Analysis of elevator PLC control system
Abstract: With the acceleration of urban construction, the number and height of high-rise buildings are increasing, and elevators in high-rise buildings have become an important means of transportation for daily travel. The quality of elevator operation directly affects people's travel, so the technical content should be improved while the elevator quality is running normally, among which safety index and stability index are the most important.
Keywords: elevator; PLC control system; Program logic controller
China Library ClassificationNo.: TU857 Document ID: A DocumentNo.:1674-7712 (2013)16-0000-01.
Elevator is a kind of up-and-down means of transportation, which frequently starts and stops during operation, and the load of elevator also changes significantly during operation. When running at no load, the load of elevator motor is minimized, and self-generating state may occur. When the elevator runs beyond the load capacity, the load of the elevator motor rises to the maximum, and then the electrical state appears. At this time, the elevator motor is required to run forward and backward, electric and generate electricity.
First, the development and control of elevators
As a vertical transportation equipment, elevator has become an indispensable part of high-rise buildings and important institutions. With the rapid development of microcomputer technology, information processing technology and electrical automation technology, the current elevator has gradually become an efficient elevator under the situation of electromechanical integration. With the acceleration of urban construction, the number of high-rise buildings is increasing and the height is getting higher and higher. Building developers have strengthened the hardware facilities of various residential buildings in the construction of new buildings, and household elevators have also quickly entered the market.
One of the necessary and sufficient conditions for any kind of elevator movement is that the elevator should have a certain running direction, so all the control links used to determine the running direction of the elevator are called direction links for short. In the whole control system of all elevators, the directional link is also a crucial link, just like the automatic door opening and closing control link of elevators. How to reasonably use the hardware resources of PLC, save the input and output ports of PLC and reduce the design cost is the key to realize the control of passenger elevators with PLC. At the same time, make full use of software resources to simplify control procedures, shorten the scanning period of PLC, and improve the safety, reliability and flexibility of elevator operation; In addition, the control program should be as simple as possible and have certain regularity, which is suitable for developing the control requirements of various floors.
Second, the PLC control system
Programmable logic controller, abbreviated as PLC, can also be called programmable logic controller, which replaces the previous relay control device. Programmable logic controller has been rapidly popularized and widely used in the world. At the same time, the function of process logic controller is constantly updated. With the continuous development of computer technology, signal processing technology, control technology and network technology and the continuous improvement of users' needs, the programmable logic controller has added analog processing and motion control functions on the basis of switching value processing. The current process logic controller is no longer just logic control, but also plays a very important role in servo control, post-event control and other fields.
Process logic controller is developed by combining relay control principle. The prophase process logic controller only controls the switching value, and the process logic controller executes one by one according to the stored program content to complete the operation required by the process flow. There is a program counter in the CPU of the program logic controller, which indicates the storage address of the program step. During the running of the program, the counter will be automatically incremented at each step. From the beginning of the program, the basic serial number is zero, and then the program is executed to the last step in turn, and then returns to the initial step for loop operation. The time required for the process logic controller to complete each cycle operation is called a scanning cycle. The periodic scanning period of different models of process logic controllers is between 1 microsecond and tens of microseconds. The program logic controller adopts ladder diagram programming, which embodies the advantage of quick solution logic. On the microsecond level, the solution of 1K logic program is less than1ms. It treats all inputs as switches, and bits 16 and 32 are analog. The remote logic controller uses another CPU to complete the operation of analog quantity. The calculation result is sent to the controller of the process logic controller.
At present, elevator control modes can be generally divided into button control (AZ, AS), signal control (XH), centralized control (JX), parallel control (BL), cascade control (QK) and microcomputer control (w). So how do we start to judge and distinguish them? I think we can learn from the selection structure in C language algorithm, that is? If (conditional expression) statement 1else statement 2? Write an expression? Program? To analyze and judge. The main difference between centralized selection and decentralized selection (signals and buttons) is that centralized selection can be manipulated without the driver, while buttons and signals can only work normally under the control of the driver because of their low degree of automation. Therefore, the judgment method is to see whether it can be operated without driving: register any floor in the car, then people get off the car, and later see if the elevator automatically closes and goes to the designated floor. If yes, it is controlled by the driver, and it can be judged that it belongs to the category of centralized selection, and vice versa. Expressed in C language, it is centralized class control of if (controlled by drivers = 1) and decentralized class control of else.
Third, the elevator PLC control system
The normal operation of the elevator depends on the external indication signal and the elevator itself, and the instructions are not fixed every time. The PLC control system is a control system in which people and motors work together. When people send out control instructions, the PLC control system will quickly make storage instructions, and then send out instructions after calculation by control logic. The PLC control system determines the direction of the elevator after receiving the actual instruction. After giving instructions to the frequency converter, the frequency converter adjusts the speed after receiving instructions from the PLC control system. When the elevator motor starts, the speed quickly increases to the maximum, and the control is reliable. When the critical point of the command is reached, the PLC control system issues a stop command, and the frequency converter has instructed to reduce the speed to a slow state in advance after receiving the command.
From the appearance and practical application of PLC control system to the present, it has changed the promotion of old relay wiring logic to storage logic. Realized logic control to digital control; Its application field is more and more extensive, and it has achieved a leap from simple control of a single device to competent motion control, process control and distributed control. Today's PLC control system has greatly improved its ability in dealing with simulation, data calculation, man-machine interface and networking, and has become the mainstream controller in the field of automation control, playing a huge role in all walks of life. The elevator control system is based on PCL and process logic control motherboard. Elevator group control technology includes centralized selection control and stochastic logic control. The running performance, safety performance, ride comfort and energy saving of elevators have all developed to a certain extent. In order to ensure the normal operation and safe use of elevators, all elevators should be equipped with personnel with elevator professional knowledge. They must fully understand and master the working principle, performance characteristics and control operation of the elevator in order to use and maintain the elevator correctly.
The elevator with PLC control system is bound to be the mainstream trend in the future, which fully shows the symbol of the country's comprehensive strength in manufacturing and practical application. Moreover, in the first-tier cities of China, such as Beijing, Shanghai, Shenzhen and other densely populated cities, people's demand for material culture is getting higher and higher. Due to the increasing number and height of high-rise buildings, elevators in high-rise buildings have also become an important means of transportation for daily travel. The quality of elevator operation directly affects people's travel, so the technical content should be improved while the elevator quality is running normally, among which safety index and stability index are the most important.
References:
Olivia, Luo Jianhua. Elevator PLC control strategy and its program design [J]. Lifting and transportation machinery, 2006(07).
Huang Yi, Wang Lili, Zhang Zhiyong. PLC transformation of mine hoist control system based on SIMADYND [J]. Microcomputer Information, 2006( 16).
Ye Yuguang, Liang Nanding. Electric control system of mine hoist based on PLC technology [J]. Mechatronics, 2004(06).
Did you get a look at him? Elevator control technology paper? People still see:
1. Technical paper on elevator control system
2. Elevator technical papers
3. Technical paper on elevator maintenance
4. Elevator published according to the topic of the paper.
5. Essays on Motor and Control Technology