外文翻译原文-基于PLC的电梯控制系统的设计和实现.pdf

Design and Practice of an Elevator Control System Based on PLC Xiaoling Yang1 2 Qunxiong Zhu1 Hong Xu1 1 College of Information Science and greatly affects the elevator s running quality Therefore entrusted by an enterprise we have improved electrical control system of a relay controlled 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 composed of 2 parts 2 1 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 cabinet s disadvantages such as big volume and high noise are overcome efficiently 2 2 Signal control system The elevator s control signals are mostly realized by PLC The input signals are operation modes operation control signals car calls hall calls 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 hall 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 is showed in Figure 1 Figure 1 PLC signal control system diagram 2 3 Requirements The goal of the development of the control system is to control 2 elevators in a 9 storey residential building For each elevator there is a sensor located at every floor We can use these sensors to locate the current 2008 Workshop on Power Electronics and Intelligent Transportation System 978 0 7695 3342 1 08 25 00 2008 IEEE DOI 10 1109 PEITS 2008 44 94 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 1 Running with a single elevator Generally an elevator has three operation states normal mode fire protection mode and maintenance mode The maintenance mode has the highest priority Only the maintenance mode is canceled can the other operation modes be implemented The next is fire protection mode the elevator must return to the bottom floor or base station immediately when the fire switch acts The elevator should turn to normal operation mode when the fire switch is reset Under normal operation mode the control system s basic task is to command each elevator to move up or down to stop or start and to open and close the door But is has some constraints as follows Each elevator has a set of 9 buttons on the car control panel one for each floor These buttons illuminate when they are pressed and cause the elevator to visit the corresponding floor The illumination is canceled when the corresponding floor is visited by the elevator Each floor except the first and the top floor has two buttons on the floor control panel one to request an up elevator one to request a down elevator These buttons illuminate when they are pressed The illumination is canceled when an elevator visits the floor then moves in the desired direction The buttons on the car control panel or the floor control panel are used to control the elevator s motion The elevator cannot pass a floor if a passenger wants to get off there The elevator cannot stop at a floor unless someone wants to get off there The elevator cannot change direction until it has served all onboard passengers traveling in the current direction and a hall call cannot be served by a car going in the reverse direction If an elevator has no requests it remains at its current floor with its doors closed 2 Parallel running with two elevators In this situation there are two elevators to serve the building simultaneously It runs at 7am to 9am and 5pm to 7pm every day When an elevator reaches a level it will test if the stop is required or not It will stop at this level when the stop is required At the same time to balance the number of stops the operation of two elevators will follow a certain dispatching principle An elevator doesn t stop at a floor if another car is already stopping or has been stopped there The normal operation of elevators is implemented by cooperation of its electric power driving system and logic control system 3 Software design Due to the random nature of call time call locations and the destination of passengers the elevator control system is a typical real time random logic control system Here we adopted collective selective control method with siemens PLC S7 200 CPU226 and its extension modules There are 46 input points and 46 output points in the system The I O points are showed in Table1 and Table 2 Table 1 Input points description address 1 8 floor up hall call I0 0 I0 7 2 9 floor down hall call I1 0 I1 7 1 9 floor car call I2 0 I2 7 I3 0 1 9 arrival sensor I3 1 I3 7 I4 0 I4 1 door open button I4 2 door close button I4 3 door close location switch I4 4 door open location switch I4 5 up leveling sensor I4 6 down leveling sensor I4 7 fire switch I5 0 driver operation switch I5 1 touch panel switch of car door I5 2 overload I5 3 Forced speed changing switch I5 4 full load I5 5 Table 2 Output points description address 1 8 floor up hall call lamp Q0 0 Q0 7 2 9 floor down hall call lamp Q1 0 Q1 7 1 9 floor car call lamp Q2 0 Q2 7 Q3 0 up moving lamp Q3 1 down moving lamp Q3 2 Seven segment LED display of elevator s position Q3 3 Q3 7 Q4 0 4 1 door opening Q4 2 door closing Q4 3 up moving Q4 4 down moving Q4 5 full load lamp Q4 6 high speed operation Q4 7 low speed operation Q5 0 acceleration of starting Q5 1 deceleration of braking Q5 2 Q5 4 alarm beeper Q5 5 About software designing we adopt the modularized method to write ladder diagram programs The information transmission between modules is achieved by intermediate