Actuator Arm Velocity Control for Hard Disk Servo Writing
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Solution Overview
Problem
Traditional servo writing methods for hard disk drives (HDDs) are costly and become impractical as track density increases, leading to imperfections in servo spirals written during self-servo-write (SSW) operations, which reduce storage capacity.
Innovation Solution
A system comprising a self-servo-write (SSW) module and a control module that generates servo signals and control currents to quickly accelerate the actuator arm to a predetermined velocity using a crashstop spring, allowing perfect servo spirals to be written closer to crashstops, thereby increasing usable storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional servo writing methods are used, then manufacturing precision is maintained, but manufacturing cost increases and becomes impractical as track density increases
Solution Approach 1:
The patent implements self-servo-write (SSW) where the hard disk drive writes its own servo patterns using its own actuator and read/write heads during normal operation, eliminating the need for external servo writing equipment. This self-service approach reduces manufacturing costs while maintaining precision through closed-loop feedback control that monitors and corrects actuator position in real-time
Solution Approach 2:
The patent changes the operating parameters of the actuator by controlling acceleration and velocity profiles during servo spiral writing. By optimizing these motion parameters, the system achieves precise servo pattern writing at lower costs, resolving the contradiction between manufacturing precision and ease of manufacture
2Productivity
If actuator arm accelerates during servo spiral writing, then writing speed increases, but imperfections occur in the servo spirals
Solution Approach 1:
The patent employs dynamic control of the actuator arm by continuously adjusting acceleration and velocity during the servo writing process. The system monitors actual position feedback and dynamically corrects for deviations caused by acceleration, enabling high-speed writing without sacrificing spiral quality. This dynamic adaptation resolves the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent implements closed-loop feedback control where the read element monitors the written servo patterns in real-time and provides position information back to the control system. This feedback mechanism allows the system to detect and correct imperfections caused by acceleration, maintaining high writing speed while ensuring spiral quality through continuous error correction
3Productivity
If servo spirals are written closer to crashstops, then storage capacity increases, but actuator arm control precision must improve
Solution Approach 1:
The patent replaces purely mechanical positioning with a hybrid system that uses electromagnetic actuation (voice coil motor) combined with electronic feedback control. This substitution enables more precise control of the actuator arm at the extremes of its travel range near crashstops, allowing servo spirals to be written closer to these boundaries and thereby increasing storage capacity while maintaining control precision
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 system reduces imperfections in servo spiral writing by accelerating the actuator arm to a target velocity, enabling the writing of perfect spirals closer to crashstops, thus enhancing storage capacity and reducing manufacturing costs.
Implementation Method 1
discontinues the first current to release the spring and accelerate the actuator arm
Data Source
AI summary
A system includes a first current generator and a second current generator. The first current generator generates a first current to bias an actuator arm against a spring when a control signal is received. The first current generator discontinues the first current to release the spring and accelerate the actuator arm when servo signals are generated. The second current generator generates a second current that biases the actuator arm away from the spring when the first current is discontinued.