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The applications of HDD in mobile and compact devices pose higher requirement on the vibration rejection capability of HDD servo control. A novel vibration suppression method is proposed in this paper. It is not model based, so it is less sensitive to the variation of the plan parameters. It avoids obtaining disturbance observation by differentiation of position signal. It is an add-on feedforward...
This paper investigates a factorization approach to sensitivity loop shaping for disturbance rejection in hard disk drives (HDDs). The advantage of the factorization approach is that the system sensitivity function can be expressed explicitly in terms of a unique design parameter. This greatly simplifies the control design process to make the system sensitivity function match a chosen target sensitivity...
Nowadays hard disk drives (HDD) are more widely used in video/audio devices; for such applications the acoustic level of HDD is a crucial performance index. This paper proposes a Two-Degree-Freedom seeking controller for minimizing the acoustics. A systematic way of design for low acoustics is given. The sinusoidal wave is used as the model reference input to ensure the smooth current profile, with...
To shorten the development and production time of hard disk drives (HDDs), an integrated servo-mechanical design procedure combining mechanical structure prototyping and fast servo evaluation is essential. In this paper, a system identification procedure is developed for estimation of residues, damping ratios, and natural frequencies of resonant modes for the actuators in a dual-stage HDD. The coefficients...
Most servo control algorithm implementations have been realized using digital signal processors (DSPs) due to large amount of digital signal processing. Nowadays, parallel programmable logic devices, such as the field programmable gate array (FPGA), have become powerful hardware options, offering low cost, high execution speed, reconfigurability and parallelism. This work intends to exploit the current...
Hard disk's head (HDH) is one of the most important parts in a hard disk. Because the floating height between the HDH and the platter is very narrow, it is necessary to make sure that the HDH's pitch angle and roll angles are from -0.05?? to 0.05?? on the Head Stack Assembly (HSA). The maximum error is 0.0226?? for pitch angle and 0.0288?? for roll angle according to our experimental results. This...
A promising approach for ultra high data storage capacities in magnetic hard disk drives is the use of bit-patterned media (BPM) that allows both higher track densities and increased linear bit spacing of data. To allow for such ultra high track densities, it is important to select an embedded servo pattern within the BPM that provides a Position Error Signal (PES) with sufficient quality to maintain...
This paper introduces a new method for synthesizing multiple-period repetitive controllers, which are suitable for integration into a combined adaptive-repetitive control scheme. The proposed synthesis method can be implemented recursively reducing the complexity of controller design considerably when compared with other methods available in the literature. In order to exemplify the synthesis procedure,...
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...
This paper addresses the optimal nonlinear gain tuning methods for the composite nonlinear feedback (CNF) control law. The parameter tuning problem is formulated as an optimization problem, which can be solved efficiently via numerical methods. The parameters of the nonlinear function are tuned by solving the optimization problem. Moreover, a hard disk drive (HDD) servo system is designed by using...
This paper investigates optimal reset law design of reset control systems with fixed reset time instants. Firstly, closed-loop reset control system is changed to discrete linear control system with reset values as control input. Then the optimal reset law design problems are transferred to standard linear quadratic regulation problems and the optimal reset laws are then obtained by solving some Riccati...
Recently, actuator arms in hard disk drive (HDD) have been rapidly developed. However resonance problem of HDD emerges to be a concerning issue because the HDD package is required to be smaller but data capacity must be higher. As a result, the actuator arm is developed to have multiple layers and its characteristic, i.e. natural frequency respond, becomes more complex for either minimizing or shifting...
This paper proposes the modified zero phase error tracking-feedforward control (ZPETm-FFC) system. The ZPETm-FFC system is higher-speed and more precise control system than the conventional control systems which are the feedback controller of phase lead-lag filters or the ZPET-FF control (ZPET-FFC) system. Numerical simulations show the performances of ZPET-FFC system in detail of practical conditions,...
In a short-span seeking mode of hard disk drives, the two-degree-of-freedom control is generally used. Authors' group proposed the perfect tracking control (PTC) method in order to achieve high accuracy and high speed control. However, tracking error is caused in acceleration and deceleration period by the modeling error. As a result, it causes the overshoot, and seeking-time becomes longer. In this...
This paper demonstrates the hard disk drive (HDD) performance improvement by nonvolatile FeRAM cache. First, the 128 Mb ChainFeRAM?? design and power supply system design to meet HDD application are presented. Second, the concept of nonvolatile FeRAM cache and the simulated and measured HDD performance improvement are presented. The read/write bandwidth improvements to 1.12 times, 3.3 times and 1...
Conventional disturbance observer (DOB) requires plant model inverse to retrieve the input to the actual plant in order to estimate the input disturbance imposed on the plant for compensation. This paper proposes a general form of disturbance observers, which does not need to solve the plant model inverse, and uses H?? control method to design the Q-filter in the disturbance observer. The conventional...
In this paper, we characterize three different sets of disk-level traces collected from enterprise systems. The data sets differ in the granularity of the recorded information and are called accordingly the millisecond, the hour, and the lifetime traces. We analyze the disk-level utilization, the availability of idleness, the dynamics of the read and write traffic, over time and across an entire drive...
Cogging torque results from the interaction of the rotor magnets acting on the stator teeth or poles independent of any current. It is desirable to reduce the cogging torque since it may cause speed ripple and vibration, particularly at light load and low speed. When the motor equipped ring magnet, it is very effective to reduce the cogging torque as changing only the magnetization patterns of the...
In this paper, we present a network server architecture which concentrates popular data on both HDD and NAND flash. Popular Data Concentration (PDC) is a well known technique to reduce the power consumption of disk arrays. We extended PDC by adding NAND flash based Solid State Drive (SSD) and achieved better performance and energy savings. We developed a novel file placement policy which places popular...
A programmable Gm-C filter with digital calibration for hard disk drive read channels was developed. The filter has gm and boost tuning circuits and DC offset cancellation circuits. Moreover, it has two types of digital calibrations for achieving a robust filter response. One is an initial calibration to compensate for the filter response variations over process changes. The other is a periodic calibration...
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