Dual-Stage Actuator Disturbance Compensation for Magnetic Head Tracking
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Solution Overview
Problem
Magnetic disk devices face challenges in ensuring tracking control accuracy due to the limitations of voice coil motors, particularly with the miniaturization of track pitches, which necessitates a more precise actuation mechanism.
Innovation Solution
A dual-stage actuator configuration is employed, combining a coarse-movement voice coil motor with a fine-movement piezoelectric microactuator, along with a disturbance vibration detection and compensation system to correct movement positions and suppress disturbance vibrations, enhancing tracking accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a voice coil motor is used as an actuator to move a magnetic head, then the device structure is simple and easy to manufacture, but the tracking control accuracy deteriorates due to limitations in positioning precision
Solution Approach 1:
The actuator is divided into two independent stages: a coarse-movement actuator (voice coil motor) for large displacements and a fine-movement actuator (piezoelectric element) for precise positioning. Each stage operates independently within its optimal range, with the fine-movement actuator mounted on the coarse-movement actuator to provide hierarchical control and achieve high tracking accuracy without excessive overall complexity.
Solution Approach 2:
The patent combines two different actuation mechanisms (voice coil motor and piezoelectric element) into a single integrated dual-stage actuator system. The piezoelectric fine-movement actuator is mounted directly on the voice coil coarse-movement actuator, merging their functions to simultaneously achieve large travel range and sub-micrometer positioning precision that neither actuator could achieve alone.
2Manufacturing precision
If a dual-stage actuator is used to improve tracking accuracy, then positioning precision is enhanced, but the device complexity increases due to additional components and control systems
Solution Approach 1:
The patent implements a feedback control system using a disturbance vibration detector that monitors vibrations affecting the fine-movement actuator. The detected disturbance signals are fed back to the disturbance compensation module, which generates correction signals to counteract the disturbances in real-time, thereby maintaining high positioning accuracy despite the increased system complexity from additional sensors and control circuits.
Solution Approach 2:
The disturbance compensation module acts as an intermediary between the disturbance vibration detector and the fine-movement actuator. It processes the detected disturbance signals, applies appropriate compensation algorithms, and generates correction commands that are applied to the fine-movement actuator, thereby mediating the effect of disturbances and protecting the positioning accuracy without requiring direct modification of the actuator structure.
3Stability of the object's composition
If disturbance compensation is implemented to suppress vibrations, then tracking stability is improved, but the control system complexity increases
Solution Approach 1:
The disturbance compensation system uses real-time feedback from the disturbance vibration detector to continuously monitor and counteract vibrations. The compensation module processes disturbance signals and applies corrective actions to the fine-movement actuator, creating a closed-loop control system that maintains tracking stability by actively suppressing disturbances as they occur, thereby achieving enhanced stability through systematic feedback control.
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 dual-stage actuator system improves the positioning accuracy of the magnetic head by effectively compensating for disturbance vibrations across a broader bandwidth, including radio frequencies, thereby enhancing the tracking precision and operational stability.
Implementation Method 1
a fine-movement actuator incorporating a piezoelectric element
Implementation Method 2
a coarse-movement actuator incorporating a voice coil motor
Implementation Method 3
a disturbance vibration detector that detects a disturbance vibration component with respect to the fine-movement actuator
Data Source
AI summary
A magnetic disk device according to one embodiment includes: a disturbance vibration detector; a movement position controller; and a disturbance compensation module. The disturbance vibration detector detects a disturbance vibration component with respect to a fine-movement actuator. The movement position controller drives each of the fine-movement actuator and a coarse-movement actuator to control a movement position of a magnetic head. The disturbance compensation module corrects the movement position so as to suppress the disturbance vibration component detected by the disturbance vibration detector.