US-12620915-B2 - Magnetic levitation of permanent magnet for three-axis attitude control

US12620915B2US 12620915 B2US12620915 B2US 12620915B2US-12620915-B2

Abstract

Embodiments provided herein include rotatable magnets (e.g., spherical dipole magnets) disposed within sets of coils that can be used to operate the magnets as reaction/momentum “spheres” and/or as control moment gyroscopes. The coils are able to exert three-dimensional torques onto the magnet in order to effect attitude control of a satellite or other system. The coils can also optionally exert translational forces onto the magnet in order to maintain the magnet in position and avoid contact with static components. Diamagnetic materials can also be included to provide stabilizing repulsive magnetic forces to maintain the magnet in position and/or to reduce the necessary performance of the coils with respect to applying stabilizing translational forces.

Inventors

Matthew Ware
Alexander Rider
Allen Hsu
Mark Tinkle

Assignees

SRI INTERNATIONAL

Dates

Publication Date: 20260505
Application Date: 20231215

Claims (20)

1 . A system comprising: a set of coils; a dipole magnet disposed within the set of coils such that the dipole magnet has three degrees of freedom of rotation within the set of coils; a first sensor configured to detect an orientation of the dipole magnet relative to the set of coils; and a second sensor configured to detect a location of the dipole magnet relative to the set of coils, wherein the set of coils is operable to control a location and orientation of the dipole magnet relative to the set of coils based on outputs of the first sensor and second sensor.
2 . The system of claim 1 , wherein the set of coils comprises at least six pairs of coils, wherein each pair of coils of the at least six pairs of coils comprises a respective first coil and a respective second coil that are aligned with each other and disposed opposite the dipole magnet.
3 . The system of claim 2 , wherein the at least six pairs of coils are disposed around the dipole magnet in a dodecahedral arrangement.
4 . The system of claim 2 , further comprising a controller configured to: operate the first sensor to determine an orientation of the dipole magnet relative to the set of coils; operate the second sensor to determine a location of the dipole magnet relative to the set of coils; and based on the detected orientation and location of the dipole magnet, operate the at least six pairs of coils to maintain a location of the dipole magnet within the at least six pairs of coils.
5 . The system of claim 4 , further comprising diamagnetic material, wherein the diamagnetic material is disposed around the dipole magnet to stabilize the location of the dipole magnet within the at least six pairs of coils.
6 . The system of claim 4 , wherein the set of coils additionally comprises three coils, and wherein the controller is additionally configured to, based on the detected orientation and location of the dipole magnet, operate the three coils to adjust an orientation of the dipole magnet relative to the set of coils.
7 . The system of claim 4 , wherein the controller is additionally configured to, based on the detected orientation and location of the dipole magnet, operate the at least six pairs of coils to adjust an orientation of the dipole magnet relative to the set of coils.
8 . The system of claim 4 , wherein the controller is additionally configured to obtain an anticipated motion of the system, and wherein the controller operating the at least six pairs of coils to maintain the location of the dipole magnet within the at least six pairs of coils comprises operating the at least six pairs of coils based on the anticipated motion of the system and the detected orientation and location of the dipole magnet.
9 . The system of claim 1 , further comprising diamagnetic material, wherein the diamagnetic material is disposed around the dipole magnet to stabilize the location of the dipole magnet within the set of coils.
10 . The system of claim 9 , wherein a first portion of the diamagnetic material located at a first location has a first crystal orientation, wherein a second portion of the diamagnetic material located at a second location that differs from the first location and that has a second crystal orientation, and wherein the first and second orientations differ from each other and are both directed towards the dipole magnet.
11 . The system of claim 1 , wherein the dipole magnet is a first dipole magnet and the set of coils is a first set of coils, and wherein the system further comprises: a second dipole magnet; a second set of coils; and a controller configured to: during a first period of time, control an orientation of the system by operating the second set of coils to control a rotation of the second dipole magnet and, based on outputs of the first sensor and second sensor, operating the first set of coils to control a rotation of the first dipole magnet; determine, subsequent to the first period of time, that an operational capacity of the first dipole magnet, first set of coils, first sensor, and second sensor has degraded; and responsive to determining that the operational capacity has degraded, control an orientation of the system by operating the second set of coils to control a rotation of the second dipole magnet.
12 . The system of claim 1 , further comprising a controller configured to: operate the set of coils to cause the dipole magnet to rotate about a first axis relative to the set of coils; and subsequently operate the set of coils to adjust the axis of rotation of the dipole magnet from the first axis to a second, different axis relative to the set of coils.
13 . The system of claim 1 , wherein the dipole magnet is at least one of a spherical dipole magnet, a cylindrical dipole magnet with flat ends, a cylindrical dipole magnet with curved ends, or a spherical shell of magnetic material enclosing a non-magnetic material.
14 . A system comprising: a set of coils; a dipole magnet disposed within the set of coils such that the dipole magnet has three degrees of freedom of rotation within the set of coils, wherein the set of coils is operable to control an orientation of the dipole magnet relative to the set of coils; and diamagnetic material, wherein the diamagnetic material is disposed around the dipole magnet to stabilize the location of the dipole magnet within the set of coils.
15 . The system of claim 14 , wherein a first portion of the diamagnetic material located at a first location has a first crystal orientation, wherein a second portion of the diamagnetic material located at a second location that differs from the first location and that has a second crystal orientation, and wherein the first and second orientations differ from each other and are both directed toward the dipole magnet.
16 . The system of claim 14 , further comprising a controller configured to: operate the set of coils to cause the dipole magnet to rotate about a first axis relative to the set of coils; and subsequently operate the set of coils to adjust the axis of rotation of the dipole magnet from the first axis to a second, different axis relative to the set of coils.
17 . A system comprising: a set of coils; a dipole magnet disposed within the set of coils such that the dipole magnet has three degrees of freedom of rotation within the set of coils; diamagnetic material disposed around the dipole magnet to stabilize the location of the dipole magnet relative to the set of coils; and a controller configured to operate the set of coils to maintain a location of the dipole magnet relative to the set of coils and to control an orientation of the dipole magnet relative to the set of coils.
18 . The system of claim 17 , wherein the set of coils comprises at least six pairs of coils disposed around the dipole magnet in a dodecahedral arrangement, and wherein the controller operating the set of coils to maintain the location of the dipole magnet relative to the set of coils comprises the controller operating the at least six pairs of coils to maintain the location of the dipole magnet within the at least six pairs of coils.
19 . The system of claim 18 , wherein the controller operating the set of coils to control the orientation of the dipole magnet relative to the set of coils comprises the controller operating the at least six pairs of coils to control the orientation of the dipole magnet.
20 . The system of claim 17 , wherein the controller is additionally configured to obtain an anticipated motion of the system, and wherein the controller operating the set of coils to maintain the location of the dipole magnet relative to the set of coils comprises operating the set of coils based on the anticipated motion of the system.

