First, HMI Introduction
HMI is the abbreviation of HumanMachineInterface, "human-machine interface", also called human-machine interface. The human-machine interface (also known as user interface or user interface) is the medium of interaction and information exchange between the system and the user, which realizes the conversion between the internal form of information and the form acceptable to human beings. Wherever involved in human-computer information exchange in the field of human-computer interface exists.
Second, the interface type of HMI
HMI has many types of interfaces, RS232, RS485, CAN, RJ45 network interface.
For example, in a factory, we have to collect the temperature, humidity, and the state of the factory machine in each area of the factory and other information. Through a master controller to monitor and record these parameters, and in the event of some unexpected conditions can be dealt with. This is a very typical SCADA / HMI utilization.
In general, HMI systems must have several basic capabilities:
Real-time data trend display - to capture the information immediately displayed on the screen.
Automatic data logging - automatically store data into a database for later viewing.
Historical Data Trend Display - visualize the data in the database.
Report Generation and Printing - Data can be converted into a report format and printed out.
Graphical interface control - the operator can directly control the machine and other devices through the graphical interface.
Alarm generation and recording - the user can define the conditions for generating some alarms, such as excessive temperature or pressure exceeding the threshold value, in such conditions the system will generate an alarm to notify the operator to deal with.
HMI human-machine interface HMI summary of the eight major knowledge points
Third, the composition and working principle of HMI human-machine interface products
HMI products are composed of two parts: hardware and software. The hardware part includes processor, display unit, input unit, communication interface, data storage unit, etc. The performance of the processor determines the performance of the HMI products and is the core unit of HMI. According to the different levels of HMI products, the processor can be selected 8-bit, 16-bit, 32-bit processor, HMI software is generally divided into two parts, namely, running in the HMI hardware in the system software and running on a PC under the Windows operating system screen configuration software. Users must first use the HMI screen configuration software to create a "project file", and then through the PC and HMI products serial communication port, the preparation of the "project file" downloaded to the HMI processor to run.
Fourth, the basic functions of HMI human-machine interface products
(1) equipment status display
(2) data, text input operation, printout; (3) production formula storage, equipment production.
(3) production formula storage, equipment production data logging.
(4) Simple logic and numerical operations.
(5) Can be connected to a variety of industrial control equipment network.
Fifth, HMI human-machine interface product selection indicators
(1) display size and color, resolution.
2) HMI's processor speed performance.
(3) Input mode: touch screen or membrane keyboard;
(4) screen storage capacity, pay attention to the manufacturer's labeled capacity unit is byte, or bit.
(5) the type and number of communication ports, whether to support the print function.
Six, the human-machine interface HMI 8 knowledge
1. Can HMI only connect to PLC?
Not so. HMI products are designed to solve the PLC human-computer interaction problems arising, but with the development of computer technology and digital circuit technology, a lot of industrial control equipment are equipped with serial communication capabilities, so as long as there is a serial communication capabilities of industrial control equipment, such as frequency converters, DC speed controllers, temperature control instrumentation, digital acquisition module, etc. can be connected to the HMI products to achieve the function of human-computer interaction.
2. What is the difference between HMI and what is often called "touch screen"?
Strictly speaking, the two are fundamentally different. Because the "touch screen" is only the hardware part that may be used in the human-machine interface products, it is an alternative to the mouse and keyboard part of the function, installed in the front of the display of the input device; while the human-machine interface products are a kind of human-computer interaction equipment that contains hardware and software. In the industry, people often have touch input function of human-machine interface products called "touch screen", but this is not scientific.
3. Is there an operating system in the HMI product?
Any human-machine interface products have a system software part, the system software runs in the HMI processor, support for multi-tasking functions, the processor needs to have a small operating system to manage the operation of the system software. Tablet PC-based high-performance HMI products, generally use WinCE, Linux and other general-purpose embedded operating systems.
4. What is the difference between HMI and configuration software?
HMI products, often referred to as "touch screen", including HMI hardware and the corresponding special screen configuration software, in general, different manufacturers of HMI hardware to use different screen configuration software, connected to the main types of equipment is PLC. The configuration software is running on the PC hardware platform, windows operating system under a general tool software products, and PC or industrial control machine can also be composed of HMI products; general configuration software to support a very wide range of devices, such as a variety of PLCs, PC boards, meters, inverters, modules and other devices, and because of the PC's hardware platform performance is strong (mainly reacting to the speed and storage capacity), the general configuration software is also very strong function, applicable to the Large-scale monitoring system.
5. Whether the equipment with communication function can be connected with HMI products?
It should be so. Because common HMI products provide a large number of commonly used device communication drivers for selection; in general, as long as the screen configuration software in the HMI interface to select and connect the device corresponding to the communication driver, you can complete the communication connection between HMI and the device. If the configuration software of the selected HMI product does not have a communication driver for the connected device, the user can inform the manufacturer of the HMI product of the type of the communication port and the content of the protocol of the device to be connected, and ask the HMI manufacturer to prepare a communication driver for the device on behalf of the manufacturer.
6. PC plus touch screen, can directly communicate with PLC to complete the HMI function?
Of course. However, we also need to prepare the corresponding HMI software in order to make the PC become a real HMI product.
7. HMI can only be connected to other devices through the standard serial communication port?
In most cases this is the case. However, with the development of computer and digital circuit technology, the interface capability of HMI products is getting stronger and stronger. In addition to the traditional serial (RS232, RS422/RS485) communication interface, some HMI products have a network port, parallel port, USB port and other data interfaces, they can have a network port, parallel port, USB port and other interfaces connected to the industrial control equipment to achieve the human-machine interaction of the equipment.
8. What is the future development trend of human-machine interface?
With the development of digital circuits and computer technology, the future of the human-machine interface products in the function of high, medium and low division will be less and less obvious, HMI functions will be more and more rich; 5.7 inches above the HMI products will be all color display, screen life will be longer. Due to the reduction in the cost of computer hardware, HMI products will be flat-panel PC computers for HMI hardware for high-end products, because this high-end products in the processor speed, storage capacity, the type and number of communication interfaces, networking capabilities, software resource sharing have a greater advantage in the future direction of development of HMI products. Of course, small size (display size less than 5.7 inches) HMI products, due to its advantages in size and price, with its further enhancement of functionality (such as increasing the IO function), will be widely used in small machinery and equipment for human-computer interaction applications.