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Research on the transfers to Halo orbits from the view of invariant manifolds

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Science China(Physics,Mechanics & Astronomy) 2012年第4期55卷 671-683页

作者： xu ming TAN Tian xu shijie Beijing University of Aeronautics andAstronautics Beijing 100191China DFH Satellite Co.Ltd. Beijing 100094China

This paper discusses the evolutions of invariant manifolds of Halo orbits by low-thrust and lunar gravity. The possibility of applying all these manifolds in designing low-thrust transfer, and the presence of single-impulse trajectories under lunar gravity are also explained. The relationship between invafiant manifolds and the altitude of the perigee is investigated using a Poincare map. Six types of single-impulse transfer trajectories are then attained from the geometry of the invariant manifolds. The evolutions of controlled manifolds are surveyed by the gradient law of Jacobi energy, and the following conclusions are drawn. First, the low thrust （acceleration or deceleration） near the libration point is very inefficient that the spacecraft free-flies along the invariant manifolds. The purpose is to increase its velocity and avoid stagnation near the libration point. Second, all con- trolled manifolds are captured because they lie inside the boundary of Eatlh＇s gravity trap in the configuration space. The evo- lutions of invariant manifolds under lunar gravity are indicated from the relationship between the lunar phasic angle and the altitude of the perigee. Third and last, most of the manifolds have preserved their topologies in the circular restricted three-body problem. However, the altitudes of the perigee of few manifolds are quite non-continuous, which can be used to generate single-impulse flyby trajectories.

关键词： libration point Halo orbit transfer trajectory invariant manifolds low thrust lunar perturbation

Attitude Control Considering Variable Input Saturation Limit for a Spacecraft Equipped with Flywheels

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Chinese Journal of Aeronautics 2012年第3期25卷 437-445页

作者： TIAN Lin xu shijie School of Astronautics Beihang University Beijing 100191China

A new attitude controller is proposed for spacecraft whose actuator has variable input saturation limit. There are three identical flywheels orthogonally mounted on board. Each rotor is driven by a brushless DC motor （BLDCM）. Models of spacecraft attitude dynamics and flywheel rotor driving motor electromechanics are discussed in detail. The controller design is similar to saturation limit linear assignment. An auxiliary parameter and a boundary coefficient are imported into the controller to guaran- tee system stability and improve control performance. A time-varying and state-dependent flywheel output torque saturation limit model is established. Stability of the closed-loop control system and asymptotic convergence of system states are proved via Lyapunov methods and LaSalle invariance principle. Boundedness of the auxiliary parameter ensures that the control objective can be achieved, while the boundary parameter＇s value makes a balance between system control performance and flywheel utilization efficiency. Compared with existing controllers, the newly developed controller with variable torque saturation limit can bring smoother control and faster system response. Numerical simulations validate the effectiveness of the controller.

关键词： spacecraft attitude control variable input saturation limit Lyapunov methods flywheels brushless DC motor

Decentralized adaptive sliding mode control of a space robot actuated by control moment gyroscopes

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Chinese Journal of Aeronautics 2016年第3期29卷 688-703页

作者： Jia Yinghong xu shijie School of Astronautics Beihang University

An adaptive sliding mode control （ASMC） law is proposed in decentralized scheme for trajectory tracking control of a new concept space robot. Each joint of the system is a free ball joint capable of rotating with three degrees of freedom （DOF）. A cluster of control moment gyroscopes （CMGs） is mounted on each link and the base to actuate the system. The modified Rodrigues parameters （MRPs） are employed to describe the angular displacements, and the equations of motion are derived using Kane＇s equations. The controller for each link or the base is designed sep- arately in decentralized scheme. The unknown disturbances, inertia parameter uncertainties and nonlinear uncertainties are classified as a ＂lumped＂ matched uncertainty with unknown upper bound, and a continuous sliding mode control （SMC） law is proposed, in which the control gain is tuned by the improved adaptation laws for the upper bound on norm of the uncertainty. A gen- eral amplification function is designed and incorporated in the adaptation laws to reduce the control error without conspicuously increasing the magnitude of the control input. Uniformly ultimate boundedness of the closed loop system is proved by Lyapunov＇s method. Simulation results based on a three-link system verify the effectiveness of the proposed controller.

