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The envelope of a hypersonic vehicle is affected by severe fluctuating pressure, which causes the airborne antenna to vibrate slightly. This vibration mixes with the transmitted signals and thus introduces additional multiplicative phase noise. Antenna vibration and signal coupling effects as well as their influence on the lock threshold of the hypersonic vehicle carrier tracking system of the Ka band are investigated in this study. A vibration model is initially established to obtain phase noise in consideration of the inherent relationship between vibration displacement and electromagnetic wavelength. An analytical model of the Phase-Locked Loop(PLL), which is widely used in carrier tracking systems, is established. The coupling effects on carrier tracking performance are investigated and quantitatively analyzed by imposing the multiplicative phase noise on the PLL model. Simulation results show that the phase noise presents a Gaussian distribution and is similar to vibration displacement variation. A large standard deviation in vibration displacement exerts a significant effect on the lock threshold. A critical standard deviation is observed in the PLL of Binary Phase Shift Keying(BPSK) and Quadrature Phase Shift Keying(QPSK) signals. The effect on QPSK signals is more severe than that on BPSK signals. The maximum tolerable standard deviations normalized by the wavelength of the carrier are 0.04 and 0.02 for BPSK and QPSK signals,respectively. With these critical standard deviations, lock thresholds are increased from à12 andà4 d B to 3 and à2 d B, respectively. 相似文献
694.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(5):1333-1343
This paper investigates the motion control system of an optical telescope system used for precision satellite tracking and ranging applications. The system uses direct-drive permanent magnet synchronous motors (PMSMs) for high precision positioning. To overcome the performance limitations due to system dynamics and position dependent plant variations, a disturbance observer based control system is utilized. This paper contributes the detailed analysis, design and implementation of such an advanced control concept for the performance improvement of precision satellite tracking systems. Satellite tracking experiments are conducted to verify the performance of the proposed system. Utilizing the proposed control concept, the RMS servo error is reduced by a factor of 3.8 to well below the arcsecond range, achieving seeing limited tracking. 相似文献
695.
《中国航空学报》2020,33(8):2212-2223
The data association problem of multiple extended target tracking is very challenging because each target may generate multiple measurements. Recently, the belief propagation based multiple target tracking algorithms with high efficiency have been a research focus. Different from the belief propagation based Extended Target tracking based on Belief Propagation (ET-BP) algorithm proposed in our previous work, a new graphical model formulation of data association for multiple extended target tracking is proposed in this paper. The proposed formulation can be solved by the Loopy Belief Propagation (LBP) algorithm. Furthermore, the simplified measurement set in the ET-BP algorithm is modified to improve tracking accuracy. Finally, experiment results show that the proposed algorithm has better performance than the ET-BP and joint probabilistic data association based on the simplified measurement set algorithms in terms of accuracy and efficiency. Additionally, the convergence of the proposed algorithm is verified in the simulations. 相似文献
696.
Jianqiao Zhang Dong Ye James D. Biggs Zhaowei Sun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(3):1161-1175
This paper addresses the relative position tracking and attitude synchronization control problem for spacecraft formation flying (SFF). Based on the derived relative coupled six-degree-of-freedom dynamics, a robust adaptive finite-time fast terminal sliding mode controller is proposed to achieve the desired formation in the presence of model uncertainties and external disturbances. It is shown that the designed controller is effective for changing information exchange topology making it robust to node failure. Then, the artificial potential function method is employed to generate collision avoidance schemes to modify the controller such that inter-agent collision avoidance can be ensured during the formation maneuver, which is critical for practical missions. The stability of the overall closed-loop system is proved by using Lyapunov theory. Finally, numerical examples for a given SFF scenario are presented to illustrate the performance of the controller. 相似文献
697.
Qijia Yao 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(6):1830-1843
Space manipulator is considered as one of the most promising technologies for future space activities owing to its important role in various on-orbit serving missions. In this paper, a novel adaptive fuzzy neural network (FNN) control scheme is proposed for the trajectory tracking control of an attitude-controlled free-flying space manipulator in the presence of output constraints and input nonlinearities. The parametric uncertainties and external disturbances are also taken into the consideration. First, a model-based controller is designed by using the barrier Lyapunov function (BLF) to prevent the position tracking errors from violating the predefined output constraints. Then, an adaptive FNN controller is designed by using two FNNs to compensate for the lumped uncertainties and input nonlinearities, respectively. Rigorous theoretical analysis for the semiglobal uniform ultimate boundedness of the whole closed-loop system is provided. The proposed adaptive FNN controller can guarantee the position and velocity tracking errors converge to the small neighborhoods about zero, while ensuring the position tracking errors within the output constraints even in the presence of input nonlinearities. To the best of the authors’ knowledge, there are relatively few existing controllers can achieve such excellent control performance in the same conditions. Numerical simulations illustrate the effectiveness and superiority of the proposed control scheme. 相似文献
698.
介绍了一种FFT并行结构的全数字宽带接收机,接收机中包括载波恢复,定时恢复和匹配滤波器三个主要功能部分。其特点是信号处理速率比输入Nyquist采样速率低得多,而且其中的匹配滤波器和定时校正恢复可以在频域上有效地实现,这种结构特别适合于卫星通信中每秒几百兆比特速率的高速数据传输应用。 相似文献
699.
Liang Sun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(7):2229-2238
A saturated fault-tolerant attitude tracking controller for disturbed rigid spacecraft is derived using nonlinear state feedback control method. The proposed controller achieves the constraints of control inputs by directly using the bounded function instead of the traditional saturation compensator technique, and the active tolerance to the partial loss of actuator effectiveness is also achieved by directly using the known bounds of the actuator faults in the controller. Specifically, compared with the traditional saturated control methods, a continuously bounded nonlinear function in the proposed controller is used to guarantee that the actuator outputs are smoothly bounded under the prescribed constraints. Based on some properties of the attitude tracking dynamics, the proposed controller can ensure the attitude tracking errors converge to small neighborhoods of zero via stability analysis in the Lyapunov framework. Simulation results are presented to illustrate the effectiveness of the control scheme. 相似文献
700.