Conventional Voice Coil Motor Research Articles

Multi-mode sliding mode control for precision linear stage based on fixed or floating stator

This paper presents the control performance of a linear motion stage driven by Voice Coil Motor (VCM). Unlike the conventional VCM, the stator of this VCM is regulated, which means it can be adjusted as a floating-stator or fixed-stator. A Multi-Mode Sliding Mode Control (MMSMC), including a conventional Sliding Mode Control (SMC) and an Integral Sliding Mode Control (ISMC), is designed to control the linear motion stage. The control is switched between SMC and IMSC based on the error threshold. To eliminate the chattering, a smooth function is adopted instead of a signum function. The experimental results with the floating stator show that the positioning accuracy and tracking performance of the linear motion stage are improved with the MMSMC approach.

Separated pivot-shaft actuator for small skew angle in hard disk drives

A large skew angle in a hard disk drive (HDD) adversely affects the flying stability of the head sliders and the off-track capability of the read/write head. A novel actuator in the form of a separated pivot-shaft actuator (SPA) with a small skew angle is proposed in this paper. The SPA was particularly designed for a four-disk 3.5-in. HDD and has a skew angle of ±1.6°, which is approximately one-tenth of that of a conventional voice coil motor. The SPA was numerically analyzed by a finite element method, and its mechanical characteristics were compared with those of a long-arm actuator (LAA) (which is a strong candidate for a small-skew-angle actuator) with respect to the seek performance and frequency response. It was found that the SPA had a higher resonant frequency, which enabled the achievement of a wider servo-bandwidth compared to the LAA, and that the average seek time of the SPA was significantly shorter than that of the LAA.

A new loudspeaker for low frequency radiation by linear motion type piezoelectric ultrasonic actuators

The authors had proposed new direct-radiator loudspeaker constructions with a conventional paper cone radiator driven by ultrasonic motors (USM), as a substitution for voice-coil motor. However, those models needed a revolution to linear motion conversion mechanism, and avoiding zero region non-linearity, like class A amplifier. These complications came from the conventional USM, since it is a rotational and having zero region non-linearity inherently. Here, the authors would propose a new mechanism by using new ultrasonic linear actuators, called longitudinal-bending multilayered transducers with independent electrodes (LBMTIE). The beauty of LBMTIE is linear and to control vertical motion and horizontal motion independently, hence zero region non-linearity avoided. Therefore, it is possible to substitute the voice-coil motor directly, which avoids the complicated mechanisms mentioned above. In this LBMTIE driven loudspeaker, vertical movement voltage be fixed and horizontal voltage is driven by audio signal, like voice-coil motor. In addition, there is a big contrast against conventional voice-coil motor, which is a typical transducer, as its electrical input and sound pressure output are direct proportion each other. This is because LBMTIE driven loudspeaker may behave a sort of modulator, which is not direct proportion in between input electric power and output sound pressure level.

Modeling and Control of a Dual Stage Actuator Hard Disk Drive

A data-based approach is presented for modeling and controller design of a dual-stage servo actuator in a hard disk drive. The servo actuator in this hard disk drive consists of a conventional voice coil motor and a piezo-electrically actuated suspension. A weighted Hankel matrix based realization algorithm that uses frequency domain data is applied to estimate a discrete-time model of the voice coil motor and the piezoelectric actuator. Based on the discrete-time models, different dual-stage track-following controllers were designed using classic and H∞ loop shaping techniques. The controllers were implemented in real-time in the investigated hard disk drive. A stable feed-back control and good agreement between measurements and simulations show the promising result of data based modeling and control.

이미지 센서 모듈을 위한 자동-초점 기능의 전력-효율적인 구동 방법에 대한 연구

We present a power-efficient driving scheme that consists of piezoelectric actuator and driver IC for AF (Auto-Focus) on ISM (Image Sensor Module). The piezoelectric actuator is more power-efficient than conventional voice coil motor actuator. And high power-efficiency driver IC is designed. So the proposed driving scheme using designed piezoelectric actuator and driver IC is more close to recent trend of green IT. The diver IC should guarantee fast and accurate performance. So, the optimum driving method and high accurate frequency synthesizer are proposed. The die area of designed driver IC is <TEX>$2.0{\times}1.6mm^2$</TEX> and power consumption is 2.8mW.

