Hard Disk Drive Servo System Based on Field-Programmable Gate Arrays

Abstract

Servo systems are essential components of current magnetic storage hard disk drives (HDDs). In this paper, we demonstrate a novel servo scheme using a field-programmable gate array (FPGA). Adjacent magnetic tracks with two different frequencies are recorded on the magnetic disk and are used as servo tracks to encode the position information. A discrete Fourier transform is employed to decode the magnetic head position and to obtain the position error signal (PES). The PES is defined in terms of the difference of the magnitudes of the two frequencies. The relationship between the displacement and the PES is obtained by offline calibration. A real-time signal acquisition and processing system using a commercial FPGA, analog-to-digital converter chips, and digital-to-analog converter chips is built to do the high-speed spectrum analysis and generate the PES. The PES is transmitted to a laboratory virtual instrument engineering workbench (LabVIEW) real-time control target to implement the control algorithm. The computed control output from the real-time control target is amplified to drive a piezoelectric stage, which moves the magnetic head along the radial direction to compensate for the position error. A simple repetitive and proportional-integral-derivative control algorithm is implemented for head positioning and to verify this new servo scheme in this paper. With the controller, most of the major disturbances, such as the harmonics of the spindle runout, have been effectively attenuated compared with an open-loop control scheme.Index Terms-Field-programmable gate arrays (FPGAs), hard disks, servo systems.

State of the Art of Repetitive Control in Power Electronics and Drive Applications

“…The block diagram of the control structure is shown in Fig. 11, where G 4L (s) is the transfer function (TF) of the 4-leg converter defined in (10), G F (s) is the TF of the output filter defined in (11), G load (s) is the TF of the equivalent load, G lf (s) is the TF of the second-order low-pass Butterworth filter defined in (12).…”

“…), and frequency variations of the power devices (inverters, rectifiers, etc.) connected to the electric distribution network [10], [11]. This problem leads to a dramatic decay of the controller performance [12].…”

Adaptive feedforward cancellation with gain and damping control system considering helium leakage in HDDs

“…The positioning accuracy should be improved to read/write data in a smaller area. Therefore, various technologies have been developed to improve positioning accuracy [3][4][5][6][7]. Fluid-induced vibrations deteriorate positioning accuracy.…”

Full FPGA Tracking Control System Based on Error-Based Communication Disturbance Observer Considering Time Delay for Optical Disc System

“…However, it is difficult to realize a fastsampling control system that has a complex structure. On the other hand, the FPGA system realizes a fast sampling period for complicated control systems (10)- (12) . The high-performance controller is also implemented in the FPGA (11) (12) .…”

“…The high-performance controller is also implemented in the FPGA (11) (12) . The highperformance control system of a hard disk drive has been embedded by using the FPGA (10) . Digital control systems usually suffer from time delay, which affect both the calculation and conversion times in a digital control system.…”