Integrated GPS/inertial navigation apparatus providing improved heading estimates
First Claim
1. Apparatus for use with two antennas on a mobile platform, the two antennas being capable of receiving signals from one or more satellites, each satellite signal comprising one or more component signals, each component signal having a different carrier frequency, the apparatus comprising:
- a receiver which obtains satellite ephemeris data and measures the carrier phase of each of one or more component signals of one or more satellite signals received from one or more satellites by each of the two antennas during successive time periods of duration Tp, phase measured during a Tp time period being called Tp -phase, only one component signal of one satellite signal received by one antenna being measured during any single Tp time period, the receiver utilizing the Tp -phases of each component signal obtained during a Tk time period by each antenna to estimate the phase of the component signal at the end of the Tk time period, the estimated phase at the end of the Tk time period being called the Tk -phase, Tk being equal to or greater than Tp ;
an inertial navigation system comprising inertial sensors and a digital processor, the inertial navigation system utilizing measurements of platform acceleration and platform angular rotation rate in determining the positions of the two antennas and the heading of the platform, the inertial navigation system utilizing the satellite ephemeris data and the positions of the two antennas to obtain computed ranges from the two antennas to the satellites, the inertial navigation system utilizing the computed ranges and the Tk -phases in determining the error in the heading of the vehicle.
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Accused Products
Abstract
The integrated GPS/inertial navigation apparatus utilizes satellite signals received with two spatially-separated antennas to achieve improved heading estimates for a mobile platform. Each satellite signal comprises one or more component signals with each component signal having a different carrier frequency. The integrated GPS/inertial navigation apparatus consists of a receiver and an inertial navigation system. The receiver measures the carrier phase of each of one or more component signals of one or more satellite signals received by each of the two antennas during successive time periods of duration Tp. Phase measured during a Tp time period is called Tp -phase. Only one component signal of one satellite signal received by one antenna is measured during any Tp time period. The receiver utilizes the Tp -phases of each component signal obtained during a Tk time period to estimate the phase of the component signal at the end of the Tk time period, the estimated phase at the end of the Tk time period being called the Tk -phase. The inertial navigation system, comprising inertial sensors and a digital processor, utilizes the Tk -phases in determining the heading of the vehicle and the displacement of each of the two antennas from the inertial sensors of the inertial navigation system. The measured phase of a component signal is subject to error as a result of the satellite signal traversing the ionosphere. The inertial navigation system achieves more accurate estimates of heading and antenna displacements by utilizing the Tk -phases in determining ionospheric corrections to phase.
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Citations
10 Claims
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1. Apparatus for use with two antennas on a mobile platform, the two antennas being capable of receiving signals from one or more satellites, each satellite signal comprising one or more component signals, each component signal having a different carrier frequency, the apparatus comprising:
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a receiver which obtains satellite ephemeris data and measures the carrier phase of each of one or more component signals of one or more satellite signals received from one or more satellites by each of the two antennas during successive time periods of duration Tp, phase measured during a Tp time period being called Tp -phase, only one component signal of one satellite signal received by one antenna being measured during any single Tp time period, the receiver utilizing the Tp -phases of each component signal obtained during a Tk time period by each antenna to estimate the phase of the component signal at the end of the Tk time period, the estimated phase at the end of the Tk time period being called the Tk -phase, Tk being equal to or greater than Tp ; an inertial navigation system comprising inertial sensors and a digital processor, the inertial navigation system utilizing measurements of platform acceleration and platform angular rotation rate in determining the positions of the two antennas and the heading of the platform, the inertial navigation system utilizing the satellite ephemeris data and the positions of the two antennas to obtain computed ranges from the two antennas to the satellites, the inertial navigation system utilizing the computed ranges and the Tk -phases in determining the error in the heading of the vehicle. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for determining the heading of a vehicle utilizing inertial sensors and at least one satellite signal, each satellite signal comprising one or more component signals, each component signal having a different carrier frequency, the method comprising the steps:
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(a) obtaining satellite ephemeris data and measuring during successive time periods of duration Tp the phase of each of one or more component signals of one or more satellite signals received from one or more satellites at first and second predetermined points on the vehicle, the phase of only one component signal being measured during any Tp time period, a phase measured during a Tp time period being called a Tp -phase; (b) computing the phase of each component signal of each satellite signal received at each of the first and second predetermined points at the end of a Tk time period utilizing the Tp -phases for that component signal measured during the Tk time period, the computed phase of a component signal at the end of a Tk time period being called a Tk -phase; (c) utilizing measurements of platform acceleration and platform angular rotation rate referenced to a third predetermined point on the vehicle in determining the positions of the first and second predetermined points and the heading of the vehicle and then utilizing satellite ephemeris data and the positions of the first and second predetermined points to compute ranges from the first and second predetermined points to the one or more satellites at the end of a Tk time period; (d) determining the error in vehicle heading at the end of a Tk time period utilizing the measurements and computations made in steps (a), (b), and (c); (e) repeating steps (a), (b), (c), and (d) indefinitely. - View Dependent Claims (9, 10)
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Specification