Dynamic Modeling and Control of a Piezo-Electric Dual-Stage Tape Servo Actuator

We present a data-based approach for modeling and controller design of a dual-stage tape servo actuator. Our method uses step response measurements and a generalized realization algorithm to identify a multivariable discrete-time model of the actuator. The data acquisition and modeling can be implemented in the servo firmware of a tape drive. We have designed a dual-stage controller, based on the model, using loop shaping techniques adopted for multivariable control problems. We applied the procedure to the prototype of a dual-stage actuator tape head to reduce the effect of lateral tape motion. The prototype consists of a conventional voice coil motor for coarse positioning and a micro-actuator for fine positioning. The micro-actuator, which is mounted on the voice coil motor, uses a piezo crystal to follow high-frequency lateral tape motion (up to the kilohertz regime), while the voice coil motor follows only low-frequency lateral tape motion. Compared to a single-stage design, the dual-stage servo design provides a 25% bandwidth improvement and a voice coil motor control signal that is much smaller in magnitude.

High Positioning Repeatability of Miniature Actuator

Autofocusing actuators in camera phones should have a reduced profile and an improved performance in accordance with the requirements of consumer electronic products. In this study, we first discuss the detailed design of the miniature actuator presented in our previous work(10) and then describe an experiment to test its positioning repeatability. As compared with conventional voice coil motor (VCM) actuators positioned by open-loop control, the proposed miniature VCM actuator is small, has a high positioning repeatability and can improve the positioning repeatability by 87.5% of the typical value.

Design and Characterization of Miniature Auto-Focusing Voice Coil Motor Actuator for Cell Phone Camera Applications

When designing an auto-focusing actuator for use in cell phone cameras, it is essential to minimize the device size, maximize the positioning repeatability, and minimize the power consumption. In a previous study, we presented a miniature auto-focusing voice coil motor (VCM) actuator for cell phone camera applications in which the lens was precisely positioned by a closed-loop feedback signal generated by a Hall element. Our study characterizes the performance of this device by using an experimental approach. The results show that the proposed actuator is not only smaller than a conventional VCM actuator with an open-loop positioning system, but also has improved positioning repeatability, a more rapid response, and lower power consumption.

A miniaturized low-power VCM actuator for auto-focusing applications

In keeping with consumer preferences for ever smaller electronic products, a requirement exists for compact, high-performance auto-focusing actuators for the camera modules deployed in cell phones. Accordingly, the present study proposes a miniaturized electromagnetic-based actuator comprising a voice coil motor (VCM) and a closed-loop position control system in which an auto-focusing capability is achieved by using a position feedback signal generated by a Hall element to dynamically adjust the position of the lens module. The experimental results show that the holding current required to maintain a lens module weighing 200 mgw in the vertical position is 17 mA +/- 2 mA. Compared to conventional VCM actuators deployed in cell phone camera applications, the actuator presented in this study has a smaller size (6.5 mm x 6.5 mm x 4 mm) and an improved power efficiency. In particular, the miniaturized actuator reduces the holding current required to maintain the lens module in the focusing position by around 75% of that required in a traditional actuator.

VCM design with round coil and axe-shaped magnet for hard disk drive actuator

In this paper, we proposed a novel single-sided magnet voice coil motor (VCM) design that can reduce out-of-plane force. Out-of-plane force of a VCM causes the actuator vibration, which results in settling vibration and acoustic noise. The proposed single-sided magnet VCM consists of a round coil and an axe-shaped magnet. We designed the optimized configuration by using numerical magnetic field simulation and compared its performance with those of a conventional VCM. Torsional moment was reduced by 90% at the worst position of the middle track, and bending moment was reduced by 50% at the worst position of the inner track compared with a conventional VCM. Rotational moment in our VCM was almost the same as that of the conventional one. We manufactured an actuator with the new design VCM and confirmed that the new single-sided magnet VCM shows a good performance as expected, although its magnet volume and coil resistance were almost the same as a conventional design. The measured frequency response of the actuators from the coil current to the head displacement showed that the coil torsional mode vibration of the proposed VCM is reduced remarkably.

Multisegmented Magnet Array on Voice Coil Motor in Rotating Data Storage Devices

The swing-arm-type voice coil motor (VCM) is widely used as an actuator in rotating data storage devices. Recently, it has been found that to achieve a faster data transfer rate and a higher data storage areal density, a high performance actuator is required. Moreover, a small form factor has become desirable for portable devices. In this paper, a novel magnetic circuit of VCM with multisegmented magnet array (MSMA) is proposed. Both the magnetic circuits of the conventional VCM and the MSMA VCM are optimized using the 3D finite element method. Sample magnetic circuits are fabricated with optimally designed parameters and a comparative analysis is carried out. The performances of magnetic circuits are evaluated and the experimental results prove the effectiveness of the proposed magnet array.