关键词： Adaptation law Ball joint Control moment gyroscopes Sliding mode control Space robot Trajectory tracking

Underactuated spacecraft angular velocity stabilization and three-axis attitude stabilization using two single gimbal control moment gyros

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Acta Mechanica Sinica 2010年第2期26卷 279-288页

作者： Lei Jin shijie xu Department of Guidance Navigation and Control School of Astronautics Beihang University 100191 Beijing China

Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros （SGCMGs） as actuators is investigated. First of all, the dynamic model of the underactuated spacecraft is established and the singularity of different configurations with the two SGCMGs is analyzed. Under the assumption that the gimbal axes of the two SGCMGs are installed in any direction, and that the total system angular momentum is not zero, a state feedback control law via Lyapunov method is designed to globally asymptotically stabilize the angular velocity of spacecraft. Under the assumption that the gimbal axes of the two SGCMGs are coaxially installed along anyone of the three principal axes of spacecraft inertia, and that the total system angular momentum is zero, a discontinuous state feedback control law is designed to stabilize three-axis attitude of spacecraft with respect to the inertial frame. Furthermore, the singularity escape of SGCMGs for the above two control problems is also studied. Simulation results demonstrate the validity of the control laws.

关键词： Single gimbal control moment gyro ·Undcractuated spacecraft · Angular velocity stabilization · Three-axis attitude stabilization·Singularity

Resolution Enhancement in Ultrasonic TOFD Imaging by Combining Sparse Deconvolution and Synthetic Aperture Focusing Technique(Sparse-SAFT)

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Chinese Journal of Mechanical Engineering 2022年第5期35卷 141-149页

作者： xu Sun Li Lin shijie Jin School of Materials Science and Engineering Dalian University of TechnologyDalianChina

The shallow subsurface defects are difficult to be identified and quantified by ultrasonic time-of-flight diffraction(TOFD)due to the low resolution induced by pulse width and beam *** this paper,Sparse-SAFT is proposed to improve the time resolution and lateral resolution in TOFD imaging by combining sparse deconvolution and synthetic aperture focusing technique(SAFT).The mathematical model in the frequency domain is established based on the l1 and l2 norm constraints,and the optimization problem is solved for enhancing time *** this basis,SAFT is employed to improve lateral resolution by delay-and-sum *** simulated and experimental results indicate that the lateral wave and tip-diffracted waves can be decoupled with *** shallow subsurface defects with a height of 3.0 mm at the depth of 3.0 mm were detected quantitatively,and the relative measurement errors of flaw heights and depths were no more than 10.3%.Compared to conventional SAFT,the time resolution and lateral resolution are enhanced by 72.5 and 56%with Sparse-SAFT,***,the proposed method is also suitable for improving resolution to detect the defects beyond dead zone.

关键词： Time resolution Lateral resolution Time-of-flight diffraction(TOFD) Sparse deconvolution Synthetic aperture focusing technique(SAFT) Sparse-SAFT

Path planning of a free-floating space robot based on the degree of controllability

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Science China(Technological Sciences) 2017年第2期60卷 251-263页

作者： HUANG XingHong JIA YingHong xu shijie School of Astronautics Beihang University Beijing 100191 China

An effective and more efficient path planning algorithm is developed for a kinematically non-redundant free-floating space robot(FFSR) system by proposing a concept of degree of controllability(DOC) for underactuated systems. The DOC concept is proposed for making full use of the internal couplings and then achieving a better control effect, followed by a certain definition of controllability measurement which measures the DOC, based on obtaining an explicit and finite equivalent affine system and singular value decomposition. A simple method for nilpotent approximation of the Lie algebra generated by the FFSR system is put forward by direct Taylor expansion when obtaining the equivalent system. Afterwards, a large-controlla- bility-measurement(LCM) nominal path is searched by a weighted A* algorithm, and an optimal self-correcting method is designed to track the nominal path approximately, yielding an efficient underactuated path. The proposed strategy successfully avoids the drawback of inefficiency inherent in previous path-planning schemes, which is due to the neglect of internal couplings, and illustrative numerical examples show its efficacy.

