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系统辨识与实时控制斗轮式装载机的液压系统土方设备摘要土方设备行业的迅速整装待发，准备在近期实现数字化控制技术在其产品的快速部署的效率，性能，安全性和操作舒适巨大收益。世界上主要有两种类型的移动设备操作的最多:挖掘机和轮式装载机。现在挖掘机已受到业界的关注。轮式装载机产品在本文研究的是另一种高容量多功能机在配置频谱的另一端的例子。一个先进的电液开放中心的非压力补偿阀控制系统的状态进行了研究，以评估通过实施数字化速度伺服控制的潜在收益。控制目标是满足运营商自觉响应要求，满足运营商认为光滑度要求，创建一个子系统，可以接受命令弗勒曼自治区高层次的规划控制。数字化速度的闭环控制是成功实施的一个货架轮式装载机采用标准比例积分（PI）和阀的动态变换算法的议案。动态转换阀是液压流量功能，是一种发动机转速和气缸压力杆端功能。鲁棒性的性能进行了验证，通过广泛的系统建模，验证，并在大卡特彼勒轮式装载机型号的硬件测试。简介汽车行业已经在效率，性能，安全性巨大收益和乘客由最近在其产品的数字化控制技术的广泛和快速部署的舒适度。地球发展的行业正在迅速整装待发，准备在短期内实现类似的收益。主要有两种类型的推土设备：挖掘机和轮式装载机。长远目标是建立一个独立的产品，不再操作技巧和耐力依靠最大限度地提高性能。衡量其性能的吨/小时，该材料的处理最小化的运作在成本/吨的形式加工材料成本的形式。我们的目标是开发控制子系统，改善经营人/机的性能，降低运营成本，这将作为较低级别控制子在自治区控制器的等级制度。轮式装载机（WTL中）有许多大小。工作重量范围从15000-350000和马力马力范围从100-1200。小到中型机器的应用程序（例如，施工和材料处理应用）最广泛而较大的机器往往是用于矿山的应用为主。 WTL的一个常见的功能是利用卡车装载。卡车装载周期是一个重复的四个步骤，其中一些类型的材料是从股票桩运到卡车上。这个过程开始时，运营商的股票桩公羊和命令的联系，以提升负载，而在同一时间向后摇桶（步骤1：旅行，股票桩和挖）。当水桶已满载，逆向操作的变化和旅行转向时向后一个位置，使他有足够的空间，然后转移到前进，前往卡车。经营者继续这次旅行期间提出的部分，以便它清除车床上时，他减慢，达到卡车（步骤2：前往卡车）负载。运转员接着命令桶倾倒从而释放负载到卡车床（步骤3：转储）。最后，操作命令把水桶架回其水平位置。同时，旅游经营者进入反向变化和命令的联系，以降低再挖周期（步骤4：行程开始位置）返回地面。本研究的重点是数字化速度的闭环控制的执行情况在执行子一个先进的轮式装载机移动设备的接地电流状态系统。这项技术的应用不仅限于WTL以及实际上已经到了地球的各种移动设备的广泛应用。挖掘机液压子系统的控制问题已引起广泛关注最近有液压子在一般系统。描述轮式装载机的子系统 土方设备可细分为4个子系统。（1）动力装置，（2）制动系统，（三）工作装置，（4）液压传动器。上电列车由一个电源，通常是一个柴油发动机。电力传输到一种通过液力变矩器然后连接到差距机械传动，驱动器和最后轮胎。这通常是对WTL案件。挖掘机有水文静态驱动列车（即，液压泵和马达）连接到一个轨道。几个发动机功率起飞通过泵提供动力转向液压系统运行，制动系统是典型的液压和液压执行系统。该液压驱动系统包含地面从事工具，提供了力量和运动，从事土壤或其他材料需要处理。2.1自由车度出租车经营者被认为有六个自由度：三线性（前，后部，横向，纵向）和三个角（偏航，俯仰，roll0。铲斗有两个自由度。督导是一种额外的自由程度。因此，车辆有着9年的自由程度。为了简化即将举行的分析，两限制将在系统规定。首先，前帧运动不会允许旋转相对于后车架。第二，后车架议案将限制在一个平面上。第一个约束消除了单自由度（转向）学位从分析中。第二个约束消除了三自由度：运营商横向直线运动，偏航角和滚动角运动的议案。因此，我们认为只有五个自由度在我们的模型：电梯和倾斜落实桶议案和操作前，尾部和垂直直线运动和俯仰角的议案。2.2. 连锁 有几种类型的WTL的实现使用目前的联系。一个非常普遍的例如，所谓的Z型连杆。它是自由的两个学位四体联动（提升臂，杠杆，链接，桶）和两个组成的非对称液压缸（升降机及倾斜），由九个旋转脚关节连在一起。2.3. 主要液压系统 一个普通液压系统通常用来实现控制流量的电梯WTL的倾斜和一缸采用开放中心非压力补偿阀芯型阀。这个系统包含一个水泵/释压阀的流体传送到主换向阀从而分区到液压缸和坦克流。 组件和它们的运作是最好的形容按照液压流体通过各种运行条件下的电路。最简单的条件是在没有命令从流脑放大器电流。该电梯线轴和倾斜，因为将集中在E/小时阀电磁铁将不会被激活。在这种情况下，通过发送泵单向阀的负载流量（最大操作设置压力）的倾斜阀芯。由于这阀芯为中心，流动收益上的电梯阀芯，这也是为中心，返回循环水箱。命名为“开放中心“的事实，即当阀门在中立的立场来，流体循环从通过到罐的阀门泵。 如果倾斜阀芯中心及电梯阀芯右移，一开口就罐区称为泵罐区（星期三）而受到限制。泵的压力建立起来，克服了负载止回阀发送流向头端（HE）的对在另一口的升降油缸称为至气缸区（PC）的泵。在同时，流体从杆端（重新）电梯在另一口缸流量所谓的气缸罐区（CT）和再循环，再进行坦克。因此，电梯活塞杆延伸提高一个可能在桶中的负载。如果电梯阀芯左移相反的情况。从他流体流经对坦克的CT，从泵流体流动以及整个阀芯如果没有足够的转移完全关闭的PT太平洋横跨可再生能源的电脑。因此，电梯活塞杆缩回桶降低到地面。如果电梯阀芯居中和倾斜阀芯被激活时，倾斜油缸的行为类似于电梯缸。 在WTL车辆，电梯管道与阀芯系列倾斜。此配置被称为倾斜优先事项，因为电路的倾斜流量需求可以通过预约和关闭电梯电路。此外，气缸安全阀可能被添加到每个RE和他如果每个部分各不相同的最高工作压力的主要救济结构寿命或安全的关注。化妆阀往添加到这些系统很好。这些止回阀提供缸罐流向稀土在事件或作真空操作过程中创建。这样，空化可以显着减少。这是如电梯武装以重力驱动的功能降低或问题桶中的CT倾倒区已设计提供限制产量快速缸速度。在这种情况下，泵的流量与气缸无法比拟从气缸流向低压槽和空化创造。这是非常以来的液压系统可控的闭环控制是不可取空蚀过程中有效地失去了。2.4. 电液压先导 一个先导泵供应流到压力调节阀，它维护一个稳定供应的压力，一个E/小时阀这也是连接到油箱。细胞外基质中的驱动程序发送到电磁铁电流其中移动一个控制阀芯。由于这阀芯移动，一米的连接口供应压力端口和一个节流孔连接到油箱比例开放保持或接近控制压力。这种压力作用在主阀芯造成它移位，打开主孔区（即，电脑断层，铂，电脑）。在某些情况下，位置主阀芯是用来提供反馈闭环位置控制阀芯。2.5数字化控制系统 基本低成本的组件将被选为这项研究将与一致目前的做法在这个行业。通常情况下，7位微处理器，其中使用大会编码须达到20毫秒循环时间。旋转式电位器用于传感器反馈以及参考输入信号。3） 动态模式：平面倾斜和车辆动态电路 倾斜的动态电路模型，从投入产出关系点的观点。输入是倾斜电路阀芯的位置。的输出是：（1）由于角速度斗缸位移倾斜，（2）平面运动（X,，）的车辆。下面的假设和近似作出的模型：（1）电梯电路以象征式升降机固定角度。因此，我们期望获得不同面值不同倾斜位置电梯电路电路模型。（2）车辆被建模为一个在二维空间质量弹簧阻尼器系统，有三个自由度：的x，y，美国这是一个相当不错的，因为车身逼近和轮胎像一个大众弹簧阻尼系统。（3）软管量和水力损失包括在水力模型。（4）电液阀是一个二阶滤波器，包括动态0.707阻尼比。这是符合实际的英/ H阀使用行为是一致的在WTL车辆。（5）电子/小时阀芯区（称为计量）不是阀芯位置的线性函数。阀芯面积几何精确建模为非线性函数的阀芯位置。（6）标准孔板方程来描述流程之间的关系率（Q）和阀芯位置（因此测光区域），压差时，P。（7）灵活性，由于石油是考虑到压缩为体积模量液压油。阀芯位置之间的水桶和角速度的输入输出关系获得三个逼近阶段：（1）稳态之间的阀芯位移和倾斜缸输入输出功能倾斜速度被称为调制。该模型的非线性静态捕捉死区的几何关系，包括与阀门缸增益。