Understanding basic human-machine interface (HMI) concepts is essential for beginners. HMI products consist of both hardware and software. Hardware includes components such as processors, display units, input units, communication interfaces, and data storage units. HMI software generally comprises two parts: system software running on the HMI hardware and screen configuration software running on a PC with a Windows operating system. This article provides a detailed introduction to 10 fundamental concepts of human-machine interfaces.
Human-Machine Interaction (HMI)
Commonly used terms: touchscreen, HMI, human-machine interface
(I) Basic Functions and Selection Criteria of Human-Computer Interface Products
(1) Basic functions:
Equipment operating status display, such as indicator lights, buttons, text, graphics, curves, etc.;
Data and text input operations, and printing output;
Production formula storage and equipment production data recording;
Simple logic and numerical operations;
It can connect to a network of various industrial control devices.
(2) Selection criteria:
Display screen size, color, and resolution;
HMI's processor speed performance;
Input method – touchscreen or membrane keyboard;
Screen storage capacity – Is the capacity unit bytes or bits?
The type and number of communication ports, and whether printing functionality is supported, etc.
(3) Product Classification:
Entry-level products: membrane keypad input, display size typically less than six inches.
Mid-range products: Touchscreen input, display size typically larger than six inches.
High-end products: computer input type, display size typically larger than ten inches.
(II) Routine Usage Procedures of Human-Computer Interface
(1) Define the monitoring task requirements and select a suitable HMI product;
(2) Edit the "project file" on the PC using the screen configuration software;
(3) Test and save the edited "project file";
(4) Connect the PC to the HMI hardware and download the "project file" to the HMI;
(5) Connect the HMI and industrial controllers (such as PLC, instruments, etc.) to realize human-machine interaction.
(III) What is the difference between a human-computer interface and what people commonly refer to as a "touchscreen"?
Strictly speaking, there is a fundamental difference between the two. A "touchscreen" is merely a hardware component that may be used in human-computer interface products; it is an input device installed in front of the display screen that replaces some functions of a mouse and keyboard.
Human-machine interface (HMI) products are devices that combine hardware and software for human-computer interaction. In industry, HMI products with touch input capabilities are often referred to as "touchscreens," but this is not accurate.
(iv) What are the differences between human-machine interface and configuration software?
Human-machine interface products, often referred to as "touchscreens," consist of HMI hardware and corresponding dedicated screen configuration software. Generally, different manufacturers use different screen configuration software for their HMI hardware, and the main type of device they connect to is a PLC.
Configuration software is a general-purpose tool software product that runs on a PC hardware platform and Windows operating system. It can also be used together with a PC or industrial control computer to form an HMI product. General-purpose configuration software supports a wide variety of devices, such as various PLCs, PC boards, instruments, frequency converters, modules, etc. Moreover, due to the powerful performance of the PC hardware platform (mainly reflected in speed and storage capacity), the functions of general-purpose configuration software are also much stronger, making it suitable for large-scale monitoring systems.
(v) Does the human-computer interface product have an operating system?
Every human-machine interface (HMI) product has a system software component. This system software runs on the HMI's processor, supports multitasking, and requires a small operating system to manage the system software. High-performance HMI products based on tablet computers typically use common embedded operating systems such as WinCE and Linux.
(vi) Can the human-machine interface only be connected to a PLC?
That's not the case. Human-machine interface (HMI) products were developed to solve the human-machine interaction problem of PLCs. However, with the development of computer technology and digital circuit technology, many industrial control devices have serial communication capabilities. Therefore, any industrial control device with serial communication capabilities, such as frequency converters, DC speed controllers, temperature controllers, and data acquisition modules, can be connected to HMI products to achieve human-machine interaction functions.
(vii) Can the human-machine interface only be connected to other devices through a standard serial communication port?
That's not the case. However, with the development of computer and digital circuit technology, the interface capabilities of human-machine interface products are becoming increasingly powerful. In addition to traditional serial (RS232, RS422/RS485) communication interfaces, many human-machine interface products now have data interfaces such as network ports, parallel ports, and USB ports. These can be connected to industrial control equipment with interfaces such as network ports, parallel ports, and USB ports to realize human-machine interaction.
(viii) Does a device with communication capabilities necessarily connect to a human-machine interface product?
That should be the case. Because general-purpose HMI products offer a large number of readily available communication drivers for commonly used devices; typically, simply selecting the corresponding communication driver for the connected device in the HMI's configuration software is sufficient to establish a communication connection between the HMI and the device. If the selected HMI product's configuration software does not have a communication driver for the device to be connected, the user can inform the HMI product manufacturer of the communication port type and protocol of the device to be connected, requesting the HMI manufacturer to develop a communication driver for that device.
(ix) Can a PC with a display screen communicate directly with a PLC to complete the functions of an HMI?
Of course, you can. However, you'll need to develop the corresponding configuration software for the PC to become a true HMI product.
(x) What are the future development trends of human-computer interfaces?
With the development of digital circuits and computer technology, the distinction between high, medium and low functionality in future human-machine interface products will become less and less obvious, and the functions of HMIs will become richer and richer; HMI products with an inch or larger will all be color displays, and the lifespan of the screens will also be longer.
Due to the decreasing cost of computer hardware, HMI products will primarily feature high-end tablet PCs as their hardware. These high-end products offer significant advantages in processor speed, storage capacity, the variety and number of communication interfaces, networking capabilities, and software resource sharing, representing the future direction of HMI product development. Of course, smaller-sized HMI products (display size less than 5.7 inches), with their advantages in size and price, will find widespread application in human-computer interaction for small mechanical devices as their functionality is further enhanced (such as by adding I/O capabilities).
Some machinery industries, such as machine tools, textile machinery, and electronic equipment, have been developing in China for decades and are relatively mature. However, in the long run, these industries still have a need for equipment upgrades. During this process, some small manufacturers that have consistently used lower-end products will indeed be eliminated. But many companies will also redefine their needs during equipment upgrades, seeking equipment suppliers that align with their development plans and help them improve their productivity.
Given this demand, future changes to human-machine interfaces will encompass changes in shape, concept, and application scenarios, leading to successive revolutions in the core technologies of industrial control computers. Generally speaking, the future development trend of human-machine interfaces is characterized by six modernizations: platform embedding, brand nationalization, equipment intelligence, interface modernization, communication networking, and energy conservation and environmental protection.
