Communication layer. The communication layer is the lowest layer of the control system. The downward interface is the interface with the hardware device. It directly calls the driver interface library function of various communication hardware or the read/write operation function provided by the operating system, and provides the standard for the task scheduling layer. Analog input and output interface, digital input and output interface. Since the hardware provided by different vendors does not follow a consistent interface standard, the communication layer must develop different modules for different hardware, but must provide a consistent interface API that can be called by its upper layer (real-time multi-tasking scheduling layer).
The communication system communication system is responsible for realizing the information exchange mechanism between the system platform and various functional modules of the system and each functional module. It specifies the information exchange protocol standard between the system platform and each functional module. The communication system is responsible for completing the top-down and bottom-up closed-loop transmission of control information and data information. Dynamic Configuration System The configuration system of the open control system includes pre-run configuration and runtime configuration. The system instantiates the control module before the system is running, and performs real-time setting and dynamic selection control algorithms for various indicator parameters during system operation. The open control system can be configured to meet different control requirements and adapt to different control objects without having to recompile and connect the system.
Aiming at the above reference model, this paper proposes a configuration method based on configuration file, which realizes the number and type of control quantity according to the controlled object according to the required control before operation, and the dynamic selection control algorithm at runtime. On-demand instantiation of the system for different control objects clearly requires the system to handle different types of control in a consistent manner. The definition of the instruction data format has realized that the system can process different types of instructions in a consistent manner, so the relevant configuration information is read from the configuration file before the system is run, and the instruction data corresponding to each control quantity and its corresponding processing are instantiated. Modules, which enable the number and type of on-demand configuration controls. The instruction format contains an algorithm selection code, and the dynamic selection of the algorithm at runtime can be realized by discriminating the value.
Multi-task scheduling uses the high-precision multimedia timer provided by Windows system as the interrupt trigger source to solve the problem of poor real-time Windows message loop, which can meet most of the device control requirements. A configuration-based dynamic configuration system is implemented. In this example, after the dynamic configuration system before operation, the rotary bending machine and the tension arm bending machine are successfully adapted, and the control algorithm can be dynamically selected during operation.
Conclusion Software-based controller is the development trend of open CNC system. Based on the in-depth study of software NC technology, this paper proposes a reference model to realize the full openness of user functions and the limited opening of system kernel. The four-layer structure considers both openness and conciseness, and its organizational structure is reasonable. It has important theoretical significance for promoting the research of software NC technology. The developed control system has great application prospects for the rapid numerical control of various special equipments.
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