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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.

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.

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.

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.

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.

Liu Q.,Science and Technology on Inertial Laboratory | Liu Q.,Fundamental Science on Novel Inertial Instrument and Navigation System Technology Laboratory | Fang J.-C.,Science and Technology on Inertial Laboratory | Fang J.-C.,Fundamental Science on Novel Inertial Instrument and Navigation System Technology Laboratory
Mocaxue Xuebao/Tribology | Year: 2013

To study the fretting behaviors of locking device for magnetically suspended flywheel under different locking forces, the swept-sine vibration and random vibration were carried out to simulate the vibration environment during launch. The fretting displacements between stator and rotor measured by eddy current displacement sensor indicate the composite fretting regime including tangential and radial fretting in locking surface. After tests, the surfaces of three contacts including 1Cr18Ni9Ti/GCr15, nitrided 1Cr18Ni9Ti/GCr15 and GCr15/GCr15 were analyzed using scanning electronic microscopy. The results show that with the increase of locking force from 200 N to 300 N, the maximum fretting displacement decreased from 60 μm to 8 μm and its corresponding amplitude decreased from 25 μm to 4 μm. This results in tangential fretting transition from slip regime to partial slip regime and reduced the fretting damage. In addition, the micro-slip and radial fretting damage can be avoided by increasing contact stiffness and choosing similar contact bodies. The two fretting resistances can inhibit composite fretting damage in locking surface.

Han B.-C.,Fundamental Science on Novel Inertial Instrument and Navigation System Technology Laboratory | Han B.-C.,Science and Technology on Inertial Laboratory | Yuan Q.,Fundamental Science on Novel Inertial Instrument and Navigation System Technology Laboratory | Yuan Q.,Science and Technology on Inertial Laboratory
Yuhang Xuebao/Journal of Astronautics | Year: 2012

To improve the efficiency and to get the best design parameters of the large-sized magnetic suspension CMG (Control Moment Gyroscope) system being used in space station, a optimization design and analysis method about the rotor with high speed (1200r/min) and big angular momentum (1000 N·m·s) has been proceeded. A combinatorial optimization strategy based on Genetic Algorithm (GA) and Sequential Quadratic Programming (NLPQL) is proposed to optimize the rotor system. ANSYS is used to build a parameterization model, INIGHT and ANSYS are integrated to finish the optimization motor mass and maximal equivalent stress taken to be minimum respectively are chose as the design objects. The wheel disk dimensions are taken as design variables. Size, strength and effectiveness are taken as constraints according to the rotor working condition. Compared with GA and NLPQL in operating efficiency and optimization result, it is found that the combinatorial optimization strategy is better than a global or a local optimization algorithm to be used only. The combinatorial optimization strategy's result indicates that the mass decreases 3.92 percent, the safety factor improves 2.69 percent. The experimental result demonstrates the combinatorial optimization strategy's design result.

Ren Y.,Science and Technology on Inertial Laboratory | Fang J.,Science and Technology on Inertial Laboratory
IEEE Transactions on Industrial Electronics | Year: 2014

To resolve the common contradictions between the decoupling precision and robustness to model the errors of a magnetically suspended control moment gyro and to avoid high control effort, a high-precision and strong-robustness control strategy is presented in this paper. The described method is based on the modal separation control and rotation motion decoupling strategy. The simplified modal controller and modified feedback linearization algorithm are employed to realize the two objectives, respectively. Simultaneously, a new phase compensation approach is proposed, and its design method is presented to improve the decoupling performance and system stability. A robust servo regulator is adopted for the decoupled plants to guarantee the control performances and robustness. Comparative simulations and experiments have been developed to evaluate the effectiveness and superiority of the proposed control method. © 1982-2012 IEEE.

Zhang W.,Science and Technology on Inertial Laboratory | Quan W.,Science and Technology on Inertial Laboratory | Guo L.,Science and Technology on Inertial Laboratory
Sensors (Switzerland) | Year: 2012

The precision of star point location is significant to identify the star map and to acquire the aircraft attitude for star sensors. Under dynamic conditions, star images are not only corrupted by various noises, but also blurred due to the angular rate of the star sensor. According to different angular rates under dynamic conditions, a novel method is proposed in this article, which includes a denoising method based on adaptive wavelet threshold and a restoration method based on the large angular rate. The adaptive threshold is adopted for denoising the star image when the angular rate is in the dynamic range. Then, the mathematical model of motion blur is deduced so as to restore the blurred star map due to large angular rate. Simulation results validate the effectiveness of the proposed method, which is suitable for blurred star image processing and practical for attitude determination of satellites under dynamic conditions. © 2012 by the authors; licensee MDPI, Basel, Switzerland.

Lei X.L.,Science and Technology on Inertial Laboratory | Li J.L.,Science and Technology on Inertial Laboratory
Sensors (Switzerland) | Year: 2012

This paper presents an adaptive information fusion method to improve the accuracy and reliability of the altitude measurement information for small unmanned aerial rotorcraft during the landing process. Focusing on the low measurement performance of sensors mounted on small unmanned aerial rotorcraft, a wavelet filter is applied as a pre-filter to attenuate the high frequency noises in the sensor output. Furthermore, to improve altitude information, an adaptive extended Kalman filter based on a maximum a posteriori criterion is proposed to estimate measurement noise covariance matrix in real time. Finally, the effectiveness of the proposed method is proved by static tests, hovering flight and autonomous landing flight tests. © 2012 by the authors; licensee MDPI, Basel, Switzerland.

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