cycle in response to a reduction of the sensed VCM speed.