Positioning and Trajectory Control of an Autonomous Helicopter using Real Time Kinematic GPS

Abstract: During this master’s thesis project a control system for a quadrocopter has been developed. A quadrocopter is a small helicopter with four rotors which is controlled by a hand held controller by an operator positioned on the ground. This master thesis report treats three different main subjects. The first one is about evaluating a Real Time Kinematic Global Positioning System (RTK-GPS). The second one is about defining smooth motion paths which the aircraft autonomously shall be able to fly along. The third one is about improving the control system in the aircraft to obtain better flight performance under manual control and to enable autonomous features such as altitude hold. The result is that it is possible to achieve centimetre accuracy in estimated position with the evaluated RTK-GPS system. It is also discussed how the performance of the RTK-GPS system can be maximized. A smooth path can be defined in different ways. It is desirable that the path has continuous first and second derivatives. Therefore cubic spline curves are used to represent the path. The control system was improved by transforming forces and angular velocities between the two different coordinate systems. This resulted in improved abilities by making the steering and control of the aircraft smoother.