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Article

Ghassan Al-Sinbol, Mario G Perhinschi and Brenton K Wilburn

A simplified global positioning system (GPS) error model including models for a variety of abnormal operational conditions and failures is developed to provide simulation…

Abstract

Purpose

A simplified global positioning system (GPS) error model including models for a variety of abnormal operational conditions and failures is developed to provide simulation tools for the design, testing, and evaluation of autonomous flight fault tolerant control laws. The paper aims to discuss these issues.

Design/methodology/approach

Analysis and experimental data are used to build simplified models for GPS position and velocity errors on all three channels. The GPS model is interfaced with West Virginia University unmanned aerial vehicles (UAV) simulation environment and its utility demonstrated through simulation for several autonomous flight scenarios including GPS abnormal operation.

Findings

The proposed simplified GPS model achieves desirable levels of accuracy and realism for all components for the purpose of general UAV dynamic simulation and development of fault tolerant autonomous flight control laws.

Research limitations/implications

The simplified GPS model allows investigating GPS malfunction effects on the performance of autonomous UAVs and designing trajectory tracking algorithms with advanced fault tolerant capabilities.

Practical implications

The simplified GPS model has proved to be a flexible and useful tool for UAV simulation and design of autonomous flight control laws at normal and abnormal conditions.

Originality/value

The outcomes of this research effort achieve a level of detail never attempted before in modeling GPS operation at normal and abnormal conditions for UAV simulation and autonomous flight control laws design using a simplified framework.

Details

International Journal of Intelligent Unmanned Systems, vol. 3 no. 1
Type: Research Article
ISSN: 2049-6427

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Article

Wang Xinlong and Li Yafeng

The purpose of this paper is to discuss the applicability of Global Positioning System (GPS) ionospheric delay correction models. Ionospheric delay is the most influential…

Abstract

Purpose

The purpose of this paper is to discuss the applicability of Global Positioning System (GPS) ionospheric delay correction models. Ionospheric delay is the most influential error source in GPS positioning, and ionospheric refraction is difficult to be corrected by dual frequency measurement for the common single frequency GPS receivers. Generally, ionospheric models are employed to correct errors. In order to analyze the ionospheric influence to GPS signals and the accuracy and adaptability of GPS ionospheric error correction models a quantificational analysis for ionospheric error correction models is absolutely necessary.

Design/methodology/approach

On the base of the mechanism of ionospheric error, the Klobuchar model that is widely used and actual measured correction model (including local and global ionospheric error correction models) are analyzed in detail. With the data about ionosphere obtained from GPS authority Crustal Dynamics Data Information System, the precision and adaptability of two kinds of ionospheric error correction model are validated, and a predigested method of investigating precision of local ionospheric error correction model is presented.

Findings

Klobuchar model has higher precision in middle or low latitude than in high latitude, and ionospheric delay fluctuates acutely in a day with a day‐cycle. Ionospheric delay varies as the latitude changes: ionospheric delay is largest around equator and smallest in the areas of two poles, which shows symmetry. The relationship between ionospheric delay and longitude is similar to the relationship between ionospheric delay and latitude. The fitting model has better effect than Klobuchar model.

Originality/value

This paper thoroughly researches GPS ionospheric error correction models. The conclusions are presented for the selection of GPS correction models, that it is useful for practical engineering application and will be the theoretic foundation for the improvement of the GPS accurate positioning.

Details

Aircraft Engineering and Aerospace Technology, vol. 81 no. 4
Type: Research Article
ISSN: 0002-2667

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Article

Yu Jie, Wang Xinlong and Ji Jiaxing

The purpose of this paper is to improve the tracking performance of the carrier phase lock loop (PLL) in the strapdown inertial navigation system/global positioning system…

Abstract

Purpose

The purpose of this paper is to improve the tracking performance of the carrier phase lock loop (PLL) in the strapdown inertial navigation system/global positioning system (SINS/GPS) integrated system with an innovative scheme of ultra‐tight integration.

