【作者】 杨军宏；

【导师】 李圣怡；

【作者基本信息】 国防科学技术大学 ， 机械工程， 2007， 博士

【摘要】 基于各种不同的目的,国内外许多公司和研究机构都进行了运动模拟平台的研制,其中大多数采用的都是Stewart并联机构,Stewart并联机构的优点是高刚度、高承载能力和结构简单,缺点是各个作动器之间存在严重的耦合,并且垂荡运动范围由于要小于作动器的运动范围而受到制约。本文结合晕船病研究的需要,设计了一种结构新颖的船舶运动模拟平台,该模拟平台由“剪叉式”结构实现大幅度的垂荡运动模拟,由两个并联的“跷跷板”结构实现纵摇和横摇运动模拟。所设计的船舶运动模拟平台采用高性能的位置跟踪阀控非对称缸系统驱动,高性能的位置跟踪阀控非对称缸系统在现代国防工业和民用工业上也有极大的需求,对其进行深入的研究很有必要。围绕所设计的船舶运动模拟平台及其液压伺服驱动系统,开展了下面一系列的研究工作:1.对所研制的船舶运动模拟平台进行了运动学分析,给出了运动学正解方程和反解方程。采用达朗贝尔原理,推导机构的动力学方程。在动力学分析中,提出了直接采用连续坐标旋转变换方法获得纵摇横摇伺服缸的姿态角速度与角加速度的简单方法;提出了把纵摇横摇机构及上层平台上的负载这个整体当作垂荡机构的一个动态负载来考虑,从而简化了垂荡机构的动力学分析过程。最后进行了运动学和动力学仿真,仿真结果表明纵摇横摇机构中两液压缸的耦合程度很小,垂荡机构的运动放大系数约为2。2.推导了阀控非对称缸系统正反向统一的非线性模型,仿真和实验的对比结果表明了模型的准确性;针对目前各种文献关于非对称缸系统负载压力与负载流量定义的混乱,给出了负载压力与负载流量的定义应该遵循的原则,利用所定义的负载压力和负载流量,通过泰勒展开近似方法建立了阀控非对称缸系统的局部线性化模型;通过非线性状态反馈变换,实现了非线性模型的全局线性化,并对全局线性化模型的内部状态变量的零动态稳定性进行了分析;利用所建立的非线性状态空间模型,仿真分析了某些非线性环节对系统性能的影响。3.利用分岔理论,形象描述和分析了各种不确定因素对系统稳定性的影响过程,得出了一些对系统稳定性设计有用的结论,如:同等程度参数的变化对液压缸正向运动时稳定性的影响比对反向运动时稳定性的影响要大;进油管道越长,系统的稳定性越差,当管道长度超过某一值之后系统稳定性进一步变差的程度非常小;进油管道直径越大,系统稳定性越好,当进油管道直径超过某一值之后系统稳定性进一步变好的程度非常小;液压油弹性模量的降低会使系统稳定性变差。最后还给出了有关的参数稳定域。4.详细分析和总结了目前国内外关于定量反馈控制(QFT)的文献中确定不确定性模型的过程,在此基础上,提出了四种获得系统不确定模型的方法,分别指出了这四种方法的优缺点;设计了OFT位置跟踪鲁棒控制器,在发现跟踪曲线相位误差较大的情况下,直接采用零相差跟踪控制器代替前置滤波器,并设计了零相移低通滤波器来抑制零相差跟踪控制器的高频增益;针对阀控非对称缸系统中存在的饱和非线性,利用改进型饱和非线性补偿控制器来进行抑制,在设计过程中利用等效传递函数来简化控制器的结构。然后在所研制的船舶运动模拟平台样机上,对控制器设计过程中的各个环节进行了试验,并与自学习滑模模糊控制进行了对比试验研究。实验结果表明,在相同的负载干扰下,所设计的基于OFT的高精度位置跟踪鲁棒控制器具有更高的控制精度。最后还进行了晕船病运动环境模拟试验,试验结果表明,所研制的船舶运动模拟平台样机能够满足晕船病研究的需要。更多还原