请注意有效的死区和增益是（1）流量的功能（这是一个功能发动机转速在WTL的情况），和（2）外部负载。换句话说，直流增益传递函数是一个流量，外部负载的非线性函数，名义电梯电路的位置。（2）线速度之间的倾斜缸和铲斗几何线性关系速度是描述联动雅可比。这是表示为一系列针对不同的电梯位置曲线（插表作为实时实现的）。（3）最后，我们从后台处理模型的液压电路的动态过滤效果位置倾斜缸速度。稳态增益在获取信息的调制和倾斜倾斜运动学模型。因此，在特区动态模型的倾斜收益将约为团结（0分贝）。此外，这将是电梯的位置和外部负载的函数。因此，所有三个模型块组件方面的评估，预计全扫一电梯的位置和负载值。/小时阀是一个开放的中心型阀。由于阀芯命令转变的阀芯，铂（泵罐）区开始关闭，电脑（泵缸）面积开始打开一样的C- T的（缸罐）区。泵的压力开始建立自的P- T是限制其流动油箱。当泵的压力超过了何气缸压力，负载单向阀泵的流量持久性有机污染物允许进入气缸他说。这种流动延伸圆柱的部队从各地稀土流缸在C - T区油箱。由于外部负载变化时，阀芯的最低金额需要匹配通过泵压变化，以及不同加载命令。这结果有效的死区和增益变化。如果外部负载相反（即超过运行负荷状态），延长了气缸率将主要取决于除两端的压降压降的CT区的CT是这样的：流量比泵进入气缸的何流更少。接着率将延长泵驱动。（4）闭环控制系统的性能目标液压系统元件（泵，油缸，伺服阀）的大小，以便它们能提供必要的功率级（流量和压力）为移动的WTL是设计用来处理负载范围内桶。在这里，我们将不再重复液压控制系统元件尺寸分析，但是，我只想说这它们大小，以满足下列议案的电源要求：电梯电路在全面提高10秒，电梯的电路全部在3.5降低，倾斜在4.0的电路全机架，倾斜电路充分潮湿条件下，最大负荷2.5秒。最大负载能力是斗1.2锰。（5）结果：仿真和实验该实验模型上进行了卡特彼勒WTL的889种类的车辆。为倾斜电路的控制算法实现用微型控制器，对船上的8位分辨率的A / D，D / A转换。有效的死区是负载和发动机转速的功能。在实时实现不同低估死区值使用，以避免过冲。不准确的死区补偿的响应是在Fig.14.It显示延时效果观察到，在响应时间减少到低于0.2的时候赔偿范围内，其实际有效价值1.0毫米的。图15显示了上升时间敏感阀改造的收益。据观察，为了满足时间要求提高0.5秒的增益必须相当准确。图16shows一两个实验和分析比较下一个完整的电梯，完全转储，无负荷，高怠速架步反应的条件。造成这种状况的性能标准的0.5秒和5上升时间小于0.2秒的延迟就形成一个关心过冲阀变换的动态执行中遇到的压力是再反馈级过滤反应所需的稳定。据推测，压力应低通滤波在或低于闭环系统带宽，以一个临界值。在这样的闭环控制能够响应增益的变化，就好像他们是死区对系统干扰。实验和分析都反映了这种过滤。虽然没有显示，在稳定性上WTL的模型进行的实验都保持990.Therefore，这样一种高血压控制用PI型制度的有效控制闭环控制加阀变换模型为基础的补偿要求非常精确的模型。(6) 总结一个先进的电液开放为中心的非压力补偿的实现系统状态进行了研究，以评估执行速度伺服控制，同时满足运营商的响应和平滑性能规格的潜力，并建立一个模块化的子系统，将接受从命令自治区高层次上的WTL的车辆规划控制器。闭环速度控制成功地实施了倾斜电路货架使用标准的比例积分控制器，具有动态转换阀偶函数。阀的动态变换是发动机转速（液压流量）和杆端气缸压力的作用。阀门共享的动态变换在实时控制算法提供的自由化效果类似压力补偿的负荷传感液压系统和元件成本降低的结果。强大的性能进行了验证，通过广泛的系统建模与一个 WTL model990车试验。Modeling identification and real time control of bucket hydraulic system for a wheel type loader earth moving equipmentAbstractThe earth moving equipment industry is quickly gearing up to achieve great gains in efficiency, performance, safety, and operator comfort by the rapid deployment of recent digital control technology in its products.There are two major types of earth moving equipment operating in large numbers: excavators and wheel type loaders. Excavators have received much attention by the industry recently. The wheel type loader product studied in this paper is another example of a high volume versatile machine at the opposite end of the configuration spectrum.A state of the art electro-hydraulic open centered non-pressure compensated valve control system is studied to evaluate the potential gains by implementing digital velocity servo control. The control objectives are to meet operator perceived response requirements, meet operator perceived smoothness requirements, create a sub-system that could accept commands froman autonomous high level planning controller. Closed loop digital velocity control is successfully implemented in the racking motion of a wheel loader using a standard proportional-integral (PI) and a dynamic valve transform algorithm. The dynamic valve transform is a function of hydraulic flow rate which is a function of engine speed and rod end cylinder pressure. Robustness of performance was verified through extensive system modeling, validation, and hardware tests on a large Caterpillar wheel loader model. IntroductionThe automotive industry has made great gains in efficiency, performance, safetyand passenger comfort by the extensive and rapid deployment of the recent digital control technologies in its products. The earth moving industry is quickly gearing up to achieve similar gains in the short term. There are two major types of earth moving equipment: excavators and wheel type loader . The long term goal is to develop an autonomous product that no longer relies on the operator skill and endurance to maximize performance. The performance is measured in the form of tons/h of the material processed and minimizing the cost of the operation in the form of cost/ton of material processed. The goal is to develop controlled sub-systems that improve operator/machine performance, reduce operation cost, and that would serve as lower level control sub-system in the autonomous controller hierarchy.Wheel type loaders (WTL) come in many sizes. Operating weight ranges from 15000-350000ib and horsepower ranges from 100-1200 hp. The small to mid-size machines have the broadest spectrum of applications (e.g., construction and material handling applications) while the larger machines tend to be used mostly in mining applications. One common function WTL are utilized for is truck loading.The truck loading cycle is a repetitive four step process by which some type of material is transported from a stock pile to a truck. The process starts when the operator rams the stock pile and commands the linkage to lift load while at the same time the bucket is racked backwards (step 1: travel, to stock pile and dig).When the bucket has a full load, the operator shifts into reverse and travels backwards while steering to a position that allows him enough room to then shift into forward and travel to the truck. The operator continues to raise the load during this travel portion so that it clears the truck bed when he slows down and reaches the truck (step 2: travel to truck). The operator then commands the bucket to dump thus releasing the load to the truck bed (step 3: dump). Finally, the operator commands the bucket to rack back to its level position. At the same time, the operator shifts into reverse travel and commands the linkage to lower back to the ground for another dig cycle (step 4:travel to start position). This study focuses on the implementation of closed loop digital velocity control on the implement sub-system of a current state of the art wheel type loader earth moving equipment. The application of this technology is not limited to WTL and in fact has broad applications to a variety of earth moving equipment .The excavator hydraulic sub-system control problem has received much attention recently as have hydraulic sub-systems in general.Description of the wheel type loader sub-systemEarth moving equipment can be broken down into four sub-systems. (1) power-train,(2) brakes,(3) steering, and (4) hydraulic actuators. The power-train consists of a power source which is typically a diesel engine. Power is transmitted to a mechanical transmission via a torque converter which then connects to differentials, drives and finally tires. This is typically the case for WTL. Excavators have a hydro-static drive train (i.e., hydraulic pumps and motors) that connects to a track. Several engine power take-offs provide power via pumps to run the steering hydraulic system, the brake system which is typically hydraulic，and the hydraulic actuator system. The hydraulic actuation system contains the ground engaging tool that provides the force and motion to engage the soil or other material that needs to be processed.2.1. Vehicle degrees of freedom The operator cab is considered to have six degrees of freedom: three linear (fore-aft, lateral, vertical) and three angular (yaw, pitch, roll). The