Human Machine Interface

Human machine interface, shortly HMI, is used to control and monitor machines, processes and so on in industry. A very common HMI that is encountered in daily life is an ATM machine. In order to dispense or deposit certain amount of money, the screen and push buttons enable operation of the machine. In industry, HMI is an
important member of having a great automated process. HMIs can either be form a screen, kind of like a computer screen, or touch screen mostly. An authorized operator can handle and oversee a process or machine through HMI. They may include information like temperature, pressure, sensor information etc. HMIs use special software so that engineering can be done properly. Different brands of panels use different software accordingly. The software allows engineer to design what the operator will actually see on the screen, what they can monitor on the screen, what buttons can bu pushed, or how the operator can manipulate the system. However, designing an HMI screen is not as simple as placing the necessary items on the screen with drag & drop. Each indicator or button in HMI screen has to be programmed to a specific input or output address of a PLC. The conclusion that can be drawn here is that HMI and PLC need to be compatible. In other words, they have to communicate each other. Like many existing protocols, PROFINET communication protocol can be used for such communication.

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Within the scope of the thesis work, an HMI screen is designed for both control and monitoring of the conveyor belt system. At the same time, the working structure of the system, i.e. the redundant structure or safe structure, can be decided on the HMI screen. Under normal industrial conditions, the choice of the structure of the system is not left to the operator. The structure of the system is predetermined and the system is programmed accordingly. The reason for making such a design in this project is to show that the system can operate in both safe and redundant structure without changing the established communication structure given in Figure. The root screen of the designed HMI within the scope of this project is given in Figure.

When designing an HMI screen, it should be considered that the operator responsible for this does not know anything, so that it is detailed and understandable accordingly. When the root screen given in Figure is examined, the operator has 3 things to choose: language, operation and system structure. After the system structure is selected, a new screen is opened according to the relevant structure and the conveyor is monitored on that screen. If the language or operation selection is forgotten by the operator and the system structure is selected, the relevant error message appears on the next screen and the operator is forced to return to the home screen. As a result, the HMI screen has been designed in proportion to possible errors that can be made by the operator. In this way, the effect of human error is aimed to be minimized. On the other hand, when a conveyor error occurs, the specially designed alarm screen appears immediately and directs the operator. Thereby, possible dangerous consequences are prevented.

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