Positioning Performance Comparison Between Collocated Slider-Driven PZT Actuators and Conventional Suspension-Driven Actuators

2013 ◽  
Author(s):  
Keiji Aruga
Keyword(s):  
Reaction Force ◽  
Hard Disk Drives ◽  
Performance Comparison ◽  
Disk Drives ◽  
Pzt Actuator ◽  
Physical Limit ◽  
Dual Stage ◽  
Dual Stage Actuator ◽  
Sway Frequency ◽  
Fundamental Resonance Frequency

The recording density of hard disk drives is achieving the physical limit due to the recording magnet size limitations. Therefore, the bit density BPI (Bits per inch) is saturated. The residual aim is to increase track density TPI (tracks per inch), because reducing mechanical track misregistration has a possibility of increasing TPI. The Dual Stage Actuator using a PZT microactuator which enables better positioning accuracy, is widely used in 3.5 inch high density drives. The latest PZT actuator called a “Milli” actuator drives the whole suspension. However, the mass of the suspension is around several milli-grams, thus the reaction force of PZT driving sometimes causes excitation to attached arm resonance at 8–9 kHz. In addition, the fundamental resonance frequency of a milli-actuator is around 20–25 kHz, the sway frequency of whole suspension.

High-bandwidth controller design for dual-stage actuator system in hard disk drives

2022 ◽  
pp. 107754632110623
Author(s):  
Shota Yabui ◽  
Takenori Atsumi
Keyword(s):  
Controller Design ◽  
Hard Disk Drives ◽  
Voice Coil Motor ◽  
Hard Disk ◽  
Disk Drives ◽  
Positioning Accuracy ◽  
Micro Actuator ◽  
Dual Stage ◽  
Actuator System ◽  
Dual Stage Actuator

Large-capacity hard disk drives are important for the development of an information society. The capacities of hard disk drives depend on the positioning accuracy of magnetic heads, which read and write digital data, in disk-positioning control systems. Therefore, it is necessary to improve positioning accuracy to develop hard disk drives with large capacities. Hard disk drives employ dual-stage actuator systems to accurately control the magnetic heads. A dual-stage actuator system consists of a voice coil motor and micro-actuator. In micro-actuators, there is a trade-off between head-positioning accuracy and stroke limitation. In particular, in a conventional controller design, the micro-actuator is required to actuate such that it compensates for low-frequency vibration. To overcome this trade-off, this study proposes a high-bandwidth controller design for the micro-actuator in a dual-stage actuator system. The proposed method can reduce the required stroke of the micro-actuator by increasing the gain of the feedback controller of the voice coil motor at low frequencies. Although the voice coil motor control loop becomes unstable, the micro-actuator stabilizes the entire feedback loop at high frequencies. As a result, the control system improves the positioning accuracy compared to that achieved by conventional control methods, and the required micro-actuator stroke is reduced.

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