Dual-Stage Actuator Head Position Estimation with Microactuator Gain Correction
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Solution Overview
Problem
Magnetic disk drives with dual-stage actuators face challenges in accurately estimating head positions during switching due to variations in microactuator displacements and gains, leading to errors in inter-head offsets and increased seek times.
Innovation Solution
A magnetic disk drive configuration with a first and second microactuator, a voice coil motor actuator, a storage unit, a head position detector, and a head position estimator that measures and corrects inter-head offsets by accounting for microactuator displacements and gains, allowing for precise head position estimation during switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microactuators are applied to enable fine movement of heads, then positioning precision is improved, but inter-head offset variation increases due to individual gain differences
Solution Approach 1:
The patent measures and stores individual gain parameters for each microactuator, then uses these parameters to calculate and apply correction values that compensate for gain differences. This transforms the fixed inter-head offset into a dynamically corrected value based on actual microactuator performance
Solution Approach 2:
The system measures the actual head position using a head position detector, compares it with the expected position based on microactuator displacement, and applies feedback correction to compensate for gain variations and individual differences among microactuators
2Speed
If head switching is performed without correcting for microactuator displacements, then switching speed is maintained, but head position estimation accuracy deteriorates
Solution Approach 1:
The patent performs preliminary measurement and storage of inter-head offsets and microactuator gain parameters when heads are in a known reference position. During subsequent head switching, these pre-measured values are quickly retrieved and applied for rapid position estimation without requiring time-consuming real-time measurements
3Device complexity
If conventional head position estimation is used without microactuator compensation, then device complexity is minimized, but seek operation accuracy deteriorates during head switching
Solution Approach 1:
The patent separates the actuator system into two independent control stages: the VCM actuator for coarse position control and microactuators for fine position adjustment. Each stage is controlled independently with its own measurement and correction mechanisms, allowing complex functionality to be achieved through modular segmentation
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 enables accurate head position estimation and reduced seek times by correcting inter-head offsets, improving the accuracy and efficiency of head switching operations in magnetic disk drives with dual-stage actuators.
Implementation Method 1
a voice coil motor actuator that causes coarse movement of the first head and the second head
Implementation Method 2
a first microactuator that causes fine movement of a first head associated with a first disk surface
Data Source
AI summary
According to one embodiment, a magnetic disk drive includes a storage unit, a head position detector and a head position estimator. The head position detector detects a position of a first head if the first head is switched to a second head. The head position estimator estimates a position of the second head based on the position of the first head, first and second voltages, polarities of first and second microactuators, gains of the first and second microactuators, and a first inter-head offset. The first and second voltages are applied to the first and second microactuators, respectively. The first inter-head offset is stored in the storage unit.