机电类外文翻译【FY107】数控系统辅助液压挖掘机的概念【PDF+WORD】【中文6600字】
收藏
资源目录
压缩包内文档预览：
编号：446356
类型：共享资源
大小：975.10KB
格式：ZIP
上传时间：2015-07-03
上传人：棒***
认证信息
个人认证
康**（实名认证）
湖北
IP属地：湖北
12
积分
- 关 键 词：
-
机电类
外文
翻译
fy107
数控系统
辅助
液压
挖掘机
概念
pdf
word
中文
- 资源描述：
-
机电类外文翻译【FY107】数控系统辅助液压挖掘机的概念【PDF+WORD】【中文6600字】,机电类,外文,翻译,fy107,数控系统,辅助,液压,挖掘机,概念,pdf,word,中文
- 内容简介：
-
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 工具轨迹的优化 nts实验发现 1， 2由于重型机械工装的作用，在土壤运动过程中，沿着滑线方向形成了刚性区域（清楚科技昂的裂纹）。沿着滑线方向，材料的参数改变了（初始的内聚力 C 减小到残余值接近 Cr=0）。在简单工具推挤垂直墙的过程中，力转移关系表明水平力随着推挤垂直墙过程而增长，但处在一个不稳定状态。在力减弱的同时，一个运动学 机制在工具作用结束而产生。这种机制周期的产生，而且能用塑性理论的可容学机制来描述 4 8（如图 1）。 图 1 年行土壤在水平工具向前推挤过程中的典型变形（在理论上） 下了很大的功夫作了描述土壤切削过程的塑性变形理论 , 那里的问题 ,积极施压刚性壁对颗粒介质 (下平面应变作出反应 ) 被假设为简化模型土壤搡 . 在这种情况下 , 该方法的特点是采用 3,9和若干理论方法 (静力学和运动学 ) ,得下 假设刚性塑性土壤中的行为 . 虽然一些边值问题解决这个方式 存在若干局限在获取完整的解决方案 ,甚至运动学 -根据十大受理的 9 尤其是对于更先进的地球切削过程 . 另一种方法 ,基于动准予三方机制 建议后来 5和应用的描述更先进地球搡钨十大流程 6,7,10-12 。 让我们讨论推挤平面应变刚性墙问题，如图 1所呈现的。假设材料使刚塑性的并且服从库伦莫尔屈服准则： 在这里， C-材料凝聚力， -内部摩擦力。 流规则的形式： nts在这里， G( ij)代表塑性潜力。 在发生时可能是描述的屈服准则（如公式（ 1）， 关联流动法则是假设 ,当另一项功能被采用时 ,流动规律是不相关。 利用这种方法 ,并假定改变材料参数的滑移线 6， 7, 不同动受理解刚性壁搡过程中 ,才能提出和解决预测最小能量搜查 。 对于形状如“ L”形的刚性墙的动力学允许的解在图 1 中体现，主要展示经验观察的结果。随着进程的进展，横向力愈来愈来不稳定，并且当这种力减少的时候，在工具的末端同时产生了动力学机制，这种机制周期的产生。这种理论描述的预计情况和实验的主要结果比较吻合 6,7,10-12 。 考虑到实验观察和理论的方法，试验的表示是可能的，一旦滑线在前后连续的材料里面产生，那么工具的尖端很可能沿着先前的产生的滑线运动 12。实验在基于平面应变的情况下的特殊实验室内完成 1,12,应用人工合成的材料，这种材料模仿粘土和其相应的参数，这种材料由 50的水泥， 20的斑脱土， 18的砂子和白色的凡士林混合构成。白色的凡士林的使用是为了得到粘性土壤，是土壤的参数不受空气的温度和液体流的影响，并且确保这些参数在实验过程中保持稳定。 典型的实验结果 12，在图 2和图 4中展示出来，以相同的方 法挖出相同等的材料（约 60N）。“ L”形的工具以 58 的角模拟倾斜了现实过程（ LA=180mm），是首先推入到一个特定的位置斜度（如图 2 b）。当工具以 45 向前时，工具的尖端作用于材料的自由边界，滑线就周期的被产生了。在下一个阶段（缩回阶段）工具的尖端沿着三个垂直的线运动（如图 2 c），伴随着工具的旋转，工具被挖起的材料填满（如图 2 d）。那些直线倾斜的角度 30 ， 40 和 50 。角的 值是 40 和 50 的更接近工具的水平推挤过程形成的滑线的倾 斜度（如图 2 c）。在如此的情况下，它的意思是工具的末端几乎沿着滑线移动，在滑动过程中，材料的内聚力 c由于材料的软化而急剧下降。 这些过程的具体能量适合不同的初步水平位移，在每次测试中选择确定的相似的挖出量（ 600N）。如图 3所示，可以看出在 30 的情况下，具体的能量单元比在 40 和 50 时都高（甚至高出 100）。然而，在进行刀尖沿线倾斜的角度，类似的角度滑线的倾向，填土过程的具体的能量可以大大减少。 nts 图 2 斜坡样本的实验过程：（ a）工具和斜坡模型；（ b）过程的第一阶段水平移动； （ c）轨迹变化和水平移动发展阶段；（ d）过程的最后阶段 图 3 在两相分明的轨迹情况下撤回线在不同斜度下的具体工作值 实验结果表明，发生在粘性土推土过程中：（ 1）沿着滑线材料形成刚性区域，这里的材料参数极大的改变（内聚力）；（ 2）机器的工具沿着先前产生的滑线移动，推土过程极大的节省能量（填土工具）。这个观察可能是填充过程的基础。 3 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。 nts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。 4 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 15,在第一步中，计划和决定轨迹的形状。在第二步中，轨迹曲线已决定性的方法 按时间进行参数化，这种决定性的方法把轨迹定义在广义坐标内。在此基础上，推广到广义坐标的时间描述机器构造空间被决定。挖掘机在这种nts情况下，液压缸的长度都是相匹配的。然后，它们作为控制系统信号被用于重复计划好的轨迹。有些系统能力描述如下。 4.1 工具沿着指定好的路线移动 为实验平台建立的控制系统，在挖掘机工作空间或是在其构造空间内运动应用“点对点”技术用这种方法，坐标的最初和最终的点以及足够数量的特有的节点被定义。然后描述这个点的值被导入系统，而其余各点的轨迹的计算采用内差值法。线性的或是三次多项式差值法被应 用。轨迹的时间参数化才能通过确定的轨迹运行时间，以及其划分个别路径环节而被认识。考虑到系统计算液压缸的速度的一些限制，测定两个相邻点之间的运行时间（或者在最优化的情况下）。 在这样的标准挖掘施工情况下，很难精确实现轨迹，在这里同时移动两三个液压缸是必要的。 4.2 工具运动建模 另一种控制装置运动的方法控制建模，它有些象机器人上的控制单元，这种控制依靠幻影执行。理解为运动学的重复或是机械运动学的模型 18，配备有系统测量的移动参数。以这种方式控制的挖掘机成了要控机器 19。 设定模型是按 K-111 挖掘机 装置的 1/10 建立的模型，位于该板块。三个电位计位于旋转轴的模型单元里。来自这些电位计的信号允许我们决定装置的构造。机械底部提供的模型，限制了个别装置元件，来自 K-111 挖掘机的转角值。特别开关启动系统。 设定模型是只能用于规划中刀具的路径，以及在其运动的刀具轨迹并用点的方法把它们记录下来，当以 2下两种情况下轨迹点被记录：较以前的位置相比，液压缸的总长度增加到高于假设时；与前面的记录时间相比时记录的数据更晚时。 路径的点在不包括断点的定时间隔下被记录。路径的节点以相应的装置液压缸的长度来定义。