Abstract This article introduces a 5-layer elevator control system designed using a Mitsubishi FXZN-80MR programmable controller. A frequency converter is used as the actuator to test the operation status of the elevator PLC control system. Keywords : PLC; Frequency conversion device; system; elevator 1 Introduction The electrical system of an elevator consists of a drive system and a control system. Traditional electrical control systems using relay logic control are gradually being phased out due to drawbacks such as numerous contacts, high failure rate, poor reliability, and large size. Elevators using PLC-frequency converter control offer advantages such as accurate control, convenient debugging, stable operation, and simple circuitry. The core of a PLC-controlled elevator is a PLC. Currently, elevator designs utilize programmable logic controllers (PLCs), requiring the control system to perform the following operations: determine the car's direction of travel based on its position and the floor number of the passengers; ensure the car decelerates upon leveling and stops at the selected floor; simultaneously, stop along the designated route based on floor calls and automatically open and close the doors; additionally, indicator lights inside and outside the car must display the elevator's direction of travel and the floor number. 2. Elevator Main Control Circuit and its Working Principle The traction motor in the elevator is directly controlled by a frequency converter, whose input control signals are provided by the PLC. In the circuit, the motor acts as the terminal device, providing drive capability to the elevator and also serving as the actuator for the frequency converter; the frequency converter is an intermediate device, acting as a transmitter and transmitter in the circuit, controlling the main unit, door operator, and rotary encoder according to the instructions output by the PLC, and then feeding back the execution results to the PLC; the PLC is both the interface between people and the elevator and the core of the elevator control system, receiving switch commands input by passengers and transmitting these commands to the frequency converter; the rotary encoder is the detection mechanism during elevator operation, detecting the elevator's travel distance. 2.1 Elevator Operation Control (Assuming the motor rotates upwards) See Figure 1 for elevator operation training. DYD is the power indicator light; it illuminates when the external power supply is connected. Turning on the power switch GK and pressing the start button activates the power contactor HKC, providing power input to the frequency converter. KC is the run/stop switch (controlled by the operation controller); the elevator's operation mode is controlled by the PLC. The control method is as follows: Y11, Y14 output: The elevator moves upward at the rated speed (this speed is used under normal elevator conditions); Y11, Y14 output: The elevator moves upward at the rated speed; Y12, Y14 output: The elevator moves upward at a crawling speed (this speed is used when the elevator is being tested or under maintenance); Y12, Y14 output: The elevator moves upward at a crawling speed; Y01, Y14 output: The elevator moves upward at a maintenance speed (this speed is used when the elevator is under maintenance); Y01, Y14 output: The elevator moves upward at a maintenance speed; Y13, Y14 output: The elevator moves upward at the first medium speed (this speed is used when the elevator is lightly loaded); Y13, Y14 output: The elevator moves upward at the first medium speed. 2.2 Working principle of rotary encoder The function of rotary encoder is to count the number of rotations of the motor, and then calculate the elevator's travel distance based on the motor speed and the counted number of rotations, thereby realizing the detection of the elevator's travel distance. L=nZT Where: L - elevator travel distance (m); n - motor speed (r/s); Z - travel distance per revolution of the motor (m/r); T - motor travel time (s). [align=center] Figure 1 Elevator Main Control Circuit[/align] 3 PLC Electrical Control Circuit The PLC is the core of this elevator control system. All elevator operations are controlled by the PLC. This PLC uses a common anode relay output type, as shown in Figure 2. The functions and protection features of the PLC input/output interfaces are described below: AJ: Safety relay switch, closed when the elevator is running. MJS: Door lock relay switch, closed when the elevator is running. MQG: Leveling magnetic sensor switch, open during normal operation, closed when leveling. SHK: Upper forced speed change switch, when this switch is closed, the elevator forcibly decelerates; when normal, it is open. XHK: Lower forced speed change switch, when this switch is closed, the elevator forcibly decelerates; when normal, it is open. NH K: Car Inspection Switch. When connected to X7, Y01 outputs, and the elevator is in car inspection mode. During normal operation, this switch is