数控系统辅助液压挖掘机的概念课程毕业设计外文文献翻译@中英文翻译@外文翻译

Abstract A concept of digital control system to assist the operators of hydraulic excavators is presented and discussed. Then, control system based on described ideas was mounted on a special numerically controlled stand, equipped with D r A and A r D converters, where small hydraulic backhoe excavator K-111 fixtures were used. Experimental results shows that it fulfils all described requirements and can be used as the machine operator assist. It enables for precision tool guidance. automatic repetition of realized movements, realization of specific tool trajectories including energetically optimal path sand automatic improvement or optimization of realized paths. Tool trajectories can also be prescribed using the setting model, making excavator the machine of tele operator class. Presented system can be used as a basis for real machine control system. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Digital control system; Hydraulic excavators; Tool trajectories 1. Introduction The automation of heavy machines, including hydraulic excavators, began in mid-1970s and was possible due to invention of real time controllers and hydraulic elements with good dynamic properties. The first excavator equipped with several mechatronics systems, which was shown as a working model, was the excavator FUTURE prepared by Orenstein and Koppel for BAUMA83 Fairs. Since that time, machines equipped with systems automating the engine operation, pumps operation, machine fixtures, machine diagnostic, etc., are presented and offered. Such systems bring real help to the operator and clear economical profit. For example, LIEBHERRR902 excavator equipped with LITRONIC System. has for a trench digging the efficiency 40% higher and unit costs 30% lower, than similar machine without such automatic system. Although automation . in some case, optimization of several machine systems develops quite fast, the main machine process the shoving processhas no proper understanding and description until now. Its automation is quite limited to systems repeating already performed. movements, laser levelling systems, etc. and systems optimizing such processes are not developed yet. Quite new experimental results show clear idea for energetically optimal tool trajectories in the case of cohesive materials. The tool tip has to be guided along slip lines, which are generated from the tip tool during the previous stage of the shoving process. To realize such trajectories for practical purpose and real machines, it is necessary to build a special control system for the tool motion, which enables automatic realization of such trajectories as well as realization of other tasks that help the operator. 2. The basic concept of the computer aided control systemIt It was shown before that analyzing the the soil deformation during the shoving process, it is possible to determine energetically optimal cutting tool trajectories. Hence, the automatic tool movement along slip lines generated in cohesive material has to be a quite important option of proposed system. It should also enable precision tool guidance, automatic repetition of already realized movements . for example, teach-in , realization of some tool movements impossible to realize manually, etc. Taking into account to-day experience with automation of heavy machines, such system should be constructed to assist machine operator, who still plays a main decisive and control role. Hence, the proper separation of tasks, between the control sys-tem and the operator, is necessary. Such control system for excavators was built on laboratory scale. Its basic assumptions can be stat d w x . as follows 13 : 1 operation of the central control system is based on cooperation of two digital systems. The first one controls directly the motion of the machine fixture using the control system of the hydraulic cylinders position. The second one works . out control signals for the first one. 2 Under the standard work conditions, action of the proportional hydraulic valves of the fixture cylinders is controlled through the computer. The direct operator control is . possible only in case of emergency conditions. 3The feedback between the machine environment and control system is realized through the operator. He participates continuously in the process of the con- . control of machine fixtures motion. 4 For realization of the tool motions which are impossible for manual control, the operator has a possibility to coordinate displacement of separate cylinders by means of hard- . ware or software. 5 The operator has a possibility to switch into automatic control of the fixture motionto realize a special tool trajectories. For example, it can be energetically optimal tool trajectory where tool tip moves along slip lines or specific trajectory . realized and stored previously. 