For the case of air-to-surface missile with guidance system composed of infrared system and millimeter wave system against ground targets, a new design scheme of nonlinear terminal guidance law with robustness is proposed. An engagement model in the pitch plane is formulated, in which states are chosen as relative distance and relative velocity, by combining the relative relationship between missile and target, where the information is obtained directly from the infrared system and millimeter wave system. By adopting the sliding mode control, an adaptive nonlinear control law of the system is designed so that the missile can hit the target accurately with the index of optimizing the relative distance. The stability of the closed-loop system is also proven by utilizing the Lyapunov stability theory. Finally an illustrative example of attacking a ground target is given to confirm the usefulness of the proposed design scheme.
Yang Yu-Bin;Tang Guo-Jian;Guo Jian-Guo;Zhou Jun;Bao Wei-Min
Yuhang Xuebao Journal of Astronautics
© 2015 Chunye Gong et al. We present a survey of fractional differential equations and in particular of the computational cost for their numerical solutions from the view of computer science. The computational complexities of time fractional, space fractional, and space-time fractional equations are O(N2M), O(NM2), and O(NM(M + N)) compared with O(MN) for the classical partial differential equations with finite difference methods, where M, N are the number of space grid points and time steps. The potential solutions for this challenge include, but are not limited to, parallel computing, memory access optimization (fractional precomputing operator), short memory principle, fast Fourier transform (FFT) based solutions, alternating direction implicit method, multigrid method, and preconditioner technology. The relationships of these solutions for both space fractional derivative and time fractional derivative are discussed. The authors pointed out that the technologies of parallel computing should be regarded as a basic method to overcome this challenge, and some attention should be paid to the fractional killer applications, high performance iteration methods, high order schemes, and Monte Carlo methods. Since the computation of fractional equations with high dimension and variable order is even heavier, the researchers from the area of mathematics and computer science have opportunity to invent cornerstones in the area of fractional calculus.
Gong Chunye;Bao Weimin;Tang Guojian;Liu Jie;Jiang Yuewen
Mathematical Problems in Engineering
© 2015 The Authors. In this paper, we propose an uncertainty analysis and design optimization method and its applications on a hybrid rocket motor (HRM) powered vehicle. The multidisciplinary design model of the rocket system is established and the design uncertainties are quantified. The sensitivity analysis of the uncertainties shows that the uncertainty generated from the error of fuel regression rate model has the most significant effect on the system performances. Then the differences between deterministic design optimization (DDO) and uncertainty-based design optimization (UDO) are discussed. Two newly formed uncertainty analysis methods, including the Kriging-based Monte Carlo simulation (KMCS) and Kriging-based Taylor series approximation (KTSA), are carried out using a global approximation Kriging modeling method. Based on the system design model and the results of design uncertainty analysis, the design optimization of an HRM powered vehicle for suborbital flight is implemented using three design optimization methods: DDO, KMCS and KTSA. The comparisons indicate that the two UDO methods can enhance the design reliability and robustness. The researches and methods proposed in this paper can provide a better way for the general design of HRM powered vehicles.
Zhu Hao;Tian Hui;Cai Guobiao;Bao Weimin
Chinese Journal of Aeronautics
© 2015, Science China Press and Springer-Verlag Berlin Heidelberg. To obtain a conceptual design for a hybrid rocket motor (HRM) to be used as the Ascent Propulsion System in the Apollo lunar module, the deterministic design optimization (DDO) method is applied to the HRM design. Based on the results of an uncertainty analysis of HRMs, an uncertainty-based design optimization (UDO) method is also adopted to improve the design reliability. The HRM design process, which is a multidisciplinary system, is analyzed, and a mathematical model for the system design is established to compute the motor performance from the input parameters, including the input variables and model parameters. The input parameter uncertainties are quantified, and a sensitivity analysis of the model parameter uncertainties is conducted to identify the most important model parameter uncertainties for HRMs. The DDO and probabilistic UDO methods are applied to conceptual designs for an HRM to be used as a substitute for the liquid rocket motor (LRM) of the Ascent Propulsion System. The conceptual design results show that HRMs have several advantages as an alternative to the LRM of the Ascent Propulsion System, including nontoxic propellant combination, small motor volume, and comparable functions, such as restarting and throating. Comparisons of the DDO and UDO results indicate that the UDO method achieves more robust and reliable optimal designs than the DDO method. The probabilistic UDO method can be used to develop better conceptual designs for HRMs.
