U.S. patent application number 16/027505 was filed with the patent office on 2019-02-21 for virtual roll gyro for spin-stabilized projectiles.
The applicant listed for this patent is The Charles Stark Draper Laboratory, Inc.. Invention is credited to Simone B. Bortolami, Juha-Pekka J. Laine.
Application Number | 20190056202 16/027505 |
Document ID | / |
Family ID | 63036355 |
Filed Date | 2019-02-21 |
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United States Patent
Application |
20190056202 |
Kind Code |
A1 |
Bortolami; Simone B. ; et
al. |
February 21, 2019 |
Virtual Roll Gyro for Spin-Stabilized Projectiles
Abstract
A method is described for determining roll rate for a
spin-stabilized projectile. A yaw signal and a pitch signal are
measured for the projectile, wherein: (i) for a trajectory path
being travelled by the projectile over the Earth's surface,
projectile stability is created by spinning of the projectile about
a longitudinal spin axis oriented tangent to the projectile
trajectory, (ii) the yaw signal represents yaw motion of the
projectile about a yaw axis oriented along a line through the
Earth's center and orthogonal to the spin axis, and (iii) the pitch
signal represents pitch motion of the projectile about a pitch axis
orthogonal to the spin axis and the yaw axis, and wherein the yaw
signal and the pitch signal are modulated by spin rate of the
projectile spinning about the spin axis. A roll rate signal is
extracted from one of the yaw signal and the pitch signal.
Inventors: |
Bortolami; Simone B.;
(Belmont, MA) ; Laine; Juha-Pekka J.; (Boston,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Charles Stark Draper Laboratory, Inc. |
Cambridge |
MA |
US |
|
|
Family ID: |
63036355 |
Appl. No.: |
16/027505 |
Filed: |
July 5, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62528557 |
Jul 5, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F41G 9/00 20130101; F41G
7/36 20130101; G01C 21/10 20130101; F42B 10/26 20130101 |
International
Class: |
F41G 9/00 20060101
F41G009/00; F42B 10/26 20060101 F42B010/26 |
Claims
1. A computer-implemented method employing at least one hardware
implemented computer processor for determining roll rate for a
spin-stabilized projectile, the method comprising: operating the at
least one hardware processor to execute program instructions to:
measure a yaw signal and a pitch signal for the projectile,
wherein: (i) for a trajectory path being travelled by the
projectile over the Earth's surface, projectile stability is
created by spinning of the projectile about a longitudinal spin
axis oriented tangent to the projectile trajectory, (ii) the yaw
signal represents yaw motion of the projectile about a yaw axis
oriented along a line through the Earth's center and orthogonal to
the spin axis, (iii) the pitch signal represents pitch motion of
the projectile about a pitch axis orthogonal to the spin axis and
the yaw axis, and wherein the yaw signal and the pitch signal are
modulated by spin rate of the projectile spinning about the spin
axis; extract a roll rate signal from one of the yaw signal and the
pitch signal; and provide the yaw signal, the pitch signal, and the
roll rate signal to an inertial measurement unit (IMU) configured
to control orientation of the projectile with respect to the
trajectory path.
2. The method according to claim 1, wherein the yaw signal is
measured by a yaw gyroscopic sensor within the projectile.
3. The method according to claim 1, wherein the pitch signal is
measured by a pitch gyroscopic sensor within the projectile.
4. The method according to claim 1, wherein the roll rate signal is
extracted by detecting zero crossings of one of the yaw signal and
the pitch signal.
5. The method according to claim 1, wherein the roll rate signal is
extracted by deconvolving one of the yaw signal and the pitch
signal.
6. The method according to claim 1, wherein the IMU is configured
to measure the yaw signal and the pitch signal.
7. The method according to claim 1, wherein the IMU is configured
to extract the roll rate signal.
8. A non-transitory tangible computer-readable medium having
instructions thereon for determining roll rate for a
spin-stabilized projectile, the instructions comprising: program
code for measuring a yaw signal and a pitch signal for the
projectile, wherein: i. for a trajectory path being travelled by
the projectile over the Earth's surface, projectile stability is
created by spinning of the projectile about a longitudinal spin
axis oriented tangent to the projectile trajectory, ii. the yaw
signal represents yaw motion of the projectile about a yaw axis
oriented along a line through the Earth's center and orthogonal to
the spin axis, iii. the pitch signal represents pitch motion of the
projectile about a pitch axis orthogonal to the spin axis and the
yaw axis, and wherein the yaw signal and the pitch signal are
modulated by spin rate of the projectile spinning about the spin
axis; program code for extracting a roll rate signal from one of
the yaw signal and the pitch signal; and program code for providing
the yaw signal, the pitch signal, and the roll rate signal to an
inertial measurement unit (IMU) configured to control orientation
of the projectile with respect to the trajectory path.
9. The computer-readable medium according to claim 8, wherein the
yaw signal is measured by a yaw gyroscopic sensor within the
projectile.
