Since the invention of the first push-button switch, Human-Machine Interface (HMI) monitoring systems have become an indispensable part of industrial production. At General Motors, HMI systems assist engineers in fault diagnosis and equipment maintenance. However, at GM, the primary role of HMI is to ensure the trouble-free operation of equipment. The key to extending equipment uptime through HMI systems lies in optimizing the production process. Effective maintenance and accurate fault diagnosis will contribute to normal production. Reviewing the development history of HMI systems will help us understand their future direction and how to better achieve factory operation goals—improving efficiency and increasing uptime. Early Equipment Early HMI applications included numerous push-button switches, indicator lights, selector switches, and other simple control devices, with functions limited to starting and stopping equipment and displaying its status. In a sense, this was also a control system. Such control systems were very simple, typically implemented by combining many relays. At that time, a key design philosophy was to keep control circuits as simple as possible, and the prototype of the HMI was influenced by this idea. The application of buttons, switches, and indicator lights in control systems represents a significant advancement. Early HMI systems often failed to effectively diagnose faults due to their rudimentary nature. At General Motors, if equipment stopped working, we weren't allowed to find the fault by inspecting and testing the control system circuitry. The only detection technique was to use probes to check the continuity from each test point to the equipment control circuitry and the control panel. Now, even without dedicated fault diagnosis functions, HMIs and automation control systems can diagnose faults much faster than previous systems. The introduction of PLCs The advent of programmable logic controllers (PLCs) brought about the first leap forward for HMI monitoring systems. This allowed for the expansion of HMI system functionality by connecting necessary devices to the PLC. When equipment malfunctions, the HMI system can not only communicate with the stopped equipment but also understand why it stopped. Users can identify erroneous bytes in the program through the programming terminal. When equipment malfunctions, the PLC can even be programmed to automatically dial emergency contact numbers. Meanwhile, the monitoring scope of HMI systems began to expand. They could communicate with equipment and acquire its status information, calculate the output of a particular workshop, and display this information through numerous indicator lights, becoming a common sight in workshops at the time. The large amount of information acquired by HMI systems meant that operators had to observe far more indicator lights than before, sometimes struggling to process the information quickly and effectively. Unless the operator was very familiar with the machines, they would be overwhelmed by the sheer volume of information. The introduction of display devices: From simple indicator lights to seven-segment displays, and then to letter displays, these display devices enabled HMI monitoring systems to more accurately reflect the system's status to operators, thereby reducing fault diagnosis time. Through the seven-segment LED displays often seen on old-fashioned calculators, users could obtain equipment status information more accurately. Early fault diagnosis systems could display a faulty I/O number or some numbers on the screen; users had to look these numbers up in the manual to find out what the fault was. The advent of letter displays allowed HMI systems to display text information. Users could also display text in different colors and add variables to the text information, such as output data for different workshops. At this point, operators could easily access information about a wider range of equipment. However, as the complexity of the monitored equipment increased, a significant amount of time was required to program the displays. The most important breakthrough in the development of HMI systems was the emergence of fully programmable HMI devices, which replaced traditional buttons and indicator lights. Virtual objects of programmable buttons and indicator lights were drawn on a CRT monitor, and engineers then programmed these virtual buttons and indicators to display them as required. Soon, the limitations of CRT monitors became apparent—only a limited number of buttons could be displayed on a single screen at a time. Therefore, engineers had to spend a considerable amount of time programming, placing multiple buttons and indicator lights on different screens. This significantly increased design costs. For sequential machining, machining step sheets quickly became the preferred field user guide. Workers could see the precise machining steps and perform the corresponding operations according to these steps, including when to add workpieces, etc. Processes could be quickly adjusted and modified. Meanwhile, this processing step provides a unified interface for both small and large applications, eliminating the need for multiple screens to display the entire process. Instead, a single list is dynamically updated based on the workpiece's processing status. Now, the visual display more vividly reflects the status of the controlled equipment. Operators can not only learn which device caused the downtime through text messages but also observe the machine's status on the screen and indicate the location of the faulty device. This feature reduces the time required to repair faults, but developing a visual display for each device requires considerable effort. Design costs increase with the size and complexity of the equipment. Current and Future HMIs: Current HMI systems have made significant strides, achieving previously unimaginable functions at a more affordable price. Developers and programmers use specialized programs for system development, enabling them to handle the increasing functionality of HMIs while maintaining low development costs. Modern HMI systems offer multiple buttons and displays, allowing control of all identical equipment in the factory from a single screen. Developers only need to specify which device to collect data from for HMI display purposes; the required functions are then displayed as a text list. Therefore, adding new functions to the system only requires adding a new text, thus saving screen space. ● Hardware-wise, PC-based HMI systems have seen significant development over the past decade, but most HMI systems still use dedicated equipment designed for industrial environments. PC-based HMI systems (including control systems) face a series of critical issues that hinder their further adoption. Industrial