【Abstract】 Based on various purposes, SMS (Ship Motion Simulator) was developed by a lot of domestic and overseas companies and institutions. Traditionally, the Steward parallel mechanism is adopted, because it possesses the advantages of high rigidity, high load-capacity, and structural simplicity. The disadvantages are that there exist strong coupling among different actuators, and the amplitude of heaving is limited by the range of actuator movement. With the requirement of research on seasickness, a novel-structure SMS is designed. This SMS achieves the large motion of heaving simulation through " scissor " mechanism and the large motion of pitching and rolling simulation through "seesaw " mechanism. The position tracking valve controlled asymmetrical hydraulic cylinder system with high precision is applied to the designed SMS and is also required greatly in the modern national defense and civil industry. Hence it is very necessary to study the valve controlled asymmetrical hydraulic cylinder system thoroughly. Based on the SMS and its hydraulic servo driving system, a series of researches are carried out as follows:1. The kinematics is analyzed for the SMS, and forward kinematics and inverse kinematics are discussed. The dynamic equation is set up through the D’Alembert’s principle. In the process of dynamics analysis, the method to directly adopt sequential coordinates rotation transformation is presented to obtain the attitude angular velocity and angular acceleration of the pitching and rolling servo cylinders, and the idea that the pitching and rolling mechanism and the load on upper platform is wholely regarded as a dynamic load on the heaving mechanism is presented to simplify the dynamics analysis for the heaving mechanism. Finally, the kinematics and dynamics are simulated. Results of simulation give the load range of cylinders and show that weak coupling exists between both the cylinders of the pitching and rolling mechanism and the motion magnification is about 2.2. One nonlinear model suitable for forward and inverse motion is deduced for the valve controlled asymmetrical cylinder system, and the model is proved correct by comparing simulation with experiment. Aiming to clarify the confusion of definitions of load pressure and load flow in nowadays correlative literatures, the principle for defining load pressure and load flow is given to establish the local linearized model by Taylor expansion approximation. The global linearized model is established by nonlinear state feedback transformation, and the stability is analyzed for its zero dynamic state. The effect on the system’s performance caused by some nonlinearities is simulated through the established nonlinear state-space model.3. Using bifurcation theory, process of effect on the system’s stability caused by various uncertain factors is described and analyzed, and some conclusions are drawn as follows. Under the same extent of change of parameters, the effect on stability is greater when cylinder moves forward than that when cylingder moves backward.The longer oil inlet pipe, the worse the stability, and the degree that the stability becomes worse is very small when the length of pipe exceeds a certain value. The bigger the diameter of oil inlet pipe, the better the stability, and the degree that the stability becomes better is very small when the diameter of pipe exceeds a certain value. The stability also becomes bad when the fluid bulk modulus reduces. Finally some parameters’ stability field is given.4. The process of determining uncertainty model in domestic and overseas literatures on quantitative feedback theory (QFT) is analyzed and summarized in detail. On the above basis, four ways are presented to derive the system’s uncertainty model, and at the same time, the advantages and disadvantages of the four ways are concluded. The QFT position tracking robust controller is designed. After finding notable tracking phase error, the zero phase error tracking controller is designed to replace the feedforward filter, and a zero phase-shift low-pass filter is designed to reduce the high frequency gain of the zero phase error tracking controller. An improved saturation compensator is designed to bate the saturation nonlinearity in the valve controlled asymmetrical cylinder system. In designing all the controllers, the equivalent transfer function is applied to simplify the controller structure. A lot of experiments are done for every part of the controller during the designing process by means of the developed SMS prototype. The comparative experiment is done between high precision position tracking robust controller and self-learning fuzzy sliding mode controller, and the result shows that the precision of the former is higher with the same load disturbance. Finally, the experiment is done for simulating motion causing seasick, and it indicates that the SMS prototype can meet the motion requirements for researching seasick.更多还原