关 键 词：

机械毕业设计全套

资源描述：

JX01-189@滚轮式脚踏式液压升降平台车设计,机械毕业设计全套

内容简介：

毕业设计（论文）任务书 I、毕业设计 (论文 )题目： 滚轮式脚踏式液压升降平台车设计 II、毕 业设计 (论文 )使用的原始资料 (数据 )及设计技术要求： 已知：额定载重量 500kg 自重 130kg 1050mm 升降台最大高度 950mm 升降台最小高度 435mm 左右 平台尺寸 1010 520mm 通过脚踏式液压泵提起货物，要求后轮固定，设置过载安 全阀，确保操作者安全。刹车安全可靠。可在升程内任意位置停止升降。 要求： 1、绘制总装 图纸及零件图。 2、运动分析 3、总体强度受力分析计算。 4、要求成本核算 III、毕 业设计 (论文 )工作内容及完成时间： 1、开题报告 2 周 2、总体设计 2 周 3、常规设计 9 周 4、 成本核算 1 周 5、编写毕业设计说明书 2 周 6、外文资料翻译 1 周 nts 、主 要参考资料： 1、 沈纫秋主编 工程材料与制造工艺教程 北京： 航空工业出版社 1991.5 2、 机械设计手册 新版 第 4 卷 液压、气动与液力传动与控制 北京：机械工业出版社 3、左键民 .液压与气压传动 .北京：机械工业出版社， 2008 4、濮良贵等 .机械设计 .北京：高等教育出版社， 2006 5、徐灏 .机械设计手册 .北京：机械工业出版社， 1995 6、李壮云 .中国机械设计大典 5.南昌 :江西科学技术出版社， 2002 7、 T. Morita,Modeling and control of power shovel, SICE 22 1 1986 69 75. 航空 工程 系 机械设计制造及其自动化 专业类 0681053 班 学生（签名）： 日期： 自 2010 年 3 月 1 日至 2010 年 7 月 2 日 指导教师（签名）： 助理指导教师 (并指出所负责的部分 )： 系（室）主任（签名）： nts 毕业设计（论文）外文翻译 题目 液压挖掘机的半自动控制系统 专 业 名 称 机械设计制造及其自动化 班 级 学 号 068105334 学 生 姓 名 殷艳岗 指 导 教 师 袁 宁 填 表 日 期 2010 年 3 月 7 日 nts液压挖掘机的半自动控制系统 Hirokazu Araya ,Masayuki Kagoshima 日本机械工程研究实验室 Kobe Steel, Ltd., Nishi-ku, Kobe Hyogo 651 2271, 2000年 7月 27日 摘要 开发出了一种应用于液压挖掘机的半自动控制系统。采用该系统，即使是不熟练的操作者也能容易和精确地操控液压挖掘机。构造出了具有控制器的液压挖掘机的精确数学控制模型，同时通过模拟实验研发出了其控制算法，并将其应用在液压挖掘机上，由此可以估算出它的工作效率。依照此法，可通过 正反馈及前馈控制、非线性补偿、状态反馈和增益调度等各种手段获得较高的控制精度和稳定性能。自然杂志 2001 版权所有 关键词：施工机械；液压挖掘机；前馈；状态反馈；操作 1引言 液压挖掘机，被称为大型铰接式机器人，是一种施工机械。采用这种机器进行挖掘和装载操作，要求司机要具备高水平的操作技能，即便是熟练的司机也会产生相当大的疲劳。另一方面，随着操作者年龄增大，熟练司机的数量因而也将会减少。开发出一种让任何人都能容易操控的液压挖掘机就非常必要了 1-5。 液压挖掘机之所以要求较高的操作技能，其理由如下。 1.液压挖掘机的操作，至少有两个操作手柄必须同时操作并且要协调好。 2.操作手柄的动作方向与其所控的臂杆组件的运动方向不同。 例如，液压挖掘机的反铲水平动作，必须同时操控三个操作手柄（动臂，斗柄，铲斗）使铲斗的顶部沿着水平面（图 1）运动。在这种情况下，操作手柄的操作表明了执行元件的动作方向，但是这种方向与工作方向不同。 如果司机只要操控一个操作杆，而其它自由杆臂自动的随动动作，操作就变得非常简单。这就是所谓的半自动控制系统。 开发这种半自动控制系统，必须解决以下两个技术难题。 nts1. 自动控制系统必须采用普通的 控制阀。 2. 液压挖掘机必须补偿其动态特性以提高其控制精度。 现已经研发一种控制算法系统来解决这些技术问题，通过在实际的液压挖掘机上试验证实了该控制算法的作用。而且我们已采用这种控制算法，设计出了液压挖掘机的半自动控制系统。具体阐述如下。 2液压挖掘机的模型 为了研 究液压挖掘机的控制算法 ,必须分析液压挖掘机的数学模型。液压挖掘机的动臂、斗柄、铲斗都是由液压力驱动，其模型如图 2所示。模型的具体描述如下。 nts 2.1 动态模型 6 假定每一臂杆组件都是刚体，由拉格朗日运动方程可得以下表达式： 其中 g 是重力加速度； i 铰接点角度； i 是提供的扭矩； li 组件的长度； lgi转轴中心到重心之距； mi 组件的质量； Ii 是重心处的转动惯量 (下标 i=1-3;依次表示动臂，斗柄，铲斗 )。 2.2 挖掘机模型 每一臂杆组件都是由液压缸驱动，液压缸的流量是滑阀控制的，如图 3所示。可作如下假设： 1.液压阀的开度与阀芯的位移成比例。 nts2.系统无液压油泄漏。 3.液压油流经液压管道时无压力损失。 4.液压缸的顶部与杆的两侧同样都是有效区域。 在这个问题上，对于每一臂杆组件，从液压缸的压力流量特性可得出以下方程： 当 时； 其中， Ai是液压缸的有效横截面积 ;hi 是液压缸的长度 ;Xi是滑芯的位置； Psi是供给压力 ;P1i是液压缸的顶边压力； P2i是液压缸的杆边压力； Vi 是在液压缸和管道的油量；Bi是滑阀的宽度； 是油的密度； K是油分子的黏度； c是流量系数。 2.3 连杆关系 在图 1所示模型中，液压缸长度改变率与杆臂的旋转角 速度的关系如下： (1)动臂 nts (2)斗柄 (3)铲斗 当 时， 2.4 扭矩关系 从 2.3节的连杆关系可知，考虑 到液压缸的摩擦力，提供的扭矩 i 如下 nts 其中， Cci是粘滞摩擦系数 ;Fi是液压缸的动摩擦力。 2.5 滑阀的反应特性 滑阀动作对液压挖掘机的控制特性产生会很大的影响。因而，假定滑阀相对参考输入有以下的一阶延迟。 其中， 是滑芯位移的参考输入； 是时间常数。 3 角度控制系统 如图 4所示， 角基本上由随动参考输入角 通过位置反馈来控制。为了获得更精确的控制，非线性补偿和状态反馈均加入位置反馈中。以下详细讨论其控制算法。 3.1 非线性补偿 在普通的自动控制系统中，常使用如伺服阀这一类新的控制装置。在半自动控制系统中，为了实现自控与手控的协调，必须使用手动的主控阀。这一类阀中，阀芯的位移与阀的nts开度是非线性的关系。因此，自动控制操作中，利用这种关系，阀芯位移可由所要求的阀的开度反推出来。同时，非线性是可以补偿的（图 5）。 3.2 状态反馈 建立在第 2节所讨论的模型的基础上，若动臂角度控制动态特性以一定的标准位置逼近而线性化（滑芯位移 X 10，液压缸压力差 P 110，动臂夹角 10 ），则该闭环传递函数为 其中， Kp是位置反馈增益系数； nts 由于系统有较小的系数 a1,所以反应是不稳定的。