其它的轨迹点的 计算由计算机在构造空间内以插值法配置。不在轨迹上的点的计算依靠建模标记。并可以忽视在区间的节点这相当于若干采样周期。这种轨迹的参数的实现是基于假设的液压反馈输出上的。因此，系统通过节点的记录和为装置液压缸位置控制系统而设定的决定点进行操作（基于已经描述的节点和假设输出反馈）。 nts如果建模的装置移动变慢，对于适当的假设反馈输出而言，真正的挖掘机装置的移动象模型移动一样。对于快速移动来说，路径规划的进展的实现依靠真正的挖掘机的装置。 实验结果表明对于依靠建模来控制的装置移动在图 4中展示出来，在这里用建模来表示挖掘机装置轨迹的阶段被展现出来。虚线表示的是建模，实线表示真正的挖掘机装置和涉及的节点路径点。在那种情况下，按照假设反馈输出，设置液压缸位置控制系统的轨迹节点在图 4也有展示。建模的轨迹也就是机械装置的轨迹，于可重复利用的值在图 5中展示。标记成 Jlw、 Jlr和 Jll的值是在移动中意味着液压缸位置（计划的和确定的位置）是错误的。 JxMax和 JyMax表示水平方向和垂直方向的最大的不同。图 6 表示的是液压缸长度建模（基本心好来源于固定线）的改变，并且计算 K-111的装置（虚线）液压缸 的改变控制系统，以及在移动中的错误响应（点线）。并于隆隆声的运转用指标（ w），臂（ r）和铲斗（ l）标记。 图 4 应用建模描述挖掘机装置轨迹的连续阶段 nts建模信号的运行和真实装置设置点之间的不同源于基于假设反馈输出的时间参数化的方法（建模的移动超过真实装置的可能的移动）。 4.3 沿 着直线的工具移动 在当前的情况下，装置的液压缸的同时移动通过硬件实现，这意思就是通过建模实现。它也可以通过软件来实现，这意思是通过机器操作者实现（用专门的按钮）。机器在任意工作空间内，工具水平或垂直切削角度保持为常数。在构造空间内，以点的方法描述工具路径。此外，机器操作者可以决定移动速度。速度靠控制系统考虑输出反馈的情况下保证正确。水平运动的控制结果在图 7和图 8中表示出来。切削工具的轨迹在图 7中表示出来。他们假设反馈的计算长度以点线表示出来。工具轨迹的时间参数化方法于建模相似，看起来操作者 给的速度太高，并且系统修正的液压缸移动适时的与假设输出反馈相保持。工具沿着斜线移动的例子在图 9 和图 10 中展示出来。在图中工具轨迹和相应液压缸被画出来，这样的移动以水平和垂直运动之和来实现（斜线以水平和垂直速度来合成）。例如，沿着斜线的轨迹可以在推挤过程的退回阶段沿着滑线或自动形成，使得土壤陡坎。 图 5 建模的路径（ Xu， Yu）和机器装置路径（ X， Y）描述的轨迹 nts 图 6 建模中液压缸的长度变化（实线），控制系统计算的液压缸的长度（虚线），在装置移动中的错误的响应（点线）。 图 7 水平运动的切削工具轨迹 nts 图 8 指示速度的装置液压缸的计算长度（实线）和反馈输出的假设计算长度（点线） 图 9 倾斜移动的切削工具轨迹 nts 图 10指示速度的装置液压缸的计算长度（实线）和反馈输出的假设 计算长度（点线） 4.4 沿着滑线的工具的自动移动 实验结果分析的土壤搡过程显示，预计理论滑线的位置合周期的优化工具轨迹是可能的。可以在验室情况下的均匀材料中实现。在现实情况下，当材料不是均匀的或是不好定义的时，材料的滑线必须自动的被探测。滑线探测的自动化过程是基于观察的，当工具开始穿透稠密的材料时，作用在工具上的水平力的增加时可以观察的。这种情况也发生在当工具尖端从沿着滑线（这里的物质密度相当小）向没有动过的材料（滑线上下没有改变的材料）移动时。然而，推力增加的观察能被用于滑线的探测。这个过程在下面简要介 绍和实现。 切削工具的移动时水平、垂直合旋转运动的合成，并且的水平反作用力被测量和跟踪。首先，当水平力下降时，工具水平向前移动，同时伴随滑线系统从末端产生，一个特别的过程（以旋转工具为例）被实现。然后，当水平力增加并且超过定义值时。工具按照指定的位移值垂直运动，并且再进行水平移动（工具的旋转被增加）。如果这样，工具再一次垂直运动（按照所描述的位移）， 并且然后水平运动等等，这样工具的尖端自动沿着滑线移动（以步进方式）。 初步测试的结果在图 11和图 12中展示出来。作为一个简化的模型，工具沿着土壤陡坡倾斜 0.61rad的可能被调查。为了定义水平力的最大值和定义垂nts直位移，控制系统自动沿着陡坡跟随工具。横向力于横向位移和工具轨迹进行滑线侦察在图 11中展示。图 11的部分放大在图 12中展示，图 12展示了控制系统的作用。 图 11横向力与横向位移和刀具轨迹进行滑移线侦查 图 12 图 11 的部分放大图 nts5 总结 实验结果表明 ,提出的控制系统能够满足上述所有要求的描述 ,可以用来作为机床操作协助。自动重复实现运动，专用工具（包括高度优化路径）轨迹的实现和自动改进或实现路径的优化。工具轨迹也可以用建模来规定，使挖掘机成为遥控机器。现行的系统能作为真实机器控制系统的基础。 致谢 这个研究得 到了 KBN7T07C00412工程用于挖掘机这类重型机械的土壤搡过程的优化的赞助，并在基尔科技大学实现。 参考文献 1、 D. Szyba, W. Trampczynski, An experimental verification of kinematically admissible solutions for incipient stage of a cohesive soil shoving process, Eng. Trans. 42 （ 3）（ 1994） 243261. 2、 A. Jarzebowski, J. Maciejewski, D. Szyba, W. Trampczyn- ski, Experimental and theoretical analysis of a cohesive soil shoving process （ the optimisation of the process） , Proc. 6th European ISTVS Conference, Sept. 2830, 1994, Vienna, Austria. 3、 W. Szczepinski, Limit states and kinematics of granular media, PWN, 1974, in Polish. 4、 R. Izbicki, Z. Mroz, Limit states analysis in mechanics of soils and rocks, PWN, 1976, in Polish. 5、 W. Trampczynski, J. Maciejewski, On the kinematically admissible solutions for soiltool interaction description in the case of heavy machine working process, Proc. 5th ISTVS European Conference, Budapest, 1991. 6、 W. Trampczynski, A. Jarzebowski, On the kinematically admissible solution application for theoretical description of shoving processes, Eng. Trans. 