Magnetic Disk Head Speed Control for Scratch Prevention
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Solution Overview
Problem
Magnetic disk devices, such as hard disk drives (HDDs), face failures due to scratches caused by contamination like dust and dirt coming into contact with the magnetic head or disk, despite maintaining a high level of cleanliness within the device.
Innovation Solution
The HDD is designed with a controller that adjusts the radial and circumferential travel speeds of the magnetic head during load and seek operations to maintain a specific speed relationship, reducing the likelihood of scratches by controlling the number of disk revolutions and head movement speeds, thereby minimizing data loss and read errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the magnetic head moves at high speed during load and seek operations, then productivity is improved, but the risk of scratches from contamination increases
Solution Approach 1:
The patent changes the operational parameters by establishing a specific speed relationship between radial and circumferential motion. By controlling the ratio of radial travel speed to circumferential travel speed to fall within a predetermined range, the system optimizes both productivity and scratch prevention simultaneously
Solution Approach 2:
The patent implements dynamic speed control during head operations. The controller adjusts the radial and circumferential travel speeds in real-time based on the operational phase (load or seek), ensuring the speed relationship remains within the optimal range to minimize contamination contact while maintaining efficient head movement
2Productivity
If the radial travel speed of the magnetic head is increased, then the load operation efficiency is improved, but the circumferential travel speed must be controlled to prevent scratches
Solution Approach 1:
The patent modifies the speed parameters by defining a specific relationship between radial and circumferential travel speeds. During load operations, the controller ensures that the ratio of radial speed to circumferential speed remains within a predetermined range, allowing efficient load operations while preventing scratches through controlled speed ratios
3Loss of time
If the seek operation speed is increased to reduce data access time, then the radial travel speed increases, but this may cause the magnetic head to contact contaminants more frequently
Solution Approach 1:
The patent changes the motion parameters during seek operations by controlling the ratio of radial to circumferential travel speeds. By maintaining this ratio within a predetermined range, the system achieves fast data access while reducing contaminant contact frequency through optimized head trajectory and speed control
4Object-affected harmful factors
If the magnetic head is designed to fly at a higher height from the disk surface, then the risk of contamination contact is reduced, but the reading precision deteriorates
Solution Approach 1:
The patent performs preliminary action by executing controlled seek operations that move the head across the disk surface in a manner that minimizes contaminant contact. This preliminary head movement establishes optimal positioning before actual data read operations, allowing the head to maintain sufficient proximity to the disk surface for high reading precision while reducing contamination risk through controlled trajectory
Data Source
AI summary
According to one embodiment, a disk device includes a rotatable magnetic disk, an actuator which supports and moves a head, a ramp which holds the head at an unloaded position, a motor which rotates the magnetic disk, and a controller which performs a load operation and a seek operation. When a radial travel speed of the head during the load operation is referred to as Vr1, a circumferential travel speed of the head is referred to as Vt1, a radial travel speed of the head during the seek operation is referred to as Vrs, and a circumferential travel speed is referred to as Vts, the controller controls at least one of the radial travel speed of the head and number of revolutions of the magnetic disk to satisfy a relationship (Vr1/Vt1)<(Vrs/Vts).