register bit of PLC 95 The whole program is mainly composed of 10 modules hall call registration and display module car call registration and display module the signal combination module the hall call cancel module the elevator location display module the floor selection module the moving direction control module the door open close module the maintenance operation module and the dispatching module under parallel running mode The design of the typical modules is described as follows 3 1 Hall call registration and display There are two kinds of calls in an elevator hall call and car call When someone presses a button on the floor control panel the signal will be registered and the corresponding lamp will illuminate This is called hall call registration When a passenger presses a button in the elevator car the signal will be registered and with the corresponding lamp illuminated This is called car call registration Figure2 shows the ladder diagram of up hall calls registration and display The self lock principle is used to guarantee the calls continuous display Figure 2 up hall call registration and display 3 2 The collective selection of the calls Here the collective selection control rules are used As showed in Figure3 M5 1 M5 7 M6 0 and M6 1 are auxiliary relays in PLC They denote the stopping request signal of 1st to 9th floor respectively The auxiliary relay M6 2 denotes the elevator driver s operation signal When there is a call in a certain floor the stopping signal of corresponding floor will output When the elevator is operated by the driver the hall calls will not be served And the elevator cannot pass a floor at which a passenger wishes to alight 3 3 The cancellation of the calls The program of this module can make the elevator response the hall calls which have the same direction as the car s current direction and when a hall call is served its registration will be canceled The ladder diagram of up hall calls cancellation is showed in Figure4 Figure 3 The combination of the calls Figure 4 The cancellation of up calls In Figure4 the auxiliary relay M4 0 is the up moving flag of the elevator When the current direction of the elevator is up M4 0 s contacts are closed on the contrary when the current direction of the elevator is down M4 0 s contacts are opened M0 1 to M0 7 denotes the car calls stopping request signal of floor 2 to floor 8 respectively This program has two functions 1 Make the elevator response the normal down hall calls when it is moving down and when a down hall call is served its registration is canceled 2 When the elevator is moving up the corresponding floor s down hall call it passing by is not served and the registration is remained 96 The cancellation of down hall calls is reversed with up hall calls 3 4 Elevator s direction The elevator may be moving up or down depending on the combination of hall calls and car calls The following ladder diagram in Fig 5 illustrates that the elevator will move up Figure 5 Up moving of the elevator Figure5 shows that when the calls corresponding floor is higher than the elevator s current location the elevator will go up Here the auxiliary relay M4 0 is used as the up moving flag When the elevator is moving up the up moving lamp is illuminated so the M4 0 is connected on When the elevator arrives the top floor the up moving lamp is off and the timer starts After 0 2s the M4 0 is disconnected the up moving display is off Here we used M4 0 to replace Q3 1 which can ensure the cancellation s reliability 3 5 Elevator s floor stopping Figure6 shows the ladder diagram of the elevator s floor stopping function As showed in Figure6 M6 4 is the flag of floor stopping signal M6 6 is the floor stopping signal sent by the driver M7 0 is the fire signal sent by the fire switch And M6 7 is the forced speed changing signal When either of these contacts act the system should send out the floor stopping signal 4 Minimum waiting time algorithm In traffic of elevator systems there are two types of control task usually The one is the basic control function to command each elevator to move up or down to stop or start and to open and close the door The other is the control of a group of elevators The main requirements of a group control system in serving both car and hall calls should be to provide even service to every floor in a building to minimize the time spent by passengers waiting for service to minimize the time spent by passengers to move from one floor to another to serve as many passengers as possible in a given time 1 Figure 6 The elevator s floor stopping There are many dispatching algorithms for elevator s group control Such as Nearest neighbor Algorithm 2 which the elevator always serve the closet request next Zoning Algorithm 3 which by analyzing the traffic of elevator system with unequal floor and population demand to dispatch the elevator and Odd even rule which an elevator only serves the odd floor and the other only serves the even floor The Nearest neighbor Algorithm minimizes the length of the elevator s empty move to the next request it usually has very small average waiting times but individual waiting times can become quite large 2 The Zoning Algorithm usually used in