Design Of Robotic Bat Wing And Research On The Force And Power Of Bat Wing

Neither belongs to birds nor to insects, bats are the only mammals which can fly properly. Although some progresses have been made on the flapping flight mechanism and bionic aircraft design areas, understanding of the bats’ flapping flight mechanism is not sufficient, and researches on bats’ aircraft design are still in the initial stage currently. Therefore, ①an in-depth understanding of bat wings’structure, size and movements, ②carrying out theoretical, computational and experimental research on natural bat wings and robotic bat wing, ③analysis of force, power and other key issues of the bat wing, will deepen our understanding of the bat flight mechanism and provide references for the development of future robotic bats aircraft.According to the measurement results of bat wing structure, size and angle data, a robotic bat wing with flap, sweep, elbow and wrist motions was designed and fabricated. In addition, computational models of natural and robotic bat were sets up; the influences of parameters and motions on the force and power were studied from observations and measurements, theoretical derivation, numerical simulation and experimental methods. The main contents and conclusions of this paper are as follows:(1) Study on the size, structure and real-time motion of the big brown bats’ wings. Based on the big brown bat (Eptesicus fuscus), the bat wing coordinate systems were established, the formulas that used to describe real-time angle changes of the flap, sweep, elbow, wrist and three digits motions were also derived. An information acquisition experimental platform of bat flight was built, based on the marker positions taken by high speed cameras, the real-time three dimensional motion data of bat wing were obtained by tracking software. Based on these data, seven real-time angles between different bones were calculated. According to the lengths of humerus, radius, digit 3, digit 4 and digit 5 as well as the angles between different bones, the limit and average values of the lengths and angles in one flapping cycle were counted. And these metrical and computed results can provide data support for the design of bionic bat wings.(2) Design of a four degrees of freedom robotic bat wing with flap, sweep, elbow and wrist motions. According to the structure, size and motions’data of bat wing, a four-degree freedom robotic bat wing was designed and fabricated. In the fabrication of skeleton and membrane aspect, the skeletons were made by 3D printers, and the membrane was made from silicone. Based on the tests’results of membrane mechanical properties on different samples, loading speed and loading cycles, the skeletons and membrane were verified to satisfy the uses requirement. In the control aspect, the motions of the robotic bat wing were controlled by motors. By defining the target position, the speed and the time to reach the target, the ’PVT’ control mode was used to make the robotic wing achieve precise motions. Furthermore, the influence of different frequency, different motion on the flap, sweep, elbow and wrist motions were studied, and the results verified that the robotic wing can achieve accurate movements as expected.(3) Study on the lift, drag and power of robotic bat wing in wind tunnel. An experiment platform was set up in the wind tunnel, and the force was measured by transducer, the power was measured and calculated by motor encoder and controller. Some key problems, including the calibration of sensors, the errors and the negative power were presented and analyzed. Except that, the effects of flapping amplitude, flapping frequency, wind velocity, downstroke ratio, stroke plane angle on lift, drag and power were studied. The main conclusions of these studies include: ①increasing the flapping amplitude, flapping frequency and wind speed can increase the wing’s lift, drag and power simultaneously; when the downstroke ratio deviate from the center of symmetry, the lift, drag and power will increase correspondingly; increasing the stroke plane angle will make the lift increase but make the drag and power have inverted u-shaped changes. ②The flapping motion provides maximum lift and drag, and consume the maximum power compared with other three movements of robotic bat wing; the wing folds in the upstroke can provide more lift and save energy; the flap and fold motions are two most important movements of the robotic bat wing.(4) Establishment of the 4DOF model and study on the inertial power and force of bat wing skeletons. Based on the robotic bat wing, a four-degree freedom computational model was established. The inertial power and inertial force were obtained by dividing the bat wings into small pieces firstly, and calculated the mass, speed and acceleration of each part next. In the aspect of theoretical research, according to the sinusoidal flapping motion, the inertial power and inertia force equations were derived. In the computational aspect, under different amplitudes of sinusoidal flapping motion, the change trends of inertial power and inertial force on different directions were studied. In the computational and experimental aspect, the influence of amplitude, frequency, mass, downstroke ratio on the inertia power and force were studied. The theoretical, computational and experimental results show that, the inertia power and inertia force will be increased accompanied by the increasing of frequency and amplitude; when the downstroke ratio deviates from the symmetric position, the inertial power and inertia force will be increased; the wing folds can decrease the inertial power and inertia force.(5) Establishment of 7DOF model and research on the inertial power and force of bat wing. Considering the actual structure, size, movements and membrane of native bats, a seven-degree freedom computational model of bat wing was established. The wing trajectories of 7DOF model,4 DOF model, robotic bat wing and native bat wing were analyzed, and the results verified the accurate motions of two computational models and the robotic wing. Under different sinusoidal and bionic motions, the inertial power and force on different directions were analyzed, and the results showed that the inertial power occupied the largest proportion on flap direction. But the inertial forces on flap, sweep and elbow directions were nearly the same, and the wing folds can decrease the inertial power and force. In addition, the effects of flap, sweep, elbow, wrist and digits’ motions on the inertial power and force were studied, and the influences of membrane, humerus, radius and five fingers on the inertial power and force were also analyzed. The results show that the flapping motion have the maximum influence, the sweep and elbow motion have the general influence, the wrist and digits’motion have the minimum influence on the inertial power and force; the membrane and radius have larger influences on inertia power and force while humerus and digits have smaller influences.