【作者】 赵志刚；

【导师】 孙毅； 赵阳；

【作者基本信息】 哈尔滨工业大学 ， 固体力学， 2013， 博士

【摘要】 空间站是人类历史上规模最大的航天器，代表着当今航天领域最全面、最复杂、最先进和最综合的科技水平，在空间生命科学、载人深空探索及新材料加工等诸多科技前沿领域发挥着重要的、其它航天器不可替代的作用。多模块空间站在轨组建过程中，需要利用空间机械臂完成舱体从轴向对接口至径向对接口的转位过程。然而柔性机械臂在执行转位任务过程中，容易激起柔性结构振动，这将影响转位对接的定位精度，严重时甚至给空间站的安全运行带来危险。因此，伴随转位过程应运而生的动力学与控制问题便成为了空间站在轨组建过程中需要解决的关键问题之一。本文重点考虑空间站机械臂转位操作这一关键环节，深入研究其相关动力学与控制问题，包括空间站转位系统的建模、机械臂柔性关节控制及振动抑制等。论文的主要研究内容和学术贡献如下：空间站在舱体转位过程中系统的姿态、偏心量将发生变化，其动力学特性极其复杂。为分析空间站在应用机械臂转位过程中的动力学特性，采用矢量力学方法推导了考虑偏心量的空间站转位系统动力学模型。使用有限元方法描述柔性臂的弹性变形，应用Newton-Euler法建立空间站机械臂转位系统转动方程，采用Lagrange法建立柔性臂振动方程；应用约束模态展开法对动力学方程进行降阶，并系统地分析了柔性机械臂的振动模态。针对机械臂这类柔性机构的主动振动控制问题，提出了负分力合成振动抑制(Negative Component Synthesis Vibration Suppression，NCSVS)方法。该方法设计的合成力同时包含正负分力，与传统分力合成(CSVS)方法相比能更迅速地抑制柔性振动。在此基础上，提出了负分力合成理论的若干定理和推论，对定理进行了严格的数学证明；并推广了分力合成方法抑制多阶模态的原则和实现鲁棒性定理，进一步发展和完善了分力合成理论。考虑到分力合成与输入成形主动振动控制方法的区别与联系，提出了改进型负输入成形(Modified Negative Input Shaping，MNIS)振动抑制方法。该方法设计成形器的脉冲序列包含多个正负依次交替的脉冲，通过所选择的脉冲数目和系统振动频率与阻尼比构成封闭形式解来直接确定脉冲作用时间和幅值。根据该方法分别针对无阻尼系统和有阻尼系统提出了改进型单位幅值输入成形器和改进型负输入成形器；所设计的改进型负成形器与相应的正成形器相比有更短的时滞时间，可以有效改善系统的上升时间，提高系统响应速度。与相应的负成形器相比，其最主要的优点是：无需对约束条件进行优化，也无需复杂计算，使得成形器的设计非常简单。在此基础上，为进一步提高控制系统的性能，提出了改进型负输入成形和最优控制相结合的振动抑制方法，并采用柔性机械臂模型验证了所提出方法的有效性。研究了空间机械臂柔性关节的高精度轨迹跟踪问题。针对建立的带扰动项和摩擦等非线性因素的柔性关节二阶级联动力学方程，通过设计虚拟控制量对该串级系统引入两个自抗扰控制器进行双闭环控制。控制器通过扩张状态观测器(ESO)实时估计扰动和摩擦等非线性因素并在控制过程中对“总扰动”加以补偿。采用该技术设计的控制器既能满足系统对快速性和稳态精度的要求，同时又有效抑制了电机不确定扰动和摩擦因素对系统的影响。控制器算法简单，适于数字化实现。仿真结果表明所设计的双闭环控制系统具有控制精度高、鲁棒性强等良好的控制品质，具有一定的工程应用价值。针对空间站机械臂转位系统的闭环控制问题进行了系统性研究。通过构造降维矩阵对转位系统模型进行了简化处理，分析了其复杂的动力学特性，得出结论：空间站转位过程中构型的改变会导致转动惯量和偏心量的较大变化，偏心量变化范围甚至已超出了空间站核心舱的几何范围。进一步提出了基于分力合成/负分力合成/改进型负输入成形(CSVS/NCSVS/MNIS)方法和反馈解耦控制相结合的闭环控制策略来解决转位控制和柔性机械臂的振动抑制问题。利用动力学系统具有转动惯量大的特点，设计了反馈解耦控制策略。该策略有效地解决了由于动力学模型的强耦合、非线性和时变性带来的闭环系统的振动频率和阻尼比具有时变性导致的难以直接设计CSVS/NCSVS/MNIS控制输入指令的问题。将CSVS/NCSVS/MNIS方法作为前馈控制和PD反馈解耦控制相结合，构成前馈+反馈的控制方案，提高了控制系统的性能指标。所设计的控制策略在提高空间站机械臂转位在轨操作的工作效率及稳定性等方面具有一定的价值。更多还原

