Shear Mode Micro-Actuator Bandwidth for Data Storage Head Positioning
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Solution Overview
Problem
Data storage manufacturing and test equipment face challenges in achieving high mechanical and electrical bandwidth for fine positioning mechanisms, leading to mis-positioning of read/write heads due to mechanical disturbances like vibration and thermal drift, especially as track widths decrease.
Innovation Solution
The implementation of a shear mode micro-actuator with a positive electrode, negative electrode, and shear mode piezoelectric material, which reduces moving mass, increases stiffness, and minimizes off-axis distortion, integrated into a head tool or spinstand, along with high-bandwidth non-contact position sensors to sense and compensate mechanical disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional positioning mechanisms are used, then device complexity is reduced, but mechanical bandwidth and positioning precision deteriorate due to insufficient ability to compensate for mechanical disturbances
Solution Approach 1:
The positioning system is divided into two independent control loops: a slow outer loop for coarse positioning and a fast inner loop for fine positioning. The coarse positioning mechanism handles low-frequency position adjustments, while the micro-actuator handles high-frequency vibration compensation. This segmentation allows each subsystem to be optimized for its specific frequency range, achieving high overall bandwidth without excessive complexity.
Solution Approach 2:
A micro-actuator is introduced as an intermediary element between the coarse positioning mechanism and the head assembly. This micro-actuator serves as a vibration compensation mechanism that actively counteracts mechanical disturbances, enabling the system to achieve high positioning precision without requiring the entire positioning mechanism to be overly complex.
2Reliability
If micro-actuators with increased bandwidth are used, then mechanical disturbance compensation improves, but moving mass increases reducing overall system bandwidth
Solution Approach 1:
The control system is segmented into frequency-based zones where the coarse positioning mechanism handles low-frequency position commands and the micro-actuator handles high-frequency vibration compensation. This frequency-domain segmentation allows the lightweight micro-actuator to provide high-bandwidth disturbance rejection without requiring the entire positioning system to move at high speeds.
Solution Approach 2:
The system employs dynamic control where the micro-actuator rapidly adjusts to compensate for vibrations while the coarse mechanism provides stable, slow positioning. This dynamic division of labor allows the system to achieve both high-speed vibration compensation and stable positioning without the mass penalty of a completely high-bandwidth positioning system.
3Manufacturing precision
If track width is decreased to increase storage capacity, then storage density improves, but positioning precision requirements increase making the system more sensitive to mechanical disturbances
Solution Approach 1:
The system uses feedback from position sensors to continuously monitor head position and track deviations caused by mechanical disturbances. This feedback is fed to the micro-actuator control system, which generates compensating signals to counteract the disturbances. This closed-loop feedback mechanism enables the system to maintain high positioning precision on narrow tracks despite the increased sensitivity to mechanical vibrations.
Solution Approach 2:
The micro-actuator serves as an intermediary vibration compensation mechanism that isolates the head assembly from mechanical disturbances. By introducing this intermediate compensation stage, the system can achieve the sub-micron positioning precision required for narrow tracks without being directly affected by the mechanical vibrations that would otherwise cause positioning errors.
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 solution enhances the mechanical and electrical bandwidth of the positioning mechanism, reducing vibration and mis-positioning errors, thereby improving track following and reducing written-in run-out and head vibration, leading to more accurate head positioning on data tracks.
Implementation Method 1
said positive electrode undergoes a single axis, in-plane position change relative to said negative electrode through the inverse piezoelectric effect
Data Source
AI summary
An apparatus and a method for improving bandwidth of a fine positioning mechanism in data storage manufacturing and test equipment that require fine positioning of a head on or about a track. The method comprises the steps of sensing separate sources of mechanical disturbance that mis-position the head with one or more non-contact position sensors, generating a compensating position control signal from one or more input signals, and positioning the head with a fine positioning mechanism and position control signal. The apparatus uses a shear mode micro-actuator as a fine positioning mechanism.