机械专业外文翻译－“挖掘机的机械学和液压学”

机械专业外文翻译－“挖掘机的机械学和液压学” 毕业设计（ 论文 政研论文下载论文大学下载论文大学下载关于长拳的论文浙大论文封面下载 ） 报告 软件系统测试报告下载sgs报告如何下载关于路面塌陷情况报告535n,sgs报告怎么下载竣工报告下载 纸 Multi-Domain Simulation: Mechanics and Hydraulics of an Excavator Abstract It is demonstrated how to model and simulate an excavator with Modelica and Dymola by using ? Modelica libraries for multi-body and for hydraulic systems. The hydraulic system is controlled by a ? “load sensing” controller. Usually, models containing 3-dimensional mechanical and hydraulic components are difficult to simulate. At hand of the excavator it is shown that Modelica is well suited for ? such kinds of system simulations. ? ? 1. Introduction ? The design of a new product requires a number of decisions in the initial phase that severely affect ? the success of the finished machine. Today, digital simulation is therefore used in early stages to look at ? different concepts. The view of this paper is that a new excavator is to be designed and several candidates ? of hydraulic control systems have to be evaluated. ? Systems that consist of 3-dimensional mechanical and of hydraulic components – like excavators – ? are difficult to simulate. Usually, two different simulation environments have to be coupled. This is often ? inconvenient, leads to unnecessary numerical problems and has fragile interfaces. In this article it is ? demonstrated at hand of the model of an excavator that Modelica is well suited for these types of systems. The 3-dimensional components of the excavator are modeled with the new, free Modelica 装 MultiBody library. This allows especially to use an analytic solution of the kinematic loop at the bucket ? and to take the masses of the hydraulic cylinders, i.e., the “force elements”, directly into account. The ? hydraulic part is modeled in a detailed way, utilizing pump, valves and cylinders from HyLib, a ? hydraulics library for Modelica. For the control part a generic “load sensing” control system is used, ? modeled by a set of simple equations. This approach gives the required results and keeps the time needed ? for analyzing the problem on a reasonable level. 订 ? 2. Modeling Choices ? There are several approaches when simulating a system. Depending on the task it may be ? necessary to build a very precise model, containing every detail of the system and needing a lot of ? information, e.g., model parameters. This kind of models is expensive to build up but on the other hand ? very useful if parameters of a well defined system have to be modified. A typical example is the 线 optimization of parameters of a counterbalance valve in an excavator (Kraft 1996). ? The other kind of model is needed for a first study of a system. In this case some properties of the ? pump, cylinders and loads are specified. Required is information about the performance of that system, ? e.g., the speed of the pistons or the necessary input power at the pump shaft, to make a decision whether ? this design can be used in principle for the task at hand. This model has therefore to be “cheap”, i.e., it must be possible to build it in a short time without detailed knowledge of particular components. ? The authors intended to build up a model of the second type, run it and have first results with a ? minimum amount of time spent. To achieve this goal the modeling language Modelica (Modelica 2002), ? the Modelica simulation environment Dymola (Dymola 2003), the new Modelica library for ? 