Local Navigation System Research Articles

Noise Immunity Analysis of LocataNet Navigation Receiver

The manuscript considers the problem of analyzing the reception characteristics of a pulse signal with intrapulse phase shift keying, used in local navigation systems such as LocataNet. Analytic formulas for the statistical characteristics of in-phase and quadrature correlators, a phase discriminator and standard errors of signal phase tracking are obtained. Noise immunity of signal acquisition and signal tracking modes is analysed. The manuscript shows that, at the same average energy of the pulse signal during the repetition period and the continuous phase-shifted signal at the same repetition period, the noise immunity of their reception both in search mode and in tracking mode is the same. Noise immunity of the received signals from LocataNet system is enhanced by increasing the navigation signal power at the receiver input.

Локальная навигационная система для автоматического причаливания судна

This paper shows that it is necessary to solve the problem of accurate ship positioning to provide automatic ship berthing. It is impossible to solve this problem using global positioning systems since they do not provide the proper precision. The principles and methods of development of a local navigation system are discussed. The system operation is based on measurement of the distance between the antennas of radio equipment installed on a ship and at the quay. Microwave propagation analysis is used for distance measurements. It is followed by a homodyne procession of microwave signals and the phase difference measurements on low-frequency signals. The block diagram of the rangefinder and its operation principles are described. The main equations that determine functioning of the system are given. The procedure of the range finding by measuring the phase difference between signals is analyzed; some limitations of the method are shown. Some aspects of system operation concerning selection of its operating frequencies are discussed. It is shown that using the proposed block diagram gives possibility to create an effective local navigation system to provide automatic ship berthing.

Improved polar inertial navigation algorithm based on pseudo INS mechanization

From the perspective of global inertial navigation system (INS), an improved inertial navigation algorithm is proposed to solve the navigation problem in polar regions. The implementation of navigation system is achieved with two executive units, navigation calculation (NC) unit and parameter transformation (PT) unit. The NC unit is executed autonomously with pseudo INS mechanization under the spherical Earth model. The pseudo INS mechanization is established with the pseudo-Earth frame, which is a generalized Earth frame and is reconstructed based on the switching position selected properly with the motion range of vehicle. Then, the smooth switching of navigation frame and the intrinsic unity of navigation algorithm can be achieved, thereby further unifying the polar navigation algorithm for both strapdown INS and platform INS in a brief form in global regions. On the other hand, the PT units are employed to correct and transform navigation parameters to a corresponding coordinate system with ellipsoidal Earth model and can be conducted simultaneously in parallel, thereby ensuring the navigation accuracy and communicating with other local navigation systems conveniently. Theoretical analysis and numerical results indicate the validity of the proposed algorithm.

Разностно-дальномерный метод определения координат потребителя применительно к построению локальных беззапросных систем навигации

Satellite navigation systems are the de-facto standard of navigation systems; however, the scope of their application is limited to an open terrain in which a sufficient number of navigation satellite signals are observed. At the same time, the development of navigation systems for enclosed spaces is a topical issue for a number of practical applications. Existing solutions that allow satellite radio navigation systems to be used in enclosed premises have a number of significant shortcomings. This circumstance generates the need of searching for alternative approaches to construction of indoor navigation systems. They differ from each other in complexity and achieved navigation accuracy. One of promising lines in constructing local radio navigation systems involves the use of ultra wide-band signals. The article considers the development of a precise non- enquiry range-difference local indoor navigation system on the basis of ultra wide-band radio modules.

Synthesis of Processing Algorithm for Signals with Different Powers in Local Radio Navigation Systems

The paper is aimed at synthesizing and analyzing an optimal algorithm for co-tracking delays and phases of pseudolite signals of different power in local navigation systems using a theory of optimal parameter estimation for several signals received by a navigation receiver in the additive mixture of the receiver internal noise. The analysis of the synthesized tracking algorithm is based on the simulation modeling of a navigation receiver taking account of nonlinear processing in discriminators. New equations describing an optimal complex tracking system that compensate the interfering signals in the processing paths of several incoming signals have been obtained. It has been shown that the use of this system ensures a reliable reception of navigational signals of significantly different power, which is relevant for local navigation systems based on pseudolites. The obtained tracking algorithms can be used in navigation equipment of local pseudolite-based navigation systems and satellite radio navigation systems GLONASS, GPS, Galileo, etc., working with the support of local navigation systems, robust principal component analysis (RPCA), total variation (TV), discriminating internal layers from radio echo sounding data of ice sheets, conjugate gradient method.

The Research of the Key Technologies in Complex Local Navigation System Based on Binocular Stereovision

In this paper, binocular stereo vision platform, visual navigation for complex local range contains a lot of moving targets. The system includes a feature detection, projection reconstruction, motion analysis, clustering target four. Whereby the field of view may be obtained of the target group number, position, relative speed and direction of movement, and a comprehensive analysis of the nature of the target. The system uses real-world scenarios to test the performance of the system in most scenes to achieve the expected goal, improved method of the present system puts forward.

