A Human Machine Interface (HMI) is generally considered to be the medium through which automated systems and users interact with each other visually. In industrial automation systems, HMIs are typically connected to industrial controllers such as programmable logic controllers (PLCs), general-purpose frequency converters, and intelligent devices to enable visual information interaction and operation between humans and machines. Conventionally, HMI products with touch input capabilities are often referred to as panels or touchscreens.
The structure, principles, and functions of Human-Machine Interface (HMI) products: HMI products consist of two parts: hardware and software. The hardware part includes a microprocessor, memory, input and display units, and communication interfaces. The microprocessor is the core of the HMI, and its performance determines the overall performance level of the product. Generally, small HMIs with membrane keypad input have small display sizes and are considered entry-level products; HMIs with touchscreen input have display sizes ranging from 5.7' to 12.1' and are considered mid-range products; high-performance HMIs based on tablet PCs generally have display sizes larger than 10.4' and are considered high-end products. Depending on the product's level, different microprocessors are typically used: 8-bit, 16-bit, and 32-bit. Display size, type, color, resolution, screen storage capacity, and microprocessor processing speed are the main technical specifications of HMI products. The operating software is divided into two categories: system software running on the HMI hardware and configuration software running on a PC Windows operating system. Some products are compatible with both, running on both the HMI hardware and the PC, such as Siemens' SIMATIC WinCC flexible 2008 configuration software.
Generally, HMI products from different manufacturers use their own configuration software, primarily supporting PLCs. Commonly used configuration software, often referred to as general-purpose configuration software, runs on PCs or Windows operating systems. It is powerful, and installing and running it on a PC or industrial computer creates an HMI product. General-purpose configuration software, such as WinCC, KingSCADA, and ForceControl, supports a wide variety of devices, including PLCs, frequency converters, PC boards, instruments, and modules. Due to the powerful performance of PCs, general-purpose configuration software offers numerous functions, making it particularly suitable for large-scale automated monitoring systems. When using an HMI, a "project file" must first be created using the HMI configuration software. This "project file" is then downloaded to the HMI's memory and run via the communication interface between the PC and the HMI product. Operating parameters or commands are written through input units (such as touchscreens and keyboards), and displayed on the screen, enabling human-machine interaction. The basic functions of human-machine interface products include real-time and historical data trend display of equipment working status (such as text, graphics, curves, etc.); data and text input operations; generation and recording of reports and alarms; printing output; storage of production formulas; automatic recording of equipment production data; logic and numerical operations; and connection to industrial control networks, allowing operators to directly control machines and devices through a graphical interface.
