Current Issue : April - June Volume : 2020 Issue Number : 2 Articles : 5 Articles
This paper presents a novel dual-band circularly polarized patch antenna for precise satellite navigation. The radiation elements are\ncomposed of the inner cross-shaped patch and the outer annular patch which are printed on the same surface of one substrate. Two\npatches work in different bands, respectively, and emit dual-band circularly polarized radiation. In order to obtain a more compact\nantenna to meet the application of precise satellite navigation, we vertically place four metal cylinders under the ends of the cross-shaped\npatch to form four capacitive loadings to lower the resonant frequency of the inner cross-shaped patch. A capacitive coupling feed\nstructure is used to match the input impedance of a patch antenna and make the antenna compact enough. The simulated and measured\nresults show that the proposed antenna can produce appropriate dual-band circularly polarized radiation patterns for precise satellite\nnavigation. The measured results of the antenna illustrate that maximum RHCP gain of the antenna is 4.72 dBi in the low band and\n3.98 dBi in the high band, the 3 dB gain bandwidth is 70MHz in the low band and 65MHz in the high band....
The feedback PID method was mainly used for the navigating control of an unmanned surface vessel (USV). However, when the\nintelligent control era is coming now, the USV can be navigated more effectively. According to the USV character in its navigating\ncontrol, this paper presents a parallel action-network ADHDP method. This method connects an adaptive controller parallel to the\naction network of the ADHDP. The adaptive controller adopts a RBF neural network approximation based on the Lyapunov\nstability analysis to ensure the system stability. The simulation results show that the parallel action-network ADHDP method has\nan adaptive control character and can navigate the USV more accurately and rapidly. In addition, this method can also eliminate\nthe overshoot of the ADHDP controller when navigating the USV in various situations. Therefore, the adaptive stability design can\ngreatly improve the navigating control and effectively overcome the ADHDP algorithm limitation. Thus, this adaptive control can\nbe one of the intelligent ADHDP control methods. Furthermore, this method will be a foundation for the development of an\nintelligent USV controller....
Hilly areas necessitate a field road vehicle with high automation to reduce the amount of labor required to transport agricultural\nproducts and to increase productivity. In this paper, an adaptive integrated navigation method (combining global navigation\nsatellite system (GNSS) and inertial navigation system (INS)) and path tracking control strategy of field road vehicles are\nstudied in view of the problems of frequent GNSS outages and high automatic control precision requirement in hilly areas. An\nindirect Kalman filter (KF) is designed for the GNSS/INS information fusion. A modified method for calculating the KF\nadaptive factor is proposed to effectively suppress the divergence of the KF and a threshold judgement method to abandon the\nabnormal GNSS measurement is proposed to deal with GNSS interruptions. To achieve automated driving, a five-layer fuzzy\nneural network controller, which takes the lateral deviation, heading deviation, and path curvature as input and the steering\nangle as output, is proposed to control vehicle autonomous tracking of the navigation trajectory accurately. The proposed\nsystem was evaluated through simulation and experimental tests on a field road. The simulation results showed that the adjusted\nKF fusion algorithm can effectively reduce the deviation of a single GNSS measurement and improve the overall accuracy. The\ntest results showed the maximum deviation of the actual travel trajectory from the expected trajectory of the vehicle in the\nhorizontal direction was 12.2 cm and the average deviation was 5.3 cm. During GNSS outages due to obstacles, the maximum\ndeviation in the horizontal direction was 12.7 cm and the average deviation was 6.1 cm. The results show that the designed\nGNSS/INS integrated navigation system and trajectory tracking control strategy can control a vehicle automatically while\ndriving along a field road in a hilly area....
Knowledge of the global navigation satellite system (GNSS) satellite clock error is crucial\nin real-time precise point positioning (PPP), seismology, and many other high-rate GNSS\napplications. In this work, the authors show the characterisation of the atomic GNSS clockâ??s stability\nand its dependency on the adopted orbit type using Allan deviation with two methods of averaging\ntime. Four International GNSS Service (IGS) orbit types were used: broadcast, ultra-rapid, rapid and\nfinal orbit. The calculations were made using high-rate 1 Hz observations from the IGS stations\nequipped with external clocks (oscillators). The most stable receiver oscillator was chosen as a\nreference clock. The results show the advantage of the newest GPS satellite block with respect to the\nother satellites. Significant differences in the results based on the orbit type used have not been\nrecorded. Many averaging time methods used in Allan deviation (ADEV) show the clockâ??s\nfluctuations, usually smoothed in 2n s averaging times....
At the present time rather diverse and interesting papers are published on\nthe basis of ground-based and satellite data of earth VLF/LF and ULF electromagnetic\n(EM) emissions observed during earthquake preparation period.\nThese phenomena are detectable both at laboratory and geological\nscale. Today in some seismic active countries of the world the network for\ncollecting VLF/LF electromagnetic emissions generated during the process\nof the earthquake preparation has been organized. Permanent monitoring of\nfrequency spectrum of earth VLF/LF electromagnetic emissions might turn\nout very useful with the view of prediction of large M greater than equal to 5 inland earthquakes.\nTo prove the prediction capabilities of earth electromagnetic emissions authors\nhave used avalanche-like unstable model of fault formation and an\nanalogous model of electromagnetic contour, synthesis of which, is rather\nharmonious. According to the opinion of the authors EM emissions observed\nduring earthquake preparation period are more universal and reliable than\nother earthquake indicators. In the presented paper, the possible methods of\nthe large earthquake prediction are offered on the base of the European Network\nof Electromagnetic Radiation (INFREP) data existent before Crete\nearthquake with M = 5.6 (25/05/2016, 08:36:13 UTC) earthquake. Offered\nmethods are capable of simultaneous determination of all three parameters\nnecessary for incoming M greater than equal to 5 inland large earthquake prediction (magnitude,\nepicenter and time of occurring) with certain accuracy....
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