Abstract
The paper mainly researches the application of advanced PLC (Programmable Logic Controller), transducer, and absolute encoder in the grab bucket crane, which takes the place of the traditional mode of the electric control and aims to improve the work efficiency of grab bucket crane and decrease its failure rate. These applications will bring a lot of advantages, such as lower maintenance costs, lower workload of maintenance, and easily to be manipulated etc. It is also achieved to be semi-automatic operation to reduce the risk of man-made operation accident with the effects of reliable running and energy-saving.
The paper primarily focuses on the principle of automatic open / close grab of grab bucket crane and proposes the principle and physical significance of the moving coordinate method. It is practical that the applied absolute encoder automatically follows the lifting and landing of grab bucket and measures the length difference value of steel wire rope to achieve the function of its automatic opening or closing and stable grabbing. According to the usual failures during the practical application of grab bucket crane, the failure display is also developed to be applied to the crane.
The paper consists of four parts:
The first part (Chapter one: Introduction) mainly describes the working principle of grab bucket crane, focusing on the problems of crane controlled in the traditional method, and further exploring the feasibility for intelligent implementation of grab bucket crane.
The second part (Chapter 2, 3, 4) describes the configuration and functional principles of PLC, transducer and encoder. It also makes a theoretical analysis for the selection of PLC, transducer and encoder, which lays a theoretical foundation for the realization of the intelligent operation of grab bucket crane in the following chapter.
The third part (Chapter 5) researches the specific schemes for intelligent implementation of grab bucket crane, such as heavy trolley, light trolley, controller configuration, PLC, transducer, electric connection of absolute encoder, working principle etc. It explicitly explained the principle of automatic open/ close grabbing of crane and the implementation of stable grabbing. It also introduces the realization principle to substitute the limit position of ascending with the utility of encoder.
The fourth part (Chapter 6) mainly introduces soft structure of intelligent operation and PLC configuration of gab bucket crane. The software program of heavy trolley, light trolley, and switching & hoisting mechanism is also composed in the paper.
In the end, it is summarized for the whole research and makes an outlook for the future research.
Key words: crane, PLC, transducer, absolute encoder, automatic opening /closing grab failure display.
摘 要
本文档主要研究抓斗起重机运用先进的可编程控制技术、变频器和绝对值编码器，取代传统的电气控制方式，提高抓斗起重机的工作效率，减小抓斗起重机的故障率，降低维修费用，使维修工作量大大减少，操作变得简单，可以实现半自动化操作，减少人为的操作事故，运行可靠，具有节能效果。
本文档着重研究抓斗起重机自动开闭斗的原理，提出游动坐标法的原理及物理意义，利用绝对值编码器自动跟踪检测抓斗起升、开闭钢丝绳的长度差值，实现自动开闭、沉抓的功能，具有实用价值。并根据抓斗起重机实际运用中经常出现的故障，开发出故障显示功能。
本文档分成四个部分：
第一部分（第一章）绪论部分主要对抓斗起重机工作原理作了介绍，着重介绍了抓斗起重机传统控制方式存在的问题，进而探讨了实现抓斗起重机智能操作的研究可能性和研究意义。
第二部分（第二、三、四章）分别对可编程控制器（PLC），变频器、绝对值编码器的组成、功能各原理作了介绍，以及PLC、变频器、编码器的选型作了理论上的分析，为下文抓斗起重机智能化控制的实现打下了理论基础。
第三部分(第五章)研究抓斗起重机智能控制的具体实现方案，大车、小车，起升开闭机构PLC、变频器、绝对值编码器的电气连接、工作原理。特别详细阐述了抓斗实现自动开闭斗的原理，以及抓斗自动沉抓功能的实现。还介绍了用编码器取代上升极限位的实现原理。
第四部分（第六章）主要介绍抓斗起重机智能控制的软件结构，PLC组态、还详细写出大车、小车、起升开闭机构的软件程序。
最后对整个研究作一总结，并且对今后的研究方向作了展望
关键词：起重机、可编程控制器、变频器、绝对值编码器、自动开闭斗、故障显示
