.. Education39/2 Control of a four-level elevator system using a programmable logic … that is because L2 and L3 are intermediate … New York, 1967). 3 I. Warnock, Programmable Controllers … International Journal of Electrical Engineering Education39/2 Control of a four-level elevator system using a programmable logic controller L. Cheded 1 and Ma’an Al-Mulla 2 1 Systems Engineering Department, KFUPM, Saudi Arabia 2 Saudi Aramco, Dhahran, Saudi Arabia E-mail: cheded@kfupm.edu.sa; maanmm@yahoo.com Abstract This project reports on the …

Many engineering systems, including elevator systems,1,2are nowadays controlled by programmable logic controllers (PLCs). The reliance on these PLCs is due to their high reliability and efficiency. In this paper, the design and implementation of a four-level elevator system controlled by a small PLC is discussed. The PLC may be considered as a special-purpose computer with a basic architecture similar to that of any other known computer such as a central processing unit (CPU).3,4It is based on a memory and a number of input and output terminals. The software used for PLC programming is based on a special language known as the ladder diagram. The ladder diagram is an easy programming language since it is based on Boolean logic functions. This makes the task of modifying any system much easier and more cost-effective. The size of the PLC is one of the factors considered when it is selected to control a process. PLCs come in various sizes and different capabilities; the sizes range from small controllers with limited inputs and outputs used for controlling small processes, to very large ones with more inputs and outputs provided which are used to control much larger processes and operations. Determining the appropriate PLC to be used is based on analysing the process to be controlled and accordingly identifying the number of inputs and outputs required. The PLC has many advantages over other control systems. It is known for its flexibility, lower cost, operational speed, reliability, ease of programming, security, and it is easy in implementing changes and correcting errors.3One of the applications using PLCs is the control of elevator systems. Asimulation of such control was successfully tested in a senior-project course in the Systems Engineering Department at KFUPM, where an Omron 12-input and 8-output PLC was used. This paper presents both the hardware and software aspects of the successful design and operation of this PLC-based controller. Objectives of the project The objective of the project is the design and implementation of a four-level elevator system controlled by a Programmable Logic Controller (PLC). The design was limited to four levels due to the limited number of inputs provided by the Omron PLC available. Some suggestions are given later as to how to extend the elevator system to more than four levels. Moreover, the design was not based on a first-come first-served basis, since this approach was not found to be practical. As a practical compromise between energy consumption and speed of response, we decided to combine all requests going in one direction (up or down), and then process them in sequential order. This was achieved in the following manner: if the elevator is going up, all ‘up’requests are given higher priority than the ‘down’requests until the elevator reaches the last destination upwards. Then the elevator goes down but now gives priority to all ‘down’requests over the ‘up’ones. More details on this will be given in the section ‘Software design’. Hardware design The objective of the hardware design is to develop the interface circuit between the PLC and the elevator system and the elevator control panel, with both external and internal requests. These requests are produced by push buttons that send continuous signals to the PLC when activated. Each push button is connected to an LED to identify the request placed. In addition, the four floors are represented by four LEDs, one for each level.

Download Control of a four-level elevator system using a programmable logic controller.Pdf