Multi-Layer PZT Suspension Assembly for Precise Head Positioning
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Solution Overview
Problem
Current microactuators in disk drive suspensions face limitations in precision and servo bandwidth due to the vertical bending of left- and right-side microactuators, which affects the positioning of the head slider over data tracks, especially under vibrations and surface irregularities.
Innovation Solution
A multi-layer piezoelectric (PZT) actuator assembly with specific electrode configurations and layer arrangements is used, including a fixed-end and hinged-end design with strategically placed electrodes to enhance the gimbal torsion mode and increase the stroke, thereby improving the positioning accuracy and servo bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional single-stage voice coil motor is used to move the suspension, then the structure is simple, but the positioning precision and servo bandwidth are insufficient
Solution Approach 1:
The suspension system is divided into two independent actuation stages: a voice coil motor for coarse positioning and a piezoelectric microactuator for fine positioning. This segmentation allows each component to specialize in its optimal operating range, with the VCM handling large movements and the PZT microactuator handling precision adjustments, thereby achieving high positioning precision without requiring a completely complex redesign of the entire suspension system.
Solution Approach 2:
The patent combines two different actuation mechanisms (voice coil motor and piezoelectric microactuator) into a single integrated suspension system. The microactuator is mounted on the suspension arm and works in conjunction with the voice coil motor, merging the benefits of both technologies to achieve superior positioning precision and servo bandwidth while maintaining reasonable structural complexity.
2Reliability
If multi-layer piezoelectric actuator assembly with specific electrode configurations is used, then the gimbal torsion mode frequency is enhanced and servo bandwidth is improved, but the manufacturing complexity increases
Solution Approach 1:
The microactuator employs a multi-layer piezoelectric structure where multiple PZT layers are stacked and nested within a single actuator body. Each layer contributes to the overall displacement output, and the nested configuration allows the actuator to achieve enhanced gimbal torsion mode frequency and improved servo bandwidth while maintaining a compact form factor that simplifies integration into the suspension assembly.
Solution Approach 2:
The patent utilizes a multi-layer stacked configuration of piezoelectric elements, transitioning from a single-layer to a multi-layer dimensional structure. This dimensional change enables the microactuator to generate larger displacements and enhance the gimbal torsion mode frequency without significantly increasing the lateral footprint, thereby improving servo bandwidth while managing manufacturing complexity through vertical stacking rather than horizontal expansion.
3Measurement precision
If left- and right-side microactuators act in push-pull fashion, then the head slider positioning is improved, but the variations at low z-height increase
Solution Approach 1:
The patent implements asymmetric electrode configurations on the left and right sides of the microactuator, with different electrode lengths tailored to each side's specific requirements. This local quality approach allows each side to be optimized for its particular function, improving head slider positioning precision while compensating for variations at low z-height through differentiated local characteristics rather than uniform symmetric design.
Solution Approach 2:
The microactuator employs asymmetric electrode arrangements where the left and right electrodes have different lengths and configurations. This asymmetry enables the push-pull mechanism to effectively counterbalance variations at low z-height while maintaining precise head slider positioning, as the unequal electrode dimensions allow for optimized force distribution on each side of the suspension arm.
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 solution enhances the gimbal torsion mode frequency and reduces variations at low z-height, leading to improved servo bandwidth and increased stroke, effectively addressing the precision and positioning challenges in disk drive suspensions.
Implementation Method 1
A multi-layer piezoelectric (PZT) actuator assembly with specific electrode configurations and layer arrangements is used
Data Source
AI summary
A piezoelectric (PZT) actuator assembly having a fixed-end and a hinged-end is provided. The assembly includes a first side electrode at the hinge-end, and a second side electrode at the fixed-end. The assembly includes a third piezoelectric layer including a top surface and a bottom surface disposed over the top surface of the second PZT layer. A fourth electrode is at least partially disposed on the top surface of the third PZT layer. The fourth electrode is connected to the second side electrode at the fixed-end.