Performance Research Of The Flight Control System Under The Digital Random Upsets

In actual flight,the flight control system is inevitably affected by the digital upsets from the external electromagnetic environment.The flight control system is in the upset state under these digital upsets,which can lead to performance degradation and even crash.In this paper,a typical distributed flight control system architecture is introduced.And then the digital logic relationship between the digital random upsets and the states of the switched flight control system is studied.In order to carry out the theoretical analysis,the linear normal and upset model of the Boeing 747 aircraft is established,which are the subsystems of the switched flight control system driven by the digital random upsets.In the performance analysis of single channel flight control system,the HMM(Hidden Markov Model)is used to describe the characteristics of digital random upsets according to their physical mechanism.Compared with the existing Markov model and Burst model,it is proved that HMM has higher accuracy.The traditional parameter estimation algorithm of HMM has the risk of data underflow and is sensitive to initial parameters,therefore,a modified algorithm and a fast initial parameters selection strategy are proposed.In the performance analysis of distributed flight control systems,the traditional methods assume that the random upsets of each redundant component is independent,while ignoring their common mode characteristics.In this paper,MDHMM(Multi-Dimensional Hidden Markov Model)is used to model and analyze the distributed digital random upsets,and the complete model parameter training algorithm is then given.It is more importantly that the analysis theory of the switched flight control system driven by the HMM and MDHMM digital upsets is developed.And the stability criterion and the formula for calculating the tracking performance of this system are given.The theoretical analysis is verified by a numerical example,which proves that the analysis theory is correct and effective.Finally,the proposed theory is applied to the Boeing 747 flight control system,and the tracking performance of single channel and distributed flight control system under different electromagnetic environment is studied.The mathematical model of digital random upsets in different electromagnetic environment is established by using the model parameter training algorithm proposed in this paper,which can be used to drive the distributed flight control system for theoretical analysis and simulation experiments.The simulation results are consistent with the theoretical predictions,and the tracking performance of this distributed flight control systems is compared with the single channel flight control system.