Closed-loop System Identification And Its Application In Tiltrotor Aircraft Model

Tiltrotor aircraft is a new type of aircraft ranging between fixed-wing aircraft andhelicopters. The key to this new aircraft control system is the smooth transition betweenthe two flight modes, a mathematical model accurately reflecting the state of motion ofthe aircraft is particularly important. In particular, the tilt-rotor model includes wavingmotion model of binary airfoil aerodynamic model, the rotor induced velocity modeland the rotor blades. These three aspects influence each other, they are the closed loopsystem in logical relationship. The closed-loop system identification techniques cansolve the parameters identified problems in rotor modeling. Therefore, this article willhave some significance using a closed-loop system identification techniquesin the rotormodel.In this paper, firstly, the theoretical basis of system identification and the open-loopidentification algorithmfor the linear regression model with additional input areintroduced, the effectiveness of the algorithm are validated by the simulation examples.Secondly, through comparative analysis the recursive least squares algorithm based onauxiliary model is introduced to the improved the closed-loop identification algorithms,and the validity and the parameter estimation accuracy of the algorithm can be verifiedthrough the analysis of simulation results. Then again, modeling for tiltrotor aircraftmodel, and linearization using the method of linearized equations，the transfer functionof the longitudinal movement is obtained through the laplace transform. Finally,discretizing the longitudinal movement of the transfer function by using the backwarddifference transformation to obtain the autoregressive model with external input modelas identification model. Using the recursive least squares based on the auxiliary modelidentification algorithm and the stochastic gradient based on the auxiliary identificationalgorithm identified parameters of the system. The obtained two results were analyzed,the recursive least squares based on the auxiliary model identification algorithm isfound more suitable for the estimation of the model parameters.The results showed that the recursive least squares based on the auxiliary modelidentification algorithm is more suitable for parameter estimation tiltrotor aircraftlongitudinal motion model. The simulation results show that the obtained parameterestimates values close to the true value and the error within the allowable range, forwhich the closed-loop system identification method is applied tiltrotor aircraft modeling. Therefore, the method of using the system identification method obtained theparameters of the tiltrotor aircraft longitudinal motion model have to be realized andreliability.