例如，大型液压挖掘机 SK-16中。 X10是 0，给出的系数 a0=2.7 10 ,a1=6.0 10 ,a2=1.2 10 .加上加速度反馈放大系数Ka，因而闭环（图 4 的上环）的传递函数就是 加入这个因素 ,系数 S 就变大，系统趋于稳定。可见，利用加速度反馈来提高反应特性效果明显。 但是，一般很难精确的测出加速度。为了避免这个问题，改用液压缸力反馈取代加速度反馈（图 4 的下环）。于是，液压缸力由测出的缸内的压力计算而滤掉其低频部分 7， 8。这就是所谓的压力反馈。 4 伺服控制系统 当一联轴器是手动操控，而其它的联轴器是因此而被随动作控制时，这必须使用伺服控制系统。例如，如图 6所示，在反铲水平动作控制中，动臂的控制是通过保持斗柄底部 Z（由 1 与 2 计算所得）与 Zr 的高度。为了获得更精确的控制引入以下控制系统。 4.1 前馈控制 由图 1计算 Z，可以得到 将方程（ 8）两边对时间求导，得到以下关系式， nts右边第一个式子看作是表达式（反馈部分）将 替换成 1，右边第二个式子是表达式（前馈部分）计算当 2 手动地改变时， 1 的改变量。 实际上，用不同的 2 值可确定 1。通过调整改变前馈增益 Kff，可实现最佳的前馈率。 采用测量斗柄操作手柄的位置（如角度）取代测斗柄的角速度，因为驱动斗柄的角速度与操作手柄的位置近似成比例。 4.2 根据位置自适应增益调度 类似液压挖掘机的铰接式机器人，其动态特性对位置非常敏感。因此，要在所有位置以恒定的增益稳定的控制机器是困难的。为了解决这个难题，根据位置的自适应增益调度并入反馈环中（图 6）。如图 7所示，自适应放大系数（ KZ 或 K ）作为函数的两个变量， 2和 Z 、 2表示斗柄的伸长量， Z是表示铲斗的高度。 5 模拟 实验结论 反铲水平动作控制的模拟实验是将本文第 4 节所描述的控制算法用在本文第 2节所讨论的液压挖掘机的模型上。（在 SK-16 大型液压挖掘机进行模拟实验。）图 8 表示其中一组结果。控制系统启动 5秒以后，逐步加载扰动。图 9表示使用前馈控制能减少控制错误的产生 . nts nts nts6 半自动控制系统 建立在模拟实验的基础上，半自动控制系统已制造出来，应用在 SK-16型挖掘机上试验。通过现场试验可验证其操作性。这一节将讨论该控制系统的结构与功能。 6.1 结构 图 10的例子中，控制系统由控制器、传感器、人机接 口和液压系统组成。 控制器是采用 16 位的微处理器，能接收来自动臂、斗柄、铲斗传感器的角度输入信号，控制每一操作手柄的位置，选择相应的控制模式和计算其实际改变量，将来自放大器的信号以电信号形式输出结果。液压控制系统控制产生的液压力与电磁比例阀的电信号成比例，主控阀的滑芯的位置控制流入液压缸液压油的流量。 为获得高速度、高精度控制，在控制器上采用数字处 理芯片，传感器上使用高分辨率的磁编码器。除此之外，在每一液压缸上安装压力传感器以便获得压力反馈信号。 以上处理后的数据都存在存储器上，可以从通信端口中读出。 6.2 控制功能 控制系统有三种控制模式，能根据操作杆 和选择开关自动切换。其具体功能如下。 nts（ 1）反铲水平动作模式：用水平反铲切换开关，在手控斗柄推动操作中，系统自动的控制斗柄以及保持斗柄底部的水平运动。在这种情况下，当斗柄操作杆开始操控时，其参考位置是从地面到斗柄底部的高度。对动臂操作杆的手控操作能暂时中断自动控制，因为手控操作的优先级高于自动控制 。 （ 2）铲斗水平举升模式：用铲斗水平举升切换开关，在手控动臂举升操作中，系统自动控制铲斗。保持铲斗角度等于其刚开始举升时角度以阻止原材料从铲斗中泄漏。 （ 3）手控操作模式：当既没有选择反铲水平动作模式，也没有选择铲斗水平举升模式时，动臂，斗柄，铲斗都只能通过手动操作。 系统主要采用 C语言编程来实现这些功能，以构建稳定模组提高系统的运行稳定性。 7 现场试验结果与分析 通过对系统进行现场试验，证实该系统能准确工作。核实本文第 3、 4节所阐述的控制算法的作用，如下所述。 7.1 单个组件的自动控制测试 对于动臂 、斗柄、铲斗每一组件，以 5 的梯度从最初始值开始改变其参考角度值，测量其反应，从而确定第 3节所描述的控制算法的作用。 7.1.1 非线性补偿的作用 图 11 表明动臂下降时的测试结果。因为电液系统存在不灵敏区，当只有简单的位置反馈而无补偿时（图 11 中的关）稳态错误仍然存在。加入非线性补偿后（图 11 中的开）能减少这种错误的产生。 7.1.2 状态反馈控制的作用 nts对于斗柄和铲斗，只需位置反馈就可获得稳定响应，但是增加加速度或压力反馈能提高响应速度。以动臂为例，仅只有位置反馈时，响应趋向不稳定。加入加速度或压力反馈后，响应的稳定性得到改进。例如，图 12 表示动臂下降时，采用压力反馈补偿时的测试结果。 7.2 反铲水平控制测试 在不同的控制和操作位置下进行控制测验，观察其控制特性，同时确定最优控制参数（如图 6所示的控制放大系数）。 7.2.1 前馈控制作用 在只有位置反馈的情况下，增大放大系数 Kp，减少 Z 错误，引起系统不稳定，导致系统延时，例如图 13 所示的 “ 关 ” ，也就是 Kp 不能减小。采用第 4.1节所描述的斗柄臂杆前馈控制能减少错误而不致于增大 Kp。如图示的 “ 开 ” 。 7.2.2 位置的补偿作用 当反铲处在上升位置或者反铲动作完成时，反铲水平动作趋 于不稳定。不稳定振荡可根据其位置改变放大系数 Kp来消除，如第 4.2节所讨论的。图 14 表示其作用，表明反铲在离地大约 2米时水平动作结果。与不装补偿装置的情况相比较，图中的关表示不装时，开的情况具有补偿提供稳定响应。 nts 7.2.3 控制间隔的作用 关于控制操作的控制间隔的作用，研究结果如下： 1.当控制间隔设置在超过 100ms时，不稳定振荡因运动的惯性随位置而加剧。 2.当控制间隔低于 50ms时，其控制操作不能作如此大提高。 因此，考虑到计算精度，控制系统选定控制间隔为 50ms。 7.2.4 受载作用 利用控制系统，使液压挖掘机执行实际 挖掘动作，以研究其受载时的影响。在控制精度方面没 有发现与不加载荷时有很大的不同。 8 结论 本文表明状态反馈与前馈控制组合，使精确控制液压挖掘机成为可能。同时也证实了非线性补偿能使普通控制阀应用在自动控制系统中。因而应用这些控制技术，允许即使是不熟练的司机也能容易和精确地操控液压挖掘机。 将这些控制技术应用在其它结构的机器上，如履带式起重机，能使普通结构的机器改进成为可让任何人容易操控的机器。 参考文献 1 J. Chiba, T. Takeda, Automatic control in construction machines, Journal of SICE 21 8 1982 40 46. nts2 H. Nakamura, A. Matsuzaki, Automation in construction machinery, Hitachi Review 57 3 1975 55 62. 