Study Of Real-time Measurement And Control System Based On Xenomai And IPC

Electric power automation equipment is of zero deadline-driven feature,which greatly helps the dispatchors to guarantee the security control, insure the initiative to dealing with the trouble, reduce or avoid the mis-manipulation or misjudgment, and improve the running management level for the electric grid in the final. Meanwhile, complex tasks of the electric power system have always made the simple flow control fail to meet the needs. So in order to fill the gap, a real-time operation system has to be introduced.Due to some features like higher prizes or a lack of syntactic and semantic compatiblity, applications of traditional RTOS have been greatly limited. A solution to the problem is to use and modify the existing GPOSs to obtain the real-time performance. GPOS like Linux which provides with the open source codes, versatile function libraries and powerful developing tools has given application designers an access to the system kernel. At present, all modifications are mainly based on the kernel. The target is to keep the task response time in microseconds and get a shorter task response time. Two approachs including Standard Kernel Preemption and Real-time Patches to the Standard are available. The Standard Kernel Preemption approach, like explicit preemption points, implicit preemption points and fully preemption can only offer soft real-time performance, while the Real-time Patches approach such as Micro Kernel, Resource Kernel Extension, POSIX Real-time Extension, and Nano Kernel can provide with the hard real-time performance. In this thesis, the Adaptive Domain Environment for Operating System (usually called Adeos for short) is introduced between the hardware platform and the standard kernel to obtain a"hareware-kernel"interface. Different operating systems can run above the same hareware platform based on Adeos. The Virtual Interrupt mechanism can also be used to diminish the interrupt dispatch time and the interrupt service time, and finally achieve the least task response time.The principle of a common RTOS emulation framework-Xenomai and Adeos are briefly introduced in the thesis. The Adeos Interrupt Pipeline which has Interrupt Shield mechanism is studied and so are the problems of a real-time task being preempted and a priority inversion, which occurs in mixable execution modes for tasks embodied in User-Space. The Xenomai/Linux dual-kernel real-time operating system is established, and by using Xenomai's RTAI emulator which offers the API, user applications'real-time tasks of the built system are realized. Non-real-time display tasks are accomplished through Svgalib function library. At the same time, real-time and non-real-time tasks can communicate with each other through Fifos. In the end, a real-time measurement and control system based on Xenomai which mimics the environment of a small electric substation has also been made on a former DOS based IPC with some necessary hardware modules in the laboratory. Tests show that microseconds task response time is achieved from the new real-time kernel, and the system meets hard real-time performance of electric power systems, which also indicate that Xenomai can be used to build a generic and versatile framework for emulating traditionl RTOS, like RTAI in the thesis and ease the development of the real-time applications.