The model of accuracy of a local radio navigation system considering unstable performance of individual elements

A mathematical model of the accuracy of the local radio navigation system was considered, built on the base of a network of pseudo satellites. It was determined that the key factor influencing the accuracy of determining the vector of status of the consumer is the geometry of the structure. However, for certain categories of consumers there is a necessity of taking into account a possibility of degradation of the structure because of malfunctioning and possible intentional damage. Existing mathematical models of accuracy do not consider a capacity of change in the topology structure. It was defined that for the assessment of the accuracy of navigation of specific consumers it is expedient to use a geometric factor that determines the degree of deterioration of finding the location relative to the accuracy of defining the pseudo remoteness from the consumer to the radio-navigation points. To consider the possibility of failure (destruction) of individual elements of the structure of a local radio navigation system, we introduce a probabilistic model that, on the base of registering the combinations of usable/faulty pseudo satellites and their relative geometric position, makes it possible to define the process of changing the accuracy of the system. As the main indicator of the accuracy, we use a root mean square deviation of the location definition (the state vector) of the consumer. As a result of the research we identified and confirmed by simulation that the maximum accuracy (minimum values of geometric factor) can be achieved in the case when a consumer is located in the centre of a regular tetrahedron. Given the sphericity of the Earth, a minimum value for a ground consumer is achieved when one pseudo satellite is in the zenith and the other three are evenly located in the horizontal plane. The combination of the base model of accuracy with a stochastic model of reliability/survivability will allow designing spatial structure of local radio navigation systems by the criterion of stable performance.

Practical local navigation system based on entorhino-hippocampal functions

Practical local navigation system based on entorhino-hippocampal functions

Persistent Navigation and Mapping using a Biologically Inspired SLAM System

The challenge of persistent navigation and mapping is to develop an autonomous robot system that can simultaneously localize, map and navigate over the lifetime of the robot with little or no human intervention. Most solutions to the simultaneous localization and mapping (SLAM) problem aim to produce highly accurate maps of areas that are assumed to be static. In contrast, solutions for persistent navigation and mapping must produce reliable goal-directed navigation outcomes in an environment that is assumed to be in constant flux. We investigate the persistent navigation and mapping problem in the context of an autonomous robot that performs mock deliveries in a working office environment over a two-week period. The solution was based on the biologically inspired visual SLAM system, RatSLAM. RatSLAM performed SLAM continuously while interacting with global and local navigation systems, and a task selection module that selected between exploration, delivery, and recharging modes. The robot performed 1,143 delivery tasks to 11 different locations with only one delivery failure (from which it recovered), traveled a total distance of more than 40 km over 37 hours of active operation, and recharged autonomously a total of 23 times.

Automatic training method applied to a WiFi+ultrasound POMDP navigation system

SUMMARYThis paper presents an automatic training method based on the Baum–Welch algorithm (also known as EM algorithm) and a robust low-level controller. The method has been applied to the indoor autonomous navigation of a surveillance robot that utilizes a WiFi+Ultrasound Partially Observable Markov Decision Process (POMDP). This method uses a robust local navigation system to automatically provide some WiFi+Ultrasound maps. These maps could be employed within probabilistic global robot localization systems. These systems use a priori probabilistic map in order to estimate the global robot position. The method has been tested in a real environment using two commercial Pioneer 2AT robotic platforms in the premises of the Department of Electronics at the University of Alcalá. Some experimental results and conclusions are presented.

Design of efficient navigation message format for UAV pseudolite navigation system

This paper presents an efficient method of designing an appropriate navigation message format for an airborne pseudolite navigation system using unmanned aerial vehicle (UAV) platforms. We briefly describe the concept of the UAV pseudolite system, which can be used as a GPS augmentation system or a local navigation system. Because the motion of UAVs is very variable, a special format is necessary for UAV navigation messages. Our approach is based on specialized message formats for each motion of the UAV, including both line and circle tracking, and the separation of nominal values and deviations. It can reduce the total size of the message and diminish the latency problem. The space saved by the smaller messages can be used for the other useful messages. To verify the proposed message format, we analyzed logged data from UAV flight tests. Although the UAV we used is an experimental vehicle with a limited control system using a single antenna GPS receiver, the overall performance was consistent with current satellite-based systems. The proposed message formats and the related design method will be capable of extension for an airship-based system or a balloon-based system.

