Note: Descriptions are shown in the official language in which they were submitted.
COMBINED PROPELLANT-LESS PROPULSION AND REACTION WHEEL DEVICE
10001 I This page is left intentionally blank.
Date Regue/Date Received 2023-03-09
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
FIELD
[0002] This disclosure relates generally to vehicle attitude control and
propulsion and relates
specifically to vehicles traveling in the vacuum of space or on bodies of
water. Additionally, the
disclosure describes and enables multiple improvements over current spacecraft
attitude control
and propulsion technology such as: launch mass, scalability, reaction wheel de-
spinning and
overall system design simplification.
BACKGROUND
[0003] Spacecraft have been used to conduct research on the earth and other
celestial bodies,
provide communication services that cover the globe and even carry man to the
moon. In addition,
efforts have begun that seek to mine asteroids for precious metals and
resources. While there have
been many advances in all of the critical systems required to accomplish a
given space mission,
the in-space propulsion system has remained largely unchanged since our first
launches.
[0004] A critical short coming of the current propulsion technology is the
need to use a chemical
propellant to generate thrust. This reliance on propellant has led to added
complexity and cost to
spacecraft design specifically the need to include fuel tanks and fuel line
routing, filtering, valves
and flow gauges. These system elements add substantially to the spacecraft
mass and because
spacecraft launch mass is a critical component in determining launch costs,
the current state of
propulsion technology is economically inefficient. In addition, the
operational life of most
spacecraft is dictated primarily by fuel consumption because once the fuel
tank is empty there is
no way to refill it once in orbit.
[0005] Recently, satellite bus structures have decreased in size as well as
operators have leveraged
the maturation of reliable, mass produced electronics, sensors and radio
components used in smart
phone technology. Unfortunately, while small in size these vehicles can still
provide a powerful
platform for communications, earth observation and interplanetary missions
traditional fuel-based
propulsion systems do not scale down in size well which has left
small/micro/nano spacecraft
without thruster capabilities. Without propulsion smaller buses operating
lifetimes are limited.
When they are in low earth orbit, they experience drag due to the earth's
upper atmosphere. This
drag continually slows the vehicles down reducing its speed and orbital
altitude until they become
2
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
inoperable and burn up in the atmosphere. The current device aims to address
both the excessive
launch mass and scalability problems associated with current propellant based
propulsion systems
by providing thrust without propellant that is capable of providing drag
makeup thrust and
maintain the spacecraft's desired orbital altitude while also being scalable
in design to work with
satellites of all sizes.
[0006] In addition, individual propellant-based thruster units are limited to
generating thrust in
only one direction. Accordingly, there exists a need for a spacecraft thruster
can address bi
directionality as well. An optimum solution would allow straightforward
mechanical and electrical
integration into the current satellite designs.
[0007] In some spacecraft attitude control is achieved through the use of
reaction wheels.
Typically, a reaction wheel is comprised of an electric motor attached to a
flywheel. The reaction
forces created while spinning up the flywheel are utilized to achieve changes
in angular orientation
of the vehicle and controlled to reach a desired pointing direction. Once the
flywheel is spun up
there is no straightforward way to de-spin it. Some spacecraft can utilize
their propulsion system
to provide counter torques in conjunction with motor commands. The present
device can not only
provide attitude control through reaction wheel mechanisms it can also de-
energize and de-spin its
own flywheel internally through elastic strain losses in its bearings. The
combination of all these
features will provide both propulsion and attitude control in a single unit
thereby significantly
simplifying spacecraft system architecture.
3
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
SUMMARY
[0008] The above and other needs are met by a method and apparatus for
providing propulsion
and attitude control. Embodiments of the present disclosure are directed
towards spacecraft by
providing a novel foun of propellant-less propulsion. A general description of
this disclosure
involves in one aspect the arrangement of a multiplicity of permanent magnets
mounted on at least
one pair of synchronized coplanar counter rotating structures/rotors. In one
aspect one rotates
clockwise CW while the other rotates counterclockwise CCW such that net
positive linear
momentum is generated through ball bearing traction. This traction is
transferred through rigid
body attachment of the inner race of the ball bears to the shafts and then
onto a support platform
and platform attachment points to the vehicle at large creating a
translational force on the system.