39（ 1）（ 1991） 7596. 7、 Z. Mroz, J. Maciejewski, Post critical response of soils andshear band evolution, 3rd Workshop on localisation and bifurcation theory for soils and rocks, Aussois, France, September 1993. 8、 R.L. Michaowski, Strain localization and periodic fluctuations in granular flow processes from hoppers, Geotechnique 40 （ 3） （ 1990） 389403. 9、 W. Trampczynski, The analysis of kinematically admissible solutions for different shape wall movement, Theor. Appl. Mechanics 1 （ 1977） 15, in Polish. 10 、 A. Jarzebowski, D. Szyba, W. Trampczynski, Application of kinematic solutions for soil shoving process description, Gornictwo Odkrywkowe 36 (1994) 2. 11、 A. Jarzebowski, D. Szyba, W. Trampczynski, On some theory of plasticity solutions for the heavy machine earth- working process, Eng. Trans. 42 (4)(1994) 399416, 45%. 12、 A. Jarzebowski, J. Maciejewski, D. Szyba, W. Trampczyn- ski, The optimization of heavy machines tools filling process and tools shapes (modelling test results), in: E. Budny, A. McCrea, ntsK. Szymanski (Eds)., Sympozjum ISARC 1995, Automation and Robotics in Construction XII, IMBiGS, 1995, pp. 159166. 13、 L. Ponecki, J. Cendrowicz, A conception of the assisting system for the hydraulic excavator operator, Proc. of X Conf. Problems of Working Machines Development, Zakopane, 1997, in Polish. 14、 L. Ponecki, J. Cendrowicz, A digital control of a hydraulic excavator fixture cylinders, Proc. of IX Conference PNEUMA95, Kielce, 1995, in Polish. 15、 L. Ponecki, J. Cendrowicz, On the excavator working tool trajectory planning, Proc. of VIII Conf. Problems of Working Machines Development, Zakopane, 1995, in Polish. 16、 L. Ponecki, J. Cendrowicz, Digital control of excavator fixture, Proc. of XII ISARC Conference, Warszawa, 1995. 17、 L. Ponecki, J. Cendrowicz, A digital control for single-bucket hydraulic excavator, PSk Reports M-54, 1995, in Polish. 18、 J. Cendrowicz, W. Gierulski, L. Ponecki, A hydraulic excavator control system with a setting model, Proc. of IX Conf. Problems of Working Machines Development, Zakopane, 1996, in Polish. 19、 M. Olszewski, Industrial robots and manipulators, WNT nts 毕业设计（论文）外文翻译 题目 RPP 平面连杆机构的动态仿真 专 业 名 称 机械设计制造及其自动化 班 级 学 号 078105102 学 生 姓 名 熊礽智 指 导 教 师 朱保利 填 表 日 期 2011 年 03 月 8 日 nts .Automation in Construction 7 1998 401411A concept of digital control system to assist the operator ofhydraulic excavatorsL. Ponecki), W. Trampczynski, J. CendrowiczAbstractA 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 DrA andArD converters, where small hydraulic backhoe excavator K-111 fixtures were used. Experimental results shows that itfulfils 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 pathsand automatic improvement or optimization of realized paths. Tool trajectories can also be prescribed using the settingmodel, making excavator the machine of teleoperator class. Presented system can be used as a basis for real machine controlsystem. q 1998 Elsevier Science B.V. All rights reserved.Keywords: Digital control system; Hydraulic excavators; Tool trajectories1. IntroductionThe automation of heavy machines, including hy-draulic excavators, began in