PZT Actuator Polarity Detection in Disk Drive Head Positioning
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Solution Overview
Problem
In disk drives with dual stage actuators, incorrect selection of PZT actuator polarity can lead to improper head positioning, causing operational issues due to incorrect direction of head movement, which is often resolved through time-consuming testing during manufacturing or setup.
Innovation Solution
A method for detecting the polarity of PZT actuators using a test signal and analyzing the resulting position signal to determine the correct polarity configuration, allowing for efficient polarity detection during manufacturing or in-field use, involving a controller with test circuitry and compensators to adjust actuator signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PZT actuator polarity is selected during setup process, then head positioning can be controlled, but wrong polarity selection causes head to move in wrong direction creating positioning problems
Solution Approach 1:
The patent applies preliminary action by performing polarity detection during the setup process before normal operation begins. The system proactively identifies the correct polarity configuration through test signals and positioning operations, preventing future positioning errors rather than correcting them later.
Solution Approach 2:
The patent uses feedback by monitoring the head's actual positioning response to test signals and comparing it against expected behavior. The system adjusts polarity configuration based on feedback from position sensors that detect whether the head moved in the correct direction or opposite direction.
2Manufacturing precision
If extensive testing is performed during manufacturing to ensure correct polarity, then head positioning accuracy is ensured, but manufacturing time and efficiency are reduced
Solution Approach 1:
The patent changes operational parameters by using different test signal configurations and measurement approaches to quickly determine polarity. Instead of extensive manual testing, the system varies electrical parameters and automatically interprets results, reducing testing time while maintaining accuracy.
Solution Approach 2:
The system performs self-service by automatically detecting polarity configuration without requiring extensive manual intervention. The setup process autonomously identifies correct polarity through programmed test sequences and automated analysis of head response, reducing dependency on skilled technicians and manual testing procedures.
3Loss of time
If polarity detection method is implemented, then setup time is reduced and manufacturing efficiency improves, but additional test circuitry and control logic are required
Solution Approach 1:
The patent applies universality by designing test circuitry that serves multiple functions: it generates test signals, measures head position response, and determines polarity configuration. The same control logic is used for both normal operation and setup/testing, reducing the need for separate dedicated test components.
Solution Approach 2:
The patent merges the test signal generation, position measurement, and polarity determination functions into the existing control system architecture. Rather than adding completely separate test equipment, the system combines these functions with normal actuator control circuitry, minimizing additional hardware complexity.
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
Enables accurate and efficient detection of PZT actuator polarity, preventing incorrect head movement and reducing the need for extensive testing, thereby improving manufacturing efficiency and ensuring correct head positioning in disk drives.
Implementation Method 1
micro piezoelectric (PZT) actuators can provide a finer actuation for each head
Implementation Method 2
cause one PZT element to contract and the other PZT element to expand, thereby causing movement of the head
Data Source
AI summary
Determining a polarity of a piezoelectric (PZT) actuator of a disk drive including a disk for storing data and a head for reading and writing data. A test signal is injected into the PZT actuator and a position signal is received which indicates a position of the head over the disk resulting from the test signal. A test compensation signal is generated based on the received position signal and the polarity of the PZT actuator is determined based on a phase of the generated test compensation signal.