外文翻译--起重机介绍

1 附 录 外文文献原文： The Introduction of cranes A crane is defined as a mechanism for lifting and lowering loads with a hoisting mechanism Shapiro, 1991. Cranes are the most useful and versatile piece of equipment on a vast majority of construction projects. They vary widely in configuration, capacity, mode of operation, intensity of utilization and cost. On a large project, a contractor may have an assortment of cranes for different purposes. Small mobile hydraulic cranes may be used for unloading materials from trucks and for small concrete placement operations, while larger crawler and tower cranes may be used for the erection and removal of forms, the installation of steel reinforcement, the placement of concrete, and the erection of structural steel and precast concrete beams. On many construction sites a crane is needed to lift loads such as concrete skips, reinforcement, and formwork. As the lifting needs of the construction industry have increased and diversified, a large number of general and special purpose cranes have been designed and manufactured. These cranes fall into two categories, those employed in industry and those employed in construction. The most common types of cranes used in construction are mobile, tower, and derrick cranes. 1. Mobile cranes A mobile crane is a crane capable of moving under its own power without being restricted to predetermined travel. Mobility is provided by mounting or integrating the crane with trucks or all terrain carriers or rough terrain carriers or by providing crawlers. Truck-mounted cranes have the advantage of being able to move under their own power to the construction site. Additionally, mobile cranes can move about the site, and are often able to do the work of several stationary units. Mobile cranes are used for loading, mounting, carrying large loads and for work performed in the presence of obstacles of various kinds such as power lines and similar technological installations. The essential difficulty is here the swinging of the payload which occurs during working motion and also after the work is completed. This applies particularly to the slewing motion of the crane chassis, for which relatively large angular accelerations and negative accelerations of the chassis are characteristic. Inertia forces together with the centrifugal force and the Carioles force cause the payload to swing as a spherical pendulum. Proper control of the slewing motion of the crane serving to transport a payload to the defined point with simultaneous minimization of the swings when the working motion is finished plays an important role in the model. 2 Modern mobile cranes include the drive and the control systems. Control systems send the feedback signals from the mechanical structure to the drive systems. In general, they are closed chain mechanisms with flexible members 1. Rotation, load and boom hoisting are fundamental motions the mobile crane. During transfer of the load as well as at the end of the motion process, the motor drive forces, the structure inertia forces, the wind forces and the load inertia forces can result in substantial, undesired oscillations in crane. The structure inertia forces and the load inertia forces can be evaluated with numerical methods, such as the finite element method. However, the drive forces are difficult to describe. During start-up and breaking the output forces of the drive system significantly fluctuate. To reduce the speed variations during start-up and braking the controlled motor must produce torque other than constant 2,3, which in turn affects the performance of the crane. Modern mobile cranes that have been built till today have oft a maximal lifting capacity of 3000 tons and incorporate long booms. Crane structure and drive system must be safe, functionary and as light as possible. For economic and time reasons it is impossible to build prototypes for great cranes. Therefore, it is desirable to determinate the crane dynamic responses with the theoretical calculation. Several published articles on the dynamic responses of mobile crane are available in the open literature. In the mid-seventies Peeken et al. 4 have studied the dynamic forces of a mobile crane during rotation of the boom, using very few degrees of freedom for the dynamic equations and very simply spring-mass system for the crane structure. Later Maczynski et al. 5 studied the load swing of a mobile crane with a four mass-model for the crane structure. Posiadala et al. 6 have researched the lifted load motion with consideration for the change of rotating, booming and load hoisting. However, only the kinematics were studied. Later the influence of the flexibility of the support system on the load motion