Research On Closed-loop Identification Methods Fora Quadrotor Generalized Attitude Model

This paper firstly establishes the generalized attitude mechanism model of the quadrotor according to the flight principle,provides prior information for the identification of the GAM of the quadrotor.Studied two GAM identification methods.In the case that the system controller of the quadrotor is unknown and can only obtain the input and output data of the forward channel.Use the prediction error closed-loop identification method.According to the input and output data collected,the GAM estimation model of the quadrotor is identified.Then the subspace identification method based on coprime factor(CF)is studied.Through the collected reference input data and input and output data.From the reference input to the system input and output,a CF model is constructed respectively.Using the subspace identification method,a GAM estimation model for quadrotor estimation is obtained.Then design a flight experiment and collect flight experiment data outdoors for identification research.Since the input is four motors to produce three channels of torque,the four-three conversion method is used to convert the four-channel PWM signals into three-channel input signals.The identification experiment is flying in an outdoor environment,so some interference noises such as random wind will directly affect the normal flight of the aircraft when collecting flight data.These will have a direct impact on the identification accuracy of the generalized attitude model,leading to certain challenges in identification research.Therefore,this paper designs a relevant analysis program to preprocess the input and output data to minimize the impact of noise.Then combined with the unknown situation of the controller model in the actual quadrotor control system,the closed-loop direct identification method and the closed-loop indirect identification method of the forecast error are studied.An extended Hankel reduction method is proposed.Finally,the continuous-time generalized attitude estimation model of the quadrotor is obtained by the bilinear transformation method.The accuracy of the generalized attitude estimation model obtained by identification needs further verification.This paper proves the accuracy of the identification model through model testing.First,the Bode diagram is drawn using the identification model,which verifies the accuracy of the mechanism model and the estimation model.Then use different data segments to fit the estimation model.Finally,the accuracy of the model is verified by the method of redesigning the loop forming robust controller.The verification result fully proves the accuracy of the generalized attitude model obtained by the identification,and further illustrates the feasibility of the identification method.