Urban road transport navigation: performance of the global positioning system after selective availability

Satellite navigation systems have a potential to support multi-modal transport navigation requirements. In road transport, the global positioning system (GPS) is currently supporting a wide variety of in-car navigation and transport telematics systems. The performance of GPS has in the past been limited by the artificial degradation of the signal through the process of selective availability (SA). With SA operational, the instantaneous horizontal positional accuracy was 100 m 95% of the time. Additional infrastructure was used with the differential concept (where range errors are determined at a known location and transmitted to users) to improve this to the level of a few metres. The US Government on 1 May 2000 removed SA. This paper presents the results of a study to assess and characterise the post-SA performance of GPS for positioning vehicles in urban areas. This is an important functionality of advanced transport telematics systems that aim to address everyday problems associated with road transport, particularly in urban areas. The performance assessment addresses, in varying levels of detail, the issues of service coverage, positioning accuracy, integrity and availability of service. Comparison is made with the results of a previous study conducted when SA was turned on. The results show an improvement in stand-alone navigation accuracy without SA compared to the period when SA was operational. Furthermore, no significant difference is seen between the level of accuracy achievable with differential positioning and post-SA stand-alone navigation. The parameters that characterise the performance of GPS determined at the analysis stage have been used to specify an architecture for a local navigation system for urban areas.

A High-Performance, High-Accuracy RTK GPS Machine Guiadance System

As technology matures, Real Time Kinematic (RTK) global positioning system (GPS) receivers are providing increased performance in accuracy, on-the-fly (OTF) initialization times, measurement speed, and latency. Leica's Dozer 2000 machine guidance system combines an MC1000 GPS sensor, graphic intensive guidance software, a digital terrain model, and a digital site plan. Figure 1 shows the operator's view of the system. The end results is a highly accurate, extremely responsive local navigation system. Engineers can easily upload design information onto a touch-screen machine guidance personal computer (PC) and greatly reduce earthmoving costs while simultaneously recording “as-built” inspection data. The Leica MC1000 machine control sensor is a true 10-Hz, centimeter-level-accuracy, open-architecture GPS sensor specifically designed for machine guidance and control. At the heart of the MC1000's performance are a very stable oven-controlled oscillator (3 × 10−11/s short-term stability), a low-power Intel 486-DX4-80 processor, and four user-configurable input/output (I7O) ports. Special algorithms mitigate the effects of multipath and Selective Availability (SA) while providing centimeter accuracy up to 10 times per second with only 30 milliseconds' latency. The high update rate and low latency are essential for machine guidance and control. The MC1000 GPS reference station is capable of outputting RTK and Differential GPS (DGPS) data simultaneously, providing and entire site with GPS information for machine guidance and control, tracking and dispatching of vehicles, and support of survey crews. This article describes how recent advances in technology have combined to produce the Leica Dozer 2000 – a machine guidance system that is ideal for a wide range of earthmoving and inspection applications. © 2000 John Wiley & Sons, Inc.

Magnetic Lineations Observed Near the Ocean Floor and Possible Implications on the Geomagnetic Chronology of the Gilbert Epoch

Lineated magnetic anomalies, with a wavelength of 6 km and a peak-to-peak amplitude of 1500 nT,* were measured within 20 km of the continental crustal block of the tip of the Baja California peninsula of Mexico. The use of a high precision, local navigation system and measurements of the magnetic field close to the sea floor show that, at least in this small region, the sea-floor-spreading process has produced magnetic anomalies which are still lineated down to a scale of less than 1 km. These magnetic anomalies were formed during the younger part of the Gilbert Epoch of the geomagnetic time scale. Assuming that these anomalies were produced by uniform sea-floor spreading from a narrow zone of intrusion, the anomaly spacings can be used to establish revised estimates of the lengths of the magnetic reversals in this part of the Gilbert Epoch. They also indicate the absence of any previously undetected reversals of a duration of greater than 10 000 years.

Precision Subsea Navigation System

A precision acoustic navigation system based upon the short-baseline method of position measurement provides a complete local navigation system for deep-ocean search and survey operations involving a surface vessel and a submersible. A unique use of a single beacon/transponder on the ocean floor and a similar unit on the submersible allows the system to accurately measure and display the relative positions between the reference beacon, the submersible, and the surface vessel. The specific equipment is the Honeywell RS-505/DE Acoustic Position Indicator with Precision Navigation Processor. The “DE” version of the standard RS-505 short-baseline system is a Deep-operating, Extended-range model. The Precision Navigation Processor consists of a digital data processor, which is used to enhance accuracy by reducing instrumentation errors and by providing compensation for the environment (sound-speed variations, ray bending, etc.). The system uses two independent sets of processors to simultaneously measure both the position of the subsea vehicle and the reference point. The position of the subsea vehicle relative to the reference point is obtained by a differential position-measurement technique. Typical accuracy performance of this system is 0.2 to 1 percent of range. The highest accuracy occurs when the reference point and submersible are within a 90-degree cone below the surface support vessel. The normal operating range is 12 times the water depth. The operating range may be extended by using additional bottom units.