Two-degree-of-freedom control scheme for flying-height and tracking-position controls with thermal actuators in HDDs
Two-degree-of-freedom control scheme for flying-height and tracking-position controls with thermal actuators in HDDs
复制标题
HDD 中热执行器飞行高度和跟踪位置控制的二自由度控制方案
DOI：
10.1299/jamdsm.2018jamdsm0019
复制
发表时间：
2018
影响因子：
0.9
通讯作者：
T. Atsumi
中科院分区：
文献类型：
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作者：
T. Atsumi
为提高硬盘驱动器（HDD）中磁头的定位精度，针对磁头定位系统提出了一种带有热定位致动器的三级致动器系统。该定位系统有三种类型的致动器：音圈电机（VCM）、压电（PZT）致动器以及热定位致动器。在该系统中，磁头有一个位于读/写元件水平方向的加热器作为热定位致动器。通过使用这种结构，控制系统能够利用加热器中电流产生的热膨胀使磁头的读/写元件在水平方向上移动位置。热致动器系统具有简单的特性，即使在高频范围内也没有机械共振模式。这意味着热致动器有利于高频范围内的定位控制。因此，三级致动器系统使我们能够比传统的两级致动器系统在寻道跟踪控制过程中提高定位精度。然而，热定位致动器会导致磁头飞行高度波动，这可能会导致磁记录性能下降。在硬盘驱动器中，磁头在读/写元件的垂直方向还有一个加热器，用于控制读/写元件的飞行高度。这个控制系统被称为热飞行高度控制系统。在先前的研究中，我们可以通过使用热飞行高度控制系统（TFC）的前馈控制方案来补偿飞行高度的波动。然而，前馈控制对装置扰动的鲁棒性较差。为解决这个问题，本文针对热定位控制（TPC）和热飞行高度控制（TFC）系统的协同控制采用了一种二自由度（TDOF）控制方案。通过使用所提出的二自由度方法，我们能够针对装置扰动补偿飞行高度的波动。仿真结果表明，所提出的方法能够提高针对装置扰动的鲁棒性能。
To improve positioning accuracy of a magnetic head in hard disk drives (HDDs), a triple-stage-actuator system was proposed with a thermal positioning actuator for a magnetic head positioning system. This positioning system has three types of actuators: a voice coil motor (VCM), piezoelectric (PZT) actuators, and the thermal positioning actuator. In this system, a magnetic head has a heater located in a horizontal direction of read / write elements as the thermal positioning actuator. By using this structure, the control system can move the position of read / write elements of the magnetic head in a horizontal direction with thermal expansion induced by the heater with an electric current. The thermal actuator systems have simple characteristics without mechanical resonant modes even in a high frequency range. This means that the thermal actuator is good for positioning control in high frequency range. As a result, the triple-stage-actuator system enable us to improve the positioning accuracy during a track-following control from conventional dual-stage-actuatorsystems. However, the thermal positioning actuator causes flying height fluctuations of the magnetic head that could lead to fall of magnetic recording performances. In HDDs, the magnetic head has another heater located in a vertical direction of read / write elements in order to control flying height of the read / write elements. This control system is called thermal flying height control system. In the previous study, we can compensate for the flying-height fluctuations by using a feedforward control scheme of the TFC system. However, the feedforward control has little robustness against the plant perturbations. To address this issue, this paper employs a two-degree-of-freedom(TDOF) control scheme for the coordinated control with the TPC and the TFC systems. By using proposed TDOF method, we can compensate for the flying-height fluctuations against the plant perturbations. Simulation results showed that the proposed method is able to improve robust performance against the plant perturbations.