Research On Key Technologies Of Realtime Scheduling And Communication For Flight Simulator Computer System

Flight simulator is one type of ground simulation equipment which can reproduce actual airplane's dynamic process in ground taxying and aerial flying. Due to merits of economical character, saftey, efficiency and environmental protection, it has been widely used in the fields of new type airplane development, flight theory study, flight control study and flight training etc. On the basis of comprehensive analysis of realtime scheduling and realtime communication technologies widely adopted by main flight simulator research institutes at domestic and overseas, with aims of satifying flight simulation tasks' realtime running requirement, improving its scheduling success ratio, reliability, and perfecting the realtime communication for hybrid network architecture in flight simulator, this thesis proposed a new kind of multiprocessor realtime scheduling and communication technology with its application in realtime computing for flight simulation system, and explored the feasibility of above methods through simulation tesing and application studies. For fulfillment of the realtime scheduling requirement of periodic simulation tasks in flight simulator, the thesis built multiprocessor realtime scheduling model for periodic simulation tasks, proposed the integrated processing method for precedence and resource accessing constraints, and designed a novel nonpreemptive EDF multiprocessor realtime scheduling algorithm. The global scheduler model for periodic simulation tasks based on symmetrical shared memory multiprocessor, feasibility judgement method for nonpreemptive EDF multiprocessor realtime scheduling algorithm and task diapatching program are serially elaborated. The simulation testings showed the method effectively improve the scheduling success ratio of periodic simulation task set under high processor load, high task computing load and too large divergence in task period circumstances, meanwhile has the merit of low executive ovrhead.Combined with function and performance requirements of flight simulator's malfunctions simulation, the thesis proposed the realtime scheduling aims for aperiodic simulation tasks, built multiprocessor realtime scheduling model for aperiodic simulation tasks, and designed a novel multiprocessor realtime scheduling algorithm for aperiodic simulation tasks baesd on heuristic search. The global scheduler model for aperiodic simulation tasks based on symmetrical shared memory multiprocessor, constitution method for heuristic evaluation function, feasibility judgement method for realtime scheduling algorithm, task diapatching and processor idle time reclaiming program are serially elaborated. Meanwhile, the processor idle time reclaiming strategy and the fault-tolerant extending method for realtime scheduling are explored and proposed in order to impove the scheduling success raio of scheduling algorithm, reduce the response time of aperiodic simulation tasks and satify the reliability requirement of malfunctions simulation. The simulation testings showed the above methods adjust well to the realtime scheduling circumstances for aperiodic simulation tasks with short residual time, low task laxity, high fault-tolerant requirement and activation events random arriving, meanwhile have merit of low executive ovrhead.Through the detailed analysis of hybrid network architecture for flight simulator, this thesis proposed a novel Ethernet realtime communication technology based on the design of virtual token and its communication control flow. Meanwhile, a novel realtime communication improving technology for CAN-bus based on the design of VNPQ and classified priorities of message, the method of dynamical allocation message transmitting priorities and partial altering the message filtering of LLC sublayer are also proposed. Serially, the realtime testings for realtime Ethernet based on virtual token and CAN-bus based on VNPQ are carried out through built the testbed whose network enviroment configurations are equal with flight simulator. The testing results showed the realtime Ethernet based on virtual token and CAN-bus based on VNPQ are effectively satify the hybrid network realtime communication requirements of flight simulator.Finally, for the above research findings, the application study of multiprocessor realtime scheduling and communication technology are carried out in the key technologies research and testing platform for flight simulator. Extensive testings for realtime running of simulation models, realtime communication of hybrid network, and the response time of flight simulation which include normal takeoff, normal landing and engine bird strike malfunction are carried out. The significance and feasibility of multiprocessor realtime scheduling and communication technology are verified by the testing results.