| The miniature flapping wing is a new concept aircraft that uses insects and birds as a bionic object.It has high aerodynamic efficiency and flexibility when flying at low Reynolds number.It also has the characteristics of small size and flight concealment.It has military and civilian fields.Important application values and prospects have become a hot topic at home and abroad.Miniature flapping aircraft are much smaller than conventional aircraft and have limited load capacity.Due to its size and weight limitations,the problem of insufficient cruising ability of the flapping wing aircraft is more prominent.The application of energy recovery technology on the flapping wing aircraft will undoubtedly help solve this problem.This paper proposes an energy harvesting scheme that collects the vibrational energy of the wings for long-lasting energy supply.Based on the analysis of energy harvesting technology at home and abroad and the application on the aircraft,a flexible piezoelectric energy harvesting wing with integrated structure support and force sensing is proposed.The PVDF piezoelectric film material was selected as the wing film of the flapping wing aircraft,and optimized according to the experimental results,the flexible piezoelectric fins with the cantilever beam structure were fabricated.The outstanding advantage of this energy recovery wing is that it does not increase the extra load of the aircraft or the passive deformation of the wings.This ensures that energy is recovered for the aircraft without affecting flight performance.The output characteristics of a typical vibration energy harvesting device depend on both its own structure and the excitation parameters.In this paper,we start from the above two points to study the effects of wing energy extraction structure and flutter parameters on piezoelectric output.At the same time,the changes of aerodynamic lift are studied,and the relationship between piezoelectric energy harvesting and aerodynamic lift is discussed.In this paper,the mathematical model derivation process of piezoelectric output and deformation,piezoelectric output and lift is introduced.Combined with the equivalent circuit theory,the key factors affecting the output voltage and power are proposed and verified in the experiment.And try to explain the situation that does not conform to the mathematical model according to the characteristics of the piezoelectric material and the characteristics of the application scene.In this paper,a single-degree-of-freedom and three-degree-of-freedom flapping wing test bench was developed to study the relationship between wing structure and stiffness.The modal analysis of wing structures with different wing width and thickness was carried out to obtain the natural frequency of multi-order vibration.The mathematical relationship between deformation and lift and output voltage is established,and the reasons for the difference between the theoretical model of piezoelectric output and experimental results are analyzed.The structural parameters and motion parameters of the piezoelectric fins suitable for flapping aircraft flight and energy harvesting are obtained.According to the experimental results,the reason for limiting the increase of power output is determined.The airfoil is divided by wet etching method to study the amplitude and phase characteristics of piezoelectric signals at different positions,and then the "L"-shaped vibration energy harvesting structure is proposed.The output power is increased from 21μW to 93.6Μw(with a flutter frequency of 15Hz),which effectively improves the output capability.In the energy harvesting circuit,14 LED lamps of a "JLU" shape are lit. |
PDF Full Text Request