Split Actuator Bonding for Multi-Head HDD Decoupling
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Solution Overview
Problem
Conventional hard disk drives face challenges in simultaneously controlling multiple read/write heads due to inter-actuator coupling, which can cause disturbances and affect the positioning of one head when another is moving, leading to reduced performance and increased I/O bandwidth limitations.
Innovation Solution
The use of a split actuator with multiple head stack assemblies bonded to bearing sleeves, featuring a ring of high-damping bonding material in an annular gap between the E-block and the outer race of the bearing, which reduces mechanical coupling and dissipates vibrational energy, allowing for independent movement of multiple heads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple head stack assemblies are mounted on a common actuator shaft, then the I/O bandwidth is increased by allowing simultaneous reading or writing to multiple heads, but inter-actuator coupling causes disturbances that affect the positioning precision of heads
Solution Approach 1:
The actuator system is segmented into multiple independent head stack assemblies, each capable of independent positioning control. The bonding material isolates each assembly from the others, preventing mechanical coupling while maintaining structural integration on the common shaft.
Solution Approach 2:
A bonding material is introduced as an intermediary between the head stack assemblies and the actuator shaft. This bonding material serves as a mechanical decoupler that allows each head stack to move independently while remaining mounted on the common shaft, thus eliminating inter-actuator coupling disturbances.
2Stability of the object's composition
If head stack assemblies are rigidly coupled to the actuator shaft, then the structural stability is improved, but mechanical coupling causes disturbances when one head moves, affecting other heads
Solution Approach 1:
The bonding material acts as an intermediary element between the head stack assemblies and the actuator shaft. It provides sufficient structural stability to mount multiple assemblies while simultaneously decoupling their mechanical movements, preventing disturbance propagation between adjacent actuators.
Solution Approach 2:
The bonding material is applied locally at the interface between each head stack assembly and the actuator shaft. This localized bonding provides stability where needed while maintaining independence of movement for each assembly, creating different mechanical properties at different locations in the system.
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 configuration improves the performance of each actuator by reducing disturbances and enabling more aggressive seeking while tracking, thereby increasing I/O bandwidth by allowing simultaneous reading or writing to multiple heads.
Implementation Method 1
a ring of bonding material filling the annular gap
Implementation Method 2
at least one bearing having an inner race coupled to an outer surface of the actuator shaft(s)
Data Source
AI summary
An apparatus includes at least one actuator shaft. First and second head stack assemblies are coaxially located on the actuator shaft(s). The first and second head stack assemblies each include: at least one bearing having an inner race coupled to an outer surface of the actuator shaft(s); an E-block surrounding an outer race of the at least one bearing; an annular gap is between the E-block and the outer race of the at least one bearing; a ring of bonding material filling the annular gap; and an access gap providing a fluid path to the annular gap from at least one of a top and a bottom of the E-block.