was investigated by the same author 7. Recently, Kilicaslan et al. 1 have studied the characteristics of a mobile crane using a flexible multibody dynamics approach. Towarek 16 has concentrated the influence of flexible soil foundation on the dynamic stability of the boom crane. The drive forces, however, in all of those studies were presented by using so called the method of kinematics forcing 6 with assumed velocities or accelerations. In practice this assumption could not comply with the motion during start-up and braking. A detailed and accurate model of a mobile crane can be achieved with the finite element method. Using non-linear finite element theory Gunthner and Kleeberger 9 studied the dynamic responses of lattice mobile cranes. About 2754 beam elements and 80 truss elements were used for modeling of the lattice-boom structure. On this basis a efficient software for mobile crane calculationNODYA has been developed. However, the influences of the drive systems must be determined by measuring on hoisting of the load 10, or rotating of the crane 11. This is neither efficient nor convenient for computer 3 simulation of arbitrary crane motions. Studies on the problem of control for the dynamic response of rotary crane are also available. Sato et al. 14, derived a control law so that the transfer a load to a desired position will take place that at the end of the transfer of the swing of the load decays as soon as possible. Gustafsson 15 described a feedback control system for a rotary crane to move a cargo without oscillations and correctly align the cargo at the final position. However, only rigid bodies and elastic joint between the boom and the jib in those studies were considered. The dynamic response of the crane, for this reason, will be global. To improve this situation, a new method for dynamic calculation of mobile cranes will be presented in this paper. In this method, the flexible multibody model of the steel structure will be coupled with the model of the drive systems. In that way the elastic deformation, the rigid body motion of the structure and the dynamic behavior of the drive system can be determined with one integrated model. In this paper this method will be called complete dynamic calculation for driven “mechanism”. On the basis of flexible multibody theory and the Lagrangian equations, the system equations for complete dynamic calculation will be established. The drive- and control system will be described as differential equations. The complete system leads to a non-linear system of differential equations. The calculation method has been realized for a hydraulic mobile crane. In addition to the structural elements, the mathematical modeling of hydraulic drive- and control systems is decried. The simulations of crane rotations for arbitrary working conditions will be carried out. As result, a more exact representation of dynamic behavior not only for the crane structure, but also for the drive system will be achieved. Based on the results of these simulations the influences of the accelerations, velocities during start-up and braking of crane motions will be discussed. 2. Tower cranes The tower crane is a crane with a fixed vertical mast that is topped by a rotating boom and equipped with a winch for hoisting and lowering loads (Dickie, 990). Tower cranes are designed for situations which require operation in congested areas. Congestion may arise from the nature of the site or from the nature of the construction project. There is no limitation to the height of a high-rise building that can be constructed with a tower crane. The very high line speeds, up to 304.8 mrmin, available with some models yield good production rates at any height. They provide a considerable horizontal working radius, yet require a small work space on the ground (Chalabi, 1989). Some machines can also operate in winds of up to 72.4 km/h, which is far above mobile crane wind limits. The tower cranes are more economical only for longer term construction operations and higher lifting frequencies. This is because of the fairly extensive planning needed for installation, together with the transportation, erection and dismantling costs. 