10. The computer-readable medium according to claim 8, wherein the
pitch signal is measured by a pitch gyroscopic sensor within the
projectile.
11. The computer-readable medium according to claim 8, wherein the
roll rate signal is extracted by detecting zero crossings of one of
the yaw signal and the pitch signal.
12. The computer-readable medium according to claim 8, wherein the
roll rate signal is extracted by deconvolving one of the yaw signal
and the pitch signal.
13. The computer-readable medium according to claim 8, wherein the
IMU is configured to measure the yaw signal and the pitch
signal.
14. The computer-readable medium according to claim 8, wherein the
IMU is configured to extract the roll rate signal.
Description
[0001] This application claims priority from U.S. Provisional
Patent Application 62/528,557, filed Jul. 5, 2017, which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to spin-stabilized
projectiles.
BACKGROUND ART
[0003] Spin-stabilized projectiles such as missiles and spacecraft
rotate around a longitudinal axis that is approximately tangent to
the flight trajectory. The spinning mass of the projectile creates
gyroscopic forces that keep the spin axis resistant to the
destabilizing forces. Course control of a spin-stabilized
projectile can be performed by counter-rotation of an internal mass
about the spin axis (e.g., on an internal boom). The projectile can
be steered by controlling the positioning of the internal mass.
See, e.g., U.S. Patent Publication 2012/0175458, which is
incorporated herein by reference in its entirety.
[0004] Spin-stabilized projectiles include on-board navigation
systems for flight-control and guidance. Inertia-based navigation
systems typically use an inertial measurement unit (IMU) and one or
more motion sensors (e.g., accelerometers) and rotation sensors
(e.g., gyroscopes) to continuously calculate via dead reckoning the
position, orientation, and velocity of a moving object such as spin
stabilized projectile. Such arrangements typically use at least one
gyro sensor and at least one accelerometer for each body axis for
the IMU to measure all six degrees-of-freedom of the vehicle
motion.
[0005] In strapdown inertial navigation systems, the inertial
instruments are rigidly attached to the projectile. The sensor
measurements then are transformed to a stabilized reference frame
to remove the effects of vehicle motion. The transform computations
are conceptually simple, but the implementation can be very complex
because of the multiple rotating coordinate frames. The IMU
measures the angular velocity and acceleration of the projectile
relative to inertial coordinates, but these measurements are sensed
in the rotating frame of the projectile body as denoted by the IMU
coordinates x.sub.i, y.sub.i, z.sub.i. But, the desired navigation
solution generally is given relative to a different rotating
Earth-centered Earth-fixed (ECEF) coordinate frame, denoted by ECEF
coordinates x.sub.e, y.sub.e, z.sub.e, with an angular velocity
{right arrow over (.omega..sub.ie )} relative to the inertial
frame. See, e.g., Bezick, Scott M., Alan J. Pue, and Charles M.
Patzelt. "Inertial navigation for guided missile systems." Johns
Hopkins APL technical digest 28.4 (2010): 331-342; which is
incorporated herein by reference in its entirety.
SUMMARY
[0006] Embodiments of the present invention are directed to a
method for determining roll rate for a spin-stabilized projectile.
A yaw signal and a pitch signal are measured for the projectile,
wherein: (i) for a trajectory path being travelled by the
projectile over the Earth's surface, projectile stability is
created by spinning of the projectile about a longitudinal spin
axis oriented tangent to the projectile trajectory, (ii) the yaw
signal represents yaw motion of the projectile about a yaw axis
oriented along a line through the Earth's center and orthogonal to
the spin axis, and (iii) the pitch signal represents pitch motion
of the projectile about a pitch axis orthogonal to the spin axis
and the yaw axis, and wherein the yaw signal and the pitch signal
are modulated by spin rate of the projectile spinning about the
spin axis. A roll rate signal is extracted from one of the yaw
signal and the pitch signal. The yaw signal, the pitch signal, and
the roll rate signal then are provided to an inertial measurement
unit (IMU) configured to control orientation of the projectile with
respect to the trajectory path.
[0007] In further specific embodiments, the yaw signal may be
measured by a yaw gyroscopic sensor within the projectile, and/or
the pitch signal may be measured by a pitch gyroscopic sensor
within the projectile. The roll rate signal may be extracted by
detecting zero crossings of one of the yaw signal and the pitch
signal, and/or by deconvolving one of the yaw signal and the pitch
signal. The IMU may be configured to measure the yaw signal and the
pitch signal and/or to extract the roll rate signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 shows various aspects of a spin stabilized projectile
according to an embodiment of the present invention.
[0009] FIG. 2 shows various logical steps in a method according to
an embodiment of the present invention.