computers are typically much more expensive than commercial computers, and their technology is less advanced; personal computers are usually used as programming terminals, so their failures won't cause production line shutdowns, but they are rarely used directly in harsh industrial environments; the hard drive of a personal computer is often considered the weakest link, and a failure in it can render it unusable in harsh environments, especially vibrating ones, thus excluding personal computers from certain critical applications; adding monitoring software and communication cards to a computer is expensive, even exceeding the cost of some dedicated industrial control equipment; manufacturers offer shorter spare parts support for consumer computers, making it difficult to purchase parts from computers used years ago. However, industrial control equipment manufacturers are well aware of the problems users face during long-term use, and therefore offer long-term support for their products. PC-based HMI systems, with their technological advantages, have significantly improved upon these shortcomings, especially in terms of price. With the widespread adoption of touchscreen displays and Windows CE-based HMI monitoring devices, PC-based HMI systems represent the future direction. As PC-based HMI products become more common, keyboards and mice will also be used in industrial systems. Interactive control between users and machines in the workshop will become as simple as operating a home computer. Color touchscreen displays are already being used in commercial HMI systems. They can be seen in grocery stores, cinemas, banks, and even shopping malls. The growth of the application market will help reduce the price of flat panel displays of different sizes, thereby eliminating price barriers and enabling wider industrial applications. With the emergence of small flat panel color touchscreen displays, portable HMIs are becoming increasingly popular. Users can directly carry these devices to the machine for control. ● On the software side, more and more universal controls are available in PC-based HMI systems; for example, radio buttons can replace traditional selector switches, and checkboxes can replace traditional buttons. These changes will help users become more familiar with the user interface, thus reducing training costs. The development of HMI software has enabled it to support multiple languages ​​within an application system, a capability that is increasingly useful in today's globally integrated market environment. Currently, most application projects require readjusting the text on every screen throughout the project when supporting multiple languages; however, by separating text from the application project, only the corresponding language file package needs to be provided when changing languages. Automated design has also been introduced into the development of HMI software. When designing HMI systems for a large number of similar machines, a series of wizards can be used to complete the process. As the number of systems increases, such automated design can significantly reduce system development costs, especially for large enterprises that install hundreds of new machines every year. HMI software also offers various open functionalities, allowing it to integrate tightly with user-defined programs, third-party libraries, and other file formats, thus providing better support for user applications. For example, industrial control companies can provide computer-aided design support software, while control system companies sell higher-value-added products, thus saving end-users total investment costs. It is believed that in the near future, HMI systems will all run on the Microsoft Windows operating system, and dedicated equipment HMI systems will gradually be phased out of the market. This will help manufacturers focus on developing software that runs on this platform and creating a unified information exchange standard. At that time, acquiring diagnostic data and developing maintenance work will become much simpler, eliminating the need to use on-device HMIs to obtain diagnostic data and then use other HMIs for maintenance. Operators will only need one HMI to diagnose and maintain faulty equipment. On-device HMIs will also be able to work collaboratively with application systems throughout the workshop or factory. Connecting PC-based HMI systems to upper-level monitoring systems will help factory information systems understand the situation on-site. Future Development Directions of HMIs: As HMI systems evolve, their functionality will continuously improve while reducing overall costs. With the development of the PC market, the following development directions are possible: ● 3D Visualization: To overcome the high costs of machine visualization graphic design, future HMI systems may directly share parameter data from the machine equipment design phase. There will be no need to spend a lot of time creating two-dimensional views; the parameter data of the machine equipment can be imported to generate more direct 3D images in the HMI system. ● Integration of Logic Control and HMI Systems: Currently, the automation design process focuses only on the initial design. The next stage of HMI development will provide automation design tools that span the entire system lifecycle. Currently, there is an inseparable link between HMI systems and logic control systems, so it is highly likely that they will be integrated in the future. ● Using Web Integration Technology: The continuous innovation of HMI systems relies on enhanced connectivity with other devices. One day, HMI users will be able to view the status of other devices through a browser and even control them. Workshop supervisors will also be able to use HMI systems embedded with web technology to obtain information about all workshop equipment for centralized management. ● .NET – Dynamic Transfer of Application Projects: The functionality of browsers ultimately cannot meet the needs of clients. To avoid embedding the entire client application project into the HMI, the application project can directly provide HMI support on the device side. .NET technology lays the foundation for this application, greatly reducing communication barriers between different platforms and hardware devices. The future of HMI systems presents a bright future, but today, the primary considerations for users when choosing an HMI system are still cost and reliability, sometimes even excluding powerful, high-end systems. With the development of the latest technologies—whether in small-scale trials or in the testing phase—manufacturers will inevitably provide users with HMI systems that are more reasonably priced, more powerful, and more stable in performance, thereby meeting the needs of future productivity improvements.