3 T. Nakano et al., Development of large hydraulic excavator,. Mitsubishi Heavy Industries Technical Review 22 2 1985 42 51. 4 T. Morita, Y. Sakawa, Modeling and control of power shovel, Transactions of SICE 22 1 1986 69 75. 5 H. Araya et al., Automatic control system for hydraulic excavator, R&D Kobe Steel Engineering Reports 37 2 1987 74 78. 6 P.K. Vaha, M.J. Skibniewski, Dynamic model of excavator, Journal of Aerospace Engineering 6 2 1990 April. 7 H. Hanafusa, Design of electro-hydraulic servo system for articulated robot, Journal of the Japan Hydraulics and Pneumatics Society 13 7 1982 1 8. 8 H.B. Kuntze et al., On the model-based control of a hydraulic large range robot, IFAC Robot Control 1991 207 212. nts.Automation in Construction 10 2001 477486rlocaterautconSemi-automatic control system for hydraulic shovelHirokazu Araya), Masayuki KagoshimaMechanical Engineering Research Laboratory, Kobe Steel, Ltd., Nishi-ku, Kobe Hyogo 651 2271, JapanAccepted 27 June 2000AbstractA semi-automatic control system for a hydraulic shovel has been developed. Using this system, unskilled operators canoperate a hydraulic shovel easily and accurately. A mathematical control model of a hydraulic shovel with a controller wasconstructed and a control algorithm was developed by simulation. This algorithm was applied to a hydraulic shovel and itseffectiveness was evaluated. High control accuracy and high-stability performance were achieved by feedback plusfeedforward control, nonlinear compensation, state feedback and gain scheduling according to the attitude. q2001 ElsevierScience B.V. All rights reserved.Keywords: Construction machinery; Hydraulic shovel; Feedforward; State feedback; Operation1. IntroductionA hydraulic shovel is a construction machinerythat can be regarded as a large articulated robot.Digging and loading operations using this machinerequire a high level of skill, and cause considerablefatigue even in skilled operators. On the other hand,operators grow older, and the number of skilledoperators has thus decreased. The situation calls forhydraulic shovels, which can be operated easily bywxany person 15 .The reasons why hydraulic shovel requires a highlevel of skill are as follows.1. More than two levers must be operated simulta-neously and adjusted well in such operations.)Corresponding author.E-mail address: arayahrknedo.go.jp H. Araya .2. The direction of lever operations is differentfrom that of a shovels attachment movement.For example, in level crowding by a hydraulicshovel, we must operate three levers arm, boom,.bucket simultaneously to move the top of a bucket.along a level surface Fig. 1 . In this case, the leveroperation indicates the direction of the actuator, butthis direction differs from the working direction.If an operator use only one lever and other free-doms are operated automatically, the operation be-comes