Global Navigation System Research Articles

Obstacle detection and tracking method for autonomous vehicle based on three-dimensional LiDAR

The movement state of obstacle including position, velocity, and yaw angle in the real traffic scenarios has a great impact on the path planning and decision-making of autonomous vehicle. Aiming at how to get the obstacle’s movement state in the real traffic scenarios, an approach is proposed to detect and track obstacle based on three-dimensional Light Detection And Ranging (LiDAR). Firstly, the point-cloud data produced by three-dimensional LiDAR after the road segmentation is rasterized, and the reuse of useful non-obstacle cells is carried out on the basis of the rasterized point-cloud data. The proposed eight-neighbor cells clustering algorithm is used to cluster the obstacle. Based on the clustering result, static obstacle detection of multi-frame fusion is worked out by combining real-time kinematic global positioning system data and inertial navigation system data of autonomous vehicle. And we further use the static obstacle detection result to detect moving obstacle located in the travelable area. After that, an improved dynamic tracking point model and Kalman filter are applied to track moving obstacle stably, and we finally get the moving obstacle’s stable movement state. A large amount of experiments on the autonomous vehicle developed by us show that the method has a high degree of reliability.

Robust Positioning and Navigation of a Mobile Robot in an Urban Environment Using a Motion Estimator

SummaryRobust positioning and navigation of a mobile robot in an urban environment is implemented by fusing the Global Positioning System (GPS) and Inertial Navigation System (INS) data with the aid of a motion estimator. To select and isolate malicious satellite signals and guarantee the minimum number of GPS signals for the localization, an enhanced fault detection and isolation (FDI) algorithm with a short-term memory has been developed in this research. When there are sufficient satellite signals for positioning, the horizontal dilution of precision (HDOP) has been applied for selecting the best four satellite signals to localize the mobile robot. Then, the GPS data are fused with INS data by a Kalman filter (KF) for a straight path and a curved motion estimator (CME) for a curved path. That is, the INS data are properly fused to the GPS data through the KF or CME process. To verify the effectiveness of the proposed algorithm, experiments using a mobile robot have been carried out on a university campus.

Precise orbit determination for BDS-3 satellites using satellite-ground and inter-satellite link observations

Since November 2017, eight BeiDou global navigation system (BDS-3) satellites equipped with Ka-band inter-satellite link (ISL) payloads have been launched into medium earth orbit. We present the pr...

Combined system of precise positioning of pilotless helicopter-type aircraft in the landing area

On-board equipment, ground equipment, and special software have been developed and tested that makes it possible to determine with high accuracy the relative coordinates of a helicopter-type unmanned aerial vehicle relative to a quick deployment runway in the absence of signals from global navigation systems.

Introduction to BeiDou‐3 navigation satellite system

China's BeiDou navigation system (BDS) has evolved from the demonstration navigation satellite system (BDS-1) to the regional navigation satellite system (BDS-2). Now, the global BeiDou navigation system (BDS-3) is in construction and is proceeding well. The design and functions of BDS-3 are quite different from those of both BDS-1 and BDS-2. In this paper, the general design, the coordinate reference system, and the system time basis of BDS-3 are introduced. Several new payloads designed to accomplish different objectives are described as well as the platforms on which they are hosted. Since BDS-3 consists of several different constellations, the general service capabilities and special service functions provided by these different constellations are described. The performances of the initial BDS-3 platforms are evaluated based on the available eight-medium Earth orbit (MEO) satellite configuration. The results of satellite orbit determination and prediction with and without the BDS-3 inter-satellite links (ISL) are compared and analyzed.

Feature coordinate estimation by time differenced vision/GPS/INS

This paper proposes a multi-baseline method to estimate absolute coordinates of point clouds and the camera attitude parameter utilizing feature points in successive images. Conventionally, 3D map generation methodologies have been based on images acquired by aerial or land vehicles. Pixels corresponding to known landmarks are manually identified at first. Next, the coordinates are directly geo-referenced and automatically allocated to pixels with high-quality Global Positioning System (GPS) and Inertial Navigation System (INS). However, it is difficult to obtain accurate coordinates by the conventional methodology with low-cost GPS and INS. With camera positions and attitude parameters, image-based point clouds can be compensated accurately. A simulation was carried out to evaluate the performance of the proposed method.

