Research On Multidisciplinary Design And Optimization Of Unmanned Rotorcraft Based On Flying Qualities Evaluation

Unmanned rotorcrafts are able to take off and land vertically,hover,possess outstanding performance while working at low altitude and low speed.Different payloads are facilitated to be installed to develop diverse mission systems,which leads to a broad application field in military and civilian.Unmanned rotorcraft technology recently is a world-wide research frontier in aeronautics.Unmanned rotorcrafts are not limited to the requirements for manned vehicles so that configuration design has more degree of freedom,is able to break the conventional configuration layout.The design diversity emerged suffering from some problems such as complicated lift,propulsive force distribution and aerodynamic interaction,etc..Additionally,there is no well-developed example as a reference.The flying qualities of unmanned rotorcraft have to be achieved by flight control systems.Thus,the flight control system and flying qualities are supposed to be considered as well on the stage of preliminary design.The effective preliminary design solution comes from a flying qualities based parameter sizing.Unmanned rotorcraft that have sufficient satisfactory configurations,are widely used.For determining the configuration,Analytical Hierarchy Process(AHP)is applied to establish the evaluation criteria and method for quantitatively evaluating the configuration.Based on the specifications and working condition,the configurations are evaluated and properly selected.For the features of diversity in unmanned rotorcraft configurations,a modularized aerodynamic modelling method is proposed.In which,aerodynamic analytic model and weight model are built for the typical aerodynamic components.Considering the characteristics of the configurations,the required power calculations for several configurations are performed in trimmed condition.Afterwards,the overall parameters are fastly tuned as the flight performance requires by using optimization algorithms.To some extent,the design is relieved of engineering experience,which works out the issure regarding insufficient reference information for unmanned rotorcraft preliminary design.Concerning the intensive issues of complicated configuration and aerodynamic interaction resulting from multi-lifting surfaces,in the stationary reference frame,the aerodynamic analytic models for single rotor,rotor/wing,coaxial rotor,tandem twin rotors are established and the fast multi-pole method is used to accelerate calculation,contributes to the foundation for flight performance and flight dynamics modeling.Aiming at obtaining effective preliminary design solution and satisfying the application requirements of unmanned rotorcrafts,a flying qualities-based overall parameter sizing method is proposed.An inverse-based model following control method is applied to design flight control law;Referencing to the ADS-33E-PRF specification,an efficacious flight quality evaluation model is studied.Using the rotor/ducted-fan vehicle as an example,the effects from the stiffness of rotor hub support on the flying qualities are studied in particular.The range of consideration covering the number of over parameters is enlarged.An effective flying qualities-based preliminary design plan is obtained to lay the technological foundation to the multidisciplinary comprehensive parameter optimization.To satisfy the requirement in preliminary and multidisciplinary design optimization of unmanned rotorcrafts,a distributed multi-objective collaborative optimization integrating flight performance,structural weight,flight dynamics,flight control,rotor aerodynamic design,etc.is applied to build a multidisciplinary comprehensive optimization model.Take the long endurance rotorcraft as an example,the conceptual parameter plan is determined by the previously illustrated configuration selection,overall parameter estimation method.Subsequently,on the basis of the plan,the parameter plan of the long endurance unmanned rotorcraft is optimized using the distributed multi-objective,and obtain the optimal parameter sizing plan for the unmanned rotorcraft.This dissertation combines theoretical modelling and verification through real vehicle example,studies the configuration selection for unmanned rotorcrafts,parameter sizing and optimization techniques.In the dissertation,a relatively complete methodology for unmanned rotorcraft overall parameter design optimization is developed,which is able to advise the preliminary design for unmanned rotorcraft.