6 The optimal cut-ting tool trajectories can also be realized as correction of trajectories given by the operator. Such correction is done mainly during the time parametrization of the tool path. 7 The trajectories given by the operator can be corrected by the system to take in toaccount such limitations as geometrical ones, maxi-mal power of the pump, maximal output of the pump, maximal pump efficiency, etc. Presented concept is based on such cooperation between the operator and control system that the fixture movements are controlled by the operator while the control system corrects him or, when ordered, can act automatically 3. Examples of the control system functioning The control system based on described above ideas was mounted on a special numerically con-trolled stand, equipped with PC computer having CrA and ArC converters, where small hydraulicw x backhoe excavator K-111 fixtures were used 1417 .The control system of the fixture motions utilizes the control system of the cylinder positions. The fixture cylinder displacement is controlled by the proportional hydraulic valves fed by the variable out putmultipiston pump. The control system for fixture cylinders is based on three control systems, each to control different cylinder displacement using PID or state control ler w x 14 . It enables control of the fixture motions using different methods of the tool trajectory planning, measuring of acting forces and displacements and determining other magnitudes related to the fixture movements. Experimental data acquisition is also possible. One of quite important problems, which should betaken into account when building the control system, is the way of the tool trajectory planning. It is . w x realized as usually in two steps 15 . In the first one, the trajectory shape is planned and determined. In the second one, the trajectory curve is parametric zed in time in a determined manner, what defines the trajectory within the generalized coordinate space. On this basis, the time runs of the generalized coordinates describing the configuration space of the machine are determined. In the case of an excavator, lengths of hydraulic cylinders are those coordinates 3.1. The tool mo ement along prescribed line The control system build for experimental standw x 1517 enables, among others, programming the work motion in the excavator work space, or in its configuration space, using point to point technique. In this method, the coordinates of the initial and final points, and sufficient number of the character isticnodal points, are defined. Values describing this points are then introduced to the system, where remaining points of the trajectory are calculated using interpolation methods. Linear or the third degree polynomial interpolation is used. The trajectory y parametrization in time can be realized through: determination of the total trajectory run-time and its division into individual segments of the path. System calculates the velocities of cylinders, determination of the run-time between following nodal points, taking into account some limitations . or conditions for optimization .In the case of standard excavator construction, it is quite difficult to precisely realize trajectories, where simultaneous movement of two or three cylinders is necessary. 3.2. The tool mo ement using the setting model along straight lines In presented case, the coordination of the fixture cylinder movement was realized by hardware, that means using the setting model. It can also be realized by software. The machine operator using special. buttons , can generate horizontal or vertical tool movement preserving the constant value of the tool cutting angle in every point of the machine working space. The prescribed tool path is stored using the point method in the configuration space. Further-more, the machine operator determines motion velocity which is corrected by control system taking in to account the feeder output. In Figs. 7 and 8, results of such control for the horizontal tool movement are shown. The cutting tool trajectory is presented in Fig. 7. In Fig. 8, the fixture cylinder lengths calculated for prescribed velocity are drawn with solid line. Their calculated lengths assumes the feed erout put are drawn with dotted line. The way of the tool path time parametrization was similar to that using the setting model. It is seen that velocities given by the operator are too high and system corrected cylinder motion timing to keep assumed feeder output. The example of the tool motion along the inclined line is presented in Figs. 9 and 10, where the tool trajectory and corresponding cylinder lengths are drawn. Such movement is realized as a sum of horizontal and vertical tool motions the line inclination depends on proportions between horizontal and. vertical velocities . For example, the tool trajectory long inclined line can be realized during the . withdraw stage of the shoving process Fig. 2 to follow the slip line or for automated, making the soil scarps. 