In this paper the performance-optimized design of an electromagnetic micro-actuator for a Probe data-storage system is described. The Probe recording system considered in this study consists of a MEMS-based recording head array that can translate relative to a Ferroelectric media substrate. The probe device is slated to achieve 1 Tb/in2 recording density and a read/write data rate of 100 Mb/s while operating within a total power budget of 100 mW. Stringent requirements apply to the form-factor and packaging, power consumption, and operating environment making the design of the mechanical architecture and in particular, the actuator a challenging task. A methodology based on an analytical model framework for performance-optimal design of the actuator meeting these constraints is developed and presented.

This paper presents a microelectromechanical systems (MEMS) capacitive position sensor for nanopositioning applications in Probe storage systems. The objective of the sensor system design is to develop a high-precision X - Y linear and rotational position sensor with a minimum sensor area and a large range of movements at high speed. To achieve this, first, a simple sensor noise model scalable with a sensor area was developed, in which all the parasitic capacitances are taken into account. Furthermore, a signal-processing solution was developed to compensate for the nonlinearities caused by rotational disturbances and, at the same time, to generate a rotational position signal for active rotation-control purposes. A MEMS capacitive sensor prototype was constructed with the design of a 13-mum pitch, a 300-mum peak-to-peak linear stroke, and a 3.46-mm 2 sensor area at a 3-mum gap. The measured sensor noise was 0.2 nm 1sigma, which corresponds to 12 mudeg 1sigma for the fabricated prototype sensor, at 25-kHz bandwidth. Furthermore, the signal linearity was significantly enhanced by the proposed sensor signal processing, with a measured sensor signal nonlinearity of 0.78% for an 80-mum peak-to-peak stroke at 200 Hz. Finally, the capacitive sensor-based dynamic closed-loop X - Y linear and rotational position control of an electromagnetic scanner was successfully demonstrated.

Many advanced microsystems rely on nanometer-resolution in-plane motion between two substrates requiring precise control of gap spacing. Accurately maintained gaps may not only provide desired mechanical response but also enable position-sensing and signal transduction between the substrates. A method of passive gap-spacing control using MEMS-fabricated rigid spacers is proposed. A model to design a low-friction and low-wear interface between the sliding substrates is developed. Prototype parts with hard-coated interfaces and with and without lubrication were fabricated and tested. Sliding friction coefficients of less than 0.1 were achieved on prototype parts with boundary lubrication over a million sliding cycles. Wear life of several million sliding cycles is predicted.

This paper presents the control design and experimentation of a prototype electromagnetic scanner with an integrated capacitive linear and rotational position sensor for small form factor probe storage. An array of probe heads is to be precisely positioned in X/Y linear and rotation directions so that high areal density (>1 terabit/in2) and high data throughput can be achieved. The scanner has X/Y motion capabilities with a linear stroke of about 300 µm. It can also generate rotational motion with offset actuators to compensate for disturbances, mechanical tolerance and nonlinearities. System characterization, modeling, MIMO control design and simulation, and preliminary experimental results are presented. The feasibility of rotation control with the developed capacitive sensor and offset actuators is experimentally confirmed.

This paper discusses head-disk spacing (HDS) control for an advanced rotary tester (ART).With active control of HDS, the ART enables testing of individual recording head sliders and evaluation of novel magnetic recording processes with great flexibility. In this paper, system characterization and servo control design for the ART are presented. Various hardware and design issues are addressed and the corresponding solutions are provided. Simulation and experimental results show that the nominal HDS can be controlled to be within 10 nm with a standard variation of 1.5 nm.

Applications involving sub-nanometer, relative, in-plane motion between two substrates require precise control of gap-spacing between substrates for, both position-sensing as well as for signal transduction between the substrates. A method of passive gap-spacing control using MEMS-fabricated rigid spacers is proposed. A model to design a low-friction and low-wear interface between the sliding substrates is developed. Prototype parts with hard-coated interfaces and with and without lubrication were fabricated and tested. Sliding friction coefficients of 0.1-0.15 or less and wear life of millions of sliding cycles were achieved on prototype parts. Better results are predicted for MEMS-scale devices.

We demonstrate full closed-loop control of electrostatically actuated double-gimbaled MEMS mirrors and use them in a free space optical cross-connect with switching times of less than 10 ms, and optical power stability of better than 0.2 dB.

We propose and demonstrate electrostatic sidewall-electrodes actuation of three-dimensional (3-D) microelectromechanical systems (MEMS) gimbal mirrors. The linearity of the mirror angle dependence on actuation voltage is improved with the sidewall-electrodes actuation. In addition, the undesired spring-softening effect commonly found in electrostatic actuation, where the mirror resonance frequency decreases with increased tilt angle, is significantly reduced. Sidewall actuation enables superior performance of 3-D MEMS mirrors including large pull-in angles, reduced actuation voltages, improved device reliability, and fast switching times.