Research On Distributed Real-time Measurement And Control System Based On Linux Operating System

At present,PC-based real-time measurement and control system is one of the important developing derections of real-time system. As universal operating systems on PC, DOS and Windows have much disadvantage in implementing the problem of real-time and multitask. Additionally,the commercial operating system are much expensive and keep secret their source codes from public although they have good performance,that causes many inconveniences to the development of real-time systems. The emergence of a free software Linux operating system gives us a chance to change this situation. this thesis expands my research: applying Linux to an industrial PC real-time measurement and control system,which is centered on improving real-time performance and solving the multitask problem. Paper firstly analyses the real-time performance of Linux kernel, the disadvantage of Linux used in real-time system is obtained; Tnternal modification and external modification are two methods for improving real-time performance of Linux,Paper analyses and compares these two methods and real-time Linux with the two methods . RTLinux is abtained through using the method of external modification to modify the Linux.In the chapter three,the implement principle of RTLinux is deeply analysed,and the key technology of RTLinux,software emulating the hardware interrupt control, scheduler of real-time tasks,real-time timer,the mechanism of inter-process communication,is in detail researched.next,the interrupt latency time and scheduling accuracy are tested,the result of test show that RTLinux can satify the requirement of hard real-time environment.At the same time,the principle of software design for RTLinux application is analysed. RTLinux is successfully applied to a pratical industrial real-time measurement and control system in the chapter four. the hardware buliding and software coding are implemented.RTLinux devides the system into real-time tasks and common tasks.Because of the high resolution of real-time timer,the real-time tasks are set as periodic,and using the RM schedule algorithm to schedule the real-time tasks.real-time tasks implements the data sample, handle and output.the common tasks is linux user application program,it implements the data save,display and management,and so on. deeply analysing the RM schedule algorithm and schedulability tests under RM algorithm,and using the RM algorithm to design a testing program,testing and analyising the schedulability and real-time performance of the system based on RTLinux through the testing program.The result of test is satified to the hard real-time requirement of application. Chapter five firstly analyses the serial communication under Linux OS in detail,next,building on a small distributed monitor system through the RS-485 bus on the basis of the IPC real-time system is discussed. the functions of user management,history reports,status display as well as reports printing are implemented in this monitor system. research result show that it is possible to apply linux to industrial measurement and control system,RTlinux can not only ensure the real-time quality of real-time task,but also these tasks can use Linux function so that real-time systems have good foundation to develope the functions.