PERFORMANCE IMPROVEMENT OF MEMS DEVICES

• US 20160097789A1
• Filed: 03/20/2014
• Published: 04/07/2016
• Est. Priority Date: 04/14/2013
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: CLARK, Jason
• Granted Patent: US 10,024,879 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/5726 Signal processing
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01P 15/02 by making use of inertia forces using solid seismic massesG01P15/14 takes precedence
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0882 for providing damping of vibrations
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]

Abstract

A microelectromechanical-systems (MEMS) device includes a driven mass and has a natural stiffness or damping. An actuator applies force to the mass, movement of which is measured by a sensing capacitor. A control circuit operates the actuator per displacement or velocity of the driven mass, so that a characteristic stiffness or damping of the mechanical subsystem is different from the respective natural value. A method of transforming a MEMS device design includes determining an aim performance value of the design and a baseline performance uncertainty of the design, selecting candidate sets of parameter values, determining a candidate, first, and second performance value for each, scoring the candidates, and repeating until one of the candidates satisfies a termination criterion, so the transformed design using that candidate set has the aim performance value and the respective first and second performance values closer to each other than the baseline performance uncertainty.

Claims

1. A microelectromechanical-systems (MEMS) device, comprising:

a) a mechanical subsystem including a driven mass, the subsystem having a natural stiffness or a natural damping, wherein the mass is at least partly movable or at least partly deformable;

b) an actuator responsive to a time-varying control signal to apply force to the driven mass;

c) a sensing capacitor including a first plate attached to and movable with the driven mass and a second plate substantially fixed in position, wherein a capacitance of the sensing capacitor varies as the driven mass moves;

d) a measurement circuit responsive to the capacitance of the sensing capacitor to provide first and second signals corresponding respectively to a displacement and to a velocity of the driven mass; and

e) a control circuit configured to provide the time-varying control signal to the actuator in response to the first signal or the second signal and in response to a selected parameter, so that a characteristic stiffness or a characteristic damping of the mechanical subsystem is different from the natural stiffness or the natural damping, respectively, while the time-varying control signal is applied to the actuator.

2. The device according to claim 1, wherein the measurement circuit is further configured to provide a third signal corresponding to an acceleration of the mass, the mechanical subsystem has a natural mass, and the control circuit is further configured to provide the time-varying control signal to the actuator in response to the third signal, so that a characteristic mass of the mechanical subsystem is different from the natural mass while the time-varying control signal is applied to the actuator.

3. The device according to claim 1, wherein the actuator is configured to apply the force to the driven mass in a direction along a displacement axis, the device further including:

a) a second actuator responsive to a second time-varying control signal to apply force to the driven mass in a second, different direction along the displacement axis;

b) a second sensing capacitor including a first plate attached to and movable with the driven mass and a second plate substantially fixed in position, wherein a second capacitance of the second sensing capacitor varies as the driven mass moves or deforms;

c) a second measurement circuit responsive to the second capacitance to provide fourth and fifth signals corresponding respectively to the displacement and to the velocity of the driven mass; and

d) a second control circuit configured to provide the second time-varying control signal to the second actuator in response to the fourth signal or the fifth signal and in response to a second selected parameter, so that a characteristic stiffness or a characteristic damping of the mechanical subsystem is different from the natural stiffness or the natural damping, respectively, while the time-varying control signal is applied to the second actuator.

4. The device according to claim 3, wherein the second measurement circuit is further configured to provide a sixth signal corresponding to the acceleration of the driven mass, the mechanical subsystem has a natural mass, and the second control circuit is further configured to provide the second time-varying control signal to the second actuator in response to the sixth signal, so that a characteristic mass of the mechanical subsystem is different from the natural mass while the second time-varying control signal is applied to the second actuator.

5. The system according to claim 1, wherein the actuator is configured to apply the force to the driven mass along a displacement axis and the driven mass includes an applicator forming an end of the driven mass along the displacement axis.

6. The device according to claim 1, wherein the actuator is configured to apply the force to the driven mass along a displacement axis and the mechanical subsystem includes a plurality of flexures supporting the driven mass and adapted to permit the driven mass to translate along the displacement axis.

7. The device according to claim 1, wherein the actuator includes a comb drive and a voltage source.

8. The device according to claim 1, wherein the measurement circuit includes a differentiator configured to receive a signal corresponding to the capacitance of the sensing capacitor and provide the second signal corresponding to the velocity.

9. A method of transforming a microelectromechanical-systems (MEMS) device design with respect to a set of one or more parameters having selected initial values, the method comprising automatically performing the following steps using a processor:

using selected uncertainty values of the parameters, automatically determining first and second parameter offset sets of the design;

using the selected initial values of the parameters and the first and second parameter offset sets, determining an aim performance value of the design and a baseline performance uncertainty of the design;

a setup step of selecting a plurality of candidate sets of parameter values using the initial values;

determining a respective candidate performance value of the design for each of the candidate sets;

applying the first and second parameter offset sets to each of the candidate sets and determining respective first and second performance values of the design;

a scoring step of determining a respective score of each of the candidate sets using the aim performance value, the respective candidate performance value, and the respective first and second performance values;

a testing step of, if none of the respective scores satisfies a selected termination criterion, repeating the setup through testing steps using a selected one of the candidate sets in place of the initial values, so that one of the candidate sets is selected as a transformation of the design, and the transformed design has the respective candidate performance value corresponding to the aim performance value and the respective first and second performance values closer to each other than the baseline performance uncertainty.

10. The method according to claim 9, wherein the setup step further includes selecting the plurality of candidate sets using selected respective limits for the parameters.

11. The method according to claim 9, further including automatically modifying the design to include the transformation.

12. The method according to claim 9, wherein the scoring step includes computing an objective function of a first difference between the respective candidate performance value and the aim performance value, and of a second difference between the respective first performance value and the respective second performance value.

13. The method according to claim 12, wherein the objective function weights the first and second differences equally.

14. The method according to claim 9, further including retrieving the design from a tangible, non-transitory computer-readable storage medium by the processor, and receiving the selected initial values via a user interface operatively connected to the processor.

15. The method according to claim 14, further including presenting the transformation via the user interface.

16. The method according to claim 9, wherein the one or more parameters include a width or a length of an element of the device, or a force to be applied to an element of the device.