mid-1970s and waspossible due to invention of real time controllers andhydraulic elements with good dynamic properties.The first excavator equipped with several mechatron-ics systems, which was shown as a working model,was the excavator FUTURE prepared by Orensteinand Koppel for BAUMA83 Fairs. Since that time,machines equipped with systems automating the en-gine operation, pumps operation, machine fixtures,machine diagnostic, etc., are presented and offered.Such systems bring real help to the operator andclear economical profit. For example, LIEBHERRR902 excavator equipped with LITRONIC System.has for a trench digging the efficiency 40% higher)Corresponding author.and unit costs 30% lower, than similar machinewithout such automatic system. Although automation.in some case, optimization of several machine sys-tems develops quite fast, the main machine processthe shoving processhas no proper understandingand description until now. Its automation is quitelimited to systems repeating already performed.movements, laser levelling systems, etc. and sys-tems optimizing such processes are not developedyet. Quite new experimental results show clear ideafor energetically optimal tool trajectories in the caseof cohesive materials. The tool tip has to be guidedalong slip lines, which are generated from the tiptool during the previous stage of the shoving process.To realize such trajectories for practical purpose andreal machines, it is necessary to build a specialcontrol system for the tool motion, which enablesautomatic realisation of such trajectories as well asrealisation of other tasks that help the operator.0926-5805r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.PII S0926-5805 98 00045-4nts()L. Ponecki et al.rAutomation in Construction 7 1998 401411402Taking into account up-to-day heavy machines de-velopment, such system has to fit for digitally con-trolled electro-hydraulic drives. The concept of suchcontrol system, and verifying experimental results,are presented in this paper.2. The optimization of tool trajectorieswxIt was experimentally found 1,2 that in the caseof earth-moving process due to heavy machine tools,the cohesive material deforms to generate rigid zones.sliding along the slip lines well visible cracks alongwhich the material substantially changes its parame-ters the initial cohesion c decreases to the residual.value close to c s0 . In the case of the simple toolrpushing process perpendicular wall, the force-dis-placement relation shows that the horizontal forcegrows as the process advances, but in an unstablemanner. The moment of reduction of the force coin-cides with creation of a kinematical mechanism orig-inating from the tool end. Such mechanisms arecreated periodically and can be described theoreti-cally using kinematically admissible mechanisms ofwx .the theory of plasticity 48 Fig. 1 .A lot of effort was made to describe the soilcutting process within the theory of plasticity, wherethe problem of active pressure exerted by a rigidwall on a granular medium under plane strain condi-.tion can be assumed as a simplified model for soilshoving. In such case, the method of