港口AGV悬挂系统的探究

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摘要

随着港口码头生产自动化、信息集成化的发展,现代工业生产对物流系统提出了更高的要求。自动引导小车(AGV)是一种能够在给定路径和场景信息布局中,完成指定运输任务的自动化运输设备。AGV运输管理系统对AGV起着管理和调度作用,是AGV系统的重要部分。本文就是在所开发的AGV的基础上,对AGV悬挂系统的发展及其影响范围进行以下几点阐述。

AGV是自动导引运输车(Automated Guided Vehicle)的英文缩写。是指装备有电磁或光学等自动导引装置,能够沿规定的导引路径行驶,具有安全保护以及各种移载功能的运输车,AGV属于轮式移动机器人(WMR Wheeled Mobile Robot)的范畴。更直接点:AGV就是无人驾驶(Driverless)的运输车。AGV装有非接触导航(导引)装置,可实现无人驾驶的运输作业。它的主要功能表现为能在计算机监控下,按路径规划和作业要求,精确地行走并停靠到指定地点,完成一系列作业功能。

AGV suspensionAGV悬挂系统的发展

The first generation of AGVs at ECT were powered by one single drive motor and had no suspension. These AGVs could transport one container at a time.

第一代在港口使用的AGV由单电机驱动并且没有设计悬挂系统。这些AGV当时只能一次运输一个集装箱。

The second generation of AGVs were also powered by one single drive motor and could also transport only one container at a time. These AGVs came with an elastomer suspension system. This was the result of research into the need for suspension, which showed that suspension improves transportation of empty containers. When transporting containers with an average load, the difference between suspension and no suspension was minor. And with heavy containers, the suspension had no effect at all, as it was completely pushed down. The only suspension would then be provided by the tyres!

第二代AGV也是由单电机驱动,并且一次只能运载一个集装箱。这些AGV装配有具有弹力的悬架系统。实际的运行结果看来,证明悬挂系统能够提高运输空箱时的运输效率。当运输载荷在一定范围内,有无悬挂系统对运输造成的影响就不大了。当运载非常重的集装箱时,悬挂系统根本不起作用了,因为已经被压死。在压死后,唯一起到悬挂作用的装置就剩下轮胎了。

第三代和以后的AGV能搭载双箱,双电机驱动,并且同时能够运载两个20英尺的集装箱。这些都是通过液压系统来实现的。这种液压悬挂系统配备有传感器来测量了水平下的力。这个力是对载荷的一种测量,它可以在AGV转弯时调节驱动电机的扭矩分布,以提高稳定性时。在实践中,液压悬挂系统是不完善的,因为AGV的倾斜和液压悬挂系统中油溢流的情况。这样,在转弯时,导致悬挂系统失效和无法调节驱动电机的扭矩分布。

AGV悬挂系统的影响范围

AGV悬挂系统对驱动桥的影响Axle kinematics
悬挂

在港口有两种相似的AGV机型

At the ECT terminal two similar types of AGV's are used. On the old type the axles are fixed rigidly to the vehicle chassis, while the newer type has a suspension with spring elements. Structural damage due to life cycle loading appears only on the axles of the newer type, even though the usage pattern is the same for both AGV types, and the old type were introduced several years earlier. With a simulation study it is demonstrated how the load on the axle changes due to the suspension kinematics. With the suspension, the load under braking results in twice the amount of torque about the Y-axis (concentrated at the support arm fixture), and a large fluctuation in vertical force due to the suspension kinematics. Under steering, the lateral reaction force in the suspended is twice the amount of the fixed axle (concentrated at the support arm fixture), and due to the kinematics also a large fluctuation in the fore-aft force occurs due to the suspension kinematics. The main difference however is the large torque about the vertical axis that applies on the suspended axle, which is not present at all in the fixed axle.