Design/methodology/approach

First, providing the Doppler frequency for PLL using SINS velocity could enlarge the loop equivalent bandwidth and reduce the dynamic effect on the carrier loop. Meanwhile, lowering the filter bandwidth could increase the immunity to noise. Second, the relationships between the PLL and SINS errors have been analyzed, and then the PLL error model is established to eliminate the correlation between the pseudo‐range‐rate error and SINS velocity error. Third, the carrier frequency is regulated to improve the tracking accuracy, according to the error estimations of Kalman filter.

Findings

The innovative ultra‐tightly integrated system could not only enhance the anti‐jamming capability and the dynamic tracking performance of the tracking loops, but also improve the pseudo‐range‐rate measurements accuracy for the integrated filter.

Originality/value

This paper provides further study on the method of enhancing the carrier‐tracking performance and improving the integration mode in the ultra‐tightly integrated system based on the software‐defined GPS receiver.

Details

Aircraft Engineering and Aerospace Technology, vol. 82 no. 1
Type: Research Article
ISSN: 0002-2667

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Book part

Abby Sneade

Purpose — The Department for Transport's 2011 GPS National Travel Survey (NTS) pilot study investigated whether personal GPS devices and automated data processing could be…

Abstract

Purpose — The Department for Transport's 2011 GPS National Travel Survey (NTS) pilot study investigated whether personal GPS devices and automated data processing could be used in place of the 7-day paper diary. Using GPS technology could reduce the relatively high burden that the diary places upon respondents, reduce costs and improve data quality.

Design/methodology/approach — Data was collected from c.900 respondents. Practical changes were made to the existing methodology where necessary, including the collection of information to support data processing. Processing was undertaken using the University of Eindhoven's Trace Annotator. Results from the GPS pilot were then compared to those from the main NTS diaries for the same period.

Findings — There were no insurmountable problems using GPS devices to collect data; however, the processed GPS data did not resemble the diary outputs, making GPS unsuitable for the NTS. The GPS data produced fewer and longer trips than the diary data. The purpose of a quarter of the GPS trips was unclear, and a disproportionate share started and ended at home.

Research limitations — Further work to manually inspect trips identified via validation as unfeasible and subsequently refine the processing algorithms would have been desirable had time permitted. GPS data processing may have been hindered by missing GPS data, particularly in the case of rail travel.

Originality/value — This research used an accelerometer-equipped GPS device to better predict the method of travel. It also combined addresses that respondents reported having visited during the travel week with GIS data to code the purpose of trips without using a post-processing prompted-recall survey.

Details

Transport Survey Methods
Type: Book
ISBN: 978-1-78-190288-2

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Article

Iris M. Bosa

The healthcare sector faces new financial and managerial accountability demands, along with their clinical accountability. Various studies show strong opposition by…

Abstract

Purpose

The healthcare sector faces new financial and managerial accountability demands, along with their clinical accountability. Various studies show strong opposition by clinicians to new accountability tools, new structures and new ways of working. Less attention is paid to the innovative roles doctors can play in leading changes that use new managerial tools and techniques. The purpose of this paper is to analyse two original case studies illustrating how general practitioners (GPs) in Germany have led radical change.

Design/methodology/approach

The paper draws upon original research in Germany to present two case studies using a qualitative method, which are analysed using Glaser and Strauss' conventions of grounded theory, structured by Wenger's communities of practice framework, supporting a comprehensive literature review.

Findings

GPs are found to be able to lead radical change in healthcare delivery models and organisation using entrepreneurial talents developed in their practice businesses and to embrace modernising tools and techniques and in the process redefine their identities to include management process in addition to medical competences.

Originality/value

The paper presents two original case studies of radical change leading to an integration of healthcare services in Germany. The approach adopted by the German GPs reveals important general lessons for practitioners, as does the analytical framework employed in the paper.

