Modeling, Simulation, and Implementation of an Autonomously Flying Robot

A full envelope mathematical model for small-scale helicopters is presented that is completely derived from underlying physical laws. It incorporates a rigid body model of the fuselage including spinning parts of two rotors and the engine. Influences of all angular momenta are fully incorporated, yielding a complete model for movements including all gyroscopic effects.

Forces and torques of the rotors acting on the helicopter are calculated by use of Blade Element Momentum Theory (BEMT), which estimates the flow field at the rotors quite accurately, so that a precise prediction of the helicopter’s behavior is possible. The complete model has been implemented by use of several numerical techniques in order to obtain an accurate simulation, which can be executed in real-time.

For control purposes, a simplified version is derived from the sophisticated complete model. It represents the basis of the controller of TU Berlin’s autonomous helicopter MARVIN. From the rigid body model an Extended Kalman Filter (EKF) is derived that estimates the helicopter’s position and movement on the base of available sensor values. Additionally, the filter takes into account control signals in order to increase the prediction performance. All components (model, controller, sensor filtering) are combined in one simulator, which is capable of accurately simulating a complete helicopter in real-time. All results and predictions are compared with measurements from experiments.