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

Abstract

We have implemented the design of a dual-stage actuator tape head for enhanced reduction of lateral tape motion (LTM) disturbance. Our design consists of a conventional voice coil motor (VCM) and a micro-actuator for coarse and fine positioning, respectively. The micro-actuator, which is mounted on the VCM, uses a piezo crystal and allows following LTM up to the kHz regime, while the VCM follows low frequency LTM. Using step response measurements and a realization algorithm, we have created a multi-input discrete-time model of the dual-stage actuator. Based on the model, we designed and implemented a dual-stage controller, using a dual-input single-output approach based on a PQ method. The dual-stage controller controls the position of both actuators and enables an increased track-following bandwidth along with a control signal that is smaller in magnitude than that for a conventional single-stage tape head.

Data based modeling and control of a dual-stage actuator hard disk drive

“…One of them is the PQ method [17] that is based on loop shaping. It is shown in [17] that by placing the closed-loop zeros of the feedback connection of plant P and compensator Q one can achieve frequency separation [16] and [18]. In this study, P yields a non-minimum phase system which limits bandwidth and makes it much more difficult to perform loop shaping based control design.…”

“…The procedure used in this paper has been previously reported in [15] and [16]. The singular value decomposition (SVD) is applied to the weighted Hankel matrix H w defined by…”

Overview of Position Servo Control Technology and Development of Voice Coil Motor

“…This kind of control structure with VCM as macro controller and PZT as micro controller was first applied to the positioning mechanism of hard disk read/write, and it is also the most widely used in this field [69]- [72]. In [42], a macro-micro control structure composed of a permanent magnet linear motor (PMLM) and a VCM is also proposed, which can achieve a positioning accuracy of 0.1um in a larger stroke range.…”

Adaptive Regulation of Time Varying Disturbances in a Tape Storage System

“…As indicated in (Wang and de Callafon, 2012), an external reference signal r(t) via an Analog to Digital Converter (ADC), a measurement of the input signal u(t) to the actuator and an external measurement of the digital PES y(t) via ZOH DAC can be used to computing an estimate of the frequency response G(jω) of the servo actuator G for curve fitting purposes. Alternatively, simple step experiments on the closed-loop system can be used to formulate a model of the servo actuator using a step-based realization algorithm (Boettcher et al, 2009).…”