very easily. We call this system a semi-auto-matic control system.When we develop this semi-automatic controlsystem, these two technical problems must be solved.1. We must use ordinary control valves for auto-matic control.2. We must compensate dynamic characteristicsof a hydraulic shovel to improve the precisionof control.0926-5805r01r$ - see front matter q2001 Elsevier Science B.V. All rights reserved.PII: S0926-5805 00 00083-2nts()H. Araya, M. KagoshimarAutomation in Construction 10 2001 477486478Fig. 1. Level crowding of an excavator and frame model of anexcavator.We have developed a control algorithm to solvethese technical problems and confirm the effect ofthis control algorithm by experiments with actualhydraulic shovels. Using this control algorithm, wehave completed a semi-automatic control system forhydraulic shovels. We then report these items.2. Hydraulic shovel modelTo study control algorithms, we have to analyzenumerical models of a hydraulic shovel. The hy-draulic shovel, whose boom, arm, and bucket jointsare hydraulically driven, is modeled as shown in Fig.2. The details of the model are described in thefollowing.2.1. Dynamic model 6Supposing that each attachment is a solid body,from Lagranges equations of motion, the followingexpressions are obtained:22J u qJ cos u yuuqJ cos u yuuqJ sin u yuuqJ sin u yuuyK sinu st. . . .11 l 12 1 2 2 13 1 3 3 12 1 2 2 13 1 3 3 1 1 122 J cos u yuuqJ u qJ cos u yuuyJ sin u yuuqJ sin u yuuyK sinu st. . . .12 1212223 23312 12123 233 2 22J cos u yuuqJ cos u yuuqJ u yJ sin u yuuqJ sin u yuuyK sinu st. . . .13 1 3 1 23 2 3 2 33 3 13 1 3 1 23 2 3 3 3 3 31.2.2where, J s m 1 q m q m 1 q I ; J s11 1 g123 112m 11 qm 11 ; J sm 11 ; J sm 12q21g 231g 313 31g 322 2g 2m 12qI ; J sm 11 ; J sm 12qI ; K s32 2 23 32g 333 3g 33 1.m 1 qm 1 qm 1 g; K s m 1 qm 1 g;1 g1213 2 2g 233K sm 1 g; and gsgravitational acceleration.33g 3u is the joint angle, t is the supply torque, 1 isiithe attachment length, 1 is the distance betweengithe fulcrum and the center of gravity, m is the massiof the attachment, I is the moment of inertia aroundithe center of gravity subscripts is13, mean boom,.arm, and bucket, respectively .2.2. Hydraulic modelEach joint is driven by a hydraulic cylinder whoseflow is controlled by a spool valve, as shown in Fig.3. We can assume the following:1. The open area of a valve is proportional to thespool displacement.2. There is no oil leak.3. No pressure drop occurs when oil flows throughpiping.nts()H. Araya, M. KagoshimarAutomation in Construction 10 2001 477486 479Fig. 2. Model of hydraulic shovel.4. The effective sectional area of the cylinder isthe same on both the head and the rod sides.In this problem, for each joint, we have thefollowing equation from the pressure flow character-istics of the cylinder:ViAhsKXPysgn X P y P 2( . .ii 0 ii si i 1i 1iKwhen,K scB 2rg P sP yP0 ii 1i 1i 2 iwhere, A seffective cross-sectional area of cylin-ider; h scylinder length; X