Details

Journal of Health Organization and Management, vol. 22 no. 5
Type: Research Article
ISSN: 1477-7266

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Article

Sanketh Ailneni, Sudesh K. Kashyap and N. Shantha Kumar

The purpose of this paper is to present fusion of inertial navigation system (INS) and global positioning system (GPS) for estimating position, velocities, attitude and…

Abstract

Purpose

The purpose of this paper is to present fusion of inertial navigation system (INS) and global positioning system (GPS) for estimating position, velocities, attitude and heading of an unmanned aerial vehicle (UAV).

Design/methodology/approach

A 15-state extended Kalman filter (EKF) and a split architecture consisting of six-state nonlinear complementary filter (NCF) and nine-state EKF are investigated in detail. In both these fusion architectures GPS and inertial measurement unit consisting of three axis accelerometers, three axis rate gyros and three axis magnetometer have been fused in open loop fashion (loosely coupled) to estimate the navigation states.

Findings

These architectures have been implemented in MATLAB/SIMULINK environment and evaluated in closed loop guidance of Black-Kite MAV with software-in-the-loop-simulation (SILS) setup. Furthermore, both the algorithms are validated with flight test data obtained from on-board data logger using an off-the shelf autopilot board (Ardupilot Mega APM-2.5) on SLYBIRD UAV.

Originality/value

The proposed architectures are of high value to accomplish INS/GPS fusion, which plays a vital role in autonomous guidance and navigation of an UAV.

Details

International Journal of Intelligent Unmanned Systems, vol. 2 no. 3
Type: Research Article
ISSN: 2049-6427

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Article

Javier Sosa, Daniel Alcaraz Real-Arce, Tomás Bautista, Juan A. Montiel-Nelson, S. Garcia-Alonso, José M. Monzón-Verona and Saeid Nooshabadi

In a global positioning system (GPS) receiver, one of the most time-consuming tasks is to identify and track the visible satellites. The paper aims to propose and examine…

Abstract

Purpose

In a global positioning system (GPS) receiver, one of the most time-consuming tasks is to identify and track the visible satellites. The paper aims to propose and examine in detail new and shorter identification patterns or lite pseudo-codes – pseudo-random numbers (PRNs) – that allow GPS receivers to reduce dramatically the computational effort to identify and track GPS satellites. Obtaining lite pseudo-codes is a multi-objective optimization problem that the paper resolves using genetic algorithms (GAs).

Design/methodology/approach

The lite PRNs are obtained by using NSGA-II and omni-optimizer multi-objective optimization techniques.

Findings

The new PRNs obtained with the proposed single/multi-objective solutions are always better than previously presented when the highest detection peak (DP) is required for the GPS receiver.

Originality/value

Results demonstrate that the problem of “obtaining lite pseudo-codes” is a multi-objective optimization problem. In other words, the solutions obtained with the single-objective approach could belong to a local minimum. The multi-objective approach provides a better solution than the single-objective approach in a 37 percent of the satellites while in other cases the multi-objective approach reaches the same DPs with a similar noise.

Details

Engineering Computations, vol. 30 no. 8
Type: Research Article
ISSN: 0264-4401

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Article

Mofetoluwa Fagbemi, Mario G. Perhinschi and Ghassan Al-Sinbol

The purpose of this paper is to develop and implement a general sensor model under normal and abnormal operational conditions including nine functional categories (FCs) to…

Abstract

Purpose

The purpose of this paper is to develop and implement a general sensor model under normal and abnormal operational conditions including nine functional categories (FCs) to provide additional tools for the design, testing and evaluation of unmanned aerial systems within the West Virginia University unmanned air systems (UAS) simulation environment.

Design/methodology/approach

The characteristics under normal and abnormal operation of various types of sensors typically used for UAS control are classified within nine FCs. A general and comprehensive framework for sensor modeling is defined as a sequential alteration of the exact value of the measurand corresponding to each FC. Simple mathematical and logical algorithms are used in this process. Each FC is characterized by several parameters, which may be maintained constant or may vary during simulation. The user has maximum flexibility in selecting values for the parameters within and outside sensor design ranges. These values can be set to change at pre-defined moments, such that permanent and intermittent scenarios can be simulated. Sensor outputs are integrated with the autonomous flight simulation allowing for evaluation and analysis of control laws.