Robust GPS/INS/DVL Navigation and Positioning Method Using Adaptive Federated Strong Tracking Filter Based on Weighted Least Square Principle

Multi-sensor integrated positioning technique that combines complementary features of the global positioning system (GPS) and inertial navigation system (INS) for navigation in challenging urban environments has been a hot research area. A variety of algorithms have been proposed over the past two decades for this well-studied field. However, with the increasing demands of seamless positioning, traditional GPS/INS integrated technique faces rigorous challenges, especially in GPS-denied environment, where traditional techniques cannot be applied directly. To improve the precision and robustness of the navigation system, a novel hybrid GPS/INS/Doppler velocity log (DVL) positioning method is proposed, which introduces DVL as the reference information to assist the GPS module to correct the divergence error of INS. A new robust adaptive federated strong tracking Kalman filter (RAFSTKF) algorithm is also presented for data fusion, which has the advantage of robustness with respect to the uncertainty of the system model. Meanwhile, we introduce the least square principle and adaptively adjust information sharing factors to obtain the optimal estimation, which can improve the reliability of the overall system. The theoretical analysis and simulation results demonstrate the effectiveness of the proposed hybrid GPS/INS/DVL positioning method based on RAFSTKF. In addition, the tracking performance of the proposed method outperforms that of traditional federated Kalman filter.

Impact of Earthquakes and Tsunamis on the Ionosphere

Diagnostics of the outer envelopes of the Earth through global satellite navigational systems and through the equally global network of ground receivers and very-low-frequency transmitters make it possible to explore fairly complex processes of lithosphere–ionosphere interactions. The effects of earthquakes and tsunamis on the ionosphere are an example of these processes. A brief review of the current advances in studying these processes is presented.

A Novel BPNN-Based Method to Overcome the GPS Outages for INS/GPS System

In order to improve the performance of the global positioning system (GPS) and inertial navigation system (INS) integrated system during GPS outages, a novel fusion algorithm based on back propagation neural network (BPNN) is proposed. A new model is built which relates the INS velocity, inertial measurement unit (IMU) outputs and the duration of GPS outages to the GPS position increment. Performance of the proposed method has been experimentally evaluated in a land vehicle navigation test. The test results show: (1) the proposed model can efficiently predict the increment of position and compensate the INS errors accumulation during GPS outage; (2) the advantage of new model on positioning accuracy becomes more obvious when the GPS observations are unavailable for a long time; (3) utilizing the current and past 2-step information as the input of BPNN model can effectively balance the computation burden and accuracy.

Integration of GNSS-IMU for increasing the observation accuracy in Condensed Areas (Infrastructure and Forest Canopies)

Position determination using satellite navigation system has grown significantly. It provides geospatial with global coverage called GNSS (Global Navigation System Satellite). GNSS satellites consists of GLONASS, GPS (Global positioning system) and Galileo.GPS is the most commonly used system and it is known to its capability to determine 3D position on the surface of the earth. In order to determine the position, a GPS receiver must be able to receive signals from at least four GPS satellites. However, the determination of position in condensed areas such as tunnels, area surrounded by high rise buildings, highly forested and in other closely-knit areas is not achieved because satellite signals cannot reach the receiver in the above-mentioned areas and also others where the signals are reflected before being received by a GPS receiver. In this paper, we present the algorithm to fuse GPS and the inertial measurement unit (IMU) to enable positioning in the above-mentioned Condensed Areas. The standard deviations of the two measurements show that GPS-IMU is better than GPS alone, the standard deviation when satellite outages occurred is - 4.57475 for GPS-IMU measurements and 0.218675 for GPS observations. We presented the results in graphics and it shows that GPS measurements are easily disturbed by external influence such as multipath but GPS-IMU graphic is continuous and robust. The advantages and disadvantages of GPS and INS are complementary and make them work together to enable the accurate measurements in the areas mentioned above. Integration of INS and GNSS can be classified into three types, loosely coupled Kalman filter, tightly coupled Kalman filters and ultratight coupled Kalman filter. In this research we used loosely coupled Kalman filter and tightly coupled Kalman filters to combine GPS and INS in one system.

Introduction to the special issue on the BeiDou navigation system

China's BeiDou Navigation Satellite System (BDS) has evolved from a demonstration system (BDS-1) to a regional navigation satellite system (BDS-2) and has finally entered the phase of a global navigation system (BDS-3). In 2018, the BDS-3 implementation achieved historic milestones. A baseline constellation with 18 MEO satellites and one GEO satellite has been established. The BDS has the ability to provide fundamental positioning, navigation, and timing (PNT) services to global users. The current BDS features some distinctive design and unique service capabilities. First, the BDS provides a regional message communication service and a global short message communication service with 1000 and 40 Chinese characters at a time, respectively. Second, the BDS also provides a global search and rescue (SAR) service, a satellite-based augmentation service (SBAS), as well as a regional precise point positioning (PPP) service. This special issue of the Institute of Navigation's journal, NAVIGATION, provides a collection of papers presenting research achievements in the BDS over the last 2 years. It covers essential fields necessary to ensure the successful operation of BDS, such as constellation design, operational and control system design and construction, frequency and signal design, updated coordinate reference system and time system, satellite orbit determination, ionospheric model, and software receiver. Papers in this special issue present the development status of the BDS from several perspectives and introduce the main performance and progress to readers, which is helpful for researchers in the field of satellite navigation and beneficial to GNSS terminal manufacturers as well. The publication of the issue also provides an opportunity to promote users' understanding and applications of the BDS. We hope that readers find useful information in this issue, and we look forward to sharing our continued success in future BDS development.

