本文主要研究柔性支撑Stewart平台的振动控制问题和柔性展开机构的动力学与控制问题。前者源于五百米口径大型射电望远镜（FAST）项目。该项目方案中，Stewart平台用作高精度馈源定位、定向与振动控制。由于采用索支撑，其控制问题归结为柔性约束条件下多体系统在随机干扰下实现末端高精度三维定位、定向的动力学与控制问题。后者源于轻型大面积太阳帆板与展开机构振颤自主控制项目。柔性展开机构的展开、锁定和机动过程涉及弹性、振动、碰撞、间隙和摩擦等因素，是该项目研究的重要内容之一，也是柔性多体系统动力学研究的重要问题。本文针对上述两类问题，在动力学与控制的数值仿真和实验两方面进行了研究，主要内容包括：1. 利用面向对象方法编制了通用的多体系统的动力学分析与控制类库。可以根据需要按照笛卡儿坐标方法或相对坐标方法建立系统模型。该软件从控制的角度，通过传感器和驱动器环节统一处理约束与相互作用力，便于扩充到机电控制系统。2. 利用多体系统动力学方法对柔性支撑Stewart平台的动力学特性进行了分析，对控制效果进行了数值仿真。将多体系统动力学仿真与特征系统实现算法（ERA）相结合，对柔性支撑Stewart平台的闭环控制特性进行了分析，提出了缩比模型的实验方案。3. 按照上述实验方案进行了柔性支撑Stewart平台缩比模型的实验研究。实验结果与数值仿真结果能够很好地吻合，为进一步的理论分析与实验研究奠定了基础。4. 建立了含摩擦、间隙和碰撞的锁定铰模型。将有限段法与有限元法结合，对含浮动中心刚体和多根铰接柔性梁的展开机构的展开过程及锁定后的动力学特性进行了数值仿真。5. 对含浮动中心刚体和多根铰接梁的展开机构进行了地面模拟的实验研究。用非接触式CCD位移实时测量系统实现了对展开机构的三维低频、大位移、大振幅的展开与振动测试。
Abstract（英文摘要）This dissertation studies the dynamics and control of Stewart platform for vibration control of a flexible supporting structure and the large flexible space deployment system. The main work of this dissertation is summarized as follows:1. Develop an object-oriented software tool for the simulation and control of multi-body system. This software tool focuses on the development of capalibities required for the closed loop system and the system with flexible bodies. The connection between bodies, including controller and constraint, is realized with an actuator and a sensor. This makes it easy to extend the software to the control design and mechatronics. 2. Models the flexible suspending Stewart parallel mechanism as a multi-body system with an elastically restrained base platform and proposes a PD control law based on the position prediction of the two platforms. Combined the simulation of multi-body systems with ERA (Eigensystem Realization Algorithm) for analysis the characteristic behavior of a complex system near its balance points. The method is used in analysis the characteristic behavior of the suspending Stewart platform and predict controllable configuration of suspension cables. 3. A small scale prototype has also been developed. For the purpose of the experiment, a double Stewart platform has been designed. The upper part is the measurement platform consisting of a fixed platform, six linear encoders and the base platform. The lower part is the vibration isolation system consisting of base platform, six legs with actuator and stabilized platform. The correlation between the simulation and the experiment shows that the mathematical model developed in this paper can give reasonable results for the system.4. A hybrid finite segment/finite element approach is proposed for modeling the large motion flexible beam in a deployment system. The method uses the finite segments to describe the inertia of the large motion beam and enables a small deformation theory for describing the elasticity of the beam in the relative coordinate systems. Together with the contact force model of the impact, this method is used to analyze the deployment of a system with internal impact in the joints. 5. The experimental set-ups that have a floating central rigid body and several articulated flexible beams and undergo locking impact have been developed. A position measuring system of linear CCD cameras is used to measure the large displacement of the systems. The correlation between the simulation and the experiment shows that the mathematical model developed in this paper can give reasonable results for the studied deployment system.