characteristicswx was used 3,9 and several theoretical solutions for.statics and kinematics were obtained under the as-sumption of rigid-perfectly plastic soil behavior. Al-though a number of boundary value problems weresolved in this manner, there exist several limitationsin obtaining complete solutions or even the kinemati-wxcally admissible ones 9 , particularly in the case ofmore advanced earth cutting processes.Another approach, based on kinematically admis-wxsible mechanisms, was proposed later 5 and appliedfor the description of more advanced earth shovingwxprocesses 6,7,1012 .Let us discuss the problem of plane strain rigidwall shoving presented schematically in Fig. 1. As-suming the material to be rigid-perfectly plastic andto obey the CoulombMohr yield criterion:11s ys q s ys sinyc coss01 . . .12 1222where: cmaterial cohesion, winternal frictionangle.The flow rule takes the form:E G s .ij sl 2 .ijEsij.where G s represents a plastic potential.ijIn the case when potential is described by the.yield criterion Eq. 1 , the associated flow rule isassumed, when another function is taken, the flowrule is non-associated.Using this approach and assuming a change ofwxmaterial parameters within the slip line 6,7 , theFig. 1. Typical deformation of cohesive soil in the case of the advanced shoving process realised by the horizontal tool motion theoretical.solution .nts()L. Ponecki et al.rAutomation in Construction 7 1998 401411 403different kinematically admissible solutions for arigid wall shoving process can be proposed and thesolution predicting minimum energy is searched.Kinematically admissible solution for rigid wallshaped as letter L is presented in Fig. 1. It showsmain effects observed experimentally. As the processadvances, the horizontal force grows in unstablemanner and the moment of reduction of the forcecoincides with creation of a kinematical mechanismoriginating from the tool end. Such mechanisms arewxcreated periodically. It was shown 2,6,7,10 thatsuch theoretical predictions describes quite well themain effects observed experimentally.Taking into account experimental observations andtheoretical solutions, it is possible to show experi-mentally that as soon as slip lines are created withincohesive material, the energetically most effectiveway of the tool filling is to follow previously createdwxslip line by the tip of the tool 12 . Experiments werewxperformed on a special laboratory stand 1,12 underplane strain conditions, using an artificial material,imitating a clay and its parameters. It consisted of:cement50%, bentonite20%, sand18% andwhite vaseline12%, and was characterized by thefollowing parameters: ws248 internal friction an-.3gle , gs18.4 kNrm . Application of white vase-line, as one of the components, resulted with obtain-ing a cohesive soil, which parameters were not influ-enced by air humidity and liquid flow. It also en-sured that those parameters were stable during allexperimental program.wxTypical experimental results 12 are shown inFigs. 