Therein, thrust or linear momentum is achieved by the vehicle. Rotation may be
created and
maintained by an electric powered motor. This motor may be integral to the
rotating structures or
separately associated therewith. Embodiments may include a plurality of
synchronized rotor pairs
sharing the same shaft pairs.
[0009] System torques may be created through interaction between the electro-
magnetic coils and
magnets mounted on one or other rotor, A variety of control architectures may
be implemented to
achieve rotation of a desired angle or angular rate. A basic control loop may
entail operating a
single electro-magnetic coil on a single rotor for a small duration of time.
Reactionary forces create
a torque on the coil and the body it is attached to. A second electro-magnetic
coil on the
neighboring rotor may be operated for an equivalent duration such that an
equivalent reactionary
torque is created in the opposite direction thereby arresting the system
rotational motion. A
relationship between the spacecraft mass and distance from the center of mass
of the individual
coils must be accounted for to achieve desired angular displacement.
[0010] In a first aspect, a propulsion method includes: providing a pair of
synchronized rotors,
each of the synchronized rotors rotatably mounted on a frame with a bearing
having a bearing
outer race, bearing balls, and bearing inner race; providing a plurality of
permanent magnets
mounted on the pair of synchronized rotors and arranged such that at least one
permanent magnet
of a first of the pair of synchronized rotors is attracted to at least one
permanent magnet of a second
of the pair of synchronized rotors when the permanent magnets are proximate
one another at an
4
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
inboard orientation; rotating the pair of synchronized rotors such that one of
the pair of
synchronized rotors rotates in a clockwise direction and the other of the pair
of synchronized rotors
rotates in a counterclockwise direction; loading an outer portion of the outer
bearing race, bearing
ball, and inner bearing race of each of the bearings relative to a point at
which the at least one
permanent magnet of the first of the pair of synchronized rotors is closest to
at least one permanent
magnet of the second of the pair of synchronized rotors, a load on the outer
portion of the bearings
corresponding to an attractive force between the permanent magnets of the pair
of synchronized
rotors. A thrust is imparted on the frame in a direction corresponding to a
direction of loading of
the inner bearing race.
[0011] In one embodiment, the propulsion method further includes providing one
or more
electromagnets located proximate to the pair of synchronized rotors, wherein
the one or more
electromagnets are aligned with the plurality of permanent magnets such that a
rotational force is
imparted on the pair of synchronized rotors when the one or more
electromagnets are activated.
[0012] In another embodiment, the propulsion method further includes a unit-
polar control circuit
for controlling the one or more electromagnets. In yet another embodiment, the
propulsion method
further includes providing one or more optical sensors and adjusting a current
applied to the one
or more electromagnets based on an output of the one or more optical sensors.
[0013] In one embodiment, the propulsion method further includes providing a
vehicle on which
the frame is mounted, wherein the thrust imparted on the frame is imparted on
the vehicle. In
another embodiment, the propulsion method further includes: providing a
controller for controlling
rotation of the pair of synchronized rotors; receiving data on the controller
from at least one of a
gyroscope and accelerometer; controlling rotation of the pair of synchronized
rotors to generate a
desired propulsion effect on the vehicle.
100141 In yet another embodiment, the pair of synchronized rotors are intel __
meshed with a spur
gear profile. In one embodiment, the propulsion method further includes
determining a time
required for the pair of synchronized rotors to stop rotating based on a load
placed on the bearing
balls at the outer portion of the outer bearing race and the inner bearing
race.
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
[0015] In a second aspect, a reaction wheel thrust mechanism includes: a first
rotor rotatably
coupled on a frame at a first bearing, the first bearing having a first outer
bearing race, a plurality
of first bearing balls, and a first inner bearing race; a second rotor
rotatably coupled on the frame
at a second bearing, the second bearing having a second outer bearing race, a
plurality of second
bearing balls, and a second inner bearing race; a plurality of permanent
magnets located on the
first rotor and the second rotor, the plurality of permanent magnets oriented
such that at a first
permanent magnet on the first rotor is attracted towards at a second permanent
magnet on the
second rotor when the first permanent magnet is at its most proximate location
relative to the
second permanent magnet; a controller for controlling rotation speeds of the
first rotor and the
second rotor. When electro-magnetic coils of the first rotor are activated by
the controller, the
electro-magnetic coils impart a torque onto the first rotor and the first
rotor will impart reactionary
torque onto the electro-magnetic coils and the frame and a vehicle attached
thereto.
