Current Issue : January - March Volume : 2017 Issue Number : 1 Articles : 5 Articles
Navigation and guidance systems are a critical part of any autonomous vehicle. In this\npaper, a novel sensor grid using 40 KHz ultrasonic transmitters is presented for adoption in indoor 3D\npositioning applications. In the proposed technique, a vehicle measures the arrival time of incoming\nultrasonic signals and calculates the position without broadcasting to the grid. This system allows\nfor conducting silent or covert operations and can also be used for the simultaneous navigation of a\nlarge number of vehicles. The transmitters and receivers employed are first described. Transmission\nlobe patterns and receiver directionality determine the geometry of transmitter clusters. Range and\naccuracy of measurements dictate the number of sensors required to navigate in a given volume.\nLaboratory experiments were performed in which a small array of transmitters was set up and the\nsensor system was tested for position accuracy. The prototype system is shown to have a 1-sigma\nposition error of about 16 cm, with errors between 7 and 11 cm in the local horizontal coordinates.\nThis research work provides foundations for the future development of ultrasonic navigation sensors\nfor a variety of autonomous vehicle applications....
This paper proposes a novel relative navigation control strategy based on the relation space method (RSM) for articulated\nunderground trackless vehicles. In the RSM, a self-organizing, competitive neural network is used to identify the space around the\nvehicle, and the spatial geometric relationships of the identified space are used to determine the vehicle�s optimal driving direction.\nFor driving control, the trajectories of the articulated vehicles are analyzed, and data-based steering and speed control modules\nare developed to reduce modeling complexity. Simulation shows that the proposed RSM can choose the correct directions for\narticulated vehicles in different tunnels. The effectiveness and feasibility of the resulting novel relative navigation control strategy\nare validated through experiments....
In the integrated navigation system with inertial base, the update frequency of Strapdown Inertial Navigation System (SINS) is\nalways higher than those of aided navigation systems; thus updating inconsistency among subsystems becomes an issue.The analysis\nindicates that the state transition matrix in Kalman filter is essentially a function of carrier motion. Based on this understanding,\na simplified Kalman filter algorithm for integrated navigation is designed for those carriers with low-dynamic motions. With this\nsimplified algorithm, when the filter is without aided information updating, only calculation and accumulation on state transition\nmatrix are executed, and when the filter is with updating, normal time and measurement update are done based on the averaged\nstate transition matrix. Thus the calculation load in the simplified algorithm will be significantly lessened. Furthermore, due\nto cumulative sum and average operation, more accurate state transition matrix and higher fusion accuracy will arrive for the\nsmoothing effect on random noise of carrier motion parameters. Simulation and test results indicate that when the carrier is\nwith a low-dynamic motion, the simplified algorithm can complete the data fusion of integrated system effectively with reduced\ncomputation load and suppressed oscillation amplitude of state vector error....
The thermal environment is an important factor in the design of optical systems. This study\ninvestigated the thermal analysis technology of optical systems for navigation guidance and control\nin supersonic aircraft by developing empirical equations for the front temperature gradient and\nrear thermal diffusion distance, and for basic factors such as flying parameters and the structure\nof the optical system. Finite element analysis (FEA) was used to study the relationship between\nflying and front dome parameters and the system temperature field. Systematic deduction was then\nconducted based on the effects of the temperature field on the physical geometry and ray tracing\nperformance of the front dome and rear optical lenses, by deriving the relational expressions between\nthe system temperature field and the spot size and positioning precision of the rear optical lens.\nThe optical systems used for navigation guidance and control in supersonic aircraft when the flight\nspeed is in the range of 1ââ?¬â??5 Ma were analysed using the derived equations. Using this new method\nit was possible to control the precision within 10% when considering the light spot received by the\nfour-quadrant detector, and computation time was reduced compared with the traditional method\nof separately analysing the temperature field of the front dome and rear optical lens using FEA.\nThus, the method can effectively increase the efficiency of parameter analysis and computation in\nan airborne optical system, facilitating the systematic, effective and integrated thermal analysis of\nairborne optical systems for navigation guidance and control....
High frequency (HF) radar installations are becoming essential components of operational real-time marine monitoring systems.\nThe underlying technology is being further enhanced to fully exploit the potential of mapping sea surface currents and wave fields\nover wide areas with high spatial and temporal resolution, even in adversemeteo-marine conditions. Data applications are opening\nto many different sectors, reaching out beyond research and monitoring, targeting downstream services in support to key national\nand regional stakeholders. In the CALYPSO project, the HF radar system composed of CODAR SeaSonde stations installed in the\nMalta Channel is specifically serving to assist in the response against marine oil spills and to support search and rescue at sea. One\nkey drawback concerns the sporadic inconsistency in the spatial coverage of radar data which is dictated by the sea state as well as by\ninterference from unknown sources that may be competing with transmissions in the same frequency band. This work investigates\nthe use of Machine Learning techniques to fill in missing data in a high resolution grid. Past radar data and wind vectors obtained\nfrom satellites are used to predict missing information and provide a more consistent dataset....
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