GNSS augmentation

About: GNSS augmentation is a research topic. Over the lifetime, 2478 publications have been published within this topic receiving 28513 citations. The topic is also known as: SBAS & Satellite Based Augmentation System.

A robust state estimation method against GNSS outage for unmanned miniature helicopters

Abstract: Most unmanned aerial robots use a Global Navigation Satellite System (GNSS), such as GPS, GLONASS, and Galileo, for their navigation. However, from time to time the GNSS fails to function due to geographical restrictions and deliberated jamming. This paper proposes an Unscented Kalman Filter-based GPS/IMU integration method in order to accurately estimate the position and velocity of an unmanned miniature helicopter even when the GNSS malfunctions completely. Different from previous GPS/IMU integration methods that cannot propagate noisy inertial measurements to the position and velocity estimations on the rapid vibratory Vertical Take-Off and Landing (VTOL) platforms during the GNSS outage, this method novelly prioritises the propagations of the states in the Unscented Kalman Filter (UKF) algorithm and leverages the time-varying GNSS dilution of precision in line with the adjustments of the measurement noise covariances. Moreover, this method models the stochastic process in the inertial sensors by the acceleration white noise bias in addition to the commonly used random walking process. Without considering the specific actuation models that vary from vehicle to vehicle, this method can particularly be applied to the quivering unmanned helicopters which equipped with two-stroke engines. It yields a rapid and precise compensation for the sensor errors in order to effectively facilitate the propagations of inertial measurements to the position and velocity estimations. Finally, the superior performance of the proposed method in terms of accuracy and endurance is empirically demonstrated using our fully instrumented JR Voyager GSR helicopter.

Autonomous GEO Satellite Navigation with Multiple GNSS Measurements

Abstract: The poor satellite visibility and the weak signal power of the Global Positioning System (GPS) signal reception in side lobes are the main constraint on the Geostationary Earth Orbit (GEO) determination, however, the situation will improve when multi-constellation Global Navigation Satellite Systems (GNSS) become available in the near future. In this study, a navigation algorithm is developed in order to determine the GEO state vector using multiconstellation GNSS measurements. The proposed navigation algorithm is based on a Kalman filter where the estimated state includes position and velocity corrections to the nominal reference trajectory and clock biases. The tests with simulated multi-GNSS measurements indicate that this algorithm meets the accuracy requirement for autonomous GEO satellite navigation.

Analysis and Compensation of RF Impairments for Next Generation Multimode GNSS Receivers

Abstract: Global navigation satellite system (GNSS) receivers require solutions that are compact, cheap and low-power, in order to enable their widespread proliferation into consumer products. Furthermore, interoperability of GNSS with non-navigation systems, especially communication systems will gain importance in providing the value added services in a variety of sectors, providing seamless quality of service for users. An important step into the market for Galileo is the timely availability of these hybrid multi-mode terminals for consumer applications. However, receiver architectures that are amenable to high-levels of integration will inevitably suffer from RF impairments hindering their easy widespread use in commercial products. This paper studies and presents analytical evaluations of the performance degradation due to the RF impairments and develops algorithms that can compensate for them in the DSP domain at the base band with complexity-reduced hardware overheads, hence, paving the way for low-power, highly integrated multi-mode GNSS receivers

High Integrity GNSS Navigation and Safe Separation Distance to Support Local-Area UAV Networks

Abstract: A local-area Unmanned Aerial Vehicle (UAVs) network can provide local-area differential corrections and optimized guidance, including the maintenance of safe separation distances, for precise and safe operation of the UAVs. In networked UAV operations, only the uncorrelated component of position error between two UAVs in the same network contributes to potential separation violations, because “in-network” UAVs share the same source of guidance and differential corrections. Therefore, models of uncorrelated errors need to be defined to establish safe separation distances between UAVs. This paper develops a methodology to estimate safe separation distance for UAVs which share the same source of guidance and local-area differential corrections. Using this methodology, ionospheric and tropospheric models for Navigation System Error (NSE) are developed theoretically. The airborne multipath error and Flight Technical Error (FTE) components which depend on hardware, environment, and operational conditions are also determined though UAV flight experiments. The standard deviation of FTE was estimated in both straight and curved flight segments. The results show that a lateral FTE error of 0.78 meters in curved segments is much greater than lateral FTE in straight segments and vertical FTE in both segments (all about 0.4 meters). This is due to the momentum of the UAV when it is taking turns and the limited controller response time of the UAV. The flight experiments also show that UAV multipath errors are reasonably well-bounded by the standard airborne multipath model developed for the Ground Based Augmentation System (GBAS). From the estimated error models, simulations of safe separation distances were conducted under the “in-network” UAVs scenario. Simulation results for a 24-satellite GPS constellation and the probabilities of safe separation suggested in prior work show that vertical separations between UAVs in the same network vary from about 3.0 – 6.5 meters, while horizontal separations vary between 2.2 and 3.5 meters. These values change with time according to the visible GPS satellite geometry and are known to the controller in real time.

Method for correcting multiple constellation SBAS system time difference

Abstract: The present invention discloses a method for correcting the time-difference of a multiple-constellation SBAS system, and the method comprises the following steps: a step1, confirming a reference time system, confirming the number of the system time-difference required calculating by the SBAS according to the number of satellite navigation system; a step2, calculating the system time-difference between different satellite navigation system and the reference system; a step3, establishing a time-difference model of the multiple-constellation SBAS system and confirming the broadcast parameter; and a step 4, calculating the wholeness information of the system time-difference. The invention can settle the problem of time-difference resolving of the multiple-constellation SBAS system, and provide a broadcast parameter of the system time-difference and a method for calculating the wholeness information of the system time-difference.