关键词： free-floating space robot(FFSR) underactuated system path planning degree of controllability controllability measurement nilpotent approximation weighted A* algorithm optimal self-correcting method

A CFD simulation of wave loads on a pile-type oscillating-water-column device

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Journal of Hydrodynamics 2019年第1期31卷 41-49页

作者： Zhenhua Huang Conghao xu shijie Huang Department of Ocean and Resources Engineering School of Ocean and Earth Science TechnologyUniversity of Hawaii at ManoaHonoluluUSA

Oscillating-water-column (OWC) devices provide a practical and convenient way to convert wave energy to *** loads on bottom-sitting WECs are important design parameters for their foundation *** study considers an OWC integrated into a bottom-sitting pile structure (an OWC pile).Results from three-dimensional numerical simulations are used to examine the wave loads on an OWC *** appears that viscous loads and lateral loads are relatively *** the inline and vertical wave forces and the resulting overturning moment are not sensitive to the variability in wave period,but increase with wave *** suitable for the wave forces and overturning moment are proposed for estimating wave loads on the OWC pile.

关键词： Numerical simulation wave energy conversion OpenFOAM foundation safety

A Backstepping Simple Adaptive Control Application to Flexible Space Structures

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Chinese Journal of Aeronautics 2012年第3期25卷 446-452页

作者： LIU Min xu shijie HAN Chao School of Astronautics Beihang UniversityBeijing 100191China

Although the simple adaptive control （SAC） is widely studied both in theory and application in flexible space structure control and other control problems, it is restricted by the almost strictly positive real （ASPR） conditions. In most practical control problems, the ASPR conditions are not satisfied. Therefore, based on the SAC theory, this paper proposes a backstepping simple adaptive control algorithm which suits the system with arbitrary relative degree with no need of parallel feed forward compensa- tor. The proposed control algorithm consists of decomposition of the arbitrary relative degree system into a known subsystem and an unknown ASPR subsystem which are connected in cascade, design of constant output feedback controller for the known subsystem, and implementation of backstepping method and SAC of the unknown ASPR subsystem. Inheriting the characteristics of the SAC, this method can be adaptive online for the parameter uncertainties. Then, the application of the proposed controller to large flexible space structure with collocated sensors and actuators is studied, and the simulation results validate the proposed controller. It is a new strategy to apply the classical SAC to high relative degree plants.

关键词： simple adaptive control almost strictly positive real backstepping flexible structure intermediate control law

Local controllability and stabilization of spacecraft attitude by two single-gimbal control moment gyros

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Chinese Journal of Aeronautics 2013年第5期26卷 1218-1226页

作者： Gui Haichao Jin Lei xu shijie School of Astronautics Beihang University

The attitude control problem of a spacecraft underactuated by two single-gimbal control moment gyros （SGCMGs） is investigated. Small-time local controllability （STLC） of the attitude dynamics of the spacecraft-SGCMGs system is analyzed via nonlinear controllability theory. The conditions that guarantee STLC of the spacecraft attitude by two non-coaxial SGCMGs are obtained with the momentum of the SGCMGs as inputs, implying that the spacecraft attitude is STLC when the total angular momentum of the whole system is zero. Moreover, our results indi- cate that under the zero-momentum restriction, full attitude stabilization is possible for a spacecraft using two non-coaxial SGCMGs. For the case of two coaxial SGCMGs, the STLC property of the spacecraft cannot be determined. In this case, an improvement to the previous full attitude stabilizing control law, which requires zero-momentum presumption, is proposed to account for the singu- larity of SGCMGs and enhance the steady state performance. Numerical simulation results demonstrate the effectiveness and advantages of the new control law.

关键词： Attitude control Single-gimbal control moment gyro Singularity Small-time local controllability Underactuated spacecraft