Study On Optimization Design Of Wings Of Bio-inspired Flapping Wing Micro Aerial Vehicles

Bio-inspired Flapping Wing Micro Aerial Vehicles(FWMAVs)is a kind of Micro Aerial Vehicles which imitates birds and insects utilizing the reciprocating motion of wings to produce force and torque to complete the forward flight,hovering,turning and inverted flight.Due to its small size,rapid take-off,highly maneuverability and flexibility,and unique bionic shape,it has a wide range of applications in military and civilian aspects.Therefore,it has become a research hotspot in the field of aviation science in recent decades.The wing is one of the most important components of FWMAVs,which directly affects the motion characteristics of the aircraft,including the generation of lift,thrust and torque.Currently,the duration of flight of FWMAVs is very short,and the hovering flight is an essential flight capability,which requires more energy than the ordinary flight mode such as the forward flight.Based on this,this paper takes a hummingbird-like FWMAV as the research object,and study on optimization design of the wings in hovering flight.The main contents are as follows:(1)Similar to insects,the flapping flight of FWMAVs is at low Reynolds number range due to its low speed and small size,and the conventional aerodynamic theory cannot explain its unique flight mechanism.Firstly,the Kutta condition that needs to be satisfied when the lift of the moving wings is generated is briefly introduced,and the relationship between lift and circulation is given.Then from a qualitative point of view,the unsteady aerodynamic mechanisms of the high lift generated by moving wings at low Reynolds number is explained.Furthermore,the spatial three-dimensional motion of the wings is defined in coordinate systems to construct a quasi-steady aerodynamic model with sufficient precision for predicting aerodynamic force and torque.Finally,the power consumption model is established by considering the two limiting cases of the energy conversion of the wings.(2)The morphological and kinematics parameters of the wings have different effects on the motion characteristics,and they need to be pretreated.Firstly,the sweeping motion,heaving motion and passive pitching motion are described mathematically.Then using experimental data and the quasi-steady aerodynamic model,a mathematical model of the wing’s rotational stiffness is established based on the least square method,and the effectiveness of the solution is verified.Finally,the screening of wing parameters that have significant impact on the lift and power consumption with Design of Experiment approach is implemented.(3)The pitching axis location significantly influences the characteristics of the passive pitching motion and thus has an effect on the motion characteristics of the wing.But most of FWMAVs use the leading edge of the wing as the pitching axis.At the same time,in order to simplify the design of drive mechanism,a considerable number of studies do not consider the effect of the heaving motion of the wing.This paper studies the optimization design of the wings in four aspects: Firstly,the shape parameters of the wings are optimized.Then the morphological and kinematic parameters of the wing are optimized based on the Design of Experiment.Furthermore,the influence of pitching axis location of trapezoidal wing and insect wing on lift and power consumption is investigated.Finally,the heaving motion of the wing is considered,and its influence on the motion characteristics is discussed.The sensitivity analysis of the optimized parameters proves the effectiveness of the optimization results.By analyzing the influence of the morphological and kinematic parameters of the wing on lift and power consumption,this paper optimizes the wing from different angles in order to obtain a set of wing design process for improving the duration of flight of FWMAVs.It provides a feasible theoretical method for the application of bio-inspired FWMAVs.