HIGHLY INTEGRATED GPS, GALILEO AND INERTIAL NAVIGATION SYSTEM
First Claim
1. A highly integrated GPS, Galileo and inertial navigation system for enhanced navigation in low signal strength, high dynamics or other GNSS or INS harsh environments, comprising:
- a Coupled Antenna (101) that provides data from the GNSS antenna and from the inertial measurement unit (IMU), where data from the first is provided to a Radio Frequency Front-End (RF-FE) and the second to the navigator, where the GNSS antenna is able to receive data from GPS and Galileo satellites and is integrated with the IMU in the same casing;
a RF-FE 102 that performs the acquisition and pre-processing of the signal transmitted by the satellite before it is passed to the phase rotation module (103);
a module (104) with a code acquisition algorithm to allow start of the tracking of the GPS and Galileo signals by providing the initial carrier phase and code;
a module (103) with a phase rotation function to allow tracking of the incoming signal'"'"'s carrier phase and frequency;
a local code generator (105) to allow generating local code replica to allow tracking of the incoming signal code phase, that is affected by different fixed delays to generate the Very-Early, Early, Prompt, Late and Very-Late replicas;
a multiplier (106) to generate a signal that will allow to correlate the local code with the incoming code;
a set (107) of integrate and dump functions to allow performing the correlation;
a data demodulator (110) to provide navigation data bits using the different local code replicas and to perform the wipe-off of such data;
a lock detector function (108) for detecting signal GNSS outages and communicate the event to a navigator (109);
a navigator (109) for determination of the navigation solution, using the GNSS data including I and Q signals when such is available and inertial sensor data to provide the necessary corrections to track the incoming GNSS signal or to keep aligned the internal local code replica during GNSS signal outages, seamlessly combined in a single filter using an accurate correlator model that relates code, phase and frequency errors, allowing the highly integrated navigation system to operate under the harsh environments;
an interface to receive navigation data from an external system, if such is available;
an interface in order to receive data from a reference station for navigation purpose, if such is available.
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Abstract
The navigation system described here utilizes GPS and Galileo satellite signals combined with Inertial Navigation Systems (INS), where a Coupled Antenna (CAN) provides both GNSS and Inertial Measurement Unit (IMU) data to a Highly Integrated GNSS-Inertial (Hi-Gi) receiver. Such receiver makes use of a high fidelity relation between GNSS unprocessed Correlator Output (COUT) I and Q data and the user trajectory, and inertial sensor data, which in turn are combined within a Kalman Filter (KF). The KF determines the navigation solution that is also used to provide feedback to the receiver demodulation signal processing stage, thus eliminating the need of dedicated structures such as Delayed Locked Loops (DLL) and Phase Locked Loops (PLL), allowing a significant improvement in navigation performance. The improvement allows this system to provide high quality measurements and operate in circumstances where usual techniques are not usable; for example during satellite signal interruption due to obstruction, or in very high dynamics or even in attenuated signal environments, due to, for example, the canopy of trees. The KF also makes use of particular Galileo signal characteristics, lock detectors and Coupled Antenna that allow the system to operate in such environments.
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Citations
11 Claims
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1. A highly integrated GPS, Galileo and inertial navigation system for enhanced navigation in low signal strength, high dynamics or other GNSS or INS harsh environments, comprising:
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a Coupled Antenna (101) that provides data from the GNSS antenna and from the inertial measurement unit (IMU), where data from the first is provided to a Radio Frequency Front-End (RF-FE) and the second to the navigator, where the GNSS antenna is able to receive data from GPS and Galileo satellites and is integrated with the IMU in the same casing; a RF-FE 102 that performs the acquisition and pre-processing of the signal transmitted by the satellite before it is passed to the phase rotation module (103); a module (104) with a code acquisition algorithm to allow start of the tracking of the GPS and Galileo signals by providing the initial carrier phase and code; a module (103) with a phase rotation function to allow tracking of the incoming signal'"'"'s carrier phase and frequency; a local code generator (105) to allow generating local code replica to allow tracking of the incoming signal code phase, that is affected by different fixed delays to generate the Very-Early, Early, Prompt, Late and Very-Late replicas; a multiplier (106) to generate a signal that will allow to correlate the local code with the incoming code; a set (107) of integrate and dump functions to allow performing the correlation; a data demodulator (110) to provide navigation data bits using the different local code replicas and to perform the wipe-off of such data; a lock detector function (108) for detecting signal GNSS outages and communicate the event to a navigator (109); a navigator (109) for determination of the navigation solution, using the GNSS data including I and Q signals when such is available and inertial sensor data to provide the necessary corrections to track the incoming GNSS signal or to keep aligned the internal local code replica during GNSS signal outages, seamlessly combined in a single filter using an accurate correlator model that relates code, phase and frequency errors, allowing the highly integrated navigation system to operate under the harsh environments; an interface to receive navigation data from an external system, if such is available; an interface in order to receive data from a reference station for navigation purpose, if such is available. - View Dependent Claims (2, 3, 4, 5, 6, 10, 11)
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7. The system of 6, wherein the Kalman Filter module comprises:
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an accurate correlator model that relates I and Q data raw measurements with code, phase and frequency error and with the position and velocity errors and that considers the integration time of the integrate and dump, discarding the need of a phase discriminator and seamlessly integrated with a set of navigation algorithms, using a code discriminator and inertial sensor data, whereby the correlator model employed provides an unique relation with receiver raw measurements of I and Q data with the actual navigation solution, providing a highly integrated navigation solution; a code discriminator to determine the error between the estimated code and the incoming one using normalised Early and Late I and Q measurements; a state vector comprising position errors such as, velocity, clock, attitude and inertial sensor; a function for determination of satellite-user distance and velocity using the navigation data based on satellite ephemeris data and navigation solution, communicating results to the GNSS tracking stage. - View Dependent Claims (8, 9)
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Specification