In order to adapt to the increasingly fierce market competition, the new generation of programmable logic controllers has made great progress in technological innovation, mainly reflected in the following aspects:
Emergence of multitasking function
The so-called multitasking means that in a programmable controller system, several CPU modules can be installed at the same time, and each CPU module performs its own tasks and controls the I/O modules related to its execution tasks.
Strengthening of network capabilities
The strengthening of network capabilities has made programmable controllers break through the original scope of use, especially after the introduction of technologies such as fieldbus, industrial Ethernet, wireless network and Internet, the application of programmable controllers has not been what it used to be. . The network topology structure of a typical programmable controller consists of three layers: equipment control layer, process control layer and information management layer. In the device control layer, the field bus is introduced, so that all field devices such as field detection instruments, frequency converters, and MCC control cabinets in the industrial production process can be directly connected to the programmable controller; in the process control layer, the traditional meaning The function of the human-machine interface has been completely renewed, enabling the programmable controller to realize cross-regional programming, monitoring, diagnosis, and management, and to realize the control of the entire workshop and the whole plant; in the information management layer, the expansion to industrial Ethernet , so that control and information management are integrated.
Rockwell Automation’s Total Automation System, Siemens’ Totally Integrated Automation System, and Schneider’s Transparent Factory are all representatives of this type of technology development.
High-speed processing function
With the strengthening of network capabilities, the control functions and control ranges realized by programmable logic controllers are expanding, which requires programmable logic controllers to achieve high-speed operation and real-time communication functions. Speeding up includes speeding up operation, speeding up data exchange with external devices, speeding up service processing of programming devices, and speeding up responses from external devices. In order to achieve high speed, some programmable logic controllers have been designed with communication functions in their cores. With the help of passive data buses, the bottleneck of the system is eliminated. This structure allows multiple processors and networks to be in one rack. It can be used without limitation, thus providing a high-performance distributed real-time control system solution.
