Systems and methods for determining a rotational position of an object
First Claim
Patent Images
1. A method of estimating a rotational position of an object, the method comprising:
- prior to flight of the object during which the object spins, preloading the object from external to the object with initialization data, wherein the initialization data comprises information associated with a preloaded intended trajectory for the object, a preloaded space vehicle ephemeris data, and a preloaded system time of a satellite positioning system;
initializing a timer based on the preloaded system time;
during flight, maintaining a timer-based time via the timer without input from satellite positioning system signals;
calculating line-of-sight (LOS) vectors based on the initialization data and the timer-based time;
acquiring satellite positioning signals from a plurality of space vehicles and generating at least one of a correlated in-phase measurement or a correlated quadrature-phase measurement from each of the acquired plurality of satellite positioning signals; and
determining a roll phase relative to each of the space vehicles corresponding to at least a selected group of the acquired plurality of satellite positioning signals by phase locking to an amplitude modulation of at least one of the correlated in-phase output signal or the correlated quadrature-phase output signal for each of the selected group of the acquired plurality of satellite positioning signals, wherein the amplitude modulation is caused by rolling of the object.
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Abstract
Apparatus and methods determine the rotational position of a spinning object. A satellite positioning system can be used to determine the spatial position of an object, which in turn can be used to guide the object. However, when the object is spinning, such as an artillery shell, then the rotational orientation should be known in order to properly actuate the control surfaces, such as fins, which will also be spinning.
17 Citations
21 Claims
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1. A method of estimating a rotational position of an object, the method comprising:
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prior to flight of the object during which the object spins, preloading the object from external to the object with initialization data, wherein the initialization data comprises information associated with a preloaded intended trajectory for the object, a preloaded space vehicle ephemeris data, and a preloaded system time of a satellite positioning system; initializing a timer based on the preloaded system time; during flight, maintaining a timer-based time via the timer without input from satellite positioning system signals; calculating line-of-sight (LOS) vectors based on the initialization data and the timer-based time; acquiring satellite positioning signals from a plurality of space vehicles and generating at least one of a correlated in-phase measurement or a correlated quadrature-phase measurement from each of the acquired plurality of satellite positioning signals; and determining a roll phase relative to each of the space vehicles corresponding to at least a selected group of the acquired plurality of satellite positioning signals by phase locking to an amplitude modulation of at least one of the correlated in-phase output signal or the correlated quadrature-phase output signal for each of the selected group of the acquired plurality of satellite positioning signals, wherein the amplitude modulation is caused by rolling of the object. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for estimating a rotational position of an object, the apparatus comprising:
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an interface configured to retrieve data from external to the object to preload a memory with initialization data, wherein the initialization data comprises information associated with a preloaded intended trajectory for the object, a preloaded space vehicle ephemeris data, and a preloaded system time of a satellite positioning system prior to flight of the object, wherein the object spins during flight; a timer configured to be initialized based on the preloaded system time, wherein the timer is configured to maintain time during flight without input from satellite positioning system signals; an LOS estimator configured to calculate line-of-sight (LOS) vectors based on the initialization data and the timer-based time; a positioning processor configured to acquire satellite positioning signals from a plurality of space vehicles and to generate at least one of a correlated in-phase measurement or a correlated quadrature-phase measurement from each of the acquired plurality of satellite positioning signals; and a SV power modulation tracker configured to determine a roll phase relative to each of the space vehicles corresponding to at least a selected group of the acquired plurality of satellite positioning signals by phase locking to an amplitude modulation of at least one of the correlated in-phase output signal or the correlated quadrature-phase output signal for each of the selected group of the acquired plurality of satellite positioning signals, wherein the amplitude modulation is caused by rolling of the object. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. An apparatus for estimating a rotational position of an object, the apparatus comprising:
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means for preloading the object from external to the object with initialization data, wherein the initialization data comprises information associated with a preloaded intended trajectory for the object, a preloaded space vehicle ephemeris data, and a preloaded system time of a satellite positioning system prior to flight of the object, wherein the object spins during flight; means for initializing a timer based on the preloaded system time; means for maintaining a timer-based time during flight via the timer without input from satellite positioning system signals; means for calculating line-of-sight (LOS) vectors based on the initialization data and the timer-based time; means for acquiring satellite positioning signals from a plurality of space vehicles and generating at least one of a correlated in-phase measurement or a correlated quadrature-phase measurement from each of the acquired plurality of satellite positioning signals; and means for determining a roll phase relative to each of the space vehicles corresponding to at least a selected group of the acquired plurality of satellite positioning signals by phase locking to an amplitude modulation of at least one of the correlated in-phase output signal or the correlated quadrature-phase output signal for each of the selected group of the acquired plurality of satellite positioning signals, wherein the amplitude modulation is caused by rolling of the object. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification