PLCs have been around for nearly 40 years. With the development of semiconductor technology, computer technology, and communication technology, the field of industrial control has undergone tremendous changes. PLCs are also constantly evolving and moving towards new technologies, mainly in the following aspects:
Firstly, there is the development of PLC networking technology, which has two trends: On the one hand, PLC network systems are no longer self-contained closed systems, but are rapidly developing into open systems. In addition to forming their own unique PLC network systems and completing equipment control tasks, major brands of PLCs can also connect to the host computer management system to achieve information exchange and become part of the entire information management system. On the other hand, fieldbus technology is widely adopted. PLCs are connected to other intelligent devices installed in the field, such as intelligent instruments, sensors, intelligent solenoid valves, and intelligent drive actuators, through a transmission medium (such as twisted pair, coaxial cable, or optical fiber) and transmit information to each other according to the same communication protocol, thus forming a field network. Compared with a simple PLC remote network, this type of network is more flexible in configuration, easier to expand, lower in cost, has a better performance-price ratio, and is also more open.
Secondly, PLCs are evolving towards high performance and miniaturization. Their functions are becoming increasingly richer, while their size is decreasing. For example, Mitsubishi's FX-IS series PLC, even the smallest model, measures only 60×90×75mm, roughly the size of a relay, yet it possesses capabilities such as high-speed counting, ramping, alternating output, and 16-bit arithmetic operations, as well as adjustable potentiometer time setting. PLCs are no longer the early products limited to switching logic operations; they now possess increasingly powerful analog signal processing capabilities, as well as other advanced processing capabilities previously only available on computers, such as floating-point arithmetic, PID control, temperature control, precise positioning, stepper drive, and report statistics. In this sense, the difference between PLC systems and DCS (Distributed Control Systems) is diminishing; a process control system can also be constructed using a PLC.
Thirdly, PLC operation is trending towards simplification. One of the current difficulties in promoting PLCs is the complexity of their programming, which deters users. Furthermore, different manufacturers use different programming languages for their PLCs, requiring users to master multiple languages, which is quite challenging. Programming and applying PID control, network communication, high-speed counters, position control, data logging, recipes, and text displays are also difficult aspects of PLC programming. Programming these using conventional methods requires familiarity with the meaning of special memory, assigning values to them during programming, and accessing them during runtime to achieve the corresponding functions. These programs often involve interrupts, making the programming process cumbersome and error-prone, hindering the further promotion and application of PLCs. The development of PLCs inevitably moves towards simplifying the programming of complex tasks. Siemens has been a pioneer in this regard. Siemens S7-200 programming software features numerous programming wizards; users only need to input some parameters in the dialog box to automatically generate user programs, including interrupt routines, greatly facilitating their use.
Fourth, embedded PLCs have great potential for development. The development of embedded PLCs is also diversified, with good performance both domestically and internationally: The netPLC launched by HRS in Germany, which combines fieldbus technology and PLC technology, is quite distinctive; several years ago in China, Huazhong University of Science and Technology loaded embedded PLC system software into the EASYCORE 1.00 core chipset as a hardware platform, developing a multi-mode human-machine interface embedded PLC; another development path is to develop a hardware/software integrated platform that combines PLC and human-machine interface, making full use of CASE tools, combining various embedded chip development platforms and hardware circuit libraries for various input/output channels, to develop customized, ODM-like dedicated PLCs specifically for electromechanical equipment.
The development potential of embedded PLCs in my country lies primarily in their ability to leverage two key characteristics of the country's automation industry: a robust market base for supporting electromechanical equipment and a sufficient number of globally competitive design and development teams. We can completely replace general-purpose PLCs with embedded PLCs designed and manufactured to meet customized requirements at the lowest cost and with high quality.
Meanwhile, embedded PLCs offer flexible and customizable hardware, software, human-machine interface, and communication functionalities, better meeting the requirements of various levels of electromechanical equipment. Based entirely on embedded system technology, embedded PLCs are readily available. Their advantages, such as SOC chips, embedded operating systems, and programming environments conforming to the EC61131-3 programming language standard, make them readily available in the market.