  

在ECT的在老式无悬挂的AGV上,车轴牢牢固定在车辆底盘上,而新型AGV上装配有悬挂系统起着弹簧的作用。但是随着使用年限的增加导致的结构破坏只在装配有悬挂系统的新型AGV的车轴上显现出来,即使两款AGV的使用模式是相同的,甚至没有装配悬挂系统的旧款AGV比新款AGV的引进时间还早几年。进一步的建议,在重型AGV上要选择合适的悬挂系统来保护驱动桥不受损。如果悬挂系统选择错误,会导致比没有悬挂系统时还要严重的机械结构损坏。所以在选择悬挂系统的时候,一定要匹配对于AGV的工况进行选择,这样会避免引起不必要的冲击叠加。

AGV悬挂效果对电气元件的影响

When a suspension system is installed between the chassis and the drive shafts, any shocks caused by putting down a container on the AGV will instantly be passed on to all components of the chassis, i.e. including all control components. When positioned properly the STS crane will put a container soft on an AGV. In that case shocks over 8g never occurred. It is however possible to put a container on an AGV without sufficient low lowering speed. The g-force generated on the chassis in that case could potentially top 10g. The sway of a container may cause a horizontal shock component. In that case the g-force on the Sick sensor could even be 17g. The elastic construction amplifies the shock on the Sick sensor. Care should be taken for a proper construction.

当一个悬挂系统安装在底盘和驱动轴之间,任何由集装箱放置于AGV上产生的冲击都会持续传递到车架底盘上的各个组件,也包括所有的控制部件。当集装箱轻放在AGV上时,无论如何都会有可能产生冲击,产生的冲击传到底盘上,情况可能会达到好几个g。集装箱也可能引起水平的冲击力。这样可能引起传递到各类电子仪器上的冲击会更加严重。悬挂的弹性结构还会加大电子器件受到的冲击。在机械设计之初就应该减少避免冲击的影响。在选用AGV上使用的电子元器件的时候要注意耐电器件的冲击性能。

AGV悬挂系统中的轮胎

一种带有悬挂机构的AGV车用底盘,它包括电机安装支架I、电机安装支架II、驱动电机I、驱动电机II以及AGV车用底板,底板中部的顶表面设置有安装块,底板底表面的四个角落均安装有万向轮,所述的电机安装支架I和电机安装支架II均设置在底板的中部,且电机安装支架I和电机安装支架II设置在安装块的两侧,电机安装支架I和电机安装支架II对称设置,电机安装支架I和电机安装支架II均由横板和两个侧板组成,横板设置在两个侧板之间,两个侧板经转轴旋转安装在安装块上,侧板与转轴之间设有轴承,电机安装支架I的两个侧板之间固定安装有驱动电机I,电机安装支架II的两个侧板之间固定安装有驱动电机II,所述的驱动电机I和驱动电机II的输出端均安装有驱动轮,所述的底板与电机安装支架I之间、底板与电机安装支架II之间分别设置有悬挂机构A和悬挂机构B,所述的悬挂机构A和悬挂机构B均由压板和两根弹簧组成,压板固定在两根弹簧之间,两根弹簧均固定在底板上,悬挂机构A的压板抵压在电机安装支架I的横板的顶部,悬挂机构B的压板抵压在电机安装支架II的横板的顶部。所述的底板的四个角落均设置有万向轮安装支架。

结论:

-1st AGV without suspension in operation for 15 years
*AGV悬挂系统的选择不当会导致更严重的冲击损坏发生
-Next AGV's with suspension; system and sensors are high maintenance
*装有悬挂系统的AGV中的全部电子类元器件都需要考虑到和悬挂系统的运行工况相匹配
-Shocks produced when putting down a container are passed on to the chassis and all control components one on one. Forces up to 17g
-In fact, the suspension system increases the load on the vehicle's axle, which potentially even leads to the axle damages.
-AGVs should not have a suspension system. This will make the construction considerably simple and economical.
-Experience has shown that engine torque adjustment with a sensor on the elastomer suspension works poorly.
-The tyres will provide suspension and an absorption system will diminish the initial shocks
*车胎提供的减震和冲击吸收系统能够减少初始的冲击,是最根本的悬挂减震装置

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