大口径空间光学望远镜系统中主镜、次镜和三镜之间具有严格的相对位姿要求，由于加工制造误差、装调误差、重力释放、温度变化和材料性质改变等原因，主镜、次镜和三镜之间的相对位姿会发生变化，从而导致望远镜成像质量的下降。因此，需要主动地调整主镜、次镜和三镜之间的相对位姿，将位姿误差限定在允许范围内。为了满足空间光学望远镜次镜和三镜系统的精密位姿调整需求，本文研究一种具有高精度、大负载-尺寸比、高纵向和横向刚度的调整机构。 为了满足上述要求，本文设计了一种新型6-P-RR-R-RR并联调整平台。与常见的6-UCU和6-UPS并联平台不同，该调整平台采用偏置RR-铰链代替传统的虎克铰链，并将支腿驱动组件安装在具有30°倾斜角的下平台台面上。该设计在保证平台运动行程的前提下，大大降低了整机高度，有利于提升整机横向刚度。同时，该设计降低了整机运动部件的质量，从而减小由于惯性力产生的对平台有害扰动。 与传统虎克铰链相比，偏置RR-铰链的两个旋转轴不相交，存在偏置量，从而有效降低了铰链在转动过程中的的干涉风险，进一步增大了整机工作空间。此外，偏置RR-铰链具有承载能力大，加工装调容易等特点。但由于偏置铰链在六自由度并联平台运动学模型中引入了额外的变量，从而使平台运动学问题变得更加复杂。本文分别采用铰点运动约束方法和串联机构D-H参数方法建立了该并联平台的逆运动学和正运动学数学模型，并采用牛顿-拉普拉森数值迭代方法进行了求解。利用MATLAB和ADAMS联合仿真方法，验证了两种运动学数值求解方法的正确性。 本文通过力学有限元仿真分析方法，研究了该并联调整平台的主要零部件及整机力学特性，并利用PATRAN软件进行模态分析，确定了各主要零部件及整机的基频以及模态振型，为进一步结构优化设计提供依据。 本文还对所设计的并联调整平台开展了试验研究。通过多自由度精密测量臂测量确定了并联平台的零位。采用六个高精度光栅长度计搭建了试验平台，并利用该试验平台验证了逆运动学解，同时还测得了并联平台的运动分辨率和重复运动精度。采用激光跟踪仪对该并联平台在六个方向上的运动行程进行了测量。此外，还对并联平台开展了静刚度和动刚度测试研究。 为了进一步提高平台刚度指标，对平台开展了力传递链分析和力学特性有限元仿真分析，确定了影响平台刚度指标的主要环节。本文对整机构型、 RR-R-RR串联支腿链的布局、支腿和铰链等转动部件、上平台和斜块等关键零件等进行了优化设计，并调整了加工和装调工艺。此外，为了进一步提高精度指标，对铰链和支腿设置了安装基准，并改进了上平台零位标定方法，利用下平台的本体几何特征线作为测量基准，从而精确确定支腿驱动斜块位置，保证平台实物零位与理论零位的一致性。 对改进前后的并联调整平台的重复定位精度、静刚度和动刚度等主要技术指标实测值进行对比，验证改进设计的合理性和有效性。本文所开展的研究工作为高精度高刚度并联调整机构的设计和测试试验方法提供参考，为未来我国大口径空间望远镜系统的研究工作提供技术和经验积累。 关键词：6-P-RR-R-RR运动链；偏置RR-铰链；运动学；刚度；重复性

 In a large aperture space optical telescope system, there are strict relative pose requirements between the primary mirror, the secondary mirror and the third mirror. Due to manufacturing and assembly errors, gravity release, temperature change and material property change, the relative pose between these mirrors will change, which will lead to the decline of imaging quality of the telescope. Therefore, it is necessary to actively adjust the relative pose between the primary mirror, the secondary mirror and the third mirror, so as to limit the pose errors within the allowable range. In order to meet the precision adjusting requirement of the pose the third mirror system of space optical telescope, a mechanism with high precision, large load-size ratio, and high stiffness in both the transverse and the vertical directions is studied in this paper. In order to meet the above requirements, a new type of 6-P-RR-R-RR parallel adjustment platform is designed in this paper. Unlike the common 6-UCU and 6-U〓S parallel platforms, the offset RR-hinges are used to replace the traditional universal hinges, and the leg drive components are installed on a slope of the lower platform, and the inclination angle between the slope and the horizontal plane is 30 degrees. On the premise of guaranteeing the motion strokes of the platform, the design greatly reduces the height of the whole machine and is conducive to improving the lateral stiffness of the whole machine. At the same time, the design reduces the mass of the moving parts of the whole machine, thereby reducing the harmful disturbance to the platform caused by inertial forces. Compared with the traditional universal hinge, the two rotating axes of the offset RR-hinge do not intersect, and there is an offset distance, which effectively reduces the risk of interference of the hinge in its rotating process, and further enlarges the working space of the whole machine. In addition, offset RR-hinge has the characteristics of large load-carrying capacity, easy processing and adjustment. However, due to the introduction of additional variables into the kinematics model of the 6-DOF parallel platform, the kinematics of the platform becomes more complex. In this study, mathematical models of the inverse and forward kinematics of the parallel platform are established by using joint motion constraint method and D-H parameter method of series mechanism respectively, and then they are solved by Newton-Raphson numerical iteration algorithm. The validity of the two kinds of kinematics modeling methods for kinematics is verified by numerical co-simulations method of MATLAB and ADAMS. The dynamic characteristics of the main parts and the whole machine of the parallel adjustment platform are studied through the finite element analysis method. The natural frequencies and modal modes of the main parts and the whole machine are determined by modal analysis in PATRAN software. The research results of simulation provide the basis for the further structural optimization design. This paper also carries out experimental research on the designed prototype of the parallel adjustment platform. The initial position of the parallel platform is determined by the measurement of multi-degree-of-freedom precision measuring arm. A motion performance test system is constructed using six high precision grating length guages, and then inverse kinematics solutions, motion resolutions and repetitive accuracies of the adjusting steps of the platform are tested using the test system. Motion strokes of the parallel platform in six directions are measured using a laser tracker. In addition, the static stiffness and dynamic stiffness of the parallel platform are also studied by testing. In order to further improve the platform stiffness index, the force transfer chain analysis and finite element simulation analysis of mechanical characteristics of the platform are carried out, and the main factors affecting the platform stiffness index are determined. In this paper, the configuration of the whole mechanism, the layout of RR-R-RR series leg chains, the key parts such as the legs and joints, the upper platform and the oblique sliders are optimized, and also the processing and assembly technique are adjusted. In addition, in order to further improve the accuracy of the platform, the installation datum of joints and legs is set up, and the initial position calibration method of upper platform is improved. The geometric characteristic lines of the lower platform are used as the measurement datum, so that the positions of the oblique sliders which are driving the legs can be accurately determined, and the consistency between the actual initial positon and the theoretical initial position can be ensured. By comparing the testing results of the repetitive positioning accuracy, static stiffness and dynamic stiffness of the parallel adjustment platform before and after the improvement, the rationality and validity of the improving design approaches are verified. The research works carried out in this paper provide a reference for the design and testing methods of high precision high stiffness parallel adjustment mechanism, and also provide technological and practical experiences for the future research work of large aperture space telescope system in China. Key words: 6-P-RR-R-RR kinematic chains, Offset RR-joint, Kinematics, Stiffness, Repeatibility