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.
Vigorously develop integrated software
At present, the proportion of the cost of developing system hardware for manufacturers of programmable logic controllers is decreasing year by year, while the proportion of developing software and integration costs is increasing year by year. Today’s software packages integrate programmable controller programming, operator interface, motion control, program debugging, fault diagnosis and processing, and communications. The human-machine interface and monitoring software integrates all open standard interfaces, which can obtain a large amount of real-time data directly from production, analyze and package this data, and then transmit it to the management level, and it can also process optimization data and production details. The parameters are quickly fed back to the control layer and the field, thus paving the way for the integration of the ERP system.
Micro programmable controllers are emerging
Traditional micro programmable logic controllers generally have 8~64 points of digital I/O and 1~4 points of analog I/O. They are small in size and can be directly installed in the machine. However, in addition to the above functions, the current micro-programmable controllers can already be compared with medium and large-scale programmable controllers in terms of network functions and human-machine interface functions. This type of micro-programmable controllers is currently the most developed Fast. The LOGO of Siemens and the PICO of Rockwell Automation are all representatives of this kind of micro programmable controller.
Infiltration of information technology into programmable logic controllers
The penetration of information technology into programmable controllers is to adapt to the development trend of the increasingly organic combination of factory control systems and enterprise information management systems, and to adapt to the control level between programmable controllers of different brands, programmable controllers and distribution. requirements for the efficient exchange of data between control systems. In fact, the realization of multitasking systems, the improvement of network capabilities, and the development of software integration make it easy for information technology to be integrated with programmable logic controller systems.
