Autonomous Helicopters (ALF)
The cell of the autonomous aircraft (ALF) is based on a commercial model helicopter for aerobatics with electric propulsion. The avionics and ground station were developed completely in-house. The avionics consists of a course/position reference system with MEMS gyroscopes and accelerometers, an inertial navigator supported by a barometer and GPS via Kalman filters, and a flight controller. The Flight Controller allows both hovering and stable speed flight.
High dynamics are achieved by means of control loops in several coordinate systems and pilot controls. Bi-directional radio links to the ground consist of several 2.4 GHz data links. The helicopter has been successfully tested under bad weather conditions, including rain, ice formation and up to wind speeds of approx. 50 km/hr. Sensors in the avionics are partially redundant, a possible required in-flight system restart takes place within approx. 30 ms.
The avionics has proven to be very reliable and can be installed in any model helicopter so that other helicopter cells can be used without any problems. In principle, control is carried out via fast setting of waypoints and the course angle, which are specified either via a standard remote control or via a web creation program.
The helicopter has so far been used in various applications, including high-resolution close-ups of the Freiburg Cathedral and power poles. A number of other operations are planned. The operation of the machine is simple and safe; it can be taken over by untrained personnel after brief instruction. The GPS is currently being expanded to include a carrier-phase GPS developed in-house, which will allow significantly higher speed and positioning accuracy than before. In addition, virtual reality components are currently being installed for stereoscopic image capture by the operator.