Active Control Techniques Of Blade Vortex Interaction Noise For Electrically Controlled Rotor

Electrically Controlled Rotor(ECR),or so called Swashplateless Rotor,uses embedded servo flaps to realize rotor control.It can fulfill the main rotor control(1W),and the high-order harmonic flap control can also be realized using ECR to reduce rotor Blade Vortex Interaction(BVI)noise.In view of this,based on ECR,active control techniques of BVI noise is studied in this paper.The main research work includes the following parts: 1.A mathematical model of BVI noise for ECR,which can be used for active control of BVI noise is established.Considering the influence of flap control on inflow distribution,the free wake model of ECR is established,including the near wake model,the far wake model and the wind tunnel trim model.Aerodynamic model of airfoil with trailing edge flap is based on look-up table method using CFD.Based on the loading noise term in the time-domain solution of FW-H equation,the loading noise calculation model is set up.Then the correctness of the established mathematical model is verified by an experiment example.2.Simulations and analysis of open-loop active control of BVI noise for ECR are carried out.Based on the active control mathematical model of BVI noise for ECR,open-loop active control simulations are carried out:(1).Frequency,amplitude and phase sweep simulations of the flap control input are carried out at the same time.The law of the harmonic active flap control on the BVI noise for ECR is summed up,and the optimal active flap control input is obtained;(2).Through the analysis of the results of the BVI noise response,the effect of the active flap control on the BVI noise for ECR is summarized and its mechanism is preliminarily revealed;(3).The transfer relationship between active flap control input and BVI noise response is obtained based on the active control mathematical analysis model of BVI noise for ECR,which lays the foundation for subsequent closed-loop control.3.A feasible closed-loop control algorithm is proposed and it is verified through simulations.Considering the control characteristics of BVI noise and based on the time-domain least mean square algorithm,a block processing least mean square algorithm is proposed for the active control of the BVI noise for ECR.Based on the previously obtained transfer function,simulations are carried out to verify the correctness of the proposed algorithm.The simulation results show that the adaptive control algorithm proposed in this paper can effectively reduce the BVI noise.Further,in view of the identification of the control channel,an improved algorithm based on the on-line identification of control channel is proposed.The simulation results show that the improved algorithm has a better noise reduction effect and the convergence speed is faster.4.Experimental verification of active control of BVI noise for ECR is completed.Firstly,based on the proposed closed-loop active control algorithm for BVI noise and the existing integrated test rig of ECR,the software and hardware system which can satisfy the measurement and control of BVI noise is developed.Then the wind tunnel and ECR comprehensive test bench are used to simulate the downward descent flight state,and the active control experiments of the BVI noise for ECR is carried out.The experiments include open-loop active control experiment,and closed-loop active control experiments of BVI noise based on golden section method and block processing least mean square algorithm.The experimental results show that the golden section algorithm can reduce the BVI noise up to 5.7d B,while the B-LMS algorithm can reduce the BVI noise up to 6.4d B.The experimental results verify the correctness and effectiveness of the proposed closed-loop active control algorithm.