2 and 4 for equal amount of dug out material.about 600 N in a following way. The L-shaped.Fig. 2. Experimental program for slope sample: a model of the.tool and slope; b initial stage of the processhorizontal move-.ment; c advanced stage of horizontal movement and various.trajectories; d the final stage of the process.Fig. 3. Values of specific work for different inclination of thewithdraw lines in the case of two-phase piece-wise trajectory.tool, inclined at an angle of 58 simulating the cess, LAs180 mm was first pushed into slope.to a certain position Fig. 2b . When the tool wasadvancing, the slip lines were created periodicallyfrom the tool tip to the material free boundary, at the.angle as458. In the next phase withdraw phase ,the tool tip was moved along three different straight.lines Fig. 2c , with simultaneous rotation of the tool.Fig. 2d to have it filled with the material. Thosestraight lines were inclined at angles as308,408and 508. The values as408 and 508 were close tothe inclination of slip lines created during the tool.horizontal pushing process Fig. 2c . It means that insuch case, the end of the tool was moved almostalong the slip line, where material cohesion c sub-stantially dropped as a result of material softeningduring the slip process.Specific energy of those processes for differentpreliminary horizontal displacements, chosen to en-sure similar amount of dug out material in every test.600 N , is shown in Fig. 3. It can be seen, that inthe case of as308, the specific unit energy is muchhigher than for as408 and as508 even over.100% . Hence, conducting the tool tip along the lineinclined at the angle similar to the angle of slip linesinclinations, the specific energy of the earth-fillingprocess can be significantly reduced.Experimental results shows that in the case of.cohesive soil earth-moving process: 1 material de-forms as rigid zones sliding along the slip lineswhere material substantially changes its parameters. .cohesion ; 2 moving the machine tools along pre-viously created slip lines, one can substantially save.energy used for earth-moving processes tool filling .nts()L. Ponecki et al.rAutomation in Construction 7 1998 401411404This observation can be the basis for the optimiza-tion of the filling process.3. The basic concept of the computer aided con-trol systemIt was shown before that analyzing the mechanicsof the soil deformation during the shoving process, itis possible to determine energetically optimal cuttingtool trajectories. Hence, the automatic tool move-ment along slip lines generated in cohesive materialhas to be a quite important option of proposedsystem. It should also enable precision tool guidance,automatic repetition of already realized movements.for example, teach-in , realization of some toolmovements impossible to realize manually, etc.Taking into account to-day experience with au-tomation of heavy machines, such system should beconstructed to assist machine operator, who stillplays a main decisive and control role. Hence, theproper separation of tasks, between the control sys-tem and the operator, is necessary.Such control system for excavators was built onlaboratory scale. Its basic assumptions can be statedwx .as follows 13 : 1 operation of the central controlsystem is based on cooperation of two digital sys-tems. The first one controls directly the motion ofthe machine fixture using the control system of thehydraulic cylinders position. The second one works.out control signals for the first one. 2 Under thestandard work conditions, action of the proportionalhydraulic valves of the fixture cylinders is controlledthrough the computer. The direct operator control is.possible only in case of emergency conditions. 