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Chapter 65438 +0 thread theory

Chapter II Overall Plan of Elevator Design

Chapter III Principle and Circuit of AC Two-speed Elevator

Chapter 4 PLC selection and I/O number allocation

Chapter V Elevator Control System

Chapter VI System Programming

Chapter VII Elevator Fault Analysis

Chapter VIII Conclusion

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Appendix I

Appendix II

[Original]

Chapter 65438 +0 thread theory

1. 1 Introduction

As a general industrial control computer, in the past 30 years, programmable controllers have grown from scratch, achieving a leap from wiring logic to storage logic in the industrial control field; Its function is from weak to strong, realizing the progress from logical control to digital control; Its application field has grown from small to large, realizing the leap from simple control of a single device to competent motion control, process control and distributed control. Nowadays, programmable controller is becoming the mainstream control equipment in the field of industrial control, and it is playing an increasingly important role in the world. Therefore, the application of PLC has become a hot issue.

Before the birth of PLC, the mainstream variety of industrial control equipment was the control device with relays and contactors as the main body. Relays and contactors are electromagnetic switches. Later, with the continuous improvement of industrial automation, the defects of using relay circuits to form industrial control systems are constantly exposed. In the 1960s and 1970s, social progress required the manufacture of small-batch, multi-variety, multi-specification, low-cost and high-quality products to meet the market demand, and constantly put forward the requirements of improving the functions of production machinery. In addition, at that time, electronic technology had developed to a certain extent, so people began to seek a new type of industrial control equipment with storage logic instead of wiring logic, which is what we now call PLC. Because PLC adopts modern large-scale integrated circuit technology and strict production technology, its internal circuit adopts strict anti-interference technology and has high reliability. From the external circuit of PLC, the control system is composed of PLC. Compared with the relay contactor system of the same scale, the electrical wiring and switch contacts are reduced to hundreds or even thousands, and the faults are greatly reduced. In addition, PLC has the function of fault circuit self-checking, which can send out alarm information in time when there is a fault.

Development of 1.2 elevator

With the continuous development of urban construction and the increasing number of high-rise buildings, elevators are widely used in national economy and life. As a vertical means of transportation in high-rise buildings, elevators are inseparable from people's daily lives. Among many transportation equipment, elevator is one of the most advanced equipment with the highest degree of automation. In the past, elevators were mainly controlled by single chip microcomputer, and their performance was not perfect. At present, PLC is mostly used in elevator control system, which greatly improves elevator performance, equipment flexibility and safety guarantee. In fact, the elevator runs according to the external call signal and its own control law, and the call is random. Elevator is actually a man-machine interactive control system, and simple sequential control or logical control can't meet the control requirements. Therefore, the elevator control system adopts random logic control. At present, elevator control generally adopts two ways. One is to use microcomputer as signal control unit to complete the collection of elevator signals, the setting of operation state and function, and realize the automatic dispatching and centralized operation of elevators, and the traction control is completed by frequency converter; In the second control mode, programmable controller (PLC) is used instead of microcomputer to realize centralized signal selection control.

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