bucket has two degrees of freedom. Steering is one additional degree of freedom. Therefore, the vehicle has nine degrees of freedom. To simplify the upcoming analysis, two constrains will be imposed on the system. First, the front frame motion will not be allowed to rotate relative to the rear frame. Second, the rear frame motion will be constrained to a plane. The First constraint eliminates one degree of freedom (steering) from the analysis. The second constraint eliminates three degrees of freedom: operator lateral linear motion, yaw angular motion and roll angular motion. Thus, we consider only five degrees of freedom in our model: lift and tilt implement motion of the bucket and operator fore-aft and vertical linear motion and pitch angular motion.2.2. LinkageThere are several types of WTL implement linkages currently in use. A very common example, called the Z-bar linkage. It is a two degrees of freedom linkage consisting of four bodies (lift arm, lever, link, bucket) and two asymmetric hydraulic cylinders (lift and tilt), all connected together by nine revolute pin joints.2.3. Main hydraulicsA common hydraulic implement system often used to control the flow to the lift and tilt cylinders of a WTL uses the open center non-pressure compensated spool type valve. This system contains a pump/relief valve which sends fluid to a main directional valve which in turn partitions the flow to hydraulic cylinders and tank.The components and their operation are best described by following the hydraulic fluid through the circuit under various operating conditions. The simplest condition is when there is no command current from the ECM amplifiers. The lift and tilt spools will be centered since the E/H valve solenoids will not be activated. In this case, the pump sends flow across a load check valve (set at maximum operating pressure) to the tilt spool. Since this spool is centered, the flow proceeds on to the lift spool, which is also centered, and back to tank for recirculation. The name open center comes from the fact that when valve is in neutral position, fluid circulates from the pump through the valve to the tank.If the tilt spool is centered and the lift spool is shifted to the right, an orifice to tank area called the pump to tank area (P-T) becomes restricted. The pump pressure builds up and overcomes the load check valve sending flow to the head end (HE) of the lift cylinder across another orifice called the pump to cylinder area (P-C). At the same time, fluid from the rod end (RE) of the lift cylinder flows across another orifice called the cylinder to tank area (C-T) and on to tank for recirculation. As a result, the lift cylinder rod extends raising a load that may be contained in the bucket. If the lift spool is shifted to the left the opposite happens. Fluid from the HE flows across the C-T to tank, fluid from the pump flows across the P-C to the RE as well as across the P-T if the spool is not shifted enough to completely close the P-T. As a result, the lift cylinder rod retracts lowering the bucket to the ground. If the lift spool is centered and the tilt spool is activated, the tilt cylinder will behave similar to the lift cylinder.In WTL vehicles, the lift spool is piped in series with the tilt spool. This configuration is called tilt priority, since the flow requirement of tilt circuit can over-ride and shut off the lift circuit. Additionally, cylinder relief valves may be added to each RE