Time filter

Source Type

Wu B.,Harbin University of Science and Technology | Xu H.,Beijing Universal Information Application Development Center | Qiao X.-W.,Xian Aerospace Precision Electromechanical Institute
Dianji yu Kongzhi Xuebao/Electric Machines and Control | Year: 2012

Considering the sharply increased computation burden caused by the increasement of state dimension multiplication in Augmented unscented Kalman filter (AUKF), a state switch unscented Kalman filter (SUKF) algorithm whose process and measurement noise has no correlation was proposed. Via selecting different state variables in time update and measurement update stage, the state dimension of real-time filtering was reduced and the number of Sigma points selected decreased, so the filter computation was reduced and speed was improved. Aming at the quaternion normalization restrictions in attitude determination, a parameter-switching algorithm was proposed. Through switching the quaternion parameter and the modified rodriguez parameter (MRPs), the quaternion weighted meanand covariance singularity problems were solved. The SINS/CCD attitude simulation results show that: compared with the AUKF, the proposed algorithm estimation accuracy is about equal and the estimation time reduces approximately 1/3. Source

Li C.,Northwest University, China | Wang Z.,Northwest University, China | Ding C.,Xian Aerospace Precision Electromechanical Institute
Lecture Notes in Electrical Engineering | Year: 2014

In response to mechanical fault in feature extraction problem, this paper presents a Fisher discrimination sparse coding method. This method is achieved by optimizing an objective function that includes two steps. First, this objective function works well in denoising where signals need to be reconstructed. Second, another objective function is added to the sparse coding framework, the discrimination power of the Fisher discriminative methods with the reconstruction property, and the sparsity of the sparse representation that can deal with the fault signal which is corrupted. Finally, the feature is extracted. In rolling bearing fault classification experiments, the new method improves the accuracy of classification. © 2014 Springer-Verlag. Source

Dai J.,Lanzhou University of Technology | Fu B.,Lanzhou University of Technology | Yao X.,Lanzhou University of Technology | Dai Y.,Lanzhou University of Technology | And 2 more authors.
Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams | Year: 2012

In order to improve the concentration efficiency and eliminate the optical aberration, the umbrella-shaped keel structure has been introduced into the deployable concentrator. The concentration performance of deployable solar paraboloid concentrator with concentration power of which working in the space environment has been investigated with the software and . Under the influence of film tension and solar wind, the maximum stress of umbrella fabric is , is which is much smaller than the threshold intensity of and keel materials. The maximum deformation of umbrella fabric is , radius of the spot size is , the geometric concentration ratio could achieve , which only reduced than the standard parabolic concentrator. The results reveal that the influence of film tension and solar wind on the working shape of concentrator has been offset to a large extent by the introduction of umbrella-shaped keel structure, which would eliminate wrinkle and enhance the umbrella-shaped keel concentrator abilities of deployable and stability, as well as the selected umbrella-shaped keel structure and materials are appropriate. Source

Wang L.,Harbin Engineering University | Wang L.,Shanghai JiaoTong University | Li G.-C.,Harbin Engineering University | Qiao X.-W.,Harbin Engineering University | And 3 more authors.
Zidonghua Xuebao/Acta Automatica Sinica | Year: 2012

In order to solve the state estimation problem of nonlinear systems without knowing prior noise statistical characteristics, an adaptive unscented Kalman filter (UKF) based on the maximum likelihood principle and expectation maximization algorithm is proposed in this paper. In our algorithm, the maximum likelihood principle is used to find a log likelihood function with noise statistical characteristics. Then, the problem of noise estimation turns out to be maximizing the mean of the log likelihood function, which can be achieved by using the expectation maximization algorithm. Finally, the adaptive UKF algorithm with a suboptimal and recurred noise statistical estimator can be obtained. The simulation analysis shows that the proposed adaptive UKF algorithm can overcome the problem of filtering accuracy declination of traditional UKF used in nonlinear filtering without knowing prior noise statistical characteristics and that the algorithm can estimate the noise statistical parameters online. Source

Xie B.,Xian Aerospace Precision Electromechanical Institute | Jiang Y.-F.,Xian Aerospace Precision Electromechanical Institute | Yan G.-M.,Northwestern Polytechnical University | Ren H.-K.,Xian Aerospace Precision Electromechanical Institute
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2013

As heading drift error remains a problem in a standalone pedestrian navigation system(PNS) that uses low-cost inertial measurement unit(IMU), an algorithm for integrating shoe-mounted IMU with building plane was proposed, and a novel auxiliary particle filter which is more applicable in indoor navigation scenario was devised. A double-deck framework comprises Kalman filter(KF) and particle filter(PF) was introduced, in which the lower KF applies zero-updating measurement for drift correction. The upper PF computes the step-wise changes of IMU position and heading to use them as measurements, and a corresponding pedestrian movement model was constructed for fusing nonlinear map-matching technique. The proposed algorithm is verified through experimental data collected from a low-performance IMU mounted on foot: the final positioning error of 300 m travel distance is less than 0.3 m. It is also shown that the consistent positioning accuracy and reliability of a PNS could be improved effectively with the modified auxiliary particle filter. Source

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