MICROELECTROMECHANICAL STEP ACTUATOR CAPABLE OF BOTH ANALOG AND DIGITAL MOVEMENTS

• US 20070222334A1
• Filed: 03/24/2006
• Published: 09/27/2007
• Est. Priority Date: 03/24/2006
• Status: Abandoned Application

• Current Assignee: Chang-Feng Wan
• Original Assignee: Chang-Feng Wan
• Inventors: Wan, Chang-Feng
• Application Number:
  US11/277,479
• Publication Number:
  US 20070222334A1
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: B81B 2201/038 Microengines and actuators not provided for in B81B2201/031 - B81B2201/037
• CPC Class Codes: B81B 3/0051 For defining the movement, i.e. structures that guide or limit the movement of an element mechanical arrangements for preventing or damping vibration or shock H01H3/60
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping
• CPC Class Codes: H01G 5/38 Multiple capacitors, e.g. ganged
• CPC Class Codes: H02N 1/006 of the gap-closing type H02N1/004 takes precedence

Abstract

An embodiment of the present invention provides a step actuator, comprising a suspended membrane comprising a plurality of movable electrodes connected by plurality of spring hinges to a payload platform; and pillars connecting said membrane to a substrate, said substrate comprising a plurality of fixed electrodes; wherein said movable electrodes of said suspended membrane and said fixed electrodes from said substrate form parallel-plate electrostatic sub-actuators. Another embodiment of the present invention provides controlled operation of the step actuator over its entire range of motion, by avoiding its instability region and both digital and analog operations with enhanced stroke. It comprises a suspended membrane comprising a plurality of fixed electrodes, a plurality of movable electrodes connected by plurality of spring hinges to a medial payload platform. The fixed electrodes comprise insulator stops that keep the movable electrodes from entering the unstable region.

Claims

1. An electrostatic step actuator, comprising a substrate and a membrane suspended on said substrate;

(1) said substrate further comprises a plurality of pillars, fixed electrodes, and insulator stops;

(2) said fixed electrodes form stairs;

(3) said insulator stops are formed on said fixed electrodes and have heights larger than or equal to 20% of the respective incremental height of the steps of said stairs;

(4) said suspended membrane further comprises a payload platform, a plurality of movable electrodes and a plurality of spring hinges;

(5) said movable electrodes are connected with said spring hinges to form at least one series of movable electrodes;

(6) one end of each said series of movable electrodes is connected to said payload platform, the other end is supported by at least one of said pillars;

(7) said fixed electrodes and said movable electrodes form a plurality of parallel-plate electrostatic sub-actuators having graduated air gaps.

2. The step actuator in claim 1, wherein said insulator stops have heights larger than or equal to 50% of the incremental step height of said stairs.

3. The step actuator in claim 1, wherein at least one of said sub-actuators are connected to a fixed capacitor in series.

4. The step actuator in claim 1, wherein at least two of said sub-actuator are connected in series.

5. The step actuator of claim 1, wherein said spring hinges comprise torsion beams.

6. The step actuator of claim 1, wherein said spring hinges comprise torsion beams, said insulator piers are on one side of said steps and have heights larger than or equal to d−

L1·

tan θ

_pi wherein L1 is the lateral distance of the insulator bump from the hinge, d is the respective incremental step height of said stairs, and θ

_pi is the pull-in angle of respective sub-actuators.

7. The step actuator of claim 1, wherein said suspended membrane comprises high resistivity material and said movable electrodes comprise interconnected metal field plates.

8. The step actuator of claim 7, wherein said interconnected metal field plates are electrically floating.

9. The step actuator of claim 8 wherein said suspended membrane further comprises a stationary metal field plate to form a fixed capacitor with a fixed electrode on said substrate, wherein one side of said fixed capacitor is grounded, and the other side is connected in series with the other sub-actuators of the series of sub-actuators.

10. The step actuator of claim 9 wherein the capacitance of said fixed capacitor is substantially larger than those of the sub-actuators.

11. The step actuator of claim 1, wherein

(1) said substrate further comprises a coplanar waveguide under said payload platform,

(2) said suspended membrane comprises high resistivity material;

(3) said payload platform comprises a metal field plate that is electrically floating and electrically isolated from said movable electrodes; and

(4) said metal field plate form capacitors with the ground lines and signal lines of said coplanar waveguide

12. The step actuator of claim 11, wherein at least one of said metal field plates is electrically floating and form at least two capacitors with said fixed electrodes.

13. The step actuator in claim 1, wherein the number of said series of sub-actuator is one and said payload platform is connected to said pillars with said spring hinges.

14. The step actuator in claim 1, wherein the number of said series of sub-actuator is two, and are oriented 180 degrees apart from each other around said payload platform.

15. The step actuator in claim 1, wherein the number of said series of sub-actuator is three, and are oriented 120 degrees apart from each other around said payload platform.

16. The step actuator in claim 1, wherein said fixed electrode is formed between said

17. Insulator stops and said substrate.

18. An electrostatic step actuator, comprising a substrate and a membrane suspended on said substrate;

(1) said substrate further comprises a plurality of pillars, fixed electrodes, and insulator stops;

(2) said fixed electrodes form stairs;

(3) said insulator stops are formed on said fixed electrodes;

(4) said suspended membrane further comprises a payload platform, a plurality of movable electrodes and a plurality of spring hinges;

(5) said movable electrodes are connected with each other in a series by said spring hinges to form at least one series of movable electrodes;

(6) one end of each said series of movable electrodes is connected to said payload platform, the other end is supported by at least one of said pillars;

(7) said fixed electrodes and said movable electrodes form a plurality of parallel-plate electrostatic sub-actuators having graduated air gaps.

(8) said stairs assume the shape of a folding, or winding staircase.