and HE if the maximum operating pressures for each section varies from main relief for structural life or safety concerns. Make-up valves are often added to these systems as well. These check valves provide tank flow to the cylinder RE or HE in the event that a vacuum is created during operation. In this way, cavitation can be significantly reduced. This is a problem for gravity driven functions such as lift arm lower or bucket dump in which the C-T area has been designed to provide restrictions that yield fast cylinder velocities. In this case, the pump flow to the cylinder can not match the flow from cylinder to tank creating low pressures and cavitation. This is highly undesirable in closed loop control since controllability of the hydraulic system is effectively lost during cavitation.2.4. Electro Hydraulic pilot valve A pilot pump supplies flow to a pressure regulation valve that maintains a constant supply pressure to an E/H valve which is also connected to tank. A driver in the ECM sends a current to the solenoid which moves a control spool. As this spool moves, a meter-in orifice connected to the supply pressure port and a meter-out orifice connected to tank proportionally open or close to maintain a control pressure. This pressure acts on the main spool causingit to shift and open the main orifice area (i.e., C-T, P-T, P-C). In some cases, position feedback of the main spool is used to provide closed loop position control of the spool.2.5. Digital control system Basic low cost components will be chosen for this study to be consistent with the current practice in this industry. Typically, 7-bit microprocessors are used in which assembly coding is required to achieve loop times of 20 ms. Rotary potentiometers are used for sensor feedback as well as reference input signals. Dynamic model: tilt circuit and vehicle planar dynamics Dynamic model of the tilt circuit is developed from an input-output relations point of view. The input is the spool position of the tilt circuit valve. The outputs are (1)bucket angular velocity due to tilt cylinder displacement, and (2) planar motion (x, y, ）of the vehicle.The following assumptions and approximations are made for the model:(1) Lift circuit is stationary at a nominal lift angle. Therefore, we expect to obtain different tilt circuit models for different nominal lift circuit positions.(2) Vehicle is modeled as a mass-spring-damper system in 2-D space which has three degrees of freedom: x, y, u. This is a fairly good approximation since vehicle body and tires act like a mass-spring-damper system.(3) Hose volume and hydraulic losses are included in the hydraulic model.(4) Electro-hydraulic valve dynamics is included as a second order filter with 0.707 damping ratio. This is consistent with the behavior of the actual E/H valves used in WTL vehicles.(5) E/H valve spool areas (called metering) are not linear functions of spool positions.The spool area geometry is accurately modeled as a nonlinear function of spool position.