3. Derrick cranes 4 A derrick is a device for raising, lowering, and/or moving loads laterally. The simplest form of the derrick is called a Chicago boom and is usually installed by being mounted to building columns or frames during or after construction (Shapiro and Shapiro, 1991).This derrick arrangement. (i.e., Chicago boom) becomes a guy derrick when it is mounted to a mast and a stiff leg derrick when it is fixed to a frame. The selection of cranes is a central element of the life cycle of the project. Cranes must be selected to satisfy the requirements of the job. An appropriately selected crane contributes to the efficiency, timeliness, and profitability of the project. If the correct crane selection and configuration is not made, cost and safety implications might be created (Hanna, 1994). Decision to select a particular crane depends on many input parameters such as site conditions, cost, safety, and their variability. Many of these parameters are qualitative, and subjective judgments implicit in these terms cannot be directly incorporated into the classical decision making process. One way of selecting crane is achieved using fuzzy logic approach. Cranes are not merely the largest, the most conspicuous, and the most representative equipment of construction sites but also, at various stages of the project, a real “bottleneck” that slows the pace of the construction process. Although the crane can be found standing idle in many instances, yet once it is involved in a particular task ,it becomes an indispensable link in the activity chain, forcing at least two crews(in the loading and the unloading zones) to wait for the service. As analyzed in previous publications 6-8 it is feasible to automate (or, rather, semi-automate) crane navigation in order to achieve higher productivity, better economy, and safe operation. It is necessary to focus on the technical aspects of the conversion of existing crane into large semi-automatic manipulators. By mainly external devices mounted on the crane, it becomes capable of learning, memorizing, and autonomously navigation to reprogrammed targets or through prt aught paths. The following sections describe various facets of crane automation: First, the necessary components and their technical characteristics are reviewed, along with some selection criteria. These are followed by installation and integration of the new components into an existing crane. Next, the Man Machine Interface (MMI) is presented with the different modes of operation it provides. Finally, the highlights of a set of controlled tests are reported followed by conclusions and recommendations. Manual versus automatic operation: The three major degrees of freedom of common tower cranes are illustrated in the picture. In some cases , the crane is mounted on tracks , which provide a fourth degree of freedom , while in other cases the tower is “telescope” or extendable , and /or the “jib” can be raised to a diagonal position. Since these additional degrees of freedom are not used routinely during normal operation but rather are fixed in a certain position for long periods (days or weeks), they are not included in the routine automatic mode of operation, although their position must be “known” to the control system. 5 外文文献中文翻译： 起重机介绍 起重机是用来举升机构、抬起或放下货 物的器械。在大多数的建设工程中，起重机是最有用、功能最多的器械。它们因结构、容量、操作模式、使用强度和费用的不同而不同。在一个大的工程项目上，一个承包商可以因为不同的利用目的而使用多种起重机。小的液压移动式起重机可以用来从卡车上卸下材料，处理小而具体的物体的安置，然而较大的爬式或塔式起重机可以用来竖立并移动框架，安置加强的钢铁，放置混凝土，竖起钢筋结构和预制混凝土横梁。 在一些建设地点，一台起重机是用来提升重物的，例如：混凝土的装料车、加强部分和模壳。随着建筑行业的提升要求不断增加并且变化多样，大量的具有综 合的和特殊性能的起重机被设计和制造出来。这些起重机被分成两类：工业用起重机和建筑用起重机。用于建筑业的最普通型式的起重机是移动式、塔式和架式起重机。 1. 移动式起重机 一台移动式起重机是一个不被局限于预先确定的轨道，在自身动力的驱动下具有运动能力的起重机。将起重机与卡车，甚至所有地带的运输工具甚至粗糙地带的运输工具，更甚至借助于所提供的爬行工具，起重机的就有运动的可能。车载起重机具有在它们自己的动力驱动下能够移动至建筑地点中的任何地方的优势。此外，移动式起重机可以在场所内移动，经常能够处理与提升一些静止部 件的工作。 移动式起重机用来装载、安装、搬运大负荷，也常用于在各种各样的障碍中，例如：力量线和相似的科技安装。在这儿必不可少的困难是当工作过程中和工作完成之后有效载荷的摆动，相关的大的角速度和底座的负的速度是其特有的。惯性力，伴着离心力和科里奥利力引起载物像一个球形钟摆一样旋转。当工作行为结束时，对同时用于将货物输送到限定地点的起重机的旋转动作进行适当的限制，在模型中起着很重要的作用。 现代的移动式起重机包括驱动和控制系统。控制系统把来自机械结构的反馈信号传送到驱动系统，大体上，它们是由柔性元件组成的闭链机 械系。 旋转、负荷和提升是移动式起重机的基础动作，在传送重物的过程中与运作过程一样，马达的驱动力、结构内应力、风力和货物的内力可以导致起重机产生一定的不希望得到的摇晃。结构内应力和货物内应力可以用数学方法进行估价，例如有限元的方法。无论怎样，驱动力是很难描述的。在起动和制动的过程中，驱动系统的外力起 6 伏变化很大。为了减小起动和制动中速度的变化，可控制的马达必须产生可变化的力矩，来影响起重机的运作。 现代的移动式起重机直到今天还在铸造，常常有 3000 吨的举重能力，而且经久不衰。起重机的结构和传动系统必须是安全、 有效和尽量轻巧的。因为经济和时间的原因，对于大的起重机不可能建造出其原型，所以，人们希望利用理论上的计算来确定起重机的电动反应。 在开放的文化中，一些反映移动式起重机动态影响的已发表文章是可以找到的。其中 70 岁的 Peeken 通过在动态方程中利用很少的自由度，并在起重机结构中利用非常简单的弹簧阻尼系统，研究了在悬臂旋转中一台移动式起重机的动态力学。之后，Maczynski 研究了起重结构上有四块模型的移动式起重机的载荷摇摆问题。 Posiadala考虑到旋转、装载和载荷提升的变化而研究了被提升的载荷的运动。无论怎 样，只有运动学被研究了。稍后，相同的作家调查了在载荷运行中的支持系统的弹性影响。最近， Kilicaslan 利用柔性综合动态方法研究了移动式起重机的特性。 Towarek 把研究弹性基壤的影响集中在悬臂式起重机的动态稳定性上。在这些研究中，通过利用所谓带有假定速度和加速度的运动力学的方法，驱动力无论怎样都有所出现。在实践中，这种假想无法和运行中的起动和制动相符合。 利用有限元的方法，一个详细且正确的移动式起重机的模型是可以实现的。利用非线性有限元理论， Gunthner 和 Kleeberger 研究了移动式起重机的 动态影响，在网格结构中，大约 2754 个光线元素和 80 个构架元素被用到。在此基础上，一个有效的关于移动式起重机计算的有效软件 NODYA 被发明出来。无论如何，通过衡量载荷的提升量或起重机的旋转，驱动系统的影响必须要考虑到。这对于起重机多种运动的计算机模拟来说，既不很有效也不方便。 对于旋转起重机动态影响的控制的问题研究是有效的。 Sato 让那个在载荷摇摆转换末尾可将重物传递到所渴望的位置的控制理论尽快的衰退。 Gustafsson 为了移动货物时没有振动并且正确地在最后位置排列货物，描述了一个旋转起重机的反馈控制系统 。然而，在研究中，只有在悬臂和绞点中的坚硬的固体和弹性节点被考虑到了。因为这个原因，所以起重机的动态影响是广泛存在的。 为了改变这种状况，关于移动式起重机的动态计算的一种新的方法将会出现。在这种方法中，钢铁结构的弹性综合模型将会同驱动系统的模型一起出现。在那种方法下，用一个独立