Fine Actuator Driver Circuits for On-Disk Activation

Solution Overview

Problem

Prior art multi-actuator disk drives require milliactuators and microactuators to be engaged only when actuator arms and read/write heads are parked on ramps, as activating them over the disk can cause destructive overshoot and physical head-disk interactions due to sudden bias current introduction.

Innovation Solution

The implementation of fine actuator driver circuits that moderate the increase in bias current to prevent overshoot, allowing milliactuators and microactuators to be safely engaged and disengaged while the actuator arms are over the disk, using configurations such as RC filters, constant current sources, and exponential rise circuits to control the activation current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If milliactuators and microactuators are activated while actuator arms are positioned over the disk, then faster operating speeds and reduced startup times are achieved, but sudden bias current introduction causes overshoot and physical head-disk interactions that are potentially catastrophically destructive

Engineering Contradiction:

Improveoperating speedVSAvoidhead-disk interaction

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary positioning of the actuator arm on the ramp before activating the milliactuator and microactuator. The driver circuit is enabled only after the actuator arm is confirmed to be positioned on the ramp, ensuring the head is away from the disk surface before current is applied to the fine actuators. This preliminary positioning action prevents harmful head-disk interactions during actuator activation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary control mechanism that monitors the position of the actuator arm and gates the activation of the milliactuator and microactuator accordingly. A controller enables the driver circuit only when the actuator arm is positioned on the ramp, acting as an intermediary safety mechanism that prevents premature activation and the resulting harmful current overshoot and head-disk interactions.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If milliactuators and microactuators are engaged only when parked on ramps, then activation safety is maintained, but startup times increase and power-saving modes are limited

Engineering Contradiction:

Improveactivation safetyVSAvoidstartup time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary positioning of the actuator arm on the ramp before activating the milliactuator and microactuator. The driver circuit is enabled only after the actuator arm is confirmed to be positioned on the ramp, ensuring the head is away from the disk surface before current is applied to the fine actuators. This preliminary positioning action prevents harmful head-disk interactions during actuator activation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary control mechanism that monitors the position of the actuator arm and gates the activation of the milliactuator and microactuator accordingly. A controller enables the driver circuit only when the actuator arm is positioned on the ramp, acting as an intermediary safety mechanism that prevents premature activation and the resulting harmful current overshoot and head-disk interactions.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 faster disk drive operating speeds and data read/write operations by allowing milliactuators and microactuators to be activated on-disk, reducing startup times and enabling power-saving modes and flexible actuator management during seek operations and debugging tasks.

Implementation Method 1

using configurations such as RC filters, constant current sources, and exponential rise circuits to control the activation current

Methodology Applied

Scientific EffectRC filter: Capacitance

Implementation Method 2

an actuator arm which is rotated about a pivot by a voice coil motor (VCM) to position the head radially over the disk

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Data Source

PatentUS11749303B2Data storage device with soft on-disk activation of fine actuators

Publication Date: 2023.09.05 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

Various illustrative aspects are directed to a data storage device comprising one or more disks; an actuator arm assembly comprising one or more actuator arms, and configured to position the one or more actuator arms over disk surfaces of the one or more disks; one or more fine actuators, disposed on the one or more actuator arms; and one or more processing devices. The one or more processing devices are configured to: output a driver current to the one or more fine actuators, wherein the one or more processing devices are configured to rate limit a rise of the driver current over time during an activation of the driver current to within a selected rate limit of current rise over time.