Development of a control system for a ballast cleaning machine using GNSS

Monitoring the geometric parameters of cutting and cleaning ballast during reconstruction and overhaul works is one of the most important tasks of ensuring high quality repair work. The paper describes a new type of automated control system to control the cutting process and the cleaning of ballast performed at major overhaul and reconstruction. This automated control system uses the data of a multisystem GNSS receiver, base Reference stations and spring-return mechanisms for installing antennas on the working body of the track machine (bar chain). Nowadays, gravel-cleaning machines have installed standard work quality control systems (depth of ballast cut and lateral slope), and other measuring control tools are also used. The disadvantages of existing technologies and instrumental testing are considered. The modern automatic control systems of various types developed by SGUPS and based on the use of global navigation systems are presented. Detailed schemes of working elements of ACS installed on the ballast cleaning machine (BCM) are presented. Algorithms to determine the depth and cross slope of the ballast cutting and control of these values are considered. The use and effectiveness of this type of ACS providing the required accuracy of work and continuous monitoring of the main quantities are substantiated.

Application of microwave motion sensors in navigation systems for ground vehicle

Effective land transport management in a controlled and unmanned mode is impossible without its accurate and continuous positioning. The paper discusses the possibility of increasing this accuracy in the absence or uncertain reception of signals from satellites of the global navigation system. Moreover, the use of an additional self-navigation inertial system to solve this problem in this case is not justified for reasons of accuracy and cost. Therefore, as an alternative autonomous navigation system, a solution based on radar Doppler sensors of modular type is proposed. The methods of measuring the velocity vector and the algorithm of direct continuous measurement of displacements are considered. It is shown that the latter measurement option can significantly reduce the cumulative error when positioning vehicles.

Systemic refractive effects in measurements performed with electromagnetic waves on transatmospheric traces

The article is devoted to the problem of increasing the accuracy of accounting for the influence of external factors on the results of precision measurements carried out with the help of electromagnetic waves in geodesy, global navigation satellite systems, etc. One of the main influencing factors for such measurements is the earth’s atmosphere, which, in general, includes two spatially separated regions — the troposphere and the ionosphere.The methods of atmospheric influence correction, which are currently used in practice in the case of measurements carried out with the help of electromagnetic waves on transatmospheric traces, suggest that the effects of influence caused by the troposphere and the ionosphere are independent and can be considered separately. Such an approach does not take into account the joint effects of these environments. This refractive effect, which is systemic, determines the spatial position of the signal trajectory and affects the accuracy of measurements.The article analyzes the publications devoted to this problem, provides general relationships for calculating systemic refractive effects, and obtains simplified formulas for their estimation. It is shown that, by the order of magnitudes, the contribution of systemic atmospheric effects corresponds to the contribution of higher-order ionospheric effects, that are now actively investigated. The conditions under which the accounting of systemic effects is necessary are considered.The current areas for further research and development to account for the systemic influence of the troposphere and the ionosphere on the measurement results carried out using global navigation satellite systems are discussed. These areas include theoretical and experimental studies, the development of convenient for practical use analytical and computer models of corrections to compensate for systemic refraction effects, the adaptation of models for correcting the systemic effects developed for global navigation systems as applied to other systems using measurements with electromagnetic waves on transatmospheric traces.

Time synchronization over a free-space optical communication channel

Future high-precision free-space optical (FSO) clock networks will require laser links to transmit time-frequency between sites and, with this information, to synchronize the times across widely separated clocks. FSO communication networks already use laser links between remote sites to transmit high-speed data. Here we repurpose a FSO digital communication system and use it directly for two-way time-frequency transfer. We demonstrate synchronization of the time between two sites separated by a turbulent air path of 4 km using binary-phase-modulated continuous-wave laser light. Under synchronization, the two sites exhibit a fractional frequency deviation below 10−15 at 1500 s averaging time and a time deviation below 1 ps at averaging times of seconds to hours. Over an 8 h period, the peak-to-peak wander is 16 ps. This method should be applicable to future ground-to-space and intra-satellite links and could lead to an improved global navigation and satellite system.

Space Experiment to Measure Ionospheric Radio Signal Delays

This paper describes a space experiment that is planned to be performed within the framework of the Russian project of the microsatellite CHIBIS AI to meaure ionospheric signal delays to determine the electron density and spatial fluctuations of the ionospheric and magnetospheric plasma. The measurements will be conducted by the phase interferometer method at two levels using signals from the onboard in-phase transmitters and GPS/GLONASS signals. The location of the radiation sources at two levels will make it possible to separate plasma variations in the ionosphere and inner magnetosphere–plasmasphere. The experimental results are of interest both for solving fundamental problems of near-Earth plasma physics and applied problems to improve positioning accuracy using global navigation systems.

