Automated control of kite power
In 2012 the kite-power group of TU Delft demonstrated the fully automated operation of a kite power system to the public. The demonstration took place in Maasvlakte, Rotterdam, The Netherlands on June 23, 2012.
A description of the distributed control system can be found in the following paper:
The current control system has a