buildings which has heavy traffic situations such as the office building at lunch time Compared to the office building and shopping mall the traffic flow of residential buildings is relatively low 97 and even in every floor Secondly people usually think of elevators as purely functional objects and the experience of riding an elevator is time waited for most of them Furthermore there exist immense problems when attempting to satisfy all requirements Considering all of the reasons above we adopted the minimum waiting time algorithm to realize the 2 elevators parallel running 4 4 1 Evaluation function The goal of the minimum waiting time algorithm is to predict the each elevator s response time according to all calls and select the elevator which has the shortest response time to serve When there is a call the system calculates out the function values of each elevator according the evaluation function showed in 1 and 2 J Min J 1 J 2 J n 1 J i Tr i KTd i KTo i i 1 2 n 2 J i is the evaluation index of each elevator Tr i denotes the time of the elevator directly moving to the destination corresponding the latest call from its current floor To i denotes the additional acceleration and deceleration time of a floor stop of the elevator Td i denotes the average time of the passenger boarding and alighting the elevator and K is the sum of hall calls and car calls But when a hall call and a car call corresponds the same floor the K is only calculated one time 4 2 Calculation of minimum waiting time In equation 2 K is a certain value To and Td can be obtained by means of statistics Tr T L where T denotes the average time of the elevator passing by one floor L denotes the desired floors of the elevator from current floor to the hall call floor In order to calculate the L value we defined the 2 elevators are A and B respectively YA YB denotes the current floor of elevator A and B respectively H is the corresponding key value when a hall call button is pressed and H floor number of the hall call We defined 4 tables for the PLC realization up hall call registration table down hall call registration table car call registration table of A and car call registration table of B When a certain call button is pressed its floor value is recorded in corresponding table Here we take elevator A as an example First define the variable MA MB and MW Where MA MB denotes the extreme value of car calls with same direction of A or B s movement respectively When elevator A is up moving set MA is equal to the maximum value in car call registration table A when elevator A is down moving set MA is equal to the minimum value in car call registration table A MW denotes the extreme value of hall calls with same direction of A s movement When elevator A is up moving and up hall call value YA set MW 0 otherwise set MW is equal to the minimum value in up hall call registration table A When elevator A is down moving and up hall call value YA set MW 0 otherwise set MW is equal to the maximum value in down hall call registration table A Thus we can determine the L value according to YA H MA and MW There are 3 situations 1 When the hall call s direction is opposite to elevator A s movement L YA MA MA H 3 2 When the hall call s direction is same as elevator A s movement and it is in the front of elevator A L YA H 4 3 When the hall call s direction is same as the elevator A s movement and it is in the back of elevator A L YA MA MA MW H MW 5 So the i th floor s minimum waiting time can be calculated by 6 as follows Time i TL i KTd i KTo i i 1 2 n 6 When the calls change during the operation of elevators the system calculates the minimum waiting time of each elevator Then it allocates the current call to the elevator which has small value When the each elevator has the same value then the current call is prior to elevator A When an elevator is wrong or not in service the system can exit the dispatching algorithm and turns to a single elevator running mode 4 3 Algorithm realization Compared with single elevator running mode the parallel running mode is mainly different at the processing method about hall calls The former uses collective selective control method and the latter uses dispatch rule combined with collective selective control method Here the system is to control a 9 storey building so we choose two Siemens S7 200 PLCs CPU226 and its Extensive Modules to control the single elevator respectively And by using PPI Protocol to realize the communication between 2 PLCs The PPI Protocol adopts master slave communication mode so we defined elevator A as the master and elevator B as the slave By communication program the 2 PLCs can exchange the massage such as the current position hall calls or car calls and moving direction Then by using minimum waiting time algorithm the system realizes the optimal operation of 2 elevators Figure7 shows the ladder program of the car calls extreme value calculation of elevator A In Figure7 VB121 VB130 is the register address of elevator A s car call corresponding to each floor Q3 1 is 98 the up moving lamp of elevator A and the car calls extreme value is saved in VB120 Figure 7 The car calls extreme value calculation of elevator A 5 Conclusions In this paper we ha