sspool displacement;P ssupply pressure; P scylinder head-side pres-si 1isure; P scylinder rod-side pressure; V soil vol-2 iiume in the cylinder and piping; B sspool width;igsoil density; Ksbulk modulus of oil; and csflow coefficient.2.3. Link relationsIn the model shown in Fig. 1, the relation be-tween the cylinder length change rate and the attach-ment rotational angular velocity is given as.follows: 1 boomf u.11h1su1OA OC sin u qb.11 1 1sy ,22(OA qOC q2OA OC cos u qb.11 1111.2 arm.f u ,u212h2su yu21.OAOCsin u yu qb qa2222 2 1 2 2sy ,22( .OAqOCq2OAOCcos u yu qb qa22 22 2222 2 1 2 2.3 bucketwhen ODsOBsBCsCD33 33 33 33YhABCsin u yu qg ya qu.3333232f u ,u ssy . 3.32322 Yu yu (AB qBC q2ABBCcos u yu qg ya qu.3233 33 3333 3 2 3 3 2nts()H. Araya, M. KagoshimarAutomation in Construction 10 2001 477486480Fig. 3. Model of hydraulic cylinder and valve.2.4. Torque relationsFrom the link relations of Section 2.3, the supplytorque t is given as follows, taking cylinder frictioniinto consideration:t syf u P1 A qf u ,u P1 A. .111 121222qf u ,u P1 A y Cfuu. .323 33 c11 1 1qsgn u Ffu 4. ./1111t syf u ,u P1 A y Cfu ,uuyu. . /221222c22 1 2 2 1qsgn u yu Ffu ,u.5/212212t syf u ,u P1 A y Cfu ,uuyu. . /332333c33 2 3 3 2qsgn u yu Ffu ,u .5/323323Where, C is the viscous friction coefficient andciF is kinetic frictional force of a cylinder.i2.5. Response characteristics of the spoolSpool action has a great effect on control charac-teristics. Thus, we are assuming that the spool hasthe following first-order lag against the referenceinput.1XX s X .5.iiTSq1spiWhere, XXis the reference input of spool dis-iplacement and T is a time constant.spi3. Angle control systemAs shown in Fig. 4, the angle u is basicallycontrolled to follow the reference angle u by posi-gtion feedback. In order to obtain more accuratecontrol, nonlinear compensation and state feedbackare added to the position feedback. We will discussdetails of these algorithms as follows.3.1. Nonlinear compensationIn the ordinary automatic control systems, newcontrol devices such as servo valves are used. In oursemi-automatic system, in order to realize the coexis-tence of manual and automatic operations, we mustuse the main control valves, which are used inmanual operation. In these valves, the relation be-tween spool displacement and open area is nonlinear.Then, in automatic operation, using this relation, thespool displacement is inversely calculated from therequired open area, and the nonlinearity is compen-.sated Fig. 5 .Fig. 4. Block diagram of control system u .nts()H. Araya, M. KagoshimarAutomation in Construction 10 2001 477486 481Fig. 5. Nonlinear compensation.3.2. State feedbackBased on the model discussed in Section 2, if thedynamic characteristics for boom angle control arelinearized in the vicinity of a certain standard condi-tion spool displacement X , cylinder differential10.pressure P , and boom angle u , the closed-loop110 10transfer function can be expressed