中国地质大学长城学院毕业论文外文资料翻译(4)

The control cabinet is the control center, from which we can send out various control commands. The control cabinet often was installed in the elevator room. The electric devices and signal systems, for example the contactors, relays, capacitances, resistors, rectifiers and transformers etc, are centralized in the control cabinet. The Power of the control cabinet was imported from the chief power of the elevator room. This power was also introduced into control panel by soft cables and was linked with each control buttons. The power lines which was derived from control cabinet was delivered to tow electric motors. Others control lines and signal lines were separately sent to each floor junction.

The design includes two parts: hardware and software. The hardware design is the base of software. Considering that the control demands are relatively complex, we design the programs separately according to the control function. Furthermore, we follow the principle as follows: When the elevator is ascending, the ascending demands are prior to other demands.When the elevator is descending, the descending demands are prior to other demands. The Sequential Function Chart(SFC) is adopted during the boxes to form elevator’s executive circuitry design. It is a method specially used in industrial sequential control. The SFC method can describe the system’s working procedure in great detail.

When all SFC are drawn and I/O address lists are presented, we can convert the SFC to Ladder Diagram(LD). Considering the strict demands for time and for locked each other, we introduce working bits to remember working steps. We should write out the working bits control program, which can link together each step and make the pervious step as the next step restriction condition. Thus the actual outputs are the logic combination of these working steps.

The system program has been debugged completely at present. Simulated experiment enunciates that the design method is viable. Application of PLC in the elevator control system is an effective method. It can make the personnel of the industry management center to long-distance monitor and control the elevator in control center, to connect the elevator system with intelligence building industry management system by Ethernet or special-purpose network such as Lon Works. The elevator, but also can lower the elevator maintenance costs etc. It is one of the developing direction of intelligence building elevator control system.

Lift control system

Lift control system is used to manipulate each control process by managing such commands as running direction, car call, landing call, load signal, landing indication, safety protection.

Lifts in different applications have different load, speed and drive / control modes. Lifts in same application may also have different control mode. Whatever control mode is

adopted, the objective is the same, to be specific, according to car call and landing call, lift control system will execute automatic logic judgment to determine which lift will receive signal, which direction lift will run towards and complete programmed control objective through electrical automatic system based on command.

Types of lift control system

Control system development chronicle indicates that there has appeared many control modes, such as such as relay control, PLC, single computer control, multiple-computer control. Prevailing in different era, these control modes are still employed in lifts now due to massive integrated circuit and computer technology development.

PLC control system

As abbreviation of programmable logic controller, PLC is an electronic system featuring digital computation. It adopts programmable EPROM to execute logic computation, order control, timing, number counting, arithmetic computation, besides, it can input and output through digital or analogy modes.

The mechanism of PLC control is as follows: input of PLC includes such command signals, as power key to home landing, car call, landing call, various safety switches, position signal, while output of PLC includes contactor, relay, indicators of car / landings and communication unit.ay, indicators inside car and switch, position signal, are input to PC, while other executing com

Programming principle is determined by lift control mode. Programming can either be made according to relay logic control circuit or individually in different phases according to lift control functions after completely separating from relay control circuit. Based on the ready made control circuit, the former is simple and easy to master, while the latter involves less programs by integrating programs of small function.

Used in lift control system, PLC has such advantages, as high reliability, stability, easy programming, user-friendliness, convenient maintenance & inspection.

Nowadays, there is a wide range and series of programmable logic controllers. Input / output points range from 30 to 8000 or above, so as to meet lift control requirements with different landing number.