[0016] In one embodiment, the first rotor and the second rotor are
synchronized with a spur gear
profile formed around the first rotor and the second rotor. In another
embodiment, the controller
adjusts speeds of rotation of the first rotor and the second rotor based on a
desired thrust to be
imparted on the vehicle. In yet another embodiment, the controller adjusts
speeds of rotation of
the first rotor and shorts the electro-magnetic coils of the second rotor to
achieve a desired rate of
angular change.
[0017] In a third aspect, a reaction wheel thrust mechanism includes: a first
rotor rotatably coupled
on a frame at a first bearing, the first bearing having a first outer bearing
race, a plurality of first
bearing balls, and a first inner bearing race; a second rotor rotatably
coupled on the frame at a
second bearing, the second bearing having a second outer bearing race, a
plurality of second
bearing balls, and a second inner bearing race; a plurality of permanent
magnets located on the
first rotor and the second rotor, the plurality of permanent magnets oriented
such that at a first
permanent magnet on the first rotor is attracted towards at a second permanent
magnet on the
second rotor when the first permanent magnet is at its most proximate location
relative to the
second permanent magnet; a controller for controlling rotation speeds of the
first rotor and the
second rotor. When electro-magnetic coils of the first rotor are activated by
the controller, the
electro-magnetic coils impart a torque onto the first rotor and the first
rotor will impart reactionary
torque onto the electro-magnetic coils and the frame and a vehicle attached
thereto. The controller
6
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
adjusts speeds of rotation of the first rotor and the second rotor based on a
desired thrust to be
imparted on the vehicle.
7
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Further features, aspects, and advantages of the present disclosure
will become better
understood by reference to the following detailed description, appended
claims, and accompanying
figures, wherein elements are not to scale so as to more clearly show the
details, wherein like
reference numbers indicate like elements throughout the several views, and
wherein:
[0019] FIG. lA shows an isometric view of one embodiment of a known self-
propelling apparatus
with integral electro-magnetic coils and permanent magnets mounted at the mid-
plane of rotors
with integrated spur gear profile for synchronization shown with a cut away in
its enclosing shell
and top plate for clarity;
[0020] FIG. 1B shows an isometric view of one embodiment of a known self-
propelling apparatus
with integral electro-magnetic coils and permanent magnets mounted at the mid-
plane of rotors
with integrated spur gear profile for synchronization shown with a cut away in
its enclosing shell
and top plate for clarity;
[0021] FIG. 2 shows an isometric view of one embodiment of a self-propelling
apparatus with
integral electro-magnetic coils and permanent magnets mounted at the mid-plane
of rotors with
integrated spur gear profile for synchronization shown without a top or
enclosing element;
[0022] FIG. 3A shows a top schematic view showing magnet pole orientation
along with a first
operating mode rotation direction and thrust direction relationship according
to one embodiment
of the present disclosure;
[0023] FIG. 3B is a top schematic view showing magnet pole orientation along
with a second
operating mode rotation direction and thrust direction relationship according
to one embodiment
of the present disclosure;
[0024] FIG. 4 is a close-up view of rotor bearings showing an outboard loading
case along with
outer-race and ball bearing rotation of both a first rotor and a second rotor
according to one
embodiment of the present disclosure;
8
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
[0025] FIG. 5 is an exploded close-up view of a single bearing ball element
and inner race element
of both a first rotor and a second rotor illustrating the loading, normal and
frictional forces
according to one embodiment of the present disclosure;
[0026] FIG. 6 is a graph showing the variation of loading in the +X direction
on a first rotor due
to the net magnetic attraction forces between its magnets and the magnets on a
second rotor
according to one embodiment of the present disclosure;
[0027] FIG. 7 is a graph showing the relationship of rotor speed to generated
thrust for rotors
subjected to loading shown in FIG. 6 according to one embodiment of the
present disclosure;
[0028] FIG. 8 is a circuit schematic view of illustrating an H-bridge unipolar
electronic speed
controller for a single set of coils around a single rotor;
[0029] FIG. 9 is a circuit schematic view of a portion of the electronic
control allows current
direction through the coils to be reversed thereby enabling thrust and
reaction wheel direction
control according to one embodiment of the present disclosure;
[0030] FIG. 10 is a schematic view illustrating a series connection of a
single set of rotor coils
according to one embodiment of the present disclosure;
[0031] FIG. 11 is a circuit schematic view of a portion of the electronic
control circuit that allows
a single set of rotor coils to be shorted to itself for enhanced reaction
wheel function according to
one embodiment of the present disclosure;
[0032] FIG. 12 is a simplified control block diagram showing how the
spacecraft controller/CPU,
propulsion / reaction wheel device and spacecraft sensors could be used
together according to one
embodiment of the present disclosure; and
[0033] FIG. 13 is a schematic illustrating the first stage of first rotor and
second rotor independent
control circuits according to one embodiment of the present disclosure.
