HGA Bimodal Modulation Test for Resonance Characterization
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Solution Overview
Problem
Disc drive head gimbal assemblies (HGAs) are prone to modulation-related failures due to resonance issues, which make them unstable and unreliable, especially when sensitive to disturbances at the head-disc interface, and existing methods struggle to individually characterize the modal response of each HGA effectively.
Innovation Solution
An in-situ test method that involves exciting opposing-effect microactuators to derive the spectral frequency response, determining the resonant frequency, and driving the microactuators at that frequency to vary the read/write fly height and correlate contact with maximum microactuator response, thereby identifying characteristic HGA modulation issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing test methods are used to characterize HGA modal response, then the testing process is simpler, but the measurement precision and reliability of HGA characterization is insufficient
Solution Approach 1:
The patent segments the HGA testing process into distinct modalities (lateral and vertical) that can be independently excited and measured. By separating the excitation and measurement into independent channels, the system achieves precise modal response characterization without requiring a completely complex integrated test setup. Each modality can be tested separately using dedicated actuators and sensors.
Solution Approach 2:
The patent introduces intermediate measurement devices and signal processing components that act as mediators between the HGA and the testing system. These intermediaries include specialized sensors, signal conditioners, and data processing algorithms that enhance measurement precision while managing the overall system complexity through modular architecture.
2Reliability
If the read/write head is kept at a stable fly height, then the head-disc interface stability is maintained, but the ability to detect resonance issues and contact problems is reduced
Solution Approach 1:
The patent applies preliminary action by intentionally inducing controlled disturbances and resonance conditions before actual operation to identify potential reliability issues. The test method proactively excites the HGA at various frequencies and amplitudes to detect resonance vulnerabilities and contact problems before they manifest during normal stable operation, allowing preventive measures to be taken.
Solution Approach 2:
The patent employs periodic action through cyclic excitation patterns that systematically vary the fly height and excitation frequency over time. This periodic testing regime allows the system to scan through different operational states, identifying resonance frequencies and contact issues that would not be apparent during static or continuously stable operation.
3Measurement precision
If microactuators are driven at resonant frequency with high amplitude, then the spectral frequency response is more pronounced, but the risk of head-disc contact and instability increases
Solution Approach 1:
The patent applies partial action by using excitation amplitudes that are sufficient to produce measurable spectral responses but controlled to remain below the threshold that causes harmful head-disc contact. The test method carefully calibrates the excitation level to achieve the minimum necessary amplitude for accurate measurement while avoiding excessive action that would trigger instability or contact.
Solution Approach 2:
The patent implements feedback mechanisms that continuously monitor the HGA response during excitation and automatically adjust the drive amplitude and frequency. When signs of head-disc contact or instability are detected through sensor feedback, the system reduces the excitation level or shifts frequency, allowing precise spectral measurement while preventing harmful effects.
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 method allows for effective in-situ characterization of HGA modulation, ensuring reliable operation by identifying and addressing resonance-related issues during manufacturing and beyond, thereby enhancing the reliability and longevity of disc drives.
Implementation Method 1
The microactuator includes a pair of piezoelectric (PZT) elements that selectively move a head gimbal assembly (HGA)
Implementation Method 2
driving voltages that produce desired PZT strain and, thus, HGA deflection
Data Source
AI summary
Apparatus and method contemplating an in-situ test method for a head gimbal assembly (HGA). The method includes individually exciting a pair of opposing-effect microactuators supporting the read/write head adjacent a data storage media; summing the outputs from the microactuators to derive a spectral frequency response of the HGA; determining a resonant frequency from the spectral frequency response; driving the microactuators at the resonant frequency; and varying the read/write fly height apart from the data storage media to correlate contact with a maximum response of the microactuators.