(6) Standard orifice equations are used to describe the relationship between the flow rate (Q) and the spool position (hence the metering area), and pressure differential, p (7) Flexibility due to the oil compressibility is taken into account as bulk modulus of the hydraulic fluid.The input-output relationship between spool position and bucket angular velocity is obtained in three stages of approximation:(1) Steady state input-output function between spool displacement and tilt cylinder velocity is called the tilt modulation. This model captures the nonlinear static relation including the geometric dead band and valve-cylinder gain. Notice that effective deadband and gain are functions of (1) flow rate (which is a function of engine speed in WTL case), and (2) external load. In other words, the DC gain of the transfer function is a nonlinear function of the flow rate, external load, and nominal lift circuit position.(2) The geometric relation between tilt cylinder linear velocity and bucket linear velocity is described by the linkage jacobian. This is represented as a series of curves (implemented in real time as interpolated table) for different lift positions.(3) Finally, we model the dynamic filtering effect of the hydraulic circuit from spool position to tilt cylinder velocity .The steady state gain information is captured in tilt modulation and tilt kinematic models. Therefore the d.c. gain of the tilt dynamic model will be approximately unity (0 dB). Furthermore, it will be function of lift position and external load. Therefore, all three block components of the model are evaluated for a full sweep of expected lift position and load values. E/H valve is an open-center type valve. As the spool command shifts the spool, the P-T (pump to tank) area starts to close, the P-C (pump to cylinder) area starts to open as does the C-T (cylinder to tank) area. The pump pressure starts to build up since the P-T is restricting its flow to tank. When the pump pressure exceeds the HE cylinder pressure, the load check valve pops allowing pump flow to enter the cylinder HE. This flow extends the cylinder which forces flow from the RE of cylinder across the C-T area to tank. As the external load varies, the minimum amount of spool command required to match the load via varying pump pressure varies as well. This results in effective deadband and gain changes. If the external load is reversed (i.e., over running load condition), the rate of cylinder extension will be primarily determined by the pressure drop across the C-T area unless the pressure drop is such that the C-T flow is less than the pump flow entering the HE of the cylinder. Then the rate of extension will be pump driven.(4) Closed loop control system performance objectives The hydraulic system components (pumps, cylinders, servo valves) were sized so that they can provide the necessary power levels (flow rate and pressure) to move the bucket for the range of loads the WTL is designed to handle. Here we will not repeat the hydraulic control system component sizing analysis, however, suffice it to say that they were sized to meet the power requirements for the following motions: lift circuit full raise in 10 s, lift circuit full lowering in 3.5 s, tilt circuit full rack in 4.0 s, tilt circuit full damp in 2.5s under maximum load condition. Maximum bucket load capacity is 1.2 MN.(5)Results: simulations and experiments The experiments were conducted on a Caterpillar model WTL 889 class vehicle. The control algorithm for the tilt circuit was implemented using a micro-controller which has 8-bit resolution A/D, D/A converters on board. Effective deadband is a function of load and engine speed. In real-time implementation different under-estimated deadband values were used in order to avoid overshoots. The effect of inaccurate deadband compensation on the delay of the response is shown in Fig.14.It i