3-dimensional mechanical systems “MultiBody” (Otter et al. 2003) and the Modelica library of hydraulic ? components HyLib (Beater 2000) was used. The model consists of the 3-dimensional mechanical ? construction of the excavator, a detailed description of the power hydraulics and a generic “load sensing” ? controller. This model will be available as a demo in the next version of HyLib. ? ? 3. Construction of Excavators In Figure 1 a schematic drawing of a typical excavator under consideration is shown. It consists of a chain track and the hydraulic propel drive which is used to manoeuvre the machine but usually not during a work cycle. On top of that is a carriage where the operator is sitting. It can rotate around a vertical axis with respect to the chain track. It also holds the Diesel engine, the hydraulic pumps and control system. Furthermore, there is a boom, an arm and at the end a bucket which is attached via a planar kinematic loop to the arm. Boom, arm and bucket can be rotated by the appropriate cylinders. 共 页 第 1 页 毕业设计（论文）报告纸 Figure 2 shows that the required pressures in the cylinders depend on the position. For the “stretched” situation the pressure in the boom cylinder is 60 % higher than in the retracted position. Not only the position but also the movements have to be taken into account. Figure 3 shows a situation where the arm hangs down. If the carriage does not rotate there is a pulling force required in the cylinder. When rotating – excavators can typically rotate with up to 12 revolutions per minute – the force in the arm ? cylinder changes its sign and now a pushing force is needed. This change is very significant because now ? the “active” chamber of the cylinder switches and that must be taken into account by the control system. ? Both figures demonstrate that a simulation model must take into account the couplings between the four ? degrees of freedom this excavator has. A simpler model that uses a constant load for each cylinder and the swivel drive leads to erroneous results ? ? ? 4. Load Sensing System ? Excavators have typically one Diesel engine, two hydraulic motors and three cylinders. There ? exist different hydraulic circuits to provide the consumers with the required hydraulic energy. A typical ? design is a Load Sensing circuit that is energy efficient and user friendly. The idea is to have a flow rate control system for the pump such that it delivers exactly the needed flow rate. As a sensor the pressure ? drop across an orifice is used. The reference value is the resistance of the orifice. A schematic drawing is ? shown in figure 4, a good introduction to that topic is given in (anon. 1992). ? The pump control valve maintains a pressure at the pump port that is typically 15 bar higher than 装 the pressure in the LS line (= Load Sensing line). If the directional valve is closed the pump has therefore ? a stand-by pressure of 15 bar. If it is open the pump delivers a flow rate that leads to a pressure drop of 15 ? bar across that directional valve. Note: The directional valve is not used to throttle the pump flow but as a ? flow meter (pressure drop that is fed back) and as a reference (resistance). The circuit is energy efficient ? because the pump delivers only the needed flow rate, the throttling losses are small compared to other ? circuits. 