Adaptive Lattice Filter for Vibration-Resistant Head Positioning
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Solution Overview
Problem
As the areal density of magnetic disc drives increases, there is a growing need for more precise position control in the presence of external vibrations, which can cause non-repeatable runout and disrupt data storage operations, especially in thinner and lighter devices with diverse vibrational characteristics.
Innovation Solution
A vibration sensor circuit and adaptive lattice filter circuit are used to generate orthogonal backward prediction errors, which are then processed by a multiple regression filter to estimate a disturbance correction signal, improving the servo control loop's ability to counteract external disturbances and maintain precise head positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional servo control loops are used, then device structure can be simpler, but position control precision deteriorates in the presence of external vibrations
Solution Approach 1:
The lattice filter performs preliminary decorrelation of the sensor signal to generate orthogonal backward prediction errors before the multiple regression filter processes them. This preliminary processing of the disturbance signal enables the regression filter to more effectively estimate and cancel vibration effects, improving position control precision under vibrational conditions.
Solution Approach 2:
The system uses a feedback mechanism where the disturbance correction signal estimated by the multiple regression filter is fed back to the servo control loop to counteract external vibrations. The lattice filter continuously processes sensor signals to generate updated orthogonal backward prediction errors, creating a closed-loop feedback system that actively compensates for vibration disturbances.
2Quantity of substance
If areal density of magnetic disc drives is increased, then data storage capacity is improved, but susceptibility to vibration-induced non-repeatable runout worsens
Solution Approach 1:
The patent replaces purely mechanical vibration isolation with a signal processing-based solution. The lattice filter and multiple regression filter process sensor signals electronically to generate disturbance correction signals, substituting mechanical approaches with electronic signal processing to maintain track following reliability in high-density storage systems.
Solution Approach 2:
The system dynamically adjusts the disturbance correction signal parameters based on real-time vibration conditions. The lattice filter adapts its coefficients and the multiple regression filter adjusts its weightings according to the statistical properties of the orthogonal backward prediction errors, enabling the system to maintain reliability across varying vibration environments in high-density drives.
3Ease of operation
If device weight is reduced for portability, then ease of operation is improved, but vibration resistance deteriorates
Solution Approach 1:
The lattice filter acts as an intermediary that processes raw sensor signals to generate orthogonal backward prediction errors, which are then used by the multiple regression filter. This intermediary processing stage enables lightweight portable devices to effectively counteract vibrations by transforming sensor data into corrected disturbance signals without requiring heavy mechanical vibration isolation components.
Data Source
AI summary
An implementation of a circuit disclose herein comprises a vibration sensor circuit that generates a sensor signal from a disturbance signal, a lattice filter circuit that decorrelates the sensor signal to generate orthogonal backward prediction errors, and a multiple regression filter that estimates a disturbance correction signal using the orthogonal backward prediction errors.