Research On The Stability And Control Method Of Time-delay System For Aero-engine’s Distributed Control System

The aero-engine control system is developing to be the full authority digital electronic control(FADEC)from mechanical hydraulic control with the development of control technology.To improve aero-engine’s thrust-weight ratio further,some researchers proposed the distributed control system.But now,it is still difficult to apply this new control system to an actual aero-engine while some important research results have been obtained through the analysis of aero-engine’s distributed control system.In a distributed control system,all the subsystems communicate by a common network,therefore,network communications will take a great effect on the dynamic performance and steadystate performance,even make the whole control system unstable.Therefore,this thesis mainly focuses on the controller design method and control system analysis method of aero-engine with the communication delay and different styles of triggers for subsystems based on control theories.The main contents and contributions of this thesis are shown as follows:(1)The aero-engine’s modeling method is studied.By using the components method and variable specific heat calculation method,a nonlinear model and its linearized model at one state point are obtained.The approach that how to turn a state-space model to be a strict feedback mathematical model is proposed.(2)The stability analysis and the design method of dynamic surface controllers for a discrete-time system with network-induced delays are studied.When the networkinduced delays are determined,the design method of an adaptive fuzzy dynamic surface controller is proposed,which combines the network-induced delays,state estimation and parameter identification in the fuzzy inference method.Compared with common fuzzy inference methods,the proposed fuzzy inference method is simpler and the unknown parameters are easier to identify.In addition,the dynamic surface control method takes into account the compensation of the network-induced delay,thus filling the gap of the dynamic surface control method for a discrete-time system with network-induced delays.When the network-induced delays are unknown,a homotopy algorithm is proposed to effectively solve the bilinear matrix inequality;The descriptor model transformation(DMT)equation is introduced during the derivation of system stability conditions based on a constructed Lyapunov-Krasovskii functional,and the system stability conditions obtained by reasonable use of Jensen’s inequality and variable substitution method are less conservative.(3)Considering network-induced delays,the analysis and controller design methods of a tracking control system without steady-state error based on predictors are studied.Firstly,the prediction algorithm of state variables is designed.In the process of deducing the system stability condition from the constructed Lyapunov functional,the double DMT equations are introduced.According to the proposed equivalent transformation method of the double dynamic equations,a linear matrix inequality that can be solved directly is obtained.This method not only broadens the upper bound of the network-induced delay but also solves the problem of transforming a nonlinear matrix inequality derived from the variable prediction algorithm and the double DMT equations into a linear matrix inequality successfully for the first time.Additionally,if the system observation matrix is invertible,three control methods are studied in detail in this thesis.Both theoretical analysis and simulation results show that these three control methods can make the control system stable.The ITAE criterion is taken as the optimization target to optimize the parameters of the controller.The controller and its optimized parameter values not only eliminate the steady-state error of a step response but also make the control system have a better dynamic performance.(4)The control system analysis and controller design methods based on an event-trigger protocol under network-induced delays are studied.For the known and constant networkinduced delays,the event-trigger protocol designed can reduce the network load;The data buffer and the algorithm designed for it can reduce the adverse effect of network-induced delays on the steady and dynamic performance of the system.In the case of unknown but bounded network-induced delays,an adaptive event-trigger control condition is added to the controller based on the research results of the continuous time-delay system,which can not only effectively reduce the network load,but also maintain the steady and dynamic performance of the system better.Combining with the designed event-trigger protocol,a system stability condition is deduced and proved.