基于RTX的软PLC多任务系统研究

软PLC是实现软数控开放性的重要组成部分。为了实现具有良好开放性的软数控系统,提出了一种基于RTX的软PLC多任务系统实现方法,该方法参照IEC61131-3,利用RTX的特性和优点,在以其为实时扩展的W indows NT操作系统中,利用V isual C ,实现了软PLC功能。规划了系统模块结构及任务,模块功能由对应的任务线程或接口函数实现,系统任务分为系统级和用户级;分析了各任务的执行时序,任务之间的切换由直接或间接调度机制平滑处理;研究了系统的程序指令集、逻辑堆栈和I/O存储器数据类型,实验表明系统具有良好的实时性和可靠性。

Research of a RTX-based Soft-PLC Multi-task System

The properties and advantages of RTX(Real-Time Extension),which is used to add "hard" real-time capabilities to Windows operating systems,are analyzed firstly.According to IEC61131-3,the paper develops a soft-PLC(Programmable Logical Controller) multi-task system based on the object-oriented approach in Visual C IDE(Integrated Development Environment).Where PLC is to be used in an open soft-CNC(Computer Numerical Control) system we are developing in the same operating system,i.e.Windows NT operating system extended with RTX.The soft-PLC system's modular structure is plotted by functions and the concrete function of different modules is realized by respective task thread or interface functions.Thereafter the system's task is particularly plotted and it includes system-level task and two different user-level tasks which are extendable.The timing plot when the!tasks are executing is particularly described.The switch of tasks is smoothly disposed by direct or indirect scheduling regime.Program instruction set,logic stack and data type of I/O memory which are tied up with tasks in the soft-PLC system are analyzed and studied.