Description

This application claims priority to U.S. Provisional Patent Application No. 63/465,753, filed May 11, 2023, the contents of which are incorporated by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with government support under Contract Number NRO000-21-C-0097 awarded by National Reconnaissance Office. The government has certain rights in the invention. BACKGROUND Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. Attitude control systems for spaceflight take size, weight, and power away from mission specific hardware. Such attitude control systems can include one or more single-axis mechanical rotors. However, such mechanical rotors are a common point of failure on spacecraft. For example, the failure of a reaction wheel on the Kepler Space Telescope led to the loss of a 500 million USD satellite. Attitude control in satellites has historically been accomplished using a mechanical reaction wheel or control moment gyroscopes. Such historical attitude control systems (ACS) have used mechanical bearings with finite lifetimes that take size, weight, and power (SWaP) away from the mission. For example, three-axis control on a satellite may be accomplished using four reaction wheels, three for control and one for redundancy. These systems rely on mechanical lubrication with finite lifetimes and physical constraints. Such systems can also be damaged in a space launch or during operation by, e.g., exceeding such constraints. Rotating wheel ACS (e.g., reaction wheels, control moment gyroscopes) may be used in combination with reaction control thrusters, e.g., to allow momentum absorbed by the rotating wheel(s) to be ‘expended’ into the space environment, in order to reduce the rate of rotation of the wheel(s) (thereby increasing their lifetime and/or avoiding the rotation rate exceeding design constraints). However, the use of reaction control thrusters in this manner results in the expenditure of propellant, which is limited. Magnetorquerers may additionally or alternatievly be used to provide a smaller measure of attitude control, but they only able to provide small amounts of torque. SUMMARY In a first aspect, a system is provided that includes: (i) a set of coils; (ii) a magnet disposed within the set of coils such that the magnet has three degrees of freedom of rotation within the set of coils; (iii) a first sensor configured to detect an orientation of the magnet relative to the set of coils; and (iv) a second sensor configured to detect a location of the magnet relative to the set of coils, wherein the set of coils is operable to control a location and orientation of the magnet relative to the set of coils based on outputs of the first sensor and second sensor. In a second aspect, a system is provided that includes: (i) a set of coils; (ii) a magnet disposed within the set of coils such that the magnet has three degrees of freedom of rotation within the set of coils, wherein the set of coils is operable to control an orientation of the magnet relative to the set of coils; and (iii) diamagnetic material, wherein the diamagnetic material is disposed around the magnet to stabilize the location of the magnet within the set of coils. In a third aspect, a system is provided that includes: (i) a set of coils; (ii) a magnet disposed within the set of coils such that the magnet has three degrees of freedom of rotation within the set of coils; (iii) a diamagnetic material disposed around the magnet to stabilize the location of the magnet relative to the set of coils; and (iv) a controller configured to operate the set of coils to maintain a location of the magnet relative to the set of coils and to control an orientation of the magnet relative to the set of coils. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A depicts elements of a system, according to example embodiments FIG. 1B depicts elements of a system, according to example embodiments FIG. 2A depicts a diamagnetically levitated control moment gyroscope (DiaCMG), according to example embodiments. FIG. 2B depicts a working example of a DiaCMG system, according to example embodiments. FIG. 3 is a schematic showing active levitation control (left), and the magnetic torque that can be applied using a constant magnetic field generated by a Helmholtz coil on the faces of a DiaCMG (right), according to example embodiments. FIG. 4 is a schematic depicting elements of an example system, according to example embodiments. FIG. 5 depicts an example feedback matrix element (channel 0, z-axis) across all (θ, φ), according to example embodiments. FIG. 6 depicts oscilloscope traces from experimental open-loop operation at 900 Hz of a working example of the embodiments described herein. FIG. 7 shows experimental results of power consumption without pyrolytic graphite. FIG. 8 shows experimental