Digital Accumulator Microactuator Velocity Control
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Solution Overview
Problem
Existing disk drive systems face challenges in precise head positioning due to limitations in controlling the velocity and acceleration of the microactuator, leading to potential head/disk contact and inadequate servoing performance.
Innovation Solution
The implementation of a digital accumulator system that generates and limits velocity and acceleration commands for the microactuator, using a closed-loop servo control system with a PID algorithm and digital-to-analog conversion, to control the head's movement over the disk, thereby reducing position error signals and preventing sharp velocity changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the microactuator velocity and acceleration are not limited, then the head positioning response speed is improved, but the risk of head/disk contact increases and servoing performance deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating and limiting velocity and acceleration commands before they are executed by the microactuator. The servo control system generates commanded velocity and acceleration values that are constrained within safe limits based on head position feedback, preventing excessive movements that could cause head/disk contact while maintaining responsive positioning performance
Solution Approach 2:
The patent implements feedback control by continuously monitoring head position through servo sectors and using this information to adjust velocity and acceleration commands in real-time. The servo control system compares actual head position with target position and modifies commanded motion parameters accordingly, ensuring reliable operation while maintaining fast response
2Manufacturing precision
If digital accumulators are used to limit velocity and acceleration, then head positioning precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical positioning mechanisms with a digital control system using accumulators. Instead of mechanical constraints or complex actuator mechanisms, the system uses digital accumulation of velocity and acceleration commands with programmable limits, achieving precise head positioning through software-based control logic implemented in the servo controller
Solution Approach 2:
The patent achieves precise positioning by dynamically changing control parameters (velocity limits, acceleration limits) based on head position feedback. The digital accumulators adjust their accumulation rates and limits according to the servo error signal, allowing flexible precision control without requiring complex hardware modifications
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 solution enables precise and controlled head positioning, reducing the risk of head/disk contact while maintaining adequate servoing performance by fine-tuning the slew rate and limiting undesirable movement effects.
Implementation Method 1
a head connected to a distal end of an actuator arm which is rotated about a pivot by a voice coil motor (VCM)
Implementation Method 2
using a closed-loop servo control system with a PID algorithm and digital-to-analog conversion
Data Source
AI summary
A disk drive is disclosed comprising a microactuator configured to actuate a head over a disk, and control circuitry comprising a first digital accumulator responsive to a first register. The first digital accumulator generates at least one of a velocity command and a position command for the microactuator, and the control circuitry configures the first register in order to limit at least one of a velocity and an acceleration of the microactuator.