Super twisting controller for on-orbit servicing to non-cooperative target

A relative position and attitude coupled controller is proposed for rendezvous and docking between two docking ports located in different spacecraft. It is concerned with servicing to a tumbling non-cooperative target spacecraft in arbitrary orbit subjected to external disturbances.By considering both kinematic and dynamical coupled effects of relative rotation on relative translation, a coupled dynamic model is established to represent the relative motion of docking port on target spacecraft with respect to another on the service spacecraft. The spacecraft control is based on the second order sliding mode algorithm of super twisting(ST). It is schemed to manipulate the relative position and attitude synchronously. A formal proof of the finite time convergence property of the closed-loop system is derived theoretically by the second method of Lyapunov. Numerical simulations with the designed ST controller are presented to validate the analytic analysis by contrast with the twisting control algorithm. Simulation results demonstrate that the proposed relative position and attitude integrated controller is characterized by high precision, strong robustness and high reliability.     

An improved numerical method for constructing Halo/Lissajous orbits in a full solar system model

An improved numerical method that can construct Halo/Lissajous orbits in the vicinity of collinear libration points in a full solar system model is investigated. A full solar system gravitational model in the geocentric rotating coordinate system with a clear presentation of the angular velocity relative to the inertial coordinate system is proposed. An alternative way to determine patch points in the multiple shooting method is provided based on a dynamical analysis with Poincare′sections. By employing the new patch points and sequential quadratic programming, Halo orbits for L_1, L_2, and L_3 points as well as Lissajous orbits for L_1 and L_2 points in the EarthMoon system are generated with the proposed full solar system gravitational model to verify the effectiveness of the proposed method.     

Overloading of Landing Based on the Deformation of the Lunar Lander

Along with the progress of sciences and technologies, a lot of explorations are taken in many countries or organizations in succession. Lunar, the natural satellite of the earth, become a focus of the space discovery again recently because of its abundant resource and high value in use. Lunar exploration is also one of the most important projects in China. A primary objective of the probe in lunar is to soft-land a manned spacecraft on the lunar surface. The soft-landing system is the key composition of the lunar lander. In the overall design of lunar lander, the analysis of touchdown dynamics during landing stage is an important work. The rigid-flexible coupling dynamics of a system with flexible cantilevers attached to the main lander is analyzed. The equations are derived from the subsystem method. Results show that the deformations of cantilevers have considerable effect on the overloading of the lunar lander system.     

A Backstepping Simple Adaptive Control Application to Flexible Space Structures

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 feedforward compensator. 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.     

具有电磁约束阻尼层梁的振动主动控制研究计算(英文)

This paper investigates vibration control of beam through electro-magnetic constrained layer damping （EMCLD） which consists of electromagnet layer, permanent magnet layer and viscoelastic damping layer. When the coil of the electromagnet is electrified with proper control strategy, the electromagnet can exert magnetic force opposite to the direction of structural deformation so that the structural vibration is attenuated. A mathematical model is developed based on the equivalent current method to calculate the electromagnetic control force produced by EMCLD. The governing equations of the system are obtained using Hamilton＇s Principle and then reduced with the assumed-mode method. A simulation on vibration control of a cantilever beam is conducted under the velocity proportional feedback to demonstrate the energy dissipation capability of EMCLD, and the beam system with the same parameter is experimented. The results of experiment and simulation are compared and the results show that the EMCLD is an effective means for suppressing modal vibration. The results also indicate that the beam system has better control performance for larger control current. The EMCLD method presented in this paper provides an applicable and efficient tool for the vibration control of structures.     

Investigation into Pilot Handling Qualities in Teleoperation Rendezvous and Docking with Time Delay

Teleoperation rendezvous and docking can be used as a backup for autonomous rendezvous and docking(RVD) for an unmanned spacecraft when the autonomous system is failure or for guiding the chaser docking with an uncooperative target.The theoretical model for analyzing the handling qualities in teleoperation RVD process is established based on the previous studies conducted by National Aeronautics and Space Administration(NASA).The predictive factor is introduced to describe the pilot’s predictive ability in the teleoperation tasks with time delay,which interrelates with the skills of a pilot and the predictive assist approach used in the tasks such as the predictive display method.Based on the semi-physical simulation system in our laboratory,900 experiments at two levels of time delay are carried out by 18 volunteers for validating the established model.The experimental results demonstrate the correctness of the theoretical model and indicate that a skilled pilot has a predictive ability of approximately 0.9 in teleoperation RVD tasks.The theoretical analysis shows that the handling qualities are greatly affected by the time delay and the predictive factor,and it is impossible to achieve a teleoperation RVD task for the skilled pilot when the time delay is larger than 9.0 s.     

