Mark David Bedillion

Charge-based scanning probe readback of nanometer-scale ferroelectric domain patterns at megahertz rates

We present a method for data storage in continuous ferroelectric (FE) media, applicable to storage systems based on one or more scanning probes. Written FE domains are read back in a destructive fashion by applying a constant voltage of magnitude greater than the coercive voltage, as is done in FE random access memory (FeRAM). The resulting flow of screening charges through the readback amplifier provides sufficient signal to allow readback of domains of minimum dimension of the order of 10 nm at MHz rates, orders of magnitude faster than previously demonstrated techniques for readback of domains in continuous FE media.

Control for Actuator Arrays

Actuator arrays are planar arrangements of simple actuators that cooperate to translate and orient objects. This paper derives the equations of motion for manipulating an object in stick/slip contact with the actuators. A controller derived from kinematics considerations is presented and its stability analyzed with the multivariable circle criterion. Stability results are verified through simulation and experimental results on a 20 unit macroscopic actuator array.

Sliding Contact Micro-Bearing for Nano-Precision Sensing and Positioning

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.

Nano-Positioning of a Electromagnetic Scanner with a MEMS Capacitive Sensor

Abstract 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/in 2 ) 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.

Head-disk spacing control for an advanced rotary tester

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.

Distributed Manipulation with an Actuator Array and Vision Feedback

Actuator arrays are planar distributed manipulation systems that use multiple single degree of freedom actuators to manipulate objects with three degrees of freedom (x, y, and thetas). This paper describes design and control of a prototype actuator array, the advanced distributed manipulation system (ADMS). Unlike prior actuator array prototypes, the ADMS uses vision feedback from a centralized camera and is large enough to include transitions between sets of supporting actuators. Control laws are presented for both regulating and trajectory tracking control and their stability properties are summarized. Experiments show the stability of proportional control, but also show the existence of limit cycles for desired equilibria that are near changes in the set of supporting actuators.

Spinstand control characterization of an electromagnetic slider microactuator

Increasing areal densities in disc drives require high performance servo tracking systems to attenuate runout. High bandwidth, large stroke microactuators are used to improve positioning accuracy by eliminating disturbances at higher frequencies. This paper details modeling and servo control of an electromagnetic slider microactuator designed at Seagate and its promise as a solution for high accuracy tracking control. The device has passive high frequency windage disturbance attenuation due to its structure. Controller design is developed for a single stage spinstand environment to show the device effectiveness.