订 If more than one cylinder is used the circuit becomes more complicated, see figure 5. E.g. if the boom requires a pressure of 100 bar and the bucket a pressure of 300 bar the pump pressure must be ? above 300 bar which would cause an unwanted movement of the boom cylinder. Therefore compensators ? are used that throttle the oil flow and thus achieve a pressure drop of 15 bar across the particular ? directional valve. These compensators can be installed upstream or downstream of the directional valves. ? An additional valve reduces the nominal pressure differential if the maximum pump flow rate or the ? maximum pressure is reached (see e.g. Nikolaus 1994)线 . ? ? 5. Model of Mechanical Part ? In Figure 6, a Modelica schematic of the mechanical part is shown. The chain track is not modeled, ? i.e., it is assumed that the chain track does not move. Components “rev1”, ..., “rev4” are the 4 revolute joints to move the parts relative to each other. The icons with the long black line are “virtual” rods that ? are used to mark specific points on a part, especially the mounting points of the hydraulic cylinders. The ? light blue spheres (b2, b3, b4, b5) are bodies that have mass and an inertia tensor and are used to model ? the corresponding properties of the excavator parts. ? The three components “cyl1f”, “cyl2f”, and “cyl3f” are line force components that describe a ? force interaction along a line between two attachment points. The small green squares at these ? components represent 1-dimensional translational connectors from theModelica.Mechanics. Translational ? library. They are used to define the 1- dimensional force law acting between the two attachment points. ? Here, the hydraulic cylinders described in the next section are directly attached. The small two spheres in ? the icons of the “cyl1f, cyl2f, cyl3f” components indicate that optionally two point masses are taken into account that are attached at defined distances from the attachment points along the connecting line. This allows to easily model the essential mass properties (mass and center of mass) of the hydraulic cylinders with only a very small computational overhead. The jointRRR component (see right part of Figure 6) is an assembly element consisting of 3 revolute joints that form together a planar loop when connected to the arm. A picture of this part of an excavator, a zoom in the corresponding Modelica schematic and the animation view is shown in Figure 7. 共 页 第 2 页 毕业设计（论文）报告纸 When moving revolute joint “rev4” (= the large red cylinder in the lower part of Figure 7; the small red cylinders characterize the 3 revolute joints of the jointRRR assembly component) the position and orientation of the attachment points of the “left” and “right” revolute joints of the jointRRR component are known. There is a non-linear algebraic loop in the jointRRR component to compute the angles of its three revolute joints given the movement of these attachment points. This non-linear system of