1、PDF外文：http:/ 英文原文 Design and Practice of an Elevator Control System Based on PLC Abstract This paper describes the development of 2 nine-storeyelevators control system for a residential building.Thecontrol system adopts PLC as controller,and uses aparallel connection dispatching rule bas
2、ed on"minimumwaiting time"to run 2 elevators in parallel mode.Thepaper gives the basic structure,control principle andrealization method of the PLC control system in detail.It also presents the ladder diagram of the key aspects ofthe system.The system has simple peripheral circuit andthe o
3、peration result showed that it enhanced thereliability and performance of the elevators. 1.Introduction With the development of architecture technology,thebuilding is taller and tallerand elevators becomeimportant vertical transportation vehicles in high-risebuildings.They are responsible to transpo
4、rt passengers,living,working or visiting in the building,comfortableand efficiently to their destinations.So the elevatorcontrol system is essential in the smooth and safeoperation of each elevator.It tells the elevator in whatorder to stop at floors,when to open or close the door andif there is a s
5、afety-critical issue. The traditional electrical control system of elevators isa relay-controlled system.It has the disadvantages such ascomplicated circuits,high fault ratio and poordependability；and greatly affects the elevators runningquality.Therefore,entrusted byan enterprise,we haveimproved el
6、ectrical control system of a relay-controlledelevator in a residential building by using PLC.The resultshowed that the reformed system is reliable in operationand easy for maintenance. This paper introduces the basic structure,controlprinciple and realization method of the elevator PLCcontrol system
7、 in detail. 2.System structure The purpose of the elevator control system is tomanage movement of an elevator in response to usersrequests.It is mainly composed of 2 parts: 2.1.Electric power driving system The electric power driving system includes:theelevator car,the traction motor,door motor,brak
8、emechanism and relevant switch circuits. Here we adopted a new type of LC series ACcontactors to replace the old ones,and used PLCscontacts to substitute the plenty of intermediate relays.The circuits of traction motor are reserved.Thus theoriginal control cabinets disadvantages,such as bigvolume an
9、d high noise are overcome efficiently. 2.2.Signal control system The elevators control signals are mostly realized byPLC.The input signals are:operation modes,operationcontrol signals,car-calls,hall-calls,safety/protect signals,door open/close signal and leveling signal,etc.All controlfunctions of t
10、he elevator system are realized by PLCprogram,such as registration,display and elimination ofhall-calls or car-calls,position judgment of elevator car,choose layer and direction selection of the elevator,etc.The PLC signal control system diagram of elevator isshowed in Figure 1.
11、 Figure 1 PLC signal control system diagram 2.3.Requirements The goal of the development of the control system is tocontrol 2 elevators in a 9-storey residential building. For each elevator,there is a sensor located at everyfloor.We can use these sensors to locate the currentposition of
12、 the elevator car.The elevatorar door can beopened and closed by a door motor.There are 2 sensorson the door that can inform the control system about thedoors position.There is another sensor on the door candetect objects when the door is closing.The elevator carsup or down movement is controlled by
13、 a traction motor. Every floor,except the first and the top floor,has apair of direction lamps indicating that the elevator ismoving up or down. Every floor,has a seven segment LED to display thecurrent location of the elevator car. The first step for the development of the elevatorcontrol is to def
14、ine the basic requirements.Informally,theelevators behavior is defined as follows. (1)Running with a single elevator Generally,an elevator has three operation states:normal mode,fire-protection mode and maintenancemode.The maintenance mode has the highest priority.Only the maintenance mode is cancel
15、ed can the otheroperation modes be implemented.The next isfire-protection mode,the elevator must return to thebottom floor or base station immediately when the fireswitch acts.The elevator should turn to normal operationmode when the fire switch is reset.Under normaloperation mode,the control system
16、s basic task is tocommand each elevator to move up or down,to stop orstart and to open and close the door.But is has someconstraints as follows: Each elevator has a set of 9 buttons on the car controlpanel,one for each floor.These buttons illuminate whenthey are pressed and cause the elevator to vis
17、it thecorresponding floor.The illumination is canceled whenthe corresponding floor is visited by the elevator. Each floor,except the first and the top floor,has twobuttons on the floor control panel,one to request an up-elevator,one to request a down-elevator.These buttonsilluminate when they are pr
18、essed.The illumination iscanceled when an elevator visits the floor,then moves inthe desired direction. The buttons on the car control panel or the floorcontrol panel are used to control the elevators motion. The elevator cannot pass a floor if a passenger wants toget off there. The elevator cannot
19、stop at a floor unless someonewants to get off there. The elevator cannot change direction until it has servedall onboard passengers traveling in the current direction,and a hall call cannot be served by a car going in thereverse direction. If an elevator has no requests,it remains at its currentflo
20、or with its doors closed. (2)Parallel running with two elevators In this situation,there are two elevators to serve thebuilding simultaneously.It runs at 7am to 9am and 5pmto 7pm every day. When an elevator reaches a level,it will test if the stopis required or not.It will stop at this level when th
21、e stop isrequired. At the same time,to balance the number of stops,theoperation of two elevators will follow a certaindispatching principle. An elevator doesnt stop at a floor if another car isalready stopping,or has been stopped there. The normal operation of elevators is implemented bycooperation of its electric power driving system and logiccontrol system.
