Central Support for Multi-Actuator HDD Structural Dynamics
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Solution Overview
Problem
High-capacity hard disk drives (HDDs) face performance limitations due to high latencies and vibration coupling between actuators on a shared pivot shaft, leading to slower data access and reduced I/O performance in clustered environments.
Innovation Solution
Implementing a multi-actuator system with independent pivot assemblies and a central support structure that provides a laterally stiff interface between opposing pivot shafts, along with the use of dampers to reduce vibration gains, allowing for concurrent operation and improved structural dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If actuators are mounted on a shared pivot shaft to increase storage capacity, then the HDD can service more disks concurrently, but vibration coupling between actuators increases causing higher latencies and reduced I/O performance
Solution Approach 1:
The patent divides the actuator mounting structure into separate pivot shafts for different actuator groups. Instead of mounting all actuators on a single shared pivot shaft, the actuators are segmented into at least two groups, each mounted on its own pivot shaft. This segmentation eliminates the vibration coupling that occurs when multiple actuators share a common pivot shaft, while still enabling concurrent servicing of multiple disks through the multi-actuator configuration.
2Strength
If a rigid support structure is used to increase structural stiffness, then structural mode frequencies increase, but the system becomes more susceptible to vibration transmission between actuators
Solution Approach 1:
The patent introduces a vibration isolation element as an intermediary component between the pivot shafts and the support structure. This intermediary element serves as a mediator that decouples the vibration paths between actuators while maintaining the structural stiffness needed for high structural mode frequencies. The vibration isolation element selectively transmits only certain vibration modes while isolating others, thus preventing harmful vibration transmission between actuators.
3Object-affected harmful factors
If dampers are added to reduce vibration gains, then lower frequency mode gains are reduced, but the device complexity increases
Solution Approach 1:
The patent combines the vibration isolation function with the existing support structure by integrating vibration isolation elements into the pivot shaft mounting mechanism. Rather than adding separate, standalone dampers throughout the system, the vibration isolation functionality is merged into the structural components that already exist, such as the pivot shaft supports and carriage structure. This approach reduces lower frequency mode gains while minimizing the increase in device complexity.
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 increases key structural mode frequencies, reduces lower frequency mode gains, and enhances servo system bandwidth, resulting in faster settle times and improved performance by mitigating vibration coupling between actuators.
Implementation Method 1
a vibration isolation element interposed between the pivot shafts and the support structure
Implementation Method 2
each actuator-pivot-VCM assembly comprises a voice coil motor (VCM) assembly
Data Source
AI summary
A multi-actuator data storage device such as a hard disk drive may include a lower actuator-pivot-VCM assembly including a lower pivot shaft and a lower motor assembly, an upper actuator-pivot-VCM assembly including an upper pivot shaft and an upper motor assembly, and a central support structure or plate sandwiched between the lower and upper pivot shafts and the lower and upper motor assemblies. The central support structure may be shaped to make contact with the motor assemblies only at discrete assembly locations and to make contact with the pivot shafts at opposing raised pads. Viscoelastic dampers may be adhered to the central support structure at the contact locations to dampen motor vibrational modes and/or to reduce the amplitude of vibration transmitted among the actuator-pivot assemblies. Such an assembly may increase the tilt and in-phase butterfly mode frequencies and decrease the gains of the tilt and coil torsion modes.