Findings

The developed sensor model can provide the desirable levels of realism necessary for assessing UAS behavior and dynamic response under sensor failure conditions, as well as evaluating the performance of autonomous flight control laws.

Research limitations/implications

Due to its generality and flexibility, the proposed sensor model allows detailed insight into the dynamic implications of sensor functionality on the performance of control algorithms. It may open new directions for investigating the synergistic interactions between sensors and control systems and lead to improvements in both areas.

Practical implications

The implementation of the proposed sensor model provides a valuable and flexible simulation tool that can support system design for safety purposes. Specifically, it can address directly the analysis and design of fault tolerant flight control laws for autonomous UASs. The proposed model can be easily customized to be used for different complex dynamic systems.

Originality/value

In this paper, information on sensor functionality is fused and organized to develop a general and comprehensive framework for sensor modeling at normal and abnormal operational conditions. The implementation of the proposed approach enhances significantly the capability of the UAS simulation environment to address important issues related to the design of control laws with high performance and desirable robustness for safety purposes.

Details

International Journal of Intelligent Unmanned Systems, vol. 7 no. 1
Type: Research Article
ISSN: 2049-6427

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Article

Wafaa Saleh and Alistair Lawson

The purpose of this paper is an investigation of driving behaviour and impacts on emissions at two traffic junctions.

Abstract

Purpose

The purpose of this paper is an investigation of driving behaviour and impacts on emissions at two traffic junctions.

Design/methodology/approach

A signalised junction and a roundabout in Edinburgh have been selected. An instrumented car has been used and a GPS to monitor driving activities as well as a gas analyser to monitor the vehicle's emissions during the evening peak hour.

Findings

Vehicles’ emissions are affected by a large number of factors including characteristics of the engine and the vehicle, characteristics of the road, the fuel used and driving behaviour.

Originality/value

Different methods and approaches have been used to investigate the behaviour of vehicles at various traffic junctions. The main aim, however, has mostly been to reduce travel times as well as traffic delays and queues at the junction. Consideration of environmental impacts has also been made, but often as a by‐product of congestion reduction and not as a main aim.

Details

World Journal of Science, Technology and Sustainable Development, vol. 10 no. 2
Type: Research Article
ISSN: 2042-5945

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Article

Wang Xinlong, Ji Jiaxing and Li Yafeng

Troposphere delay is one of the important error sources in global positioning system (GPS) positioning. The purpose of this paper is to analyze the accuracy and…

Abstract

Purpose

Troposphere delay is one of the important error sources in global positioning system (GPS) positioning. The purpose of this paper is to analyze the accuracy and adaptability of GPS troposphere error correction models, and to provide theoretic foundation for model selection in GPS accurate positioning.

Design/methodology/approach

The principle of troposphere delay error effecting on GPS signals is theoretically analyzed. The model peculiarity and modeling method of the four common troposphere delay correction models: Hopfield, Saastamoinen, Black, and Egnos models are discussed detailedly. With the measurement data from Crustal Dynamics Data Information System of the technical support institution for GPS, the accuracy and applicability of the four models are quantificationally studied.

Findings

For a low elevation, Hopfield, Saastamoinen, and Black models show great agreement with each other, and have quite high precision. In the zenith direction, the maximal troposphere delay error of three models are all less than 1 dm, but Black and Hopfield models have higher precision than Saastamoinen model. Black model can be regarded as the improved form of Hopfield model: for a high elevation, precision of two models are close, while for a low elevation, Black model shows to be more effective than Hopfield model. The precision of Egnos model is quite lower than that of Black, Hopfield, and Saastamoinen models. However, Egnos model can be a better choice when it is difficult to obtain real‐time meteorological data in certain application environment.

Originality/value

This paper makes thorough research on GPS troposphere delay error correction models. The conclusions are presented for selecting troposphere delay models, which are useful for practical engineering application.

Details

Aircraft Engineering and Aerospace Technology, vol. 81 no. 5
Type: Research Article
ISSN: 0002-2667

Keywords

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