3The feedback between the machine environment andcontrol system is realized through the operator. Heparticipates continuously in the process of the con-.trol of machine fixtures motion. 4 For realization ofthe tool motions which are impossible for manualcontrol, the operator has a possibility to coordinatedisplacement of separate cylinders by means of hard-.ware or software. 5 The operator has a possibilityto switch into automatic control of the fixture motionto realize a special tool trajectories. For example, itcan be energetically optimal tool trajectory wheretool tip moves along slip lines or specific trajectory.realized and stored previously. 6 The optimal cut-ting tool trajectories can also be realized as correc-tion of trajectories given by the operator. Such cor-rection is done mainly during the time parametriza-.tion of the tool path. 7 The trajectories given by theoperator can be corrected by the system to take intoaccount such limitations as geometrical ones, maxi-mal power of the pump, maximal output of thepump, maximal pump efficiency, etc.Presented concept is based on such cooperationbetween the operator and control system that thefixture movements are controlled by the operatorwhile the control system corrects him or, whenordered, can act automatically.4. Examples of the control system functioningThe control system based on described aboveideas was mounted on a special numerically con-trolled stand, equipped with PC computer havingCrA and ArC converters, where small hydraulicwxbackhoe excavator K-111 fixtures were used 1417 .The control system of the fixture motions utilizes thecontrol system of the cylinder positions. The fixturecylinder displacement is controlled by the propor-tional hydraulic valves fed by the variable outputmulti-piston pump.The control system for fixture cylinders is basedon three control systems, each to control differentcylinder displacement using PID or state controllerswx14 . It enables control of the fixture motions usingdifferent methods of the tool trajectory planning,measuring of acting forces and displacements anddetermining other magnitudes related to the fixturemovements. Experimental data acquisition is alsopossible.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. wxrealized as usually in two steps 15 . In the firstone, the trajectory shape is planned and determined.In the second one, the trajectory curve is parametrizedin time in a determined manner, what defines thetrajectory within the generalized coordinate space.On this basis, the time runs of the generalized coor-dinates describing the configuration space of themachine are determined. In the case of an excavator,lengths of hydraulic cylinders