【正文】 etween 7am to 9am. (2) Up–Peak This condition concerns people entering the building between 5pm to 7pm. (3) Other It covers the day from 6:00 to 0:00 except the two situations above. And in this situation, there is only one elevator running. The results are expressed via an average waiting time and maximum waiting time(both given in seconds) are collected in Tables 3 and 4. Due to the nonparallel running before the reform, so the average waiting time and maximum waiting time of down–peak and the up–peak are very longer than the reformed. The practice results have showed the better performance of the improved control system. References [1] Ricardo Gudwin, Fernando Gomide, Marcio (i998). “A Fuzzy Elevator Group Controller With Linear Context Adaptation”. IEEE World Congress on Computational intelligence . Vol. 12, No. 5, . [2] Philipp Friese, J Rambau (2021). “Onlineoptimization of multielevator transport systems with reoptimization algorithms based on setpartitioning models”. Discrete Applied Mathematics .No. 154, . [3] Zheng Yanjun, Zhang Huiqiao, Ye Qingtai, Zhu Changming. (2021). “The Research on Elevator Dynamic Zoning Algorithm and it39。 to serve as many passengers as possible in a given time[i]. . There are many dispatching algorithms for elevator?s group control. Such as Nearestneighbor Algorithm[2],which the elevator always serve the closet request next。 to minimize the time spent by passengers waiting for service。 and greatly affects the elevator?s running quality. Therefore, entrusted by an enterprise, we have improved electrical control system of a relaycontrolled elevator in a residential building by using PLC. The result showed that the reformed system is reliable in operation and easy for maintenance. This paper introduces the basic structure, control principle and realization method of the elevator PLC control system in detail. 2. System structure The purpose of the elevator control system is to manage movement of an elevator in response to user?s requests. it is mainly posed of 2 parts: . Electric power driving system The electric power driving system includes: the elevator car, the traction motor, door motor, brake mechanism and relevant switch circuits. Here we adopted a new type of LC series AC contactors to replace the old ones, and used PLC?s contacts to substitute the plenty of intermediate relays. The circuits of traction motor are reserved. Thus the original control cabi?s disadvantages, such as big volume and high noise are overe efficiently. . Signal control system The elevator?s control signals are mostly realized by PLC. The input signals are: operation modes, operation control signals, carcalls, hallcalls, safety/protect signals, door open/close signal and leveling signal, etc. All control functions of the elevator system are realized by PLC program, such as registration, display and elimination of hallcalls or carcalls, position judgment of elevator car, choose layer and direction selection of the elevator, etc. The PLC signal control system diagram of elevator is showed in Figure 1. . Requirements The goal of the development of the control system is to control 2 elevators in a 9storey residential building. For each elevator, there is a sensor located at every floor. We can use these sensors to locate the current position of the elevator car. The elevator car door can be opened and closed by a door motor. There are 2 sensors on the door that can inform the control system about the door?s position. There is another sensor on the door can detect objects when the door is closing. The elevator car?s up or down movement is controlled by a traction motor. Every floor, except the first and the top floor, has a pair of direction lamps indicating that the elevator is moving up or down. Every floor, has a seven segment LED to display the current location of the elevator car. The first step for the development of the elevator control is to define the basic requirements. informally, the elevators behavior is defined as follows.