| Abstract [eng] |
The use of composite materials in aviation is increasing because of constant need to minimise the mass of aircraft. Composite materials have excellent strength to weight ratios when compared with metal alloys and timber used in aviation, but they have a higher maximum deformation, leading to higher structural deformations in flight. Reduced stiffness can cause flutter at lower speeds and degrade the handling characteristics of the aircraft. To evaluate and compensate the negative effects of low structural stiffness, a good aeroservoelasticity model is required. An aeroservoelasticity literature analysis was performed and it was decided to develop an aeroservoelasticity model, composed of a classical kinematics model, a structural model based on stiff elements connected with torsion springs, and a vortex lattice method based aerodynamic model. This physical aeroservoelasticity model was implemented computationally using the C programming language. For comparison of results a rigid version of the flight model was also developed using the same kinematic and aerodynamic models, but ignoring the structural deformations of the aircraft. An experimental methodology was created for the validation of the developed model. A fixed-wing unmanned aircraft was built for flight testing. During flight the aircraft was filmed using two video cameras to capture it's position in 3D space. A microcontroller onboard the aircraft recorded accelerometer, gyroscope and servomotor control signal data. A computational aircraft model was created based on the unmanned aircraft used for flight testing. The inertial parameters were determined by weighing parts of the aircraft and calculating moments of inertia. The structural parameters were determined by applying a force on the structure on the aircraft, measuring the displacement and from this data calculating the stiffness of the torsion springs. Using the initial positions of the aircraft determined from the video of the flight tests, individual parts of the flight tests were modelled. The calculated accelerations were compared with the ones measured experimentally during flight testing. The error of the aeroservoelastic model were much lower than those of the rigid model, but too high for the model to be useful without further improvements. |