Two-stage open-loop velocity compensating method applied to multi-mass elastic transmission system

In this paper, a novel vibration-suppression open-loop control method for multi-mass system is proposed, which uses two-stage velocity compensating algorithm and fuzzy I ＋ P control- ler. This compensating method is based on model-based control theory in order to provide a damp- ing effect on the system mechanical part. The mathematical model of multi-mass system is built and reduced to estimate the velocities of masses. The velocity difference between adjacent masses is cal- culated dynamically. A 3-mass system is regarded as the composition of two 2-mass systems in order to realize the two-stage compensating algorithm. Instead of using a typical PI controller in the velocity compensating loop, a fuzzy I ＋ P controller is designed and its input variables are decided according to their impact on the system, which is different from the conventional fuzzy PID controller designing rules. Simulations and experimental results show that the proposed veloc- ity compensating method is effective in suppressing vibration on a 3-mass system and it has a better performance when the designed fuzzy I ＋ P controller is utilized in the control system.     

Safety modeling and simulation of multi-factor coupling heavy-equipment airdrop

Heavy-equipment airdrop is a highly risky procedure that has a complicated system due to the secluded and complex nature of factors＇ coupling. As a result, it is difficult to study the modeling and safety simulation of this system. The dynamic model of the heavy-equipment airdrop is based on the Lagrange analytical mechanics, which has all the degrees of freedom and can accurately pinpoint the real-time coordinates and attitude of the carrier with its cargo. Unfavorable conditions accounted in the factors＇ models, including aircraft malfunctions and adverse environments, are established from a man-machine-environment perspective. Subsequently, a virtual simulation system for the safety research of the multi-factor coupling heavy-equipment airdrop is developed through MATLAB/Simulink, C language and Flightgear software. To verify the veracity of the theory, the verification model is built based on dynamic software ADAMS. Finally, the emulation is put to the test with the input of realistic accident variables to ascertain its feasibility and validity of this method.     

Three-dimensional analysis of relationship between relative orientation and motion modes

Target motion modes have a close relationship with the relative orientation of missile-totarget in three-dimensional highly maneuvering target interception. From the perspective of relationship between the sensor coordinate system and the target body coordinate system, a basic model of sensor is stated and the definition of relative angular velocity between the two coordinate systems is introduced firstly. Then, the three-dimensional analytic expressions of relative angular velocity for different motion modes are derived and simplified by analyzing the influences of target centroid motion, rotation around centroid and relative motion. Finally, the relationships of the relative angular velocity directions and values with motion modes are discussed. Simulation results validate the rationality of the theoretical analysis. It is demonstrated that there are significant differences of the relative orientation in different motion modes which include luxuriant information about motion modes. The conclusions are significant for the research of motion mode identification,maneuver detection, maneuvering target tracking and interception using target signatures.     

挠性多体系统的一般动力学模型

 考虑n个互相连结的空间树形挠性多体系统,不妨按照Ho的直接路思想对系统分层标号,并选取体1为系统的主体,所有直接路均是相对体1而言的。如图1所示,选取O_Ex_By_Ez_B为地心惯性系,而O₀为整个系统的质心,O₀x₀y₀z₀为参考坐标系,系O₁x₁y₁z₁固连在主体1上,而系O_iX_iy_iZ_i（2≤i≤n）的原点在体i与其直接内连体的铰结点处,并固连在体i上,铰链点O_i允许有三自由度平动和三自由度转动,为了方便,也将O₀和O₁点看作两个虚设的铰链点。     

基于拉格朗日力学的伞-弹系统动力学模型

为了回避牛顿力学体系在多体动力学建模过程中存在的复杂约束力求解问题,以拉格朗日力学体系为基础,从分析力学的角度出发,建立了铅垂平面内降落伞-弹系统五自由度动力学模型。详细介绍了拉格朗日力学体系动力学建模过程,推导了铅垂平面内伞-弹系统动能公式,解决了伞-弹系统广义力求解问题,给出了伞-弹所受空气动力的广义力表示。算例将建立的伞-弹系统模型和牛顿力学体系下简化的伞-弹模型进行对比,两种模型计算结果吻合,验证了本文模型的正确性。降落伞-弹系统动力学模型验证了拉格朗日力学在常规飞行器动力学建模中的可行性,为使用ADAMS等基于拉格朗日力学思想建模的商业软件进行伞-弹系统动力学求解提供理论依据,可以用于指导伞-弹系统的分析和设计。     

空间站柔性展开机构仿真方法研究

空间站展开机构是典型的大型多柔体系统,其展开收拢过程涉及非线性大变形以及接触碰撞问题。首先采用绝对节点坐标法作为柔性体的建模方法,建立了梁单元的有限元单元格式,然后基于拉格朗日方法和Hertz接触理论建立了考虑接触碰撞问题的柔性多体系统动力学方程,采用向后差分方法数值求解柔性多体系统的微分代数方程,最后以自由梁、简支梁和柔性单摆进行数学仿真验证。结果表明,该方法可用作我国空间站大型柔性太阳电池翼的设计分析参考。     