9
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
DETAILED DESCRIPTION
[0034] Various terms used herein are intended to have particular meanings.
Some of these terms
are defined below for the purpose of clarity. The definitions given below are
meant to cover all
forms of the words being defined (e.g., singular, plural, present tense, past
tense). If the definition
of any term below diverges from the commonly understood and/or dictionary
definition of such
term, the definitions below control.
[0035] The terms, "for example," "e.g.," "in one/another aspect," "in
one/another scenario," "in
one/another version," "in some configurations," "in some implementations,"
"preferably,"
"usually," "typically," "may," and "optionally," as used herein, are intended
to be used to introduce
non-limiting embodiments. Unless expressly stated otherwise, while certain
references are made
to certain example system components or services, other components and
services may be used as
well and/or the example components may be combined into fewer components
and/or divided into
further components.
[0036] Embodiments herein provide a self-propelling propulsion system powered
with electricity
and utilizing at least two synchronized rotors each with a multiplicity of
electro-magnets or
permanent magnets mounted along each rotor's perimeter which interact with the
other rotor's
magnetics through attracting or repelling forces. In some embodiments the
rotors may be spun
through use of an integral set of integral electromagnetic coils or through
separate electric motors
connected with a gear box. With either embodiment the device may be used to
changed vehicle
orientation through reactionary torques produced on the integral coil or
separate electric motor
stator elements. In the following description, numerous specific details are
set forth. However, it
is understood that embodiments may be practiced without these specific
details. In other instances,
well-known materials, structures, and techniques have not been shown in detail
in order not to
obscure the understanding of this description.
[0037] Turning now to the drawings, which are included by way of example and
not limitation,
embodiments of the present disclosure are directed towards a single pair of
interacting
synchronized rotors having an equivalent number of permanent magnets mounted
on each
respectively.
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
[0038] Furthermore, in some embodiments of the self-propelling apparatus the
magnets mounted
on the rotor will utilize different magnetic orientation, size, shape and
number. Other embodiments
may make use of magnetic sensors instead of optical sensors for tracking rotor
position.
[0039] One possible configuration of a self-propelling apparatus with integral
electro-magnetic
coils 100 is shown in FIG. 1A. Top 101 and bottom 102 plates of the apparatus
are shown in FIG.
1 A along with optical source and sensor 103 and enclosure panel 104. FIG. 1B
shows a second
optical source and sensor 105 along with coil support plates 106 and mounting
L-brackets 107. In
some embodiments the plates can be made from sheet metal or carbon fiber
honeycomb panels.
[0040] FIG. 2 shows a pair of rotors with integrated spur gear profile for
synchronization 200 and
201. For clarity, the rotor on the left 200 of FIG. 2 is referred to as rotor
1 (or first rotor) and the
rotor on the right 201 is referred to as rotor 2 (or second rotor). FIG. 2
also shows integral electro-
magnetic C-coils 202 and coil clips 203. Also seen in FIG. 2 are transversely
mounted permanent
magnets 204 and magnet mounting L-brackets 205. Each rotor is shown mounted to
independent
shafts 206, 208 with bearings 207, 209.
[0041] Referring to FIG. 3A a matched pair of integrated rotors with spur gear
profile are shown
200 and 201. Orientations of permanent magnets are denoted by North N and
South S labels 306.
