Piezoelectric Microactuator Asymmetric Electrodes Mitigate Flexure Vibration
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Solution Overview
Problem
Piezoelectric (PZT) microactuators in hard disk drives face challenges in controlling flexure mode excitation and out-of-plane forces, which affect the precision of slider positioning due to variations in electrode thickness and z-height, leading to phase variations and degraded system performance.
Innovation Solution
Designing PZT microactuators with differentially thick electrodes and patterned electrodes to control the direction of movement and mitigate phase variations, allowing for improved precision and reduced phase lag, thereby enhancing system performance by offsetting the effects of z-height variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PZT microactuators are used for fine positioning, then positioning precision is improved, but phase variations and flexure mode excitation occur due to electrode thickness variations and z-height changes
Solution Approach 1:
The patent applies asymmetry by intentionally designing electrodes with different thicknesses (first electrode thicker than second electrode) to create a deliberate asymmetric structure. This asymmetric electrode configuration compensates for the effects of z-height variations and reduces phase variations in flexure mode vibration, thereby improving phase stability while maintaining positioning precision.
Solution Approach 2:
The patent implements local quality by varying the thickness of specific electrode regions rather than using uniform thickness throughout. The first electrode region is made thicker than the second electrode region, creating localized property variations that counteract the adverse effects of z-height changes and reduce flexure mode excitation, thus improving reliability without sacrificing overall positioning precision.
2Strength
If electrode thickness is increased to improve actuator strength, then actuator strength is improved, but out-of-plane forces increase causing flexure mode excitation
Solution Approach 1:
The patent uses asymmetry by designing electrodes with non-uniform thickness distribution. The first electrode is intentionally made thicker than the second electrode, creating an asymmetric structure that generates controlled out-of-plane forces to counteract harmful flexure mode vibrations while maintaining sufficient actuator strength for precise positioning.
Solution Approach 2:
The patent applies parameter changes by varying the thickness parameter of the electrodes. By changing the thickness parameter from uniform to differential (first electrode thicker than second), the patent optimizes both actuator strength and reduces harmful out-of-plane forces that cause flexure mode excitation, achieving a balance between these conflicting requirements.
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 use of differentially thick and patterned electrodes in PZT microactuators improves the precision of slider positioning and reduces phase variations, leading to better system performance and potentially eliminating the need for notch filters, resulting in a more reliable and cost-effective design.
Implementation Method 1
Piezoelectric (PZT) based and capacitive micro-machined transducers are two types of microactuators that have been proposed for use with HDD sliders
Data Source
AI summary
An approach to a piezoelectric (PZT) device, such as a hard disk drive microactuator, includes one or more layers of poled PZT material, with top and bottom surfaces coupled with respective electrode layers coupled with a power source to drive the active PZT layer(s). The electrode layers have different thicknesses, where the particular thicknesses may be configured to mitigate the variation of out-of-plane motion or bending associated with operational variations in the z-height between a corresponding actuator arm and recording medium and, likewise, the phase variation of flexure vibration.