Two-axis pointing motor

Details Two-axis pointing motor Two-axis pointing motor

1999-10-27

2001-12-04

Ponomarenko, Nicholas (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S082000, C310S152000, C310S254100

Reexamination Certificate

active

06326714

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to multiple-axes pointing motors and mechanisms, and, more particularly, to a two-axis pointing motor which may be used to position or aim a mirror, sensor, antenna, thrust vector, or the like.
BACKGROUND ART
Most commercially-available pan/tilt mechanisms are motor-on-motor devices. One rotary motor, such as a brushless DC motor or a stepper motor, is used to move an object about one axis, while a second motor controls motion about another axis. Because the second motor must drive the first along with the object, this type of design is inherently inefficient. While these devices may be powerful and reliable, they tend to be large, heavy, slow, and to require high power.
One type of device is representatively shown in U.S. Pat. No. 5,204,573 “Benderson et al.”). This reference appears to disclose a gimbaled magnet surrounded by three orthogonally-positioned coils, with no magnetic pole structure. This patent apparently teaches that the coil whose axis is aligned with the magnet axis cannot produce torque, so effectively only two coils are needed. This patent shows two forms, a moving-magnet fixed-coil form and moving-coils fixed single-axis magnet form. This device orients a magnet with respect to a set of coils, but the coils completely surround the magnet and must be pulled apart to create an opening. Aside from being inconvenient, this distorts the magnetic field which controls the magnet. In fact, it is necessary to calibrate this motor using a procedure specifically designed for the device. The control strategy is open-loop, and so has limited accuracy, especially in applications involving a changing environment.
U.S. Pat. No. 4,785,212 (“Downer et al.”) discloses an annular magnet (or solenoid coil) carried in a spherical housing by magnetic suspension bearings, and acted upon by three opposed pairs of coils on the surface of the housing to control the angular position of the magnet axis in two directions. The positioning of the coils on the surface of the sphere is not defined, but they are shown diagrammatically as being on three orthogonal axes.
U.S. Pat. No. 4,600,871 (“Idoguki et al.”) appears to disclosure a magnet in a spherical bearing with its axis perpendicular to two radial flux fields in a plane established by paired polepieces at right angles to one another and pairs of coils operatively arranged to produce flux.
U.S. Pat. No. 5,892,310 (“Kempas”) appears to disclose a hemispherical arrangement of a shell carrying segmented coil pairs in a fixed permanent magnet field.
DISCLOSURE OF THE INVENTION
The present invention provides a two degree of freedom actuator which allows servocontrol about the two axes simultaneously. In each case where these axes are orthogonal, the device can be considered a pan/tilt mechanism. As noted above, applications typically include, but are not limited to, mirror aiming, sensor or antenna pointing, thrust vectoring, tracking, navigation and the like.
The moving member, or armature, consists of a hemispherical permanent magnet mounted on a gimbal. Four coils are mounted orthogonally on a frame, configured as though on the sides of a regular pyramid. The convex face of the magnet (which corresponds to either the north or south magnetic pole) faces the coils, so that the payload faces outwardly from the bottom of the pyramid configuration.
When equal current is applied to all four coils, the magnet is pulled equally in four directions due to the electromagnetic interaction between the coil flux and the magnet flux. This holds the magnet in its centered (zero angle) position. When current is decreased in one coil and increased by the same amount in the opposite coil, a differential force is generated on the magnet. Consequently, a torque is generated about the corresponding axis of motion. This causes the armature to rotate to a position along that axis between the coils, proportional to the ratio of currents in the coils. By similarly varying the currents in the other two coils, both axes of motion can be controlled simultaneously, positioning the armature anywhere within the plane described by these two axes.
The input to the coils depends on whether or not a self-centering mechanism is used. The device can be made so that the armature magnetically centers itself when all coils are de-energized. This may be useful for applications which require a fail-centered mode or a passive “home position” in the event of a failure. In this case, the current in the coils would reverse polarity as the armature has crossed the zero-angle position. In the case where no self-centering is required, the current in each coil would vary from zero to some maximum value.
Accordingly, with parenthetical reference to the corresponding parts, portions or surfaces of the disclosed embodiment, merely for purposes of illustration and not by way of limitation, the present invention provides an improvement in a two-axis pointing motor (
20
) having a frame (
21
) and a armature (
22
). The armature has an axis (x-x) passing through a point (P). The armature is mounted on the frame for controlled omni-directional pivotal movement of the axis about the point. The motor has a permanent magnet (
24
) mounted on the armature, and has a plurality of coils (
25
,
25
,
25
,
25
) mounted on the frame for creating controllable electromagnetic fluxes for urging the armature to pivot about the point. The improvement broadly comprises: the coils being positioned such that the entire volume of each of the coils is entirely within an imaginary hemisphere (h) generated about the point. This hemisphere is of arbitrary radius, but encompasses the coils.
In the preferred embodiment, the permissible range of motion of the axis is within the hemisphere. Each coil may have a winding axis, and the coil axes are subsequently arranged to radiate outwardly from the point within the hemisphere. Each coil may have an annular end face tangent to the surface of the imaginary hemisphere. Each such coil end surface may be arranged on a side of an imaginary regular pyramid, such as having four sides. Each coil may have a flux-conductive core. The armature may have a magnetically-conductive surface that is configured as a segment of a sphere. This surface may be provided on the magnet. The magnet may have polarized domains that are parallel to the armature axis. A gimbal may be operatively arranged between the armature and the frame. Alternatively, a spherical bearing may be connected between the armature and frame.
In another aspect, the invention provides another improvement in a two-axis pointing motor of the type heretofore described. In this form, the improvement comprises: the armature having a magnetically-conductive surface which is configured as a segment of a sphere. In this form, the frame may have a concave surface configured as a segment of a sphere that is arranged to face the armature surface to form a spherical bearing therebetween.
Accordingly, the general object of the invention is to provide an improved two-axis pointing motor.
Another object is to provide an improved two-axis pointing motor which may be used to position mirrors, sensors, antennas, for thrust vectoring purposes, tracking or navigational purposes.
Another object is to provide a simplified structure that is capable of use as a two-axis pointing motor.
These and other objects and advantages will become apparent from the for going and on going written specification, the drawing, and the appended claims.


REFERENCES:
patent: 825252 (1906-07-01), Vogel
patent: 829801 (1906-08-01), Pratt et al.
patent: 994058 (1911-05-01), Coates
patent: 4611863 (1986-09-01), Isely
patent: 4719381 (1988-01-01), Miles
patent: 4739241 (1988-04-01), Vachtsevanos et al.
patent: 4785212 (1988-11-01), Downer et al.
patent: 4828376 (1989-05-01), Padera
patent: 4874998 (1989-10-01), Hollis, Jr.
patent: 5007292 (1991-04-01), Crowe et al.
patent: 5204570 (1993-04-01), Gerfast
patent: 5413010 (1995-05-01), Nakanishi et al.
patent: 5609230 (1997-03-01), Swinbanks
patent: 5798590 (1998-08-

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