Also seen in FIG. 3A are arc shaped optical slots 307 which are aligned with
an optical source and
sensors. A relationship between rotor rotation direction and thrust direction
is denoted by
clockwise arrow 300 for rotor 1 200, counterclockwise arrow 301 for rotor 2
201 and thrust arrow
in ¨Y direction 302. To help understand the loads acting on the rotor's zones
303, 304 and 305 are
shown in FIG. 3A. The zones are described as outboard zone 303 of rotor 200,
inboard zone 304
of rotors 200 and 201 and outboard zone 305 of rotor 201.
[0042] Referring to FIG. 3B, a relationship between a counterclockwise
rotating 308 rotor 200
with a clockwise 309 rotating rotor 201 will generate a thrust in the +Y
direction 310 is shown.
[0043] For magnet orientations shown in FIG. 3, it is shown that there will be
attraction between
neighboring magnets on rotor 200 and 201 as neighboring magnets travel through
inboard zone
304. FIGS. 4 and 5 show how forces are carried from the rotor to the bearing
outer race, bearing
balls and inner race. FIG. 4 shows a close up of rotor bearings 207 and 209
along with arrows
11
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
denoting loading direction 400 and 401 experienced by outer races of each
bearing assembly
during loading. It is also shown in FIG. 4 that if rotor 200 is spinning in a
clockwise direction, an
outer race 408 and bearing balls 406 will also be spinning in clockwise
direction denoted by arrows
402 and 404. It is also shown that the neighboring rotor 201 will be spinning
in the
counterclockwise direction 403 along with its outer race 409 and its bearing
balls 407.
Thrust Generation ¨ Traction Mechanism
[0044] As an example to illustrate how attracting forces as shown in the
figures will generate
thrust, twelve Neodymium Boron magnets grade N42 strength are provided with
dimension one
inch tall by one inch wide by 3/16 inches thick each mounted with orientations
shown in FIG. 3A.
FIG. 6 shows a plot of a net force in the +X direction experienced by rotor
200 due to rotor 201
during one rotation. As stated above, because of magnet orientation, a net
force between the rotors
is known and will always be attractive, and will be carried by the ball
bearings travelling on
outboard side of the bearing i.e. zones 303 and 305 of FIG 3A. Letting the
instantaneous load on
rotor 200 be L200(t) the following is defined:
L200(t) = (G200(01 + G200(02 + + G200(ON ) ; summation of all bearing ball
loads
where referring to FIG. 5, G200(t)i, 502 is a load carried by an ith outboard
ball bearing. As further
shown in FIG. 5, a normal load 506 carried by inner race 500 due to the ith
ball bearing and its
instantaneous value is expressed as N200(t)i. For non-slipping conditions, a
frictional force 504
results and is experienced by the ith bearing ball due to the inner race along
with 508 the frictional
force experienced by the inner race due to the ith ball bearing rotation as
shown in FIG. 5. Using
the above expression for normal load, the instantaneous frictional force can
be detelmined as
Ff200(t)1 = mus * N200(01 ; where mus is the static coefficient of friction
For the case of rotor 200 and its associated bearing balls rotating in
clockwise direction 406, FIG.
shows that a force experienced by its inner race 500 will be in the ¨Y
direction 508. Further,
FIG. 5 shows how forces acting in rotor 201 ball bearing will act during its
associated
counterclockwise rotationA loading on rotor 201 due to the magnets on rotor
200 will be in the ¨
X direction and vary in a similar fashion to FIG. 6 which is provided as
follows:
12
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
L201(t) = -L200(t) ; where L201(t) is the net load carried by rotor 2
where
L201(t) = (G201(01 + G201(02 + + G201(ON ) ; summation of all bearing ball
loads
Referring to FIG. 5, G201(0 503 is the load carried by the ith outboard ball
bearing. N201(t)
507 in FIG. 5 is a normal load carried by the inner race 501 due to rotor
201's ith ball bearing.
For non-slipping conditions this results in a frictional force 505 experienced
by the ith bearing
ball due to the inner race along with 509 the frictional force experienced by
the inner race due to
the ith ball bearing rotation as shown in FIG. 5. This can be written as:
Ff201(01 = mus * N201(01 ; where mus is the static coefficient of friction
Frictional forces experienced by inner races 500 and 501 are both in the ¨Y
direction and will
therefore add constructively together. This constructive action will continue
through their
associated shafts resulting in a net translational force acting from the
shafts onto the top and bottom
plates of the device. This net translational force experienced by the device
assembly will also be
transferred onto any attached free-floating body i.e. propulsion will occur.