connected to X10. DHK: Car Top Inspection Switch. Under normal circumstances, it is connected to the X01 branch. When connected to the X11 and X12 branches, the elevator is in car top inspection mode. DSA: Car Top Inspection Slow Up Button. When the elevator is in car top inspection mode, pressing this switch will cause the elevator to ascend at inspection speed. DX A: Car Top Inspection Slow Down Button. When the elevator is in car top inspection mode, pressing this switch will cause the elevator to descend at inspection speed. KMA: Door Opening Button. When the elevator stops at a floor, pressing this switch will open the car door, and the car door will simultaneously move to the landing shaft to open. Generally, the door opens automatically at each stop. GM A: Door Close Button. When the elevator stops at a floor, pressing this switch will close the car door, and the landing door will automatically close under the force of the spring. Normally, the elevator doors close with a delay at each stop. KM K: Door Opening Limit Switch. This switch opens when the car door reaches its open limit, and the door operator stops. GM K: Door Closing Limit Switch. This switch opens when the car door reaches its closed limit, and the door operator stops. OR K: Door Opening Fault Switch. The door is open when this switch is normal. SJK: Operator Switch. When this switch is closed, the elevator is controlled by the elevator operator. xF K: Fire Alarm Switch. When this switch is closed, the elevator will move passengers to the nearest floor and then stop to ensure passenger safety. CZ K: Overload Switch. This switch closes when the elevator is overloaded, triggering an alarm and stopping the elevator. SW K: Upper Limit Switch. This switch closes when the elevator overshoots the ceiling, stopping the elevator. xW K: Lower limit switch. Closes when the elevator hits the bottom, stopping the elevator. x2 7: Inverter fault switch. Opens normally, closes when the inverter malfunctions, stopping the elevator. X3 O: Deceleration switch. Closes when the elevator approaches the stop, slowing the elevator down. SP: Forced speed change switch. Closes when the elevator runs overspeed, forcing a speed change. AP KI, APK, CPK, LSS: Safety contact switch group, located on the car door safety contact plate. INA-nN: Internal command button for passenger floor selection. ISA-Sn: External upward call button, one per floor, for passenger elevator calls. IX A-nx: External downward call button, one per floor, for passenger elevator calls. Additionally, "a-9" in the diagram refers to the light-emitting diodes of segments a to 9 of the LED seven-segment display. The "9" in the diagram is used in buildings with underground floors. When "9" has a signal, the floor indicator will automatically display a negative number to represent the underground floor, such as -IF, -ZF, etc. The inverter, rotary encoder, and motor models and power are as follows: [align=center] Figure 2 PLC Electrical Control Circuit[/align] Inverter: FR-55205-0, 75K-CH; Traction Motor: YS-5634W 180W (for teaching and training; the actual power should be increased accordingly); Rotary Encoder: ZSP3.806-40lG50OBZlls-24C (for a speed ratio of 1:1 corresponding reducer). 4 Conclusion This paper uses a Mitsubishi FXZN-80MR programmable controller to design an elevator control system to complete the elevator's in-car commands, hall call commands, floor position indication, leveling speed control, door opening control, and other control tasks. The application of frequency converters in elevators enables accurate execution of PLC output instructions and flexible control of motor motion. A rotary encoder precisely calculates the elevator's travel distance and feeds the signal back to the frequency converter. The frequency converter then executes the elevator PLC control system, combining the PLC's driver program with the frequency converter's demand response to achieve load-driven operation. Practical design and debugging of the elevator experimental device in our institute's mechatronics laboratory have demonstrated that combining a PLC (Programmable Logic Controller) and a frequency converter can effectively realize the testing and operation of the elevator control system. This is beneficial for the design and testing of PLC control systems and has significant application value. References [1] Xu Miao, Wang Shuying. Electrical Control and PLC Application. Beijing: Machinery Industry Press, 2005: 116-128 [2] Practical Handbook for Elevator Maintenance. Beijing: China Textile Press, 2005: 156-165 [3] Zhang Yanbin. Illustrated Guide to Variable Frequency Speed ​​Regulation of Electric Motor. Beijing: China Electric Power Press, 2005: 187-192, 301-3 Author Introduction Wang Shaohua, born in 1970, male, from Yueyang, Hunan, senior lecturer, technician, graduated from Shandong Building Materials College (now Jinan University) in July 1992 with a major in Electrical Automation, and is now mainly engaged in applied research on mechatronics.