【作者】 张建政；

【导师】 高峰；

【作者基本信息】 上海交通大学 ， 机械设计及理论， 2012， 博士

【摘要】 具有空间六维运动的大型重载动态模拟器的典型应用是作为地震模拟振动台,而地震模拟振动台系统是振动工程研究工作中的重要实验设备之一,它能够根据需要,以记录的天然地震波或人工设计的地震波为输入,进行地震再现,以发现结构模型在地震下的断裂机理和倒塌过程,以便制定抗震标准、找到抗震方法,减少地震灾害带来的损失。以往的地震模拟器多采用液压的冗余支链驱动,以提高系统的驱动能力和承载力,这种驱动方式也带来了设备庞大、使用环境受限、造价高、低频特性不好以及控制难度大等问题。本文在分析当前地震模拟振动台技术上存在不足的基础上,提出了一种基于多电机驱动的无冗余支链而具有机械协调的冗余容错六维地震模拟器,对冗余容错驱动、适合地震模拟的机构构型方法、数学模型建立及简化、控制方法以及实验等几个关键问题进行了研究。具体内容如下:(1)针对液压驱动导致设备体积庞大、造价高昂、低频特性不好以及冗余支链驱动易产生过约束等不足,提出一种适合重载装备的以电机为驱动源的冗余容错模块,建立该模块的运动学模型,得到全工况下12种工作状态,研究其传动特性并得到三个设计准则,分析其可靠性,并进行实验验证其性能,发现该驱动模块具有理想的冗余容错特性,适合作为重载震动模拟器的驱动。(2)在总结地震运动工程特点的基础上,设计符合模拟地震运动的地震模拟振动台并联机构基本构型,其特点为:①具有空间六维运动以便模拟真实的地震运动,②无过约束的简单机构以便准确反映地震运动的三要素,③具有强的承载力和驱动能力以便体现地震的破坏力。把冗余容错驱动模块应用于此基本构型,设计多种不同类型的多电机驱动地震模拟器,以适应地震模拟装备巨型化发展的趋势。(3)对地震模拟器机构拓扑参数与运动学性能关系进行研究。从机构的拓扑参数与运动学关系、拓扑参数如何影响机构的解耦和各项同性、解耦控制时拓扑参数如何影响输出位置误差等三个方面揭示如何设置机构拓扑参数才能得到理想的运动特性,并论证了解耦控制的可行性。(4)对地震模拟器的机构结构参数和力学特性之间的关系进行研究。通过建立地震模拟器整体和各方向刚度模型,分析地震模拟模拟器机构和结构参数对刚度的影响。采用Newton-Euler方法对地震模拟器各部分进行了受力分析,建立动力学模型的开式方程,得到广义输出力解耦的机构结构参数所满足的条件。对地震模拟器进行了动力学仿真,发现该机构在低频下具有良好的动态特性。(5)针对并联机构的动力学模型具有多变量强耦合的非线性和不易实时控制的特点,在对动力学模型闭式形式进行计算复杂性分析的基础上,提出了根据机构正交特点进行动力学模型解耦简化的方法,并用简化的动力学模型和计算力矩法进行地震模拟器的控制仿真,仿真结果显示基于简化动力学模型的计算力矩控制不但精度能够满足要求而且计算效率得到提高,使基于动力学的控制成为可能。(6)开发了用于实验的地震模拟器平台,建立了符合此地震模拟器冗余容错多轴驱动的控制系统,结合使用特点开发了其软件系统。应用六维激光跟踪仪进行位置测试,加速度传感器进行加速度检测。在三个平移方向上模拟了El Centro地震波,在三个转动方向上模拟了固定频率的谐波运动,实验结果显示此地震模拟系统能够模拟真实地震波的空间六维运动并满足一定的精度要求,适合作为地震模拟装置。更多还原

