Abstract

Abstract

Along with the development of modern economy and city life, the elevator has become

a essential walking tool for people in daily life, and the performance of elevators obviously

influences people’s lives. The traditional elevator system based on relay largely decreases the

reliability and security since the mechanical and electromagnetic inertia of relay is big In

order to ensure the efficiency and reliable securities, the control method of elevator must be

changed. The programmable logic controller(PLC),which develops based on sequence logical

control, is digital operation electronic device specialized in the industrial application

environment. PLC possesses fast process speed and high reliability. Therefore, PLC can be

able to ensure the elevator run normally, securely and reliably. In addition. The drive method

of elevators has replaced the DC velocity modulation with frequency control due to the

development of AC frequency control of motors. The frequency control not only satisfies the

comfort sense of passengers and ensures the stable precision, but also decreases the loss of

power, saves resources and reduces expenses. The frequency control method based on PLC is

applied to the elevator system and further researched.

Firstly, the essay respectively presents the characteristics of the elevator system based on

relay control and PLC control, specially formulates the defects exposed from relay control

system and the advantages of PLC control system, introduces the frequency control of

elevators. Secondly, based on reading many domestic and international relative literatures.

The development of elevator techniques and elevator devices is overviewed. And then, the

relative knowledge of frequency-converter is introduced; the principle of PLC model election

and design scheme of PLC control system are introduced as well. On the basis of these, the

PLC software of elevator system is developed according to the working states demands of the

elevator. A elevator system based on PLC control is designed through combining the

characteristics of software development and the rules of PLC control. Finally, the analog

examination shows the elevator frequency control based on PLC possesses high operational

efficiency and strong system security. The system structure is simple and easily realized, and

satisfies the demands of the elevator system expected.

Key words: Elevator, Programmable Logic Control(PLC), Frequency Conversion &

Velocity Adjustment, Revolving Encoder