are those coordinatesnts()L. Ponecki et al.rAutomation in Construction 7 1998 401411 405and then they are used as signals for control systemto reproduce planned trajectory. Some system abili-ties are described below.4.1. The tool moement along prescribed lineThe control system build for experimental standwx1517 enables, among others, programming thework motion in the excavator work space, or in itsconfiguration space, using point to point technique.In this method, the coordinates of the initial and finalpoints, and sufficient number of the characteristicnodal points, are defined. Values describing thispoints are then introduced to the system, whereremaining points of the trajectory are calculated us-ing interpolation methods. Linear or the third degreepolynomial interpolation is used. The trajectoryparametrization in time can be realized through:determination of the total trajectory run-time andits division into individual segments of the path.System calculates the velocities of cylinders,determination of the run-time between followingnodal points, taking into account some limitations.or conditions for optimization .In the case of standard excavator construction, itis quite difficult to precisely realize trajectories,where simultaneous movement of two or three cylin-ders is necessary.4.2. The tool moement using the setting modelAnother method of controlling the fixture motionis to control using the setting model. It is somehowsimilar to the manipulator unit in robotics. The con-wxtrol is carried out by means of the phantom 18 ,understood as a kinematic duplicate or the model ofthe machine kinematics, equipped with systems mea-suring the motion parameters. The excavator con-trolled in this manner becomes the machine of tele-wxoperator class 19 .The setting model is the model of K-111 excava-tor fixture, situated on the plate, made in scale of1:10. Three potentiometers are located on the rota-tion axes of the model element. Signals from thesepotentiometers allow us to determine the configura-tion of the fixture. Mechanical end stops are pro-vided to the model, to limit the rotation angles ofindividual fixture elements to the values obtained inthe K-111 excavator fixture. The special switch acti-vates the system.The setting model is used only for planning of thetool path and during its movement the tool trajectoryis registered using the point method. The trajectorypoints are registered when:the sum of the cylinder length increments, com-paring with former position, is higher than as-sumed,time of data registration is later compared withformer registration time.Points of the path are registered at constant timeintervals, excluding the fixture stoppage. The pathnodal points are defined by the corresponding fixturecylinder lengths. Other path points are calculated bycomputer applying the linear interpolation in theconfiguration space. Deviation of the path calculatedin this way from that marked by the setting modelcould be disregarded at the nodal point intervalsco
- 温馨提示:
1: 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
人人文库网所有资源均是用户自行上传分享，仅供网友学习交流，未经上传用户书面授权，请勿作他用。
川公网安备: 51019002004831号