equations ? is solved analytically in the jointRRR object, i.e., in a robust and efficient way. For details see In a first ? step, the mechanical part of the excavator is simulated without the hydraulic system to test this part ? separatly. This is performed by attaching translational springs with appropriate spring constants instead of ? the hydraulic cylinders. After the animation looks fine and the forces and torques in the joints have the expected size, the springs are replaced by the hydraulic system described in the next sections. ? All components of the new MultiBody library have “built-in” animation definitions, i.e., ? animation properties are mostly deduced by default from the given definition of the multi-body system. ? For example, a rod connecting two revolute joints is by default visualized as cylinder where the diameter ? d is a fraction of the cylinder length L (d = L/40) which is in turn given by the distance of the two revolute ? joints. A revolute joint is by default visualized by a red cylinder directed along the axis of rotation of the ? joint. The default animation (with only a few minor adaptations) of the excavator is shown if Figure 8. ? The light blue spheres characterize the center of mass of bodies. The line force elements that visualize the ? hydraulic cylinders are defined by two cylinders (yellow and grey color) that are moving in each other. As ? can be seen, the default animation is useful to get, without extra work from the user side, a rough picture 装 of the model that allows to check the most important properties visually, e.g., whether the center of masses or attachment points are at the expected places. ? For every component the default animation can be switched off via a Boolean flag. Removing ? appropriate default animations, such as the “centerof- mass spheres”, and adding some components that ? have pure visual information (all visXXX components in the schematic of Figure 6) gives quickly a nicer ? animation, as is demonstrated in Figure 9. Also CAD data could be utilized for the animation, but this ? was not available for the examination of this excavator. 订 ? ? 6. The Hydraulics Library HyLib ? The (commercial) Modelica library HyLib (Beater 2000, HyLib 2003) is used to model the pump, ? metering orifice, load compensator and cylinder of the hydraulic circuit. All these components are ? standard components for hydraulic circuits and can be obtained from many manufacturers. Models of all 线 of them are contained in HyLib. These mathematical models include both standard textbook models (e. g. ? Dransfield 1981, Merrit 1967, Viersma 1980) and the most advanced published models that take the ? behavior of real components into account (Schulz 1979, Will 1968). An example is the general pump ? model where the output flow is reduced if pressure at the inlet port falls below atmospheric pressure. ? Numerical properties were also considered when selecting a model (Beater 1999). One point worth mentioning is the fact that all models can be viewed at source code level and are documented by approx. ? 100 references from easily available literature. ? After opening the library, the main window is displayed (Figure 10). A double click on the ? “pumps” icon opens the selection for all components that are needed to originate or end an oil flow ? (Figure 11). For the problem at hand, a hydraulic flow source with internal leakage and externally ? commanded flow rate is used. Similarly the needed models for the valves, cylinders and other components ? are chosen. ? All components are modeled hierarchically. Starting with a definition of a connector – a port were ? the oil enters or leaves the component – a template for components with two ports is written. This can be ? inherited for ideal models, e.g., a laminar resistance or a pressure relief valve. While it usually makes sense to use textual input for these basic models most of the main library models were programmed graphically, i.e., composed from basic library models using the graphical user interface. Figure12 gives an example of graphical programming. All mentioned components were chosen from the library and then graphically connected. 7. Library Components in Hydraulics Circuit 共 页 第 3 页 毕业设计（论文）报告纸 The composition diagram in Figure 12 shows the graphically composed hydraulics part of the excavator model. The sub models are chosen from the appropriate libraries, connected and the parameters input. Note that the cylinders and the motor from HyLib can be simply connected to the also shown components of the MultiBody library. The input signals, i.e., the reference signals of the driver of the excavator, are given by tables, specifying the diameter of the metering orifice, i.e. the reference value for ? the flow rate. From the mechanical part of the excavator only the components are shown in Figure 12 that ? are directly coupled with hydraulic elements, such as line force elements to which the hydraulic cylinders ? are attached. ? ? 8. Model of LS Control ? For this study the following approach is chosen: Model the mechanics of the excavator, the ? cylinders and to a certain extent the pump and metering valves in detail because only the parameters of ? the components will be changed, the general structure is fixed. This means that the diameter of the ? bucket cylinder may be changed but there will be exactly one cylinder working as shown in Figure 1. That is different for the rest of the hydraulic system. In this paper a Load Sensing system, or LS system for ? short, using one pump is shown but there are other concepts that have to be evaluated during an initial ? design phase. For instance the use of two pumps, or a separate pump for the swing. ? The hydraulic control system can be set up using meshed control loops. As there is (almost) no ? way to implement phase shifting behavior in purely hydraulic control systems the following generic LS 装 system uses only proportional controllers. ? A detailed model based on actual components would be much bigger and is usually not available ? at the begin of an initial design phase. It could be built with the components from the hydraulics library ? but would require a considerable amount of time that is usually not available at the beginning of a project. ? In Tables 1 and 2, the implementation of the LS control in form of equations is shown. Usually, it ? is recommended for Modelica models to either use graphical model decomposition or to define the model by equations, but not to mix both descrip- tion forms on the same model level. 订 For the LS system this is different because it has 17 input signals and 5 output signals. One might ? built one block with 17 inputs and 5 outputs and connect them to the hydraulic circuit. However, in this ? case it seems more understandable to provide the equations directly on the same level as the hydraulic ? circuit above and access the input and output signals directly. For example, ”? metOri1.port_A.p” ? used in table 2 is the measured pressure at port_A of the metering orifice metOri1. The calculated values 线 of the LS controller, e.g., the pump flow rate “pump.inPort.signal[1] = ...” is the signal at the filled blue ? rectangle of the “pump” component, see Figure 12). ? The strong point of Modelica is that a seamless integration of the 3-dimensional mechanical ? library, the hydraulics library and the non standard, and therefore in no library available, model of the ? control system is easily done. The library components can be graphically connected in the object diagram ? and the text based model can access all needed variables. ? 9. Some Simulation Results ? The complete model was built using the Modelica modeling and simulation environment Dymola ? (Dymola 2003), translated, compiled and simulated for 5 s. The simulation time was 17 s using the ? DASSL integrator with a relative tolerance of 10-6 on a 1.8 GHz notebook, i.e., about 3.4 times slower ? as real-time. The animation feature in Dymola makes it possible to view the movements in an almost ? realistic way which helps to explain the results also to non-experts, see Figure 9. ? Figure 13 gives the reference signals for the three cylinders and the swing, the pump flow rate ? and pressure. From t = 1.1 s until 1.7 s and from t = 3.6 s until 4.0 s the pump delivers the maximum flow rate. From t = 3.1 s until 3.6 s the maximum allowed pressure is reached. Figure 14 gives the position of the boom and the bucket cylinders and the swing angle. It can be seen that there is no significant change in the piston movement if another movement starts or ends. The control system reduces the couplings between the consumers which are very severe for simple throttling control. Figure 15 shows the operation of the bucket cylinder. The top figure shows the reference trajectory, i. e. the opening of the directional valve. The middle figure shows the conductance of the 共 页 第 4 页 毕业设计（论文）报告纸 compensators. With the exception of two spikes it is open from t = 0 s until t = 1 s. This means that in that interval the pump pressure is commanded by that bucket cylinder. After t = 1 s the boom cylinder requires a considerably higher pressure and the bucket compensator therefore increases the resistance (smaller conductance). The bottom figure shows that the flow rate control works fine. Even though there is a severe disturbance (high pump pressure after t = 1 s due to the boom) the commanded flow rate is fed ? with a small error to the bucket cylinder. ? ? 10. Conclusion ? For the evaluation of different hydraulic circuits a dynamic model of an excavator was built. It ? consists of a detailed model of the 3 dimensional mechanics of the carriage, including boom, arm and ? bucket and the standard hydraulic components like pump or cylinder. The control system was not modeled ? on a component basis but the system was described by a set of nonlinear equations. ? The system was modeled using the Modelica MultiBody library, the hydraulics library Hylib and a set of application specific equations. With the tool Dymola the system could be build and tested in a ? short time and it was possible to calculate the required trajectories for evaluation of the control system. ? The animation feature in Dymola makes it possible to view the movements in an almost realistic ? way which helps to explain the results also to ? ? 装 ? ? ? ? ? 订 ? ? ? ? ? 线 ? ? ? ? ? ? ? ? ? ? ? ? ? 多畴模拟：挖掘机的机械学和液压学 概要： 通过使用用于多体和液压系统的Modelica程序库，示范通过Modelica和Dymola如何模拟和仿 共 页 第 5 页 毕业设计（论文）报告纸 真挖掘机。液压系统由“负载传感”控制器控制。一般，模型包含难以模拟的三维机械和液压组 件。对于挖掘机将演示Modelica有效适用于这种系统的仿真。 1． 绪论 ? 一种新产品的设计在开始阶段需要一系列决定，这些决定对最终产品是否成功产生很大的影 ? 响。因此，今天在初始阶段使用数字模拟来检验不同的想法。这篇论文的目的是设计一台新的挖? ? 掘机并评估几个备选的液压系统。 ? 模拟包含三维机械和液压组件的系统是很难的，如挖掘机，一般，两个不同的模拟环境必须? ? 连结在一起，这一般很不方便，导致不必要的数字问 题 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 和破碎界面。在这篇文章中，将对挖掘机 ? 模型的开始进行演示以 证明 住所证明下载场所使用证明下载诊断证明下载住所证明下载爱问住所证明下载爱问 Modelica是适合这些系统的。 ? ? 挖掘机的三维组件由新近的，丰富的Modelica，联合体程序库来模拟，这使得可以使用铲斗? 运动循环的 分析 定性数据统计分析pdf销售业绩分析模板建筑结构震害分析销售进度分析表京东商城竞争战略分析 结论，并直接考虑液压缸（也就是动力元件）的质量。液压部分以详细的方法模? ? 拟，从一个用于Modelica的液压程序库中使用泵，阀和缸。在控制部分使用一个普通的负载传感 装 器，由一简单方程组模拟。这种方法得到要求的结果，并使得分析问题所需的时间限制在合理的? ? 要求内。 ? 2．模型选择 ? ? 模拟一个系统有几种方法。根据任务的需要建立一个很精确的模型，包含系统的每一个细 订 节，需要许多的信息，比如模型参数。建立这种模型很麻烦。但另一方面，如果一个定义系统的? ? 参数需要修正，建立这种模型是很有效的。挖掘机上平衡阀参数的优化就是一个特殊的例子。 ? 对一个系统的初步研究需要另外一个模型，在这种情况下，泵，阀和负载的容量是具体的，? ? 需要的是关于系统工作的信息，例如活塞的速度，泵轴所需的输入动力。从而判定这个设计是否 线 符合此任务的原则要求。因此，这种模型必须是方便的，也就是，对特殊元件没有详细了解时能? ? 在短时间内建立起来。 ? 学者们打算建立第二类的一个模型，并运行它，但在最少的时间内得到第一类的结论，为? ? 了达到此目的，使用了建摸Modelica，Modelica模拟环境Dymola，用于三维机械系统的新Modelica ? 联合体程序库，和液压组件的Modelica程序库Hylib，模型包含挖掘机的三维机械结构，动力液? ? 压学的详细描述和通用的负载传感控制器。它在Hylib的下一个版本中可应用为一种样本。 ? 3． 挖掘机的结构 ? ? 图一给出了正在考虑中的特殊挖掘机的简图。它包含履带和液压推动装置，液压推动装置用 ? 于操纵机械，但通常不在一个工作循环的时候。它的上面是供操作者坐的车厢，厢体能相对于履? 带绕垂直轴旋转，柴油发动机液压泵和控制系统却在里面，另外转臂，动臂。在末端是铲斗，铲 斗经由一平面运动回路连接到动臂上。特定的液压缸使转臂，动臂，铲斗旋转。 图二表示出油缸所需的压力是根据位置确定的，当在伸展开来的情况下，动臂油缸中的压力 共 页 第 6 页 毕业设计（论文）报告纸 比收缩的情况高60%。不仅位置，而且运动也必须考虑。图三表示动臂下降的情况，如果车厢没 有旋转，油缸则需要一个拉力，当旋转时，挖掘机旋转通常能达到每分钟12转，则动臂油缸中的 受力改变方向，此时需要一个推力。这个改变是非常重要的，因为此时活跃的油缸内箱转变，这 ? 必须由控制系统加以考虑。两幅图都表明一个仿真模型考虑挖掘机四个自由度相互之间的联结， ? 每个油缸和回转驱动使用连续载荷的简单模型将导致错误结果。 ? ? 4． 负载传感器 ? 挖掘机通常具有一台柴油发动机，两台液压马达和三台油缸，为这些消耗机器提供所需的液? ? 压油源的液压线路上不同的。一种特殊的设计是负载传感线路，它能有效控制能量，使用方便。 ? 这种想法是使泵有一个流体速率控制系统，因而能准确传递所需的流体速率。在传感器中，使用? ? 经过节孔而产生压降的方法，孔的阻力是参考值。图四给出了简图，关于这个话题的更好的介绍 ? 已经给出。 ? ? 泵控制阀，使得泵出口的压力通常比负载传感器中的压力高15MPA，如果方向阀关闭，则泵装 因此有15 MPA的压力。如果方向阀打开，泵输出一流体速度导致通过方向阀时产生15 MPA的压降。? ? 注意：方向阀不是用做泵流体，而是作为一个流体仪表（反馈的压降）和作为一个参考（阻力）。 ? 此线路对能量是有效率的，因为泵只输出所需的流体速率，相对其他线路，油管的损失很小。 ? ? 看图五，如果不只一个油缸使用这种线路，则变得复杂。如果转臂需要300 MPA的压力，铲订 斗需要300MPA的压力，则泵输出的压力高于300MPA，这会使转臂油缸产生一个不要的运动。因此，? ? 使用补偿器来约束油流体，因此达到通过特殊定向伐时产生15MPA的压降，这些补偿器可以安装? 在定向阀的前面或后面。如果达到最大泵流体速度或泵最大压力，则附加的阀减少容许压力差。 ? ? 5． 机械部分的模型 线 图六为机械部分的一个Modelica简图，履带不是模拟的，也就是，假设履带为不动的，组? ? 件“rev1„rev4”是使得相互联系的部分运动的旋转关节，长黑色线的图象是实质是的闩，用于 ? 标明机械部分上的特别的关节。特别是液压油缸的固定关节，淡蓝球是有质量和惯量张量的球体，? ? 是用于模拟挖掘机的相应部分，“cy11f.cy12f和cy13f”三个部分是线性力部件，描述两个连接? 之间沿着线的力相互作用，这些部件中的小绿方格表示Modelica机械翻译程序库中的一维翻译连? ? 接器，他们用于表示两连接关节之间的一维力法规。这里，将在下一部分中介绍饿液压油缸是直 ? 接连接的。“cy11f.cy12f和cy13f”部件图象上的两个小球表示有选择的考虑两点的质量，在沿? ? 连接线上的连接点之间的已定距离上，这方便于模拟，只有少计算液压油缸的质量部分（质量和 ? 作用中心） ? 关节RRR组件（图六右边）是包含三个旋转关节的装配元件，其中旋转关节在连接动臂时一 起形成一片面回路。图七为挖掘机这方面的一张图片，在相应的Modelica简图的一张电子放大图 象和动画制作图。当移动旋转关节“rev4”（图七下面部分中的大红油缸，表示关节RRR装配部件 共 页 第 7 页 毕业设计（论文）报告纸 中三个旋转关节的小红缸），关节RRR部件中左右旋转关节的连接点的位置和定位是已知的，关节 RRR部件中有非线性代数回路用以计算连接点运动时产生的3个旋转关节的角度。这非线性方程系 统在关节RRR中分解解决，如，一种快速有效的方法。 ? 第一步，在没有液压系统独立测试时，模拟挖掘机的机械部分，通过连接转换弹簧和代替液压油 ? 缸的合适弹簧惯量来完成。当动力制作看起来不错，节点上的力和扭矩达到要求时，弹簧以下将? ? 介绍的液压系统代替。 ? 新的联合体程序库的所有组件有内部的默认定义，也就是，默认部分都是通过联合体系统? ? 中的已知定义读用推导的，例如连接两旋转关节的闩被错误的理解为油缸，油缸的直径d相对油 ? 缸的长度很小（d=L/40）。长度反过来是由两旋转关节之间的距离确定的，旋转关节被错误的想? ? 象为沿着关节旋转轴的红色油缸，挖掘机的默认（只有一小部分采用）如图八。 ? 浅蓝色球代表质量作用点，想象为液压油缸的系列力元件，通过两种向对方运动油缸（黄色? ? 和灰色）来定义。就如所见，不用使用一方额外的工作，动作制作有效的获得一张模型的粗糙的 装 照片，照片能视觉上检测最重要的部分，如，质量中心或连接点是否在所要求的位置上。 ? ? 对于每个组件一Bodean旗能关闭默认的默认的图。移动合适的预设图象。例如，质量中心? 球。并且添加有单纯实际信息的一些组件（简图6中的所有visxxx组件）将迅速得到好看的图象。? ? 如图九所示。计算机辅助制造数据也可以使用到图象中，但这些不能用于挖掘机的试验。 订 6． 液压程序库Hylib ? ? 商业Modelica程序库Hylib用于模拟泵调节孔，负载补偿器，液压回路缸，所有这些元件是? 液压回路的标准元件，能从许多制造商获得。Hylib中包括所有这些元件的模型。这些数学模型? ? 包含教科书上的标准模型，也包含对真实元件的运行进行考虑的最先进的，如果输入口压力下降 线 到底于大气压，输出的液体就会减小，这样的普通泵模型就上例子。选择一种 模型时，还有许? ? 多因素要考虑，值得一提的一点是所有模型能被原代码水平看待，并且可以由从易得文献得来的 ? 大约100个参数来证明。 ? ? 打开程序库后，展示了主要窗口（图十），双击泵图象打开所有元件的选项。开始或结束油 ? 流体所需要元件。为了现在的问题，使用带有内泄口和外部限定流速的液压流体源。同样，选择? ? 关于阀，缸和其他元件的所需模型。 ? 所有组件都是分级模拟的，从连接器的确定开始（连接器是油进入或流出元件的通口），带? ? 有两个口的元件模版如图。这能继承下来到理想的模型。如一薄层阻力阀或释压阀。当为这些基 ? 本模型使用文字上的输入是有道理的。许多程序库主要模型以图形编制。由使用图形使用者界面? 的基本程序库模型组成。图12给出了图形编制的一个例子。所有提及的元件从程序库中选出来并 分明的连接起来。 7． 液压回路中的程序库元件 共 页 第 8 页 毕业设计（论文）报告纸 图12中的结构图是挖掘机模型图形组成的液压部分，以下的模型是从专属的程序库中选出， 连接并输入参数。注意到从Hylib来的缸和马达能简单连接为所示的多功能程序库的组件。输入 信号如，挖掘机发动机的相关信号由图框给出。使测量孔的直径具体化。如控制流体速度的参考 ? 阀。对于挖掘机的机械部分，只要图12中所示的元件直接与液压元件相连接。如液压缸接触的直 ? 线压力元件。 ? ? 8． 负载传感控制器模型 ? 在这个学习中，选择下面的方法：模拟挖掘机的机械器件，并一定程度上详细的模拟泵和? ? 测量阀。因为只有元件的参数将改变，一般结构是固定的。这意味着缸筒的直径可能改变，但确 ? 切的只有个一缸那样工作（如图1所示）这个液压系统其余部分是不同的，在这篇文章中使用一? ? 泵的负载传感系统如图所示。但在开始设计阶段还有其他的想法必须评估。例如在回转运动中使 ? 用两泵或单泵。 ? ? 根据实际元件设计的全面的模型会大得多。通常在初始设计阶段的开始不适用。它能由液 装 压程序库中的元件建立起来，但需要相当多的时间，这在工程的开始是行不通的。 ? ? 在表格1和2中所示的是LS控制器执行的方程式。一般，联合体模型选择使用图形模型分解或通过 ? 方程式定义模型。但不是在一样的模型标准上混合两种描述形式。 ? ? 对于LS系统这是不同的。因为它有7个输入信号和5个输出信号，建立带有17个输入和5个输 订 出的块。并把它们连接到液压回路。但是，在这种情况下，如上面液压回路，在一样的标准上直? ? 接提供方程式并直接输入输入信号和输出信号，看起来更加可以理解。例如，格中 ? “metoril.port.A.p”是测量孔metoril的通口的度量压力。LS控制器的计算值。例如，泵流体? ? 速率“pump.inport.signal[1]=” 是在泵元件的蓝色矩形中的信号。图12。 线 Modelica的重点是三维机械程序库和非标准的无缝连接。并且，因此在没程序库可用时，? ? 控制系统的模型很容易的处理。程序库元件在目标图表中能连接起来，根据模型的本文能得到所 ? 需的各种变化。 ? ? 9． 仿真结果 ? 使用Modelica模型和仿真环境Dymola建立完全模型，并转换，编译和模拟5秒钟，仿真时间? ? 17秒，使用一个1.8Ghz笔记本上相对误差10-6级的DASSI综合器（比真实时间满3.4倍），Dymola ? 的仿真特点使用可能在几乎真实的情况下观察运动，即使相对于非专家。这也有助于解释结果。? ? 看图9。 ? 图13给出了三个缸和摇摆的相关信号，泵流体速率和压力从t=1.1秒到t=1.7秒和t=3.6秒到? t=4.05秒。泵以最高流速工作。从t=3.1秒到t=3.6秒达到最高允许压力。图14给出了转臂缸和铲 斗缸的位置和摇动角度。能看出在另一个运动开始或结束时，活塞的运动没有重大的改变。控制 系统减少油缸之间的耦合，这种耦合在单路控制中特别严重。 共 页 第 9 页 毕业设计（论文）报告纸 图15给出铲斗缸的操作。上面数据显示参考轨道，也就是方向阀的开启中间数据，表示补 偿器的传导系数。两钉道是例外，从t = 0秒开到t = 1 s 秒，这表示在这段间隔的时间里，泵 压力由铲斗缸控制。它从t=0秒后，转臂缸需要一个相对高的压力，铲斗补偿器因此增加阻力。 ? 下面数据表明流体速率控制工作良好。即使存在一个严重的扰乱。带有小误差的要求的流体速率? 有铲斗缸供足。 ? ? 10. 结论 ? 建立一个挖掘机的动力模型以评估不同的液压回路。它包括厢体三维机构的完整模型。包括? ? 动臂，转臂，铲斗和像泵和缸等标准液压元件。控制系统不是在组件基础上的模拟，而是通过一? 系列非线性方程描述。 ? ? 使用Modelica的联合体程序库，液压程序库Hylib和一系列具体应用方程，模拟了系统。通 ? 过工具Dymola，系统得以建成并且短时间内测试。使得能计算所需的线路来评估控制系统。 ? ? Dymola仿真特性，使得有可能在几乎真实的情况下观看运动。即使对非转泵，这也有助于解 装 释结果。 ? ? ? ? ? 订 ? ? ? ? ? 线 ? ? ? ? ? ? ? ? ? ? ? ? ? 共 页 第 10 页