ORNICOPTER MODEL GROUND TESTING AND THE EFFECTS OF FLEXIBILITY

摘要

The Ornicopter is a single rotor helicopter that does not produce a reaction torque and therefore does not need a tail rotor or similar device. Forced flapping of the rotor blades is used to control the yaw motion of the aircraft. This paper describes a test of this yaw control method performed with the radio controlled Ornicopter demonstrator model. Test data show that the forced flapping method works quite well at relatively low thrust levels, but data for the higher thrust levels required for flight are not available yet. Data also show that effects of flexibility in the forced flapping system may pose some limitations on the operation of the demonstrator model, due specifically to the way forced flapping is implemented in this model.Existing blade theories for the Ornicopter do not predict these effects with sufficient accuracy. In an attempt to gain more insight into these flexibility effects a simple qualitative study of blade dynamics has been performed with the help of multi-body dynamics software. The effects of lead/lag freedom, pitch and torsional flexibility and blade bending on the effectiveness of forced flapping were investigated using a simplified representation of a flexible rotor blade.The results of this investigation indicate that the fidelity of Ornicopter blade models could be much improved by taking into account pitch flexibility and blade torsion effects. Furthermore, based on these results it is expected that some of the practical problems encountered during testing could be solved by equipping the Ornicopter demonstrator model with lead/lag hinges.