【Abstract】 The space station is the biggest scale spacecraft in human history, which hasbeen representing the most comprehensive, complicated, advanced and integratedlevel of astronautical technology. It plays an irreplaceable role in many technologyareas such as space life science, manned deep space explore, processing of the newmaterials and so on. In the modular structure of space station assembly process, itis highly dependent upon the space manipulator to transfer function module fromthe axial lord docking port of node module to radial berthing port of node module.However, it is known that the structure flexibility of a manipulator may inducevibration during this process. It may influence docking positioning accuracy andeven endanger safe running of space station. The dynamics and control is a criticalproblem during the process of space station assembly. This dissertation focuses onthe dynamics and control problems of space station assembly concerning dynamicmodeling, attitude control, vibration control of flexible manipulator and control offlexible joint. The main themes and contributions of the dissertation include:During the process of space station assembly, the attitude of space station andthe total instantaneous center of mass may change with time. The dynamics of thesystem is quite complex. To study the dynamics characteristics for transformationof the space station via manipulator system, a vector mechanics method wasadopted to deduce the dynamic equations. The dynamic modeling withconsideration of the eccentricity was established. The elastic deformation of theflexible manipulator is depicted by using the finite element (FE) method. Thedynamic model representing the attitude motion is established with Newton-Eulermethod. And the vibrations of the flexible manipulator can be obtained by usingthe Lagrange approach. The constrained mode expansion method is used to reducethe dimensions of dynamic equations. Vibration mode of the flexible manipulatoris analyzed systematically by using the dimension reduction model.A novel vibration control theorem named negative component synthesisvibration suppression (NCSVS) is presented for active vibration control of theflexible systems such as flexible manipulator. The NCSVS, as the name denotes,contains negative amplitude components and can eliminate unwanted flexiblemodes of vibration more quickly than CSVS. Several negative componentsynthesis vibration suppression theorems are proposed and proved exactiy. Thenew principle for suppression of multiple orders modes vibrations simultaneouslyand new robustness theorem is presented respectively by expanding on traditionalCSVS method. The CSVS theory is enriched and developed extensively in this work.The differences and relations between input shaping and component synthesisvibration suppression are considered, and then a new modified negative inputshaping (MNIS) method is presented for active vibration control of flexiblestructure. The present approach allows designing modified negative input shaperby using some negative impulses and positive impulses alternately in the sequenceof impulses. The modified negative input shaper is described by closed-formfunction of the numbers of selecting impulses, the system’s natural frequency anddamping ratio. The modified UM input shaper and modified negative input shapersare proposed for undamped systems and damped systems respectively. The risetime can be improved by comparing positive input shaper. In coparison withnegative input shaper, there is a significant advantage, i.e. in the MNIS method nonumerical optimization subject to time constraints is required and the number ofselecting impulses is free. Furthermore, to improve the performance of controlsystem, a new vibration reduction control strategy is presented, which integratesmodified negative input shaping (MNIS) technique with optimal control for activevibration control of the flexible manipulator systems. Simulation results indicatethe effectiveness of the proposed method.The high-precision trajectory tracking control for space manipulator flexiblejoint is researched. The second-order cascade dynamics equations withuncertainties disturbance and friction of flexible joint are established. A controlstrategy of active disturbance rejection control (ADRC) and double closed-loopcontrol are presented by using pseudo control variables based on cascade systems.Both the inner and outer loops are designed by active disturbance rejectioncontroller. In this method the disturbances are estimated using an extended stateobserver (ESO) and compensated during each sampling period. The designedcontroller not only satisfies the quick response speed and steady-state accuracydemands, but also effectively resists to the uncertainties disturbance and friction.Control algorithm is simple and it is easy to digital implement. The simulationresults indicate that the designed of the double closed-loop control system hashigh-precision and stronger robustness and has important engineering significance.A closed-loop control for the module transformation process of the spacestation is studied. The model reduction matrix from space to plane of the spacestation transformation via manipulator is proposed. The dynamics characteristicsof the system are analyzed, and the simulation result demonstrates that the overallmoment of inertia relative to the mass center change hugely in the transformationprocess of the space station. The scope of the eccentricity is beyond the scope ofthe geometry of the core module. A closed-loop control strategy based on theCSVS/NCSVS/MNIS method and feedback decoupling control is presented in order to reduce vibration. It is difficult to determine the frequency and dampingratio of the closed-loop control system due to the dynamics model for manipulatortransformation system of the space station with strong-decoupling, nonlinearityand time variation. The designed CSVS/NCSVS/MNIS control command isachieved which utilizes the frequency and damping ratio of the whole closed loopsystem by feedback decoupling control. As mentioned above, both analytical andnumerical results verified the effectiveness for vibration suppression during thetranslocation process of the control strategy. It shows great value in both theoryand practical applications due to the improved efficiency and stability for spacemanipulator working on orbit.更多还原