It should be noted that
there is an associated frictional force component in the +/- X direction as
the ball bearings rotate.
However, due to symmetry of the rotor motion and loading direction these X
direction forces will
cancel out.
[0045] FIG. 7 shows a graph relating the rotor angular speed in radians per
second to the measured
thrust in Newtons for a device with loading per FIG. 6. The relationship
between thrust and angular
speed is dependent on ball bearing and inner race material as this variable
determines the static
friction coefficient. The total number of ball bearings to also effects the
thrust to angular speed
relationship in other embodiments.
[0046] Table 1 below summarizes a relationship between the rotor loading, spin
direction and the
direction of the net thrust created.
13
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
Case Rotor 1 Rotor Traction Rotor 2 Rotor Radial Traction
Direction
Spin Radial between Spin Loading between of Thrust
Direction Loading Rotor 1 Direction Direction
Rotor 2 on
Direction ball ball Frame
bearing bearing
and fixed and fixed
race/shaft race/shaft
1 CW +x -Y CCW +x -Y +37
2 CW -x +y CCW -x +y -Y
3 CCW +x +y CW +x +y -Y
4 CCW -x -Y CW -x -Y Y
Table 1
Uni-Polar Motor Circuit Configuration and Operation
[0047] FIG. 8 shows a uni-polar control circuit configuration 800 for a single
phase of coils
mounted around the perimeter of a single rotor. This circuit embodiment has
four sections: an
optical sensor circuit 801, a pair of comparator circuits 802, a set of AND
gates 803 and an H
bridge transistor circuit 804. As shown in FIG. 8, an optical sensor circuit
801 is includes a resistor
(R led) that adjusts the current delivered to the light source (e.g., LED)
along with a resistor
(R_trans) that limits current through the optical transistor. Light emitted
from the light source will
either reflect off the rotor or travel through the optical slots cut 307 into
each rotor. When the light
is reflected the optical transistor will turn ON and pull the voltage at point
Al low. When the light
is not reflected the voltage at point Al will remain high. The low voltage
signal Al is buffered
through an operational amplifier and sent from point A2 into the positive
input terminal of
comparator circuit 1 op amp and the negative input terminal of comparator
circuit 2 op amp.
[0048] Each comparator circuit includes two resistors (e.g., R1 and R2) and an
Op Amp. In
comparator circuit 1 resistors R1 and R2 are configured in a voltage divider
arrangement such that
14
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
the voltage at point B1 is lower than point A2 when light is not reflected and
greater than A2 when
light is reflected. In comparator circuit 2 resistors R3 and R4 are configured
in a voltage divider
arrangement such that the voltage at point B2 is higher than point A2 when
light is not reflected
and lower than A2 when light is reflected. The outputs from the comparator
circuits Cl and C2
are feed into a set of AND gates and then into an H-bridge circuit. Each AND
gate also provides
for an ENA command that can be controlled with a pulse width signal that will
allow control for
the rotor speed. When the voltage at Cl is high and C2 is low Q1 and Q4 will
allow current to
flow through the NPN transistor in the upper left corner and lower right
corner of the H-bridge
circuit ie current will flow from point El to E2. When voltage at Cl is low
and C2 is high Q2 and
Q3 will allow current to flow through the NPN transistor in the lower left
corner and upper right
corner of the H-bridge circuit i.e. current will flow from point E2 to El. The
optical slots and
sensors are arranged to coincide with the rotor magnets reaching the middle of
each C-coil element
of a single-phase set of coils. Each set of phase coils can be connected in
series or parallel. A
series connection is shown in FIG. 10.
[0049] Thrust direction control is provided by sending a HI signal at G1 to
the NPN transistor 902
that will allow current to flow through the coil of a double pole double throw
relay 901 as shown
in circuit schematic 900 as seen in FIG. 9. Table 2 shows how DPDT state
setting could control
both reaction wheel and thrust direction.
