Design and Realization of Elevator Control System Based on PLC and Frequency Converter

Design and Implementation of Elevator Control System Based on PLC and Inverter

As a means of transportation, elevators carry a large number of people and logistics, and their role in the transmission of people and objects is crucial. At present, elevators generally use two control methods: the first is to use the microcomputer as the signal control unit to complete the signal acquisition, operation status and function setting of the elevator, and realize the functions such as automatic dispatch and collective operation of the elevator. The drag control is controlled by The inverter is used to complete it; the second is to replace the microcomputer with a programmable controller to realize a control method of signal selective control. Most elevators in China use the second control method, mainly because PLC control has the advantages of high reliability, simple programming, small size and compact structure, and PLC generally has self-diagnosis, fault type display and fault alarm, etc. Function. In this way, PLC control is used to control the elevator, which not only simplifies the external wiring, but also improves the safety and reliability of the elevator, and also provides convenience for future function expansion.

Schematic diagram of elevator structure The main task of the elevator is to determine the operation mode of the elevator by responding to the external input and after PLC operation. The complete running process of the elevator is the process of the traction motor from starting, running at a constant speed to decelerating and stopping. The schematic diagram of the working process is as shown.

2. Hardware design of elevator control system This control system is designed on the basis of a three-story elevator. The hardware of the system is composed of Omron's CP1H type PLC. The frequency converter (OMRON 3G3MZ) can be programmed and debugged on the computer through the corresponding programming software. During the running process of the elevator, the running status of the elevator can also be displayed through the program monitoring on the PLC and the computer.

In the hardware design, I/O addresses are first allocated according to the input points and output points of the PLC, so that each input signal corresponds to the input relay inside the PLC, and each output signal corresponds to the output relay inside the PLC.

Input signal: The control button of the control system should be located on the operation panel of the elevator. Corresponding to each floor, there should be a floor selection command button to control the travel switch input of the elevator to a certain floor. There are 6 inputs in total. The top layer needs a down call button, the bottom layer needs an up call button, the second layer needs one up and one down call button, a total of 4 inputs, 1 manual door open button input and 1 manual door close button input, 1 Door open travel switch, 1 door close travel switch, 1 elevator up limit, 1 elevator down limit, a total of 16 input points 3. Output signal: When the passenger is on the floor call, the top floor needs a down call button to display, the bottom floor One up call button is required to display, the second floor needs one up and one down call button display, a total of 4 outputs; each floor needs one floor signal display, one car floor button display, a total of 3 floors, 6 outputs In addition, 1 up indication output, 1 down indication output; 1 motor forward rotation output, 1 reverse rotation output, 1 door opening output, and 1 door closing output, a total of 16 outputs are required.

The elevator control system mainly includes PLC, frequency converter, photoelectric rotary encoder, car control panel, hall call panel, door operator and other electrical components, etc. Its structural block diagram is shown in the figure 4. The intelligent elevator control system is mainly controlled by signals The system and the drag control system are composed of two parts. The main hardware equipment includes PLC mainframe and extension, car control panel, mechanical system, hall call panel, door operator, speed control device, floor number indicator light and main drag system, etc. The core of system control is the PLC mainframe. The signal control system is realized by PLC software, including program control such as in-car command, door zone, hall call, running control, escalator cut-off, leveling signal, door opening and closing operation, etc. In the drag control system, the feedback signal of the current working state of the elevator is directly sent to the PLC, and then the PLC sends control signals such as leveling, speed switching, and starting to the drag system. m PLC elevator control system structure diagram 3. Software design of elevator control system Software design of elevator control system is the key link of control system design. The elevator control system is actually a man-machine interactive system, and various input signals appear randomly during the operation of the elevator, that is, there are many uncertain factors, and at the same time, there are a large number of self-locking and interlocking relationships, so the elevator control system Controlled by random logic. The PLC receives the call signal from the control panel and each floor, the function signal of the car and hall door system, and the status signal of the hoistway and the frequency converter, and realizes the collective selection control of the elevator through program judgment and calculation. While outputting display and monitoring signals, PLC sends signals 0 such as running direction start, deceleration running and braking stop to the inverter according to the requirements of random logic control to complete the whole process control of the elevator.

The cyclic process of the elevator operation is: detect the call and floor selection signals, determine the elevator running direction, start the operation, and perform operations such as cutting the elevator in the same direction, calling the elevator and selecting memory in the car during the running process, and executing the door opening when reaching the floor station. /Close the program. The PLC control function flowchart of the elevator in actual operation is shown in the figure. The operation of the elevator can be divided into two states: static and moving.

(1) When the elevator stops at a certain floor in a static state, there are two types of signals received by the elevator: call signals from other floors. The motor goes up or down when it is powered on; if there is a call signal on the floor where the elevator stops, the door opening and closing program will be executed, and then the elevator will go up or down according to the floor selection signal.

(2) The elevator is running, if it is going down, it only responds to the status indication of up or down, so that the call signal from the lower floor of the car inside and outside the car can be used, and only the upper floor of the car can be responded to during the upward process to clearly know the elevator. operating status. 0 call signal. The elevator has floor indication and the elevator control system model has been successfully manufactured during the running process. According to the flow chart, the ascending and descending procedures of the elevator, the door opening and closing procedures of the elevator, and the parameters of the inverter are set. After the combination of these procedures, it runs well after debugging. , to achieve the control purpose. Using PLC to control the operation of the elevator, the hardware structure of the control system is greatly simplified. At the same time, due to the program control of the "soft wiring" method, the reliability and flexibility of the system are greatly improved. Of course, the signal of the elevator control system is greatly improved. The number of input points is large. In terms of initial investment, the cost of the control system is higher than that of the relay. However, the method of saving input points can be used to solve the problem of higher cost.