Position control of parallel-plate microactuators for probe-based data storage

In this paper, we present the use of closed-loop voltage control to extend the travel range of a parallel-plate electrostatic microactuator beyond the pull-in limit. Controller design considers nonlinearities from both the parallel-plate actuator and the capacitive position sensor to ensure robust stability within the feedback loop. Desired transient response is achieved by a pre-filter added in front of the feedback loop to shape the input command. The microactuator is characterized by static and dynamic measurements, with a spring constant of 0.17 N/m, mechanical resonant frequency of 12.4 kHz, and effective damping ratio from 0.55 to 0.35 for gaps between 2.3 to 2.65 /spl mu/m. The minimum input-referred noise capacitance change is 0.5 aF//spl radic/Hz measured at a gap of 5.7 /spl mu/m, corresponding to a minimum input-referred noise displacement of 0.33 nm//spl radic/Hz. Measured closed-loop step response illustrates a maximum travel distance up to 60% of the initial gap, surpassing the static pull-in limit of one-third of the gap.

[1]  H. Nyquist,et al.  The Regeneration Theory , 1954, Journal of Fluids Engineering.

[2]  I. Horowitz.  Synthesis of feedback systems , 1963 .

[3]  I. Horowitz,et al.  Synthesis of feedback systems with large plant ignorance for prescribed time-domain tolerances† , 1972 .

[4]  J. J. Blech.  On Isothermal Squeeze Films , 1983 .

[5]  J. Freudenberg,et al.  Limitations of feedback properties imposed by open-loop right half plane poles , 1991 .

[6]  Robert G. Meyer,et al.  Analysis and Design of Analog Integrated Circuits , 1993 .

[7]  Kristofer S. J. Pister,et al.  Analysis of closed-loop control of parallel-plate electrostatic microgrippers , 1994, Proceedings of the 1994 IEEE International Conference on Robotics and Automation.

[8]  Malcolm C. Smith,et al.  The general problem of the stability of motion : Translated and Edited by A. T. Fuller. Taylor and Francis, 1992 , 1995, Autom..

[9]  T. Veijola,et al.  Equivalent-circuit model of the squeezed gas film in a silicon accelerometer , 1995 .

[10]  J. Fluitman,et al.  Electrostatic curved electrode actuators , 1995, Proceedings IEEE Micro Electro Mechanical Systems. 1995.

[11]  G. Fedder,et al.  Laminated high-aspect-ratio microstructures in a conventional CMOS process , 1996, Proceedings of Ninth International Workshop on Micro Electromechanical Systems.

[12]  J. Seeger,et al.  Stabilization of electrostatically actuated mechanical devices , 1997, Proceedings of International Solid State Sensors and Actuators Conference (Transducers '97).

[13]  E. S. Hung,et al.  Extending the travel range of analog-tuned electrostatic actuators , 1999 .

[14]  Qi Jing,et al.  A hierarchical circuit-level design methodology for microelectromechanical systems , 1999 .

[15]  S. Senturia,et al.  Speed-energy optimization of electrostatic actuators based on pull-in , 1999 .

[16]  B. Boser,et al.  DYNAMICS AND CONTROL OF PARALLEL-PLATE ACTUATORS BEYOND THE ELECTROSTATIC INSTABILITY , 1999 .

[18]  Rogelio Lozano,et al.  Energy based control of the Pendubot , 2000, IEEE Trans. Autom. Control..

[19]  Leon Abelmann,et al.  Single-chip computers with microelectromechanical systems-based magnetic memory (invited) , 2000 .

[20]  Gary K. Fedder,et al.  Low-Order Squeeze Film Model for Simulation of MEMS Devices , 2000 .

[21]  R.W. Dutton,et al.  Electrostatic micromechanical actuator with extended range of travel , 2000, Journal of Microelectromechanical Systems.

[22]  R. Aigner,et al.  Control positioning of torsional electrostatic actuators by current driving , 2000, ASDAM 2000. Conference Proceedings. Third International EuroConference on Advanced Semiconductor Devices and Microsystems (Cat. No.00EX386).

[23]  K. R. Farmer,et al.  Extending the travel range of electrostatic micro-mirrors using insulator coated electrodes , 2000, 2000 IEEE/LEOS International Conference on Optical MEMS (Cat. No.00EX399).

[24]  Bernhard E. Boser,et al.  Charge control of parallel-plate, electrostatic actuators and the tip-in instability , 2003 .