Closed loop electrostatic levitation system

• US 4,521,854 A
• Filed: 10/29/1982
• Issued: 06/04/1985
• Est. Priority Date: 10/29/1982
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Rhim, Won-Kyu, Elleman, Daniel D., Saffren, Melvin M.
• Primary Examiner(s): RUGGIERO, JOSEPH F
• Application Number:
  US06/437,912
• Time in Patent Office: 949 Days
• Field of Search: 364/400, 364/453, 364/130, 364/183, 74/5.6 D, 74/5.22, 74/5.34, 74/5.4, 74/5.41, 74/5.42, 74/5.7, 74/5 R, 204/164, 204/406, 156/DIG. 62, 33/318, 33/321, 244/1 R, 244/159, 244/161, 244/163, 358/107, 358/139, 358/160
• US Class Current: 700/90
• CPC Class Codes: H02N 13/00 Clutches or holding devices using electrostatic attraction, e.g. using Johnson-Rahbek effect
• CPC Class Codes: Y10S 117/901 Levitation, reduced gravity, microgravity, space
• CPC Class Codes: Y10T 74/1275 Electrical

Abstract

An electrostatic levitation system is described, which can closely control the position of objects of appreciable size. A plurality of electrodes surround the desired position of an electrostatically charged object, the position of the object is monitored, and the voltages applied to the electrodes are varied to hold the object at a desired position. In one system, the object is suspended above a plate-like electrode (16, FIG. 1) which has a concave upper face (26) to urge the object toward the vertical axis (20) of the curved plate. An upper electrode (18) that is also curved can be positioned above the object, to assure curvature of the field at any height above the lower plate. In another system, four spherical electrodes (81-84, FIG. 6) are positioned at the points of a tetrahedron, and the voltages applied to the electrodes are varied in accordance with the object position as detected by two sensors (94,96 FIG. 4).

Claims

1. Apparatus for electrostatically levitating a charged object, comprising:

a pair of spaced main electrodes with continuous electrically conductive plate-like surfaces that face each other, each surface having opposite sides and a substantially continuous surface extending between their opposite sides as seen in a sectional view, said surfaces facing each other along a predetermined, imaginary axis that extends substantially normal to said plate-like surfaces and passes substantially through their centers;

at least one ring-shaped electrode which surrounds a space lying between said main electrodes, said ring-shaped electrode extending in a continuous circle around said axis; and

a voltage source coupled to said main and ring-shaped electrodes to apply voltages to them without substantially passing currents around their perimeters.

2. Apparatus for electrostatically levitating a charged object, comprising:

a group of at least four electrodes, each electrode being itself of largely spherical shape, the centers of said electrodes lying at the corners of an imaginary polyhedron;

means for sensing the position of an object lying within said imaginary polyhedron along at least three axes that pass through said polyhedron; and

means for applying voltages to said electrodes of relative amplitudes selected to urge the object toward a predetermined position along said axes.

3. The apparatus described in claim 2 wherein:

said electrodes are spaced by between about one-half and twice their diameters.

4. The apparatus described in claim 2 wherein:

said group consists of four electrodes lying at the corners of an imaginary tetrahedron having triangular sides.

5. Apparatus for electrostatically levitating a charged object, comprising:

a lower electrode, and an upper electrode lying a predetermined distance above said lower electrode;

means for applying a voltage to said lower electrode to apply an electrostatic force to an object lying a small distance above the lower electrode, and for applying a lower voltage to said upper electrode than to said lower one;

said lower electrode having a concave dish-shaped surface facing upwardly and said upper electrode having a convex surface facing downwardly toward said lower electrode, whereby to urge the object toward a position directly above the lowermost portion of the concave surface.