Modelling And Gust Allevation Method For Flexible Wing Biomimetic Aircraft

Flexible-wing Biomimetic Aerial Vehicle(FBAV)is a kind of mini and small aerial vehicle with flexible wing.It is a kind of noval umanned operation system which is capable of carring out close range surveillance missions in confined and complicated environemnts.The research object of this paper is to study the small flexible wing aircraft,which is based on the small biomimetic aircraft reseach project.FBAV has features as low speed,small scale,light weight and small inertia.Due to these features,FBAV has poor flight stability,bad handling quality and vulnerable to turbulence and gust.This paper is fouced on the gust alleviation with active aeroelastic control technology,and the related works include rigidflexible coupling dynamics modelling,time-domain simulation method,model linearization method,model reduction method.In addition,this paper also developed different prototypes of FBAV.The research object is to enrich the theory and technology of the gust resistant design method of flexible wing aircrafts and contribute to the overall development of FBAV.The main contents include:First,this paper studied the modelling method.The flexible wing has unique features wich makes the aerodynamic coupling effect plays the major role in the rigid-flexible coupling dynamics.According to this,and based on quasi-static aeroelastic model of flexible wing,this paper gave the linearized dynamic model of flexible wing aircraft.In addition,as the frequencies of flexible wing's elastic mode are much higher than the frequencies of aircraft's short term motion,it is possible to use quasi-staitc relation between flight states and wing deformation to simplify the description of flexible wing deformation.Based on this,this paper gave the model reduction method which is suited for flexible wing aircraft.This low-order linearized model contains the major features of flexible wing aircraft's rigidflexible coupling dynamics,and decrease the difficulties of designing gust alleviation controller,and increase the controller's performances.Second,this paper developed a time-domain simulation method for the analysis of rigidflexible coupling dynamics.The simulation method is a vital tool for the design and analysis of gust alleviation controller.Based on the quasi coordinate system method,the inertial force and aerodynamic force are used to represent rigid-flexible coupling effect,which connectes vehicle's flight dynamic equations and structure dynamic equations.By solving the equations alternately in each time-step,the aeroelastic dynamic of flexible wing aircraft can be analyzed in time domain.This simulation method can analyze vehicle's flight states,flexible wing's deformation and wing-root structure loads.This simulation method offers the mathematic tool for the development of control method for active gust alleviation.Third,this paper studied the control method for gust alleviation with the aid of flexible wing's active aeroelastic control.An Actvie Gust Alleviation Device(AGAD)is designed.The AGAD is located on the wingtip,it controls the bending and twist deformation of the flexible wing.A Linear Quadratic Regulator(LQR)optimization controller was designed to solve the control allocation problem between AGAD and tail.And the LQR controller is able to control multiple system states simultaneously.By using AGAD and tail coordiantely.The controller can achieve much better gust alleviation results than ordinary control method.And by optimizing the control orders for maneuver flights,the active aeroelastic control of flexible wing deformation can also be used to improve the maneuvering ability of flexible wing aircraft.Fourth,this paper developed several prototypes of FBAV,and studied the design and manufacturing method of flexible wing.Based on recent advances in the filed of bionics about flying animals,this paper designed flexible wing which has similar functions of birds' wing.By summarizing the test results of prototypes for FBAV,this paper found the way to improve vehicle's flight performance and maneuvering ability by actively change the shape of flexible wing.According to simulation results and flight test results of prototupes of FBAV,it is proved that by adopting flexible wing,the mini and small aerial vehicle will have a much better adaptability of confined and complicated environemnts,the active aeroelastic control of flexible wing can grant the vehicle a much better gust alleviation control ability and improve the vehicle's overall maneuvering ability.