Description Rotor Direction Rotor Spin Thrust State Coil
Reaction
DPDT Switch Direction State
State
Rotor 1 ON CW -Y CCW
Rotor 1 OFF CCW +y CW
Rotor 2 ON CCW -Y CW
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
Rotor 2 OFF CW +y C C W
Table 2
Reaction Wheel Operation
[0050] By using independent electronic controllers to drive rotors 1 and rotor
2 integral
electromagnetic coils this device can also be operated as a reaction wheel.
Referring to Table 2, it
is shown how DPDT state setting could control both reaction wheel and thrust
direction. These
torques are characterized by rotor momentum of inertia, angular speed and
maximum current flow.
Self-De-spinning Operation/Feature
[0051] As shown in FIG. 4, the rotor experiences a load in the +x direction
during operation.
The load is carried transiently by ball bearings as the ball bearings travel
around the shaft. This
loading will compress the ball bearing. Energy of each bearing balls
compression is known and
can be expressed as
u = 1/2*sigma*epsilon ; where u is the energy density, sigma is the stress and
epsilon is the
strain
and
U = Integral of u*dV; U total energy is equal to u integrated over its volume.
[0052] The energy U for each bearing ball will be lost during each revolution
it makes. The rate
of energy loss will depend on rotor speed, the number of ball bearings and
their respective radii
and the bearing ball's material type. Rotor / reaction wheel will de-spin at a
much quicker rate than
if it were unloaded. Loss can be characterized in terms of an average torque
(Taoavg) needed to
overcome the strain energy. Power lost will be of the form
Power Loss = Taoavg *omega; omega rotor angular speed
16
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
An amount of time delta t it will take for a pair of rotors spinning with
speed omegal to come to
a stop after powered has been turned off may be estimated.
Taoavg * delta _t = 'rotor *(omegal ¨ 0); where 'rotor is the rotor moment of
inertia or
delta_t = 'rotor *Omega 1 / Taoavg
For the loading case shown in FIG. 6 Taoavg = 0.063 Nm.
[0053] Another unique feature of this system is the ability to short a set
rotor coils to enhance an
ability to exert a desired torque. One embodiment of this circuit 1100 is
shown in FIG. 11 which
illustrates how a double throw double pole relay 1101 along with a transistor
1102 may be put in
line with each set of rotor coils that will allow the coils to be shorted to
itself through resistor 1103.
Referring to Table 3, circuit configuration and system action table is shown
for one such
embodiment. FIG. 13 shows a schematic 1300 of how device rotor 1 coils 1301
and rotor 2 coils
1302 could be wired to a first enhanced mode reaction wheel relay stages 1303
and 1304.
Description Rotor Direction Rotor Spin Enhance Action on Action on
DPDT Switch Direction Torque Mode Rotor 2 Coils
Rotor 1
State Coils
Rotor 1 ON CW Rotor 2 ON CW
Rotor 1 OFF CCW Rotor 2 ON CCW
Rotor 2 ON CCW Rotor 1 ON CCW
Rotor 2 OFF CW Rotor 1 ON CW
Table 3
17
CA 03136656 2021-10-08
WO 2020/215056 PCT/US2020/028943
[0054] FIG. 12 show how an overall control block diagram might look for
integrating control of
this device into an overall spacecraft system. A central processing unit can
send out signals to
control relays along with a pulse width modulated enable signal thereby
controlling both speed
and direction of each rotor. The block diagram assumes that the spacecraft
will be equipped with
accelerometers, gyroscopes sensors and also be capable of determining the
difference to the current
state and the desired state and then make necessary adjustments to pulse width
values and or relay
settings in order to achieve the desired orientation and/or propulsion effect.
[0055] The foregoing description of preferred embodiments of the present
disclosure has been
presented for purposes of illustration and description. The described
preferred embodiments are
not intended to be exhaustive or to limit the scope of the disclosure to the
precise foi in(s) disclosed.
Obvious modifications or variations are possible in light of the above
teachings. The embodiments
are chosen and described in an effort to provide the best illustrations of the
principles of the
disclosure and its practical application, and to thereby enable one of
ordinary skill in the art to
utilize the concepts revealed in the disclosure in various embodiments and
with various
modifications as are suited to the particular use contemplated. All such
modifications and
variations are within the scope of the disclosure as determined by the
appended claims when
interpreted in accordance with the breadth to which they are fairly, legally,
and equitably entitled.
18