byKpu s ug 6.1132asqasqasqK210pwhere, K is position feedback gain; andpf u ACfu. .110 1 c11 10a sq02 APyP.KPyP(1 s111001 s1110XJqJ cosuXqJ cos uXquXDC44.10 11 12 2 13 2 3a s12 Af u P yP. .11 10 s1 110Cfu V.c11 10 1qAKK P yP(101s1110VJqJ cosuXqJ cos uXquXDC44.111 12 2 13 2 3a s .2Af u KK P yP. (1 1 10 01 s1 110This system has a comparatively small coefficienta , so the response is oscillatory. For instance, if in1our large SK-16 hydraulic shovel, X is 0, the10coefficients are given as a s2.7=10y2, a s6.001=10y6, a s1.2=10y3. Addingthe acceleration2feedback of gain K , to this the upper loop in Fig.a.4 , the closed loop transfer function is given asKpu s u .7.1 r132asq a qKsqasqK.21a 0 pAdding this factor, the coefficient of s2becomeslarger, thus, the system becomes stable. In this way,acceleration feedback is effective in improving theresponse characteristics.However, it is generally difficult to detect acceler-ation accurately. To overcome this difficulty, cylin-der force feedback was applied instead of accelera-.tion feedback the lower loop in Fig. 4 . In this case,cylinder force is calculated from detected cylinderpressure and filtered in its lower-frequency portionwx7,8 . This is called pressure feedback.4. Servo control systemWhen one joint is manually operated and anotherjoint is controlled automatically to follow the manualoperation, a servo control system must be required.For example, as shown in Fig. 6, in the level crowd-ing control, the boom is controlled to keep the arm.end height Z calculated from u and u to refer-12ence Zr. In order to obtain more accurate control, thefollowing control actions are introduced.nts()H. Araya, M. KagoshimarAutomation in Construction 10 2001 477486482.Fig. 6. Block diagram of control system Z .4.1. Feedforward controlCalculating Z from Fig. 1, we obtainZs1 cosu q1 cosu .8.1122.Differentiating both sides of Eq. 8 with respectto time, we have the following relation,Z 1 sinu22u sy y u .9.121 sinu 1 sinu11 11The first term of the right-hand side can be taken.as the expression feedback portion to convert Z tou , and the second term of the right-hand side is the1expression feedforward portion to calculate howmuch u should be changed when u is changed12manually.Actually, u is determined using the difference2value of Du . To optimize the feedforward rate,2feedforward gain K is tunned.ffThere may be a method to detect and use the arm.operating-lever condition i.e. angle instead of armangular velocity, since the arm is driven at an angu-lar velocity nearly proportional to this lever condi-tion.4.2. Adaptie gain scheduling according to the atti-tudeIn articulated machines like hydraulic shovels,dynamic characteristics are greatly susceptible to theattitude. Therefore, it is difficult to control the ma-chine stably at all attitudes with constant gain. Tosolve this problem, the adaptive gain schedulingaccording to the attitude is multiplied in the feedback.loop Fig. 6 . As shown in Fig. 7, the adaptive gain.KZ or Ku is characterized as a function of twovariables, uXand Z. uXmeans how the arm is22extended, and Z means the height of the bucket.5. Simulation resultsThe level crowding control was simulated byapplying the control algorithm described in Section 4to the hydraulic shovel model discussed in Section 2.In the simulation, our large SK-16 hydraulic shovel.was employed. Fig. 8 shows one of the results. Fiveseconds after the control started, load disturbancents()H. Araya, M. KagoshimarAutomation in Construction 10 2001 477486 483Fig. 7. Gain scheduling according to the attitude.was applied stepwise. Fig. 9 shows the use of feed-forward control can reduce control error.6. Semi-automatic control systemBased on the simulation, a semi-automatic controlsystem was manufactured for trial, and applied to theSK-16 shovel. Performance was then ascertained byfield tests. This section will discuss the configurationand functions of the control system.6.1. ConfigurationAs illustrated in Fig. 10, the control system con-sists of a controller, sensors, manmachine interface,and hydraulic control system.The controller is based on a 16-bit microcomputerwhich receives angle input signals of the boom, arm,and bucket from the sensor; determines the conditionof each control lever; selects control modes andcalculates actuating variables; and outputs the resultsfrom the amplifier as electrical signals. The hy-Fig. 8. Simulation result of level crowding.draulic control system generates hydraulic pressureproportional to the electrical signals from the electro-magnetic proportional-reducing valve, positions thespool of the main control valve, and controls theflow rate to the hydraulic cylinder.In order to realize high-speed, high-accuracy con-trol, a numeric data processor is employed for theFig. 9. Effect of feedforward control on control error of Z.nts()H. Araya, M. KagoshimarAutomation in Construction 10 2001 477486484Fig. 10. Schema of control system.controller, and a high-resolution magnetic encoder isused for the sensor. In addition to these, a pressuretransducer is installed in each cylinder to achievepressure feedback.The measured data are stored up to the memory,and can be taken out from the communication port.6.2. Control functionsThis control system has three control modes,which are automatically switched in accordance withlever operation and selector switches. These func-tions are the following.1 Level crowding mode: during the manual armpushing operation with the level crowding switch,the system automatically controls the boom and holdsthe arm end movement level. In this case, the refer-ence position is the height of the arm end from theground when the arm lever began to be operated.Operation of the boom lever can interrupt automaticcontrol temporarily, because priority is given to man-ual operation.2 Horizontal bucket lifting mode: during themanual boom raising operation with the