DETAILED DESCRIPTION
[0010] Spun projectiles conventionally need to have a roll gyro
sensor to monitor how the body frame rotates with respect to the
direction of travel in order to be able to correct their
trajectories, e.g., to the left or to the right. Such roll gyro
sensors need to have a very good scale-factor performance and to
allow for high spin rates. Generally, the part of the projectile
containing the IMU is de-spun to reduced rates to allow for it to
adequately operate. But embodiments of the present invention avoid
those requirements and instead take advantage of the high spin rate
of the projectile and avoid the usage of a dedicated roll gyro.
[0011] FIG. 1 shows various aspects of a spin stabilized projectile
100 and FIG. 2 shows various logical steps 201-204 in a method
according to an embodiment of the present invention for determining
roll rate for the spin-stabilized projectile 100 without using a
roll gyro sensor. The projectile 100 has a relatively high rate of
spin .PHI. about a longitudinal spin axis (x-axis) of the
projectile 100 that stabilizes the projectile 100 on its trajectory
(which is tangent to the spin axis). The projectile includes at
least one yaw sensor 103 (e.g. a gyroscopic sensor) that measures a
projectile yaw signal .psi., step 201, that represents yaw motion
of the projectile 100 about a yaw axis (z-axis) that is oriented
along a line through the Earth's center and orthogonal to the spin
axis. A pitch sensor 102 (e.g., a gyroscopic sensor) measures a
projectile pitch signal, step 202, that represents pitch motion of
the projectile 100 about pitch axis (y-axis) that is orthogonal to
the spin axis and the yaw axis.
[0012] An inertial measurement unit (IMU) 101 within the projectile
100 includes at least one hardware implemented processor device
controlled by software instructions to control the orientation of
the projectile 100 with respect to the trajectory path. The IMU 101
receives the yaw signal and the pitch signal, which are modulated
by the high spin rate of the projectile spinning about the spin
axis. The instructions performed by the IMU 101 then extracts a
roll rate signal from one of the yaw signal and the pitch signal,
step 203. For example, the IMU 101 my execute instruction to
extract the roll rate signal by detecting the zero crossings of one
of the yaw signal and the pitch signal. A properly designed
observer or properly calibrated open loop arrangement can then
extract the corrected and de-convolved roll rate. The IMU 101 then
provides the yaw signal, the pitch signal, and the extracted roll
rate signal, step 204, to further software processes, for example,
to control the trajectory of the projectile 100.
[0013] In some specific embodiments, the pitch sensor 102 and/or
the yaw sensor 103 may be separate devices from the IMU 101, while
in other embodiments, the pitch sensor 102 and/or the yaw sensor
103 may be integrated into the package of the IMU 101.
[0014] Existing conventional arrangements for spin-stabilized
projectiles are not known to use any sort of frequency measurement
so as to eliminate the roll gyro as described above. Since the roll
signal is convolved with the frequency characteristics of the yaw
signal and the pitch signal, then missing any samples at such high
spin rate could lead to an erroneous or inaccurate navigation
solution. By enabling the roll gyro sensor to be eliminated,
guidance packages for spin-stabilized projectiles can be less
expensive and more reliable.
[0015] Embodiments of the invention may be implemented in part in
any conventional computer programming language such as VHDL,
SystemC, Verilog, ASM, etc. Alternative embodiments of the
invention may be implemented as pre-programmed hardware elements,
other related components, or as a combination of hardware and
software components.
[0016] Embodiments can be implemented in part as a computer program
product for use with a computer system. Such implementation may
include a series of computer instructions fixed either on a
tangible medium, such as a computer readable medium (e.g., a
diskette, CD-ROM, ROM, or fixed disk) or transmittable to a
computer system, via a modem or other interface device, such as a
communications adapter connected to a network over a medium. The
medium may be either a tangible medium (e.g., optical or analog
communications lines) or a medium implemented with wireless
techniques (e.g., microwave, infrared or other transmission
techniques). The series of computer instructions embodies all or
part of the functionality previously described herein with respect
to the system. Those skilled in the art should appreciate that such
computer instructions can be written in a number of programming
languages for use with many computer architectures or operating
systems. Furthermore, such instructions may be stored in any memory
device, such as semiconductor, magnetic, optical or other memory
devices, and may be transmitted using any communications
technology, such as optical, infrared, microwave, or other
transmission technologies. It is expected that such a computer
program product may be distributed as a removable medium with
accompanying printed or electronic documentation (e.g., shrink
wrapped software), preloaded with a computer system (e.g., on
system ROM or fixed disk), or distributed from a server or
electronic bulletin board over the network (e.g., the Internet or
World Wide Web). Of course, some embodiments of the invention may
be implemented as a combination of both software (e.g., a computer
program product) and hardware. Still other embodiments of the
invention are implemented as entirely hardware, or entirely
software (e.g., a computer program product).
[0017] Although various exemplary embodiments of the invention have
been disclosed, it should be apparent to those skilled in the art
that various changes and modifications can be made which will
achieve some of the advantages of the invention without departing
from the true scope of the invention.
* * * * *