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Lei X.,Beihang University | Lei X.,Science and Technology on Inertial Laboratory | Guo K.,Beihang University
Journal of Bionic Engineering | Year: 2012

This paper proposes a model identification method to get high performance dynamic model of a small unmanned aerial rotorcraft. With the analysis of flight characteristics, a linear dynamic model is constructed by the small perturbation theory. Using the micro guidance navigation and control module, the system can record the control signals of servos, the state information of attitude and velocity information in sequence. After the data preprocessing, an adaptive ant colony algorithm is proposed to get optimal parameters of the dynamic model. With the adaptive adjustment of the pheromone in the selection process, the proposed model identification method can escape from local minima traps and get the optimal solution quickly. Performance analysis and experiments are conducted to validate the effectiveness of the identified dynamic model. Compared with real flight data, the identified model generated by the proposed method has a better performance than the model generated by the adaptive genetic algorithm. Based on the identified dynamic model, the small unmanned aerial rotorcraft can generate suitable control parameters to realize stable hovering, turning, and straight flight. © 2012 Jilin University. Source

Han B.,Science and Technology on Inertial Laboratory | Han B.,Fundamental Science on Novel Inertial Instrument and Navigation System Technology Laboratory | Han B.,Beihang University | Zheng S.,Beihang University | Hu X.,Beihang University
IEEE Transactions on Magnetics | Year: 2013

A hybrid thrust magnetic bearing (HTMB) with permanent magnet creating bias flux is used to save energy. The eddy currents have a fundamental impact on the dynamic characteristics of the magnetic bearing system. Therefore, the dynamic factor models affected by the eddy currents rather than static model are required to insure reliable and effective operation. The dynamic factor models affected by the eddy currents for the HTMB with permanent magnets and subsidiary air gap are presented in this paper. The equivalent magnetic circuit models of the HTMB are given and derived to calculate the dynamic force-current factor and the dynamic force-displacement factor. Furthermore, the dynamic factors of the HTMB are also investigated by the transient nonlinear finite element method (FEM). The analytical results show that the two dynamic factors have the different frequency response characteristics, both in the equivalent magnetic circuit model and from the results of the nonlinear FEM. Furthermore, the distribution of flux density in the air gap at different frequency response is shown and compared to static flux by using FEM. The dynamic performance is determined by the dynamic force-current factor model due to the difference between the control flux path and the permanent magnet bias flux path. The analysis results calculated by the simplified analytical model agree well with the results calculated by transient FEM. © 1965-2012 IEEE. Source

Ning X.,Beihang University | Ning X.,Science and Technology on Inertial Laboratory | Huang P.,Beihang University
Chinese Control Conference, CCC | Year: 2014

The navigation accuracy in approach phase has a significant effect on the successful capture and injection of the Mars spacecraft. On one hand, the perturbation of Mars gravity field on spacecraft's orbit increases when spacecraft gradually approaches the Mars, which results in slow change of the orbit dynamic model. On the other hand, imagines of the Mars and its satellites on sensors vary with the explorer coming to the Mars, which causes change of measurement noise. Since the statistical features of system noise and measurement noise are time-varying, the navigation accuracy will not be optimal if the filter parameters remain constant. In this paper, an adaptive points range Square-root Cubature Kalman filter (AR-SCKF) method is proposed to deal with this problem, which uses several sub-SCKFs with different cubature-points ranges to track the dynamic change of the system noise and measurement noise. The cubature-points ranges of sub-SCKFs can be adjusted automatically according to their navigation performance. Simulations demonstrate that the navigation accuracy of this method has 10% root mean square (RMS) error improvement and 30% maximum error improvement compared to the traditional SCKF. The impact factors of this method like the maximum points range and points range number are also studied. © 2014 TCCT, CAA. Source

Gong X.,Beihang University | Fan W.,Science and Technology on Inertial Laboratory | Fang J.,Science and Technology on Inertial Laboratory
Measurement: Journal of the International Measurement Confederation | Year: 2014

Airborne distributed Position and Orientation System (POS) depends on transfer alignment to obtain high accuracy motion parameters of sub-systems by using accurate motion information of main system, including position, velocity and attitude. Complicated aircraft flexure will decrease the accuracy of transfer alignment. Usually, the flexure angle is idealized as Markov process with fixed parameters, while these parameters are unknown and time-varying in real application. Accordingly, the accuracy of state model and statistic characters of noise will be incorrect, which consequently increases the error of transfer alignment. To solve the mentioned problem, this paper proposes a parameter identification method and then combines it with UKF. As a result, transfer alignment based on parameter identification UKF (PIUKF) is designed, and verified by simulations and static experiment. The results show that transfer alignment method based on PIUKF improves the accuracy of sub-systems compared with those based on UKF and strong tracking UKF. © 2014 Elsevier Ltd. All rights reserved. Source

Wu W.,Lunar Exploration and Aerospace Engineering Center | Wu W.,Beihang University | Ning X.,Beihang University | Ning X.,Science and Technology on Inertial Laboratory | And 2 more authors.
Journal of Systems Engineering and Electronics | Year: 2013

In the future lunar exploration programs of China, soft landing, sampling and returning will be realized. For lunar explorers such as Rovers, Landers and Ascenders, the inertial navigation system (INS) will be used to obtain high-precision navigation information. INS propagates position, velocity and attitude by integration of sensed accelerations, so initial alignment is needed before INS can work properly. However, traditional ground-based initial alignment methods cannot work well on the lunar surface because of its low rotation rate (0.55°/h). For solving this problem, a new autonomous INS initial alignment method assisted by celestial observations is proposed, which uses star observations to help INS estimate its attitude, gyroscopes drifts and accelerometer biases. Simulations show that this new method can not only speed up alignment, but also improve the alignment accuracy. Furthermore, the impact factors such as initial conditions, accuracy of INS sensors, and accuracy of star sensor on alignment accuracy are analyzed in details, which provide guidance for the engineering applications of this method. This method could be a promising and attractive solution for lunar explorer's initial alignment. Source

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