Zhu Hao;Tian Hui;Cai GuoBiao;Bao WeiMin
Science China Technological Sciences
© 2015, Editorial Dept. of JA. All right reserved. When a spacecraft moves toward or away from the X-ray pulsars, Doppler effects are present in the pulsar signal measured by onboard X-ray detectors. By measuring the observed pulsar frequency, the speed of the spacecraft along the line of sight of the pulsar can be derived. The mathematical model is established to characterize the spacecraft's velocity estimation by adopting the time of arrival of X-ray photons. To improve the accuracy of Doppler frequency estimation, a robust averaging technique, RANSAC, is introduced to combine with the χ2statistical method. Besides, the priori information of the spacecraft velocity is utilized to improve the computational efficiency. The Crab pulsar data observed by RXTE satellite are applied to validate the presented method and some dominating error factors are analyzed. The results demonstrate that the method can track the spacecraft's velocity effectively. For RXTE satellite with the orbit altitude 570 km, in terms of the obvious changes in spacecraft's acceleration, the velocity estimation error along the line of sight of the pulsar is about ±150 m/s, and the corresponding acceleration estimation error is ±0.5 m/s2.
Sun Hai-Feng;Bao Wei-Min;Xue Meng-Fan;Fang Hai-Yan;Li Xiao-Ping
Yuhang Xuebao Journal of Astronautics
© 2016 Elsevier Masson SAS The X-ray energy band, which has a direct impact on the detector configuration and the estimation accuracy of the pulse time of arrival (TOA), is an important physical parameter for X-ray pulsar based navigation (XPNAV). Despite nearly five decades of work, there is still no convincing quality analysis for the effect of the X-ray energy on the XPNAV. In this paper, the impacts of the X-ray energy on the XPNAV are quantified for the first time through the Cramér-Rao lower bound (CRLB) theory. A lower bound on the variance of the pulse TOA is derived, and the indicators of the geometric factor and signal to noise ratio (SNR) are presented as the basic selection criteria. The RXTE observations of the Crab pulsar about 11 years (2001–2011) are applied to subdivide the entire 2–60 keV into finer energy windows of 2–10 keV, 10–20 keV, 20–30 keV, 30–40 keV, 40–50 keV and 50–60 keV to obtain pulse profiles in different energy bands. Discrepancies of these pulse profiles are investigated, and their impacts on the navigation accuracy are evaluated. The results demonstrate that the estimation accuracy of the pulse TOA applying the energy band 2–30 keV is improved by 15.54% compared with 2–10 keV, while an improvement of about 15.95% can merely be achieved applying 2–60 keV than 2–10 keV for the Crab pulsar.
Sun Haifeng;Bao Weimin;Fang Haiyan;Shen Lirong;Xue Mengfan;Li Xiaoping
Aerospace Science and Technology
© The Institution of Engineering and Technology. The solar vector, which defines the angle between the satellite and the Sun, is an important parameter for attitude control of a nanosatellite. It is highly desirable to enable accurate attitude control of a nanosatellite without increasing size and mass. To solve this issue, this study presents a novel sun sensor based on solar panel time-division multiplexing. The mathematical relationship between the short-circuit current of the solar panel and the solar vector is derived, and a mathematical model of the time-division multiplexing for the sensor is introduced. A sample of the sensor is built and an experiment is conducted to obtain the short-circuit current data for different angles. The output of the sensor is included in the mathematical model to obtain the solar vector. The relevant measurement errors of the sensor is also derived. The results show that the sensor is capable of measuring across the 0-180° range with a maximum absolute error of measurement of 4.531° and a relative error of 2.517%.