【Abstract】 One of typical applications of a large and heavy-duty dynamic simulator with special 6-dimension movement is using as earthquake simulator equipment. Earthquake simulator system is one of the key equipments in the research field of vibration engineering. By means of inputting the data from the record of a natural earthquake or artificial seismic waves, an earthquake simulator can reproduce the earthquake motion under which failure mechanisms and collapse processes of various kinds of structures can be studied. This is help to establish the resistance standards, find the methods of earthquake resistance and reduce the cost of earthquake seismic hazards. Most of the traditional earthquake simulators are driven by hydraulically-actuated system and have redundant chains to enhance the driving force and bearing capacity. This drive mode brings about some shortcoming, such as huge system, limited application environment, high cost, undesirable characteristic of low frequency and difficult to control, and so on. Based on the analysis of disadvantages of the current earthquake simulators, this paper presents a novel motor-driven earthquake simulator which has not any redundant chains but has the characteristic of redundant-driven and fault-tolerant ability. Meanwhile, this paper focuses on several key problems, such as the actuator with redundant and fault-tolerant function, the method of designing a novel mechanism for simulating earthquake motions, building the mathematic models and its simplified strategy for real-time control, analysis of the performance index, developing the control and measure system and performing the experiments. The main contributions are as following.1. In consideration of the disadvantages of large hydraulic drive and redundant kinematic chains, a novel redundant and fault-tolerant actuator (RFTA) driven by motors is presented. This actuator is appropriate for heavy-payload equipments, including earthquake simulator. The kinematics of RFTA is built and its 12 working models are given. The translation mechanism characteristics are studied and three design guidelines are obtained. The reliability of this RFTA is also analyzed. Experiments for verifying are done and the results show the RFTA has the desirable functions of double supply and fault-tolerant.2. Based on summarizing the engineering characteristics of general seismic motion, the basic parallel mechanis as earthquake simulator is designed. This parallel mechanis has the following features: ability of 6-dimention motion in space for simulating a real earthquake motion, simple mechanism without over-constraint for responding to three essential earthquake elements, stong driving power and bearing capacity for getting the collapsing force of earthquakes. Applying the RFTA to the basic parallel mechanism, many different earthquake simulator with multi-motor are designed, which adapt to the development tendency of large earthquake simulator system.3. The relationship between the mechanical topology parameters of an earthquake simulator and its kenimatic characteristics is researched. The research consists of three parts, that is the relationship of mechanical topology parameters and inverse kinimatics, how the mechanical topology parameters affecting characteristics of the decoupling and the isotropy, and the position-errors in different mechanical topology parameters under decoupled control. The feasibility of decoupled control is discussed4. The relationship between the mechanical and structural parameters of an earthquake simulator and its dynamic characteristics is researched. The stiffness model of the whole earthquake simulator is built. The relationship between the mechanical and structural parameters of an earthquake simulator and its stiffness is discussed. The force analysis of every parts of an earthquake simulator is studied by using Newton-Euler method. The dynamics model is derived and the mechanical and structural parameters of meeting the requirement of general decoupled output forces are obtained. The dynamic simulations based on the dynamic model are performed and the results show the mechanism has the desirable dynamic characteristic under low-frequency motion.5. In view of nonlinearity, multi-variate coupling, difficulty of real-time control, this paper analyses the complexity of computing the closed dynamic model and presents a decoupled method to simplify dynamic model according to the orthogonal fearture of the parallel mechanism. Based on the simplified dynamic model, the control of computed torque method is simulated in the earthquake simulator. The result shows the control of computed torque method based on the simplified dynamic model not only meets the requirement of computing precision but also improves the computing efficency, which makes controlling a parallel mechanism based on its dynamics possible.6. An earthquake simulator system for experiments is developed. The multi-axis control system with redundant and fault-tolerant function is built for simulating seismic waves. The software system is written according to the working fearture of the equipment. The 3-D laser tracker is used to measure the position of the moving platform and the acceleration of every direction is tested by single-direction accelerometer. A typical earthquake wave, named El-Centro, is simulated on three translation-directions of the earthquake simulator. The harmonic motions with fixed-frequency are performed on its three rotation-directions. The results of experiments display the earthquake simulator is able to simulate 6-dimention motions of a natural earthquake and satisfies precision, which shows the earthquake simulator is appropriate for using as earthquake simulator.更多还原