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Dong Z.,Beihang University | Dong Z.,Science and Technology on Electronic optic Control Laboratory | Chen Z.,Beihang University | Zhou R.,Beihang University | Zhang R.,Flight automatic control research institute
Proceedings of the 2011 6th IEEE Conference on Industrial Electronics and Applications, ICIEA 2011

This article is concerned with the UAV path re-planning problem to be solved by using a novel approach based on the hybrid of virtual force and A * search algorithm (HVFA). The formulation of the UAV path re-planning is presented, and the hybrid system model of virtual force (VF) is given. The scheme of path re-planning is designed and the corresponding computational complexity is analyzed quantitatively. Simulation results prove the feasibility and usefulness of using HVFA for UAV path re-planning. Performance comparisons between the HVFA method and the fuzzy virtual force (FVF) method demonstrate that the proposed approach is fast enough to meet the real-time requirements of the online path planning problems. © 2011 IEEE. Source

Xie J.-J.,Xidian University | Yin Y.-Z.,Xidian University | Chen Y.,Flight automatic control research institute
Electronics Letters

A single-layer wideband printed slot antenna with polarisation diversity is presented using a hybrid feeding technique. The antenna consists of an aperture-coupled feeding element and a coplanar waveguide feeding element. The aperture-coupled microstrip feed line with a 180° phase difference is used to reduce the cross-polarisation level and improve the isolation level. A circular patch is connected to the coplanar waveguide feed line for good impedance matching. By introducing a fan-shaped slot to separate the ground plane of the radiating elements, the measured isolation between the two feeding ports is better than 30 dB in the whole operating band. The measured -10 dB impedance bandwidths are 49% (4.72-7.75 GHz) and 63% (3.96-7.64 GHz) at port 1 and port 2, respectively. Moreover, the proposed antenna has a compact structure and stable gain over the operating band; thus it can be used in the 5.2/5.8 GHz WLAN and 5.5 GHz WiMAX systems. © The Institution of Engineering and Technology 2013. Source

Fu Q.-W.,Northwestern Polytechnical University | Qin Y.-Y.,Northwestern Polytechnical University | Zhang J.-H.,Flight automatic control research institute | Li S.-H.,Northwestern Polytechnical University
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology

The classic recursive least-square (RLS) fine alignment method, which uses the horizontal velocity errors as measurements, needs longer time to identify the azimuth error and gyro drift errors. Besides, its convergent speed is affected by the initial value of recursive calculation. An improved method is put forward which directly uses the horizontal specific forces in one second as measurements, and neglects high-order misalignment errors in converting the cubic curve into linear model. On the basis of the simplified model, a low computational complexity RLS algorithm without initial condition is derived to speed up the convergence. The simulation and practicality experiments based on stationary base show that the improved method can identify the misalignment errors and the north gyro drift errors in 120 s, so it greatly shortens the time of initial alignment and gyro drift measurement without affecting alignment accuracy. Source

You J.-C.,Northwestern Polytechnical University | Qin Y.-Y.,Northwestern Polytechnical University | Mei C.-B.,Northwestern Polytechnical University | Xia J.-H.,Flight automatic control research institute
Yuhang Xuebao/Journal of Astronautics

Coning effects must be accurately compensated in the attitude updating of the classical strapdown inertial navigation integration algorithm. These effects are not involved in the velocity updating, though the attitude change is being taken into it. The novel velocity error term induced by the coning correction is studied in this paper. These effects as the gyro angular increment data have the influence on the velocity updating in the same way. For the assumed linear ramp model, a two-sample compensation algorithm for the novel velocity error term is deduced in detail by using the two successive integrated angular rate increment and specific force increment measurements. The weighting coefficients are then optimized for best average performance in a specific environment, i.e. the body is exposed to a coning angular vibration about the x axis of the body frame combined with a linear vibration at the same frequency and in phase along the z axis. The simulation results validate that the two-sample optimization algorithm can compensate the integrated term of the novel velocity error effectively. Source

Wang J.-A.,Changan University | Liu P.-J.,Flight automatic control research institute | Li S.-S.,Changan University
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology)

Complex close-in Galileo BOC(1, 1) multipath signals can not be estimated by traditional GPS multipath mitigation algorithms, and therefore a model containing multipath number parameter and using genetic algorithm to estimate the multipath signals was provided. When the actual multipath signal changes little, the last estimated multipath parameters is used, until the multipath model changes largely, then the genetic algorithm is used to estimate the multipath parameter. In urban valley, the multipath signals disappear and appear frequently, and the algorithm estimates all the multipath signals even when it disappears temporarily. Thus when the multipath signals appear again, the multipath parameters could be obtained quickly. The algorithm estimates the multipath signals accurately and reduces the pseudo-range measurement errors, and thereby improves positioning accuracy, and to some extent, reduces the computational complexity. Source

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