L\u00fc Xiaozhou;Tao Yebo;Xie Kai;Li Xiaoping;Wang Songlin;Bao Weimin;Chen Renjie
Iet Science Measurement and Technology
© 2017 Cong Li et al. Based on the orthogonal frequency division multiplexing (OFDM) technique, an intelligent waveform is designed, which is suitable for simultaneously performing data transmission and radar sensing. In view of the inherent high peak-to-mean envelope power ratio (PMERP) and poor peak-to-side-lobe ratio (PSLR) problems in the OFDM based radar and communication (RadCom) waveform design, we propose two technologies to deal with that. To be specific, we adopt Gray code technology to reduce the PMERP and simultaneously choose an optimal cyclic sequence to improve the PSLR of RadCom waveform. In our method, the optimal cyclic sequence is dynamically generated to continuously provide the best waveform according to the change of communication data. In addition, to meet the requirements of different radar detection tasks, two simple methods are utilized to adjust the bandwidth of RadCom waveform. To verify the advantages of the designed waveform, we conduct several simulation experiments to compare with some existing RadCom waveforms. The results show that our designed RadCom waveform can simultaneously achieve lower PMERP and higher PSLR. In addition, our designed RadCom waveform has a thumbtack type fuzzy function and shows the good ability to do multitarget detection.
Li Cong;Bao Weimin;Xu Luping;Zhang Hua;Huang Ziyang
Mathematical Problems in Engineering
© 2017 by the authors. Model training is a key technique for radar target recognition. Traditional model training algorithms in the framework of single task leaning ignore the relationships among multiple tasks, which degrades the recognition performance. In this paper, we propose a clustered multi-task learning, which can reveal and share the multi-task relationships for radar target recognition. To further make full use of these relationships, the latent multi-task relationships in the projection space are taken into consideration. Specifically, a constraint term in the projection space is proposed, the main idea of which is that multiple tasks within a close cluster should be close to each other in the projection space. In the proposed method, the cluster structures and multi-task relationships can be autonomously learned and utilized in both of the original and projected space. In view of the nonlinear characteristics of radar targets, the proposed method is extended to a non-linear kernel version and the corresponding non-linear multi-task solving method is proposed. Comprehensive experimental studies on simulated high-resolution range profile dataset and MSTAR SAR public database verify the superiority of the proposed method to some related algorithms.
Li Cong;Bao Weimin;Xu Luping;Zhang Hua
© 2001-2012 IEEE. The proximity sensor plays an important role in recognition, positioning, tracking, and avoiding of obstacles in robot movement. The existing proximity sensors cannot identify the direction and measure the distance of the approaching object simultaneously. In order to solve mentioned problem, this paper presents a novel proximity sensor based on parallel plate capacitance. The proposed proximity sensor adopts the structure wherein driving electrode and sensing electrodes are located on the same plane. The number of driving electrodes differs from the number of sensing electrodes, and sensing electrodes are symmetrically distributed around the driving electrode. In this paper, we developed the circuit model of the proximity sensor based on parallel plate capacitance, and analyzed the influence of the guard ring on sensor sensitivity. We also designed a new sensor structure, which employs four sensing electrodes to identify direction of the approaching object. In addition, the proximity sensor performances in terms of direction identification were verified by experiments, and both sensing errors and sensor repeatability were calculated. The experimental results have shown that proposed proximity sensor can distinguish four different directions and measure the object distance in the range of 1 40 mm simultaneously. The sensing errors were less than 5% and the repeatability error was 1.05%.
Lu Xiaozhou;Li Xi;Zhang Feng;Wang Songlin;Xue Dongfeng;Qi Liang;Wang Hui;Li Xiaoping;Bao Weimin;Chen Renjie
IEEE Sensors Journal