Split-Actuator Drive Victim Feedforward Compensation
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Solution Overview
Problem
In magnetic hard disk drives (HDDs) with multiple rotary actuators, mechanical interactions between actuators can significantly affect the positioning accuracy of magnetic heads, particularly when one actuator is seeking a data track, causing vibrations that impair the accuracy of another actuator.
Innovation Solution
A victim feedforward signal is added to the microactuator control signal of a 'victim' actuator in response to the voice-coil motor control signal asserted by an 'aggressor' actuator, compensating for disturbances caused by the aggressor's motion. This signal is determined based on the aggressor's control signal and asserted at a predetermined time relative to when the aggressor passes over a servo wedge, synchronizing with the victim actuator's position over a second servo wedge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple rotary actuators operate simultaneously to increase throughput, then data access performance and throughput are improved, but mechanical interaction between actuators degrades positioning accuracy
Solution Approach 1:
The system calculates and applies a feedforward compensation signal before the aggressor actuator's motion can adversely affect the victim actuator. By detecting the aggressor's control signal and pre-computing the compensation based on stored transfer function data, the system proactively counteracts expected mechanical interactions before they occur, maintaining positioning accuracy while allowing simultaneous multi-actuator operation.
Solution Approach 2:
The system uses feedback from the aggressor actuator's control signals to generate compensation signals for the victim actuator. By continuously monitoring the aggressor's motion commands and applying real-time compensation based on pre-characterized mechanical coupling, the system maintains positioning accuracy across multiple actuators operating simultaneously.
2Speed
If one actuator performs high-acceleration seeking motion, then access speed is improved, but vibrations generated by this motion degrade positioning accuracy of another actuator
Solution Approach 1:
The system applies preliminary anti-action by calculating a compensation signal that opposes the expected harmful effects of the aggressor's high-acceleration motion. Using pre-stored transfer function data that characterizes the mechanical coupling between actuators, the system pre-computes the exact compensation needed to counteract vibrations and positioning errors before they affect the victim actuator.
Solution Approach 2:
The system performs preliminary action by pre-calculating compensation signals based on the aggressor's control commands before applying them to the victim actuator. The feedforward compensation is determined in advance using stored transfer function data, allowing the system to proactively neutralize the harmful effects of high-acceleration seeking motions.
3Measurement precision
If real-time compensation is applied to maintain positioning accuracy, then positioning precision is improved, but system complexity increases
Solution Approach 1:
The system reduces real-time computational complexity by pre-storing transfer function data that characterizes the mechanical coupling between actuators. During operation, the system simply retrieves pre-computed compensation values from memory based on the aggressor's control signal, rather than performing complex real-time calculations, thus maintaining positioning accuracy while minimizing processing requirements.
Solution Approach 2:
The system uses pre-stored copies of transfer function data to determine compensation signals during operation. Instead of performing complex real-time modeling and calculation, the system retrieves pre-characterized compensation values from memory, significantly reducing computational complexity while maintaining positioning precision.
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 approach effectively reduces the impact of one actuator's motion on another, enhancing positioning accuracy and stability in multi-actuator HDDs by compensating for disturbances in real-time, thereby improving data access performance.
Implementation Method 1
a voice-coil motor (VCM) control signal that is asserted by the aggressor actuator
Implementation Method 2
the high accelerations and changes in acceleration of the actuator can generate vibrations which will significantly affect the positioning accuracy of the other actuator
Data Source
AI summary
A victim feedforward signal is added to a microactuator control signal of the victim actuator in response to a voice-coil motor (VCM) control signal that is applied to the aggressor actuator, where the victim feedforward signal is configured to compensate for disturbances to a victim head caused by assertion of the aggressor VCM control signal. Each aggressor VCM control signal is asserted at a specific time by the aggressor actuator, for example in response to the aggressor head passing over a first servo wedge. A feedforward signal that compensates for the effect of the aggressor VCM control signal is then determined based on the aggressor VCM control signal, stored, and asserted via the victim microactuator at a predetermined time relative to when the aggressor VCM control signal is asserted.