空中加油对接过程的动力学建模与仿真

空中加油的成功与否主要依赖于加油锥套与受油插头的顺利对接,对对接过程中产生的动力学行为的研究是实现顺利对接的前提。利用多刚体系统动力学建立对接过程的动力学模型,求解出加油锥套与受油装置间的广义速度;并依据建立的接触动力学模型,得到局部接触点间的相对速度。基于非线性连续碰撞理论,提出对接过程中碰撞力的计算方法,并在机械系统动力学仿真软件ADAMS的环境下,构建加油锥套和受油装置的对接虚拟样机。通过对虚拟样机的动力学仿真,得到了对接过程中的碰撞力及速度响应曲线,同时,得出能够实现成功对接时各参数的具体范围。结果表明,制约对接成功的主要参数是初始相对速度、加油锥套的俯仰角和相对偏距。该研究对空中加油的对接和受油机的导航控制具有重要的意义。     

带单侧裂纹楔梁动力特性研究

由于裂纹存在引起构件局部柔度的变化,本文用线弹性断裂力学理论导出裂纹所释放的应变能,由Ｃａｓｔｉｇｌｉａｎｏ 定理得出局部柔度矩阵诸元素,据此来修正楔形梁的刚度矩阵,借助梁有限单元法,求解带裂纹楔形梁的动力特性,并对裂纹相对深度、裂纹位置、梁的长宽比、宽厚比、厚度斜度等几何因素对固有频率的影响进行了数值研究和相应的振动响应试验     

基于Galerkin法的柔性绳系辅助返回系统的展开动力学建模与分析

以大型空间绳系辅助返回系统为背景,利用微元法和拉格朗日方程建立有分布质量的柔性绳系辅助返回系统的展开动力学模型.针对模型复杂的非线性和强耦合问题,采用Galerkin法进行离散化处理以求解;引入经典的珠子模型,以验证Galerkin法解的准确性;最后通过数学仿真来验证和分析Galerkin法解的正确性和收敛性,并对绳系...     

移动质心再入飞行器建模及自抗扰滚动控制

基于移动质心滚动控制方案,研究了其动力学系统建模和非线性耦合系统控制的问题。不同于移动质心控制系统建模中常用的牛顿力学建模和常规拉格朗日建模法,采用准坐标形式的拉格朗日法建立了完整的系统动力学方程,避免了牛顿力学中复杂的相互作用力分析和常规拉格朗日建模法物理意义不明确的缺点。鉴于移动质心滚动控制系统的非线性、耦合性和时变性,提出把系统的非线性耦合项和外部干扰统归为未知扰动,并采用自抗扰控制(ADRC)技术进行估计和补偿,相对于常用的比例微分(PD)控制,自抗扰控制器能更好地适应系统参数的变化,具有很强的鲁棒性。最后,通过数学仿真验证了整个控制方案的可行性。     

柔性杆系统压电扭转致动器/传感器优化配置研究

 针对空间柔性杆系统的扭转振动问题,提出了一类由柔性杆、电阻应变片传感器、压电扭转致动器组成的柔性杆系统。为了研究此系统的扭转振动,运用拉格朗日方程和假设模态法建立了系统的动力学方程。针对柔性杆系统中压电扭转致动器、传感器的优化配置问题,提出一种基于最小输入能量、最大能量传递、Grammian矩阵最小奇异值最大化的复合优化策略,采用遗传算法对致动器/传感器的位置进行了搜索,找到了最优位置位于柔性杆的根部。进行了数值分析研究,结果表明,与其他位置相比,最优位置最有利于致动器实施控制,同时也最有利于传感器的观测。     

STUDY ON ACTIVE CONTROL FOR A FLEXIBLE BEAM UNDER THE CONDITION OF ZERO GRAVITY

The structure/controlling coupling system is akind of dynamic feedback system in which the me-chanical load and the actuator/controller interact.Because of the influence of inertia,while the com-mon elastic structure is in rigid motion ( or largemotion) ,there inevitably exists a kind of elastic vi-bration ( or small motion) superimposed on thelarge motion.This is the phenomenon of rigid- e-lastic coupling of the motion of an elastic body.Consequently,to study the problem of the motionstabilit…     

基于混合规划策略的自由漂浮冗余机械臂减振运动规划(英文)

对自由漂浮柔性冗余机械臂系统的减振运动规划问题进行研究。首先,采用拉格朗日方法建立系统的动力学模型,并给出了减振运动规划的模型。其次,提出一种基于高斯伪谱法与直接打靶法的混合规划策略,用于求解运动规划问题。先利用高斯伪谱法将运动规划问题转化为一个非线性参数优化问题,并用遗传算法确定近似解,随后利用直接打靶法建立优化模型,将得到的近似解作为优化变量的初值,并采用序列二次规划算法求得精确解。最后,对算例进行分析,验证了基于混合规划策略得到的关节运动轨迹能够明显减小柔性臂杆的全局振动以及残余振动。数值计算的结果表明该方法对减振运动规划问题的求解是有效且稳定的。