horizontalbucket lifting switch, the system automatically con-trols the bucket. Keeping the bucket angle equal tothat at the beginning of operation prevents materialspillage from the bucket.3 Manual operation mode: when neither thelevel crowding switch nor the horizontal bucket lift-ing switch are selected, the boom, arm, and bucketare controlled by manual operation only.The program realizing these functions is primarilywritten in C language, and has well-structured mod-ule to improve maintainability.7. Results and analysis of field testWe put the field test with the system. We con-firmed that the system worked correctly and theeffects of the control algorithm described in Chaps. 3and 4 were ascertained as follows.7.1. Automatic control tests of indiidual attach-mentsFor each attachment of the boom, arm, and bucket,the reference angle was changed 58 stepwise fromthe initial value, and the responses were measured;thus, the effects of the control algorithm described inChap. 3 were ascertained.nts()H. Araya, M. KagoshimarAutomation in Construction 10 2001 477486 485Fig. 11. Effect of nonlinear compensation on boom angle.7.1.1. Effect of nonlinear compensationFig. 11 shows the test results of boom lowering.Because dead zones exist in the electro-hydraulicsystems, steady-state error remains when simple po-sition feedback without compensation is applied OFF.in the figure . Addition of nonlinear compensation.ON in the figure can reduce this error.7.1.2. Effect of state feedback controlFor the arm and bucket, stable response can beobtained by position feedback only, but adding ac-celeration or pressure feedback can improve fast-re-sponse capability. As regards the boom, with onlythe position feedback, the response becomes oscilla-tory. Adding acceleration or pressure feedback madethe response stable without impairing fast-responsecapability. As an example, Fig. 12 shows the testresults when pressure feedback compensation wasapplied during boom lowering.7.2. Leel crowding control testControl tests were conducted under various con-trol and operating conditions to observe the controlFig. 12. Effect of pressure feedback control on boom angle.Fig. 13. Effect of feedforward control on control error of Z.characteristics, and at the same time to determine theoptimal control parameters such as the control gains.shown in Fig. 6 .7.2.1. Effects of feedforward controlIn the case of position feedback only, increasinggain K to decrease error DZ causes oscillation duepto the time delay in the system, as shown by AOFFBin Fig. 13. That is, K cannot be increased. Apply-ping the feedforward of the arm lever value describedin Section 4.1 can decrease error without increasingK as shown by AONB in the figure.p7.2.2. Effects of compensation in attitudeLevel crowding is apt to become oscillatory at theraised position or when crowding is almost com-pleted. This oscillation can be prevented by changinggain K according to the attitude, as