Piezoelectric Microactuator Off-Track Motion Extraction
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Solution Overview
Problem
In data storage devices, as track density increases, it becomes challenging to maintain on-track positioning during read/write operations due to difficulties in simultaneously driving and sensing off-track motion using piezoelectric (PZT) microactuators, which are hindered by noise and the complexity of separating driving and sensing signals.
Innovation Solution
The use of PZT elements poled in the same direction, allowing for simultaneous driving and sensing, with a circuit that adds and processes their outputs to extract off-track motion, employing filtering techniques to isolate sensing signals from driving signals and reduce noise, enabling high-bandwidth feedback and feedforward control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PZT microactuators are used for simultaneous driving and sensing, then positioning accuracy is improved, but signal separation becomes difficult due to noise and complexity
Solution Approach 1:
The patent segments the sensing function by using two separate PZT elements poled in opposite directions. Each element responds differently to off-track motion, allowing the sensing signal to be extracted by combining their outputs in a specific ratio, thereby separating the sensing function from the driving function and reducing signal processing complexity
Solution Approach 2:
The patent introduces an intermediary signal processing approach where the outputs of two PZT elements are combined in a specific ratio to create a sensing-dedicated signal. This intermediary processing stage acts as a mediator that transforms the complex mixed signals into a clean off-track motion sensing signal, reducing the overall complexity of signal separation
2Quantity of substance
If track density is increased, then storage capacity is improved, but on-track positioning becomes more difficult
Solution Approach 1:
The patent implements a feedback control system where off-track motion is continuously sensed using the PZT elements and this sensing information is fed back to adjust the actuator position in real-time. This feedback mechanism enables precise positioning even at high track densities by continuously correcting deviations from the target track
Solution Approach 2:
The patent changes the operational parameters of the PZT elements by poling them in opposite directions and driving them at different phases. This parameter change allows the system to extract off-track motion signals more effectively, improving positioning accuracy at high track densities where traditional methods fail
3Measurement precision
If PZT elements are poled in opposite directions, then off-track motion extraction is improved, but driving signal separation becomes more complex
Solution Approach 1:
The patent introduces asymmetry in the poling directions of the two PZT elements, with one element poled in the positive direction and the other in the negative direction. This asymmetric configuration creates different sensitivity patterns to off-track motion, enabling better extraction of motion signals while the driving signals can be separated through appropriate phase and amplitude 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
This approach enhances the ability to maintain on-track positioning with minimal delay, providing high-bandwidth actuation and sensing capabilities, effectively mitigating the effects of disk modes and other disturbances on head position error, and simplifying implementation across various applications.
Implementation Method 1
a first piezoelectric (PZT) element poled in the same direction as a second PZT element. The first and second PZT elements are configured to be driven while simultaneously sensing motion
Data Source
AI summary
In certain embodiments, an apparatus includes a first piezoelectric (PZT) element poled in the same direction as a second PZT element. The first and second PZT elements are configured to be driven while simultaneously sensing motion. The apparatus further includes a circuit configured to add outputs of the first and second PZT elements, extract the sensed motion, and detect off-track motion from the extracted sensed motion.