Performance Analysis of GNSS/INS Loosely Coupled Integration Systems under Spoofing Attacks.

The loosely coupled integration of Global Navigation Satellite System (GNSS) and Inertial Navigation System (INS) have been widely used to improve the accuracy, robustness and continuity of navigation services. However, the integration systems possibly affected by spoofing attacks, since integration algorithms without spoofing detection would feed autonomous INSs with incorrect compensations from the spoofed GNSSs. This paper theoretically analyzes and tests the performances of GNSS/INS loosely coupled integration systems with the classical position fusion and position/velocity fusion under typical meaconing (MEAC) and lift-of-aligned (LOA) spoofing attacks. Results show that the compensations of Inertial Measurement Unit (IMU) errors significantly increase under spoofing attacks. The compensations refer to the physical features of IMUs and their unreasonable increments likely result from the spoofing-induced inconsistency of INS and GNSS measurements. Specially, under MEAC attacks, the IMU error compensations in both the position-fusion-based system and position/velocity-fusion-based system increase obviously. Under LOA attacks, the unreasonable compensation increments are found from the position/velocity-fusion-based integration system. Then a detection method based on IMU error compensations is tested and the results show that, for the position/velocity-fusion-based integration system, it can detect both MEAC and LOA attacks with high probability using the IMU error compensations.

INFORMATIONAL TECHNOLOGIES DEVELOPMENT IN MEDICAL AID SERVICE OF KRASNODAR REGION

For optimization Krasnodar region medical aid service, it’s developed software global navigational control system. Medical aid team is supported with pads. The research aim: estimate of efficiency and supporting medical aid team mobile computer devices with remote access to “AWP manager” program under Krasnodar region common control room medical aid service. The development of common informational control system of medical aid and medical aid team supporting with pads are improved basic processing indices of its work: time for medical aid teams arrival is reduced, including TA; execution of the call; TA death rate indices are reduced. The development makes it possible to carry out reception, collection of information and data handling automation about the service work and standardization, sorting calls according importance and complexity, controlling the time and the quality of medical aid service and hospitalization.

Data Fusion Based on Adaptive Interacting Multiple Model for GPS/INS Integrated Navigation System

The extended Kalman filter (EKF) as a primary integration scheme has been applied in the Global Positioning System (GPS) and inertial navigation system (INS) integrated system. Nevertheless, the inherent drawbacks of EKF contain not only instability caused by linearization, but also massive calculation of Jacobian matrix. To cope with this problem, the adaptive interacting multiple model (AIMM) filter method is proposed to enhance navigation performance. The soft-switching characteristic, which is provided by interacting multiple model algorithm, permits process noise to be converted between upper and lower limits, and the measurement covariance is regulated by Sage adaptive filtering on-line Moreover, since the pseudo-range and Doppler observations need to be updated, an updating policy for classified measurement is considered. Finally, the performance of the GPS/INS integration method on the basis of AIMM is evaluated by a real ship, and comparison results demonstrate that AIMM could achieve a more position accuracy.

On-The-Fly Ambiguity Resolution Based on Double-Differential Square Observation.

Global navigation systems provide worldwide positioning, navigation and navigation services. However, in some challenging environments, especially when the satellite is blocked, the performance of GNSS is seriously degraded or even unavailable. Ground based positioning systems, including pseudolites and Locata, have shown their potentials in centimeter-level positioning accuracy using carrier phase measurements. Ambiguity resolution (AR) is a key issue for such high precision positioning. Current methods for the ground based systems need code measurements for initialization and/or approximating linearization. If the code measurements show relatively large errors, current methods might suffer from convergence difficulties in ground based positioning. In this paper, the concept of double-differential square observation (DDS) is proposed, and an on-the-fly ambiguity resolution (OTF-AR) method is developed for ground based navigation systems using two-way measurements. An important advantage of the proposed method is that only the carrier phase measurements are used, and code measurements are not necessary. The clock error is canceled out by two-way measurements between the rover and the base stations. The squared observations are then differenced between different rover positions and different base stations, and a linear model is then obtained. The floating integer values are easy to compute via this model, and there is no need to do approximate linearization. In this procedure, the rover’s approximate coordinates are also directly obtained from the carrier measurements, therefore code measurements are not necessary. As an OTF-AR method, the proposed method relies on geometric changes caused by the rover’s motion. As shown by the simulations, the geometric diversity of observations is the key factor for the AR success rate. Moreover, the fine floating solutions given by our method also have a fairly good accuracy, which is valuable when fixed solutions are not reliable. A real experiment is conducted to validate the proposed method. The results show that the fixed solution could achieve centimeter-level accuracy.