3.3. Automatic tool mo ement along a slip line Analysis of experimental results of the soil shoving process shows that it is possible to predict theoretically the slip lines positions and energy etically optimal tool trajectories. It can be done for homogeneous material under laboratory conditions. In real situations, when material is not homogeneous and not well-defined, the material sleep lines has to be detected automatically. The procedure of automatic slip line detection is based on the observation that when cutting tool begins to penetrate more dense material, then the in crease of the horizontal force acting on the tool is observed. Such situation takes place also when the tool tip moves from the slip line where material. density is quite small to the virgin material material. not deformed beforebehind the slip line . Hence, the observed increase of the pushing force can be used for slip line detection. Such procedure, which simplified version is described below, can be realized as follows. Cutting tool motion is realized as a sum of horizontal, vertical and rotational movements and horizontal reaction of the soil is measured and followed. Firstly, the tool moves horizontally up to the moment when the horizontal force drops, that coincides with creation of slip lines system originating from the tool . end Fig. 1 . If such slip lines cannot be created as a result of horizontal pushing, a special procedure for. example tool rotation can be applied. Then, tool is moved vertically by prescribed displacement value and then moves again horizontally rotation of the. tool can be added up to the moment when horizontal force begins to increase. If so, , and then horizontally, and so on. This way, the tip of the tool automatically follows in a step way the slip line. Results of such preliminary tests are presented in Figs. 11 and 12. As a simplified model, the possibility of automatic tool movement along the soil scarpinclined with 0.61 rad. was investigated. For defined values of maximum horizontal force and defined vertical displacement, the control system automatically followed the tool along the scarp. The horizontal force vs. horizontal displacement and tool trajectory are shown in Fig. 11. The magnified fragment of Fig. 11, which shows the way in which system is acting, is presented in Fig. 12. 4. Conclusions Experimental results show that presented control system fulfils all described requirements and can be used as the machine operator assist. It enables for precision tool guidance, automatic repetition of realized movements, realization of specific tool trajectories including energetically optimal paths and automatic improvement or optimization of realized paths. Tool trajectories can also be prescribed using the setting model, making excavator the machine of tele operator class. Presented system can be used as abas is for real machine control system. Acknowledgements This research was sponsored by the Project KBN7T07C00412 Optimization of the soil shoving process due to heavy machines of an excavator type realized at Kielce University of Technology. 数控系统辅助液压挖掘机的概念 摘要 数控系统辅助液压挖掘机操作者的概念被提出和讨论。然后，基于描述概念性的控制系统被安装在专门的数控平台上，平台上配备 D/A 和 A/D 转换器，已经在小型液压拉铲挖掘机 K-111 的工装上应用。实验结果表明它能满足所有描述的需求，并且能用于辅助 机器操作员工作。它能为精密工具做引导，了解的运动的自动重复和特定工具轨道 (包括最佳的路径 )，还有自动改进或优化路径。工具轨道也能被规定使用设定模型，使挖掘机成为遥控操纵类别的机器。现行的系统能基本用于真机控制系统。 1998 Elsevier 科学 B.V. 版权所有。 关键词 ： 数控系统；液压挖掘机；工具轨道 1 介绍 重型机械的自动化，包括液压挖掘机在内，始于 20 世纪七十年代中期并成为可能。这主要由于时实控制系统和高动力性能的液压元件的发明。第一台配备若干机械电子系统的挖掘机被当作模型展示，这是 Orenstein 和 Koppel 为 BAUMA83 展览会准备的未来的液压挖掘机。自从那次以后，许多配备了自动控制系统的器被展现和要求 如引擎操作，泵操作，机器工装，机器诊断等等。这种系统带来了真正的帮助和明显的利润。举例来说 , 被装备 LITRONIC 系统的 LIEBHERR R902 挖掘机（对于挖沟机），对比没有配备这种自动控制系统的相同机型来说，效率提高达 40成本降低 30。虽然一些机器的自动系统（在一些情况下的优化）发展的相当快，但是直到现在主要的机器程序推处理 -没有适当的理解和描述。它的自动化相当的有限（如重复运动和激光平行系统等等），并且优化处理系统还没有发展。比较新的实验结果清晰地表明，优化的工装轨迹在连续材料情况下，工具的尖端不得不沿着前一个推挤过程形成的滑道运动。实际上了解这样的轨迹和真机，为工具的运动建立了一个特别的控制系统是必要的，这使得实现这样的轨迹像实现其它帮助操作员实现其它任务一样。考虑到日益加重的机器的发展，这种系统必须适应数控电 液驱动。经核实试验结果，这种控制系统的概念在这篇文章中提出。 2 计算机辅助控制系统的基本 据之前显示，在推土过程中分析土体变形的力学机理，可能决定刀具轨迹的优化。然而，在连续的材料中产生了工具沿着滑线的自动移动，这必须成为被提倡的系统的一个重要选项。这也应该成为精密工具的向导，自动重复已经确认的运动（例如“讨论会”），实现一些手工不能实现的工具动作等等。 考虑到对重型机器自动化的经验少，这样的系统应该被装配在机器 上来协助操作员，并且扮演决定性和控制性的角色。因此，在控制系统和操作员之间的适当的分离是必要的。 这种用于挖掘机上的控制系统是建立在实验室范围上的，其基本假设可以阐述如下 13，（ 1）控制中心的操作系统是基于两个数字系统的协作下的。第一个通过控制液压缸的位置来控制机械夹具的运动。第二个为第一个系统产生控制信号。（ 2）在标准工况下，夹具液压缸的比例液压阀通过计算机来控制。直接的操作员控制仅在出现紧急情况下才能用。（ 3）机器环境和控制系统之间的反馈是通过操作员来实现的。他连续的参加机器夹具运动控制的过程中。（ 4）为了了解这种人工控制不能实现的工具运动，操作员有可能通过硬件或软件来调整单个液压缸的位移。（ 5）操作员有可能转换夹具运动的自动控制来认识特殊的工具轨迹。在这里，工具的尖端沿着滑线或特定的已经确认的或是事先存在的轨迹移动。（ 6）优化的工具轨迹也可以被认为是操作员给定的轨迹的修正。（ 7）系统可以在考虑某些限制的基础上来修正操作员说给定的轨迹，如：几何关系限制，泵的最大能力限制，泵的最大输出限制和泵的最大功率限制等等。 现行的概念是基于操作员和控制系统之间的协作，这就是说夹具的移动是在控制系统修正下的操作员的 控制或是在操作员的命下控制系统的自动化控制。 3 控制系统功能实例 控制系统基于上述理念被安装在一个特殊的数控场合，配备有 PC 和 C/A、A/C 转换器。在小型液压挖掘机 K-111 的设备中有所应用 14-17。夹具利用液压缸的位置控制系统来实现夹具的位移控制。夹具液压缸位移是靠变量柱塞泵反馈的成比例液压值来控制的。夹具液压缸控制系统基于三个液压控制系统，每个控制系统应用 PID 或是状态控制器，控制不同的液压缸的位移 14。 它可以用 工具轨迹计划编制，测量作用力和位移，以及其它于夹具位移有关的量来控制夹具的 位移。实验的数据的获得也是可行的。 当建立控制系统时，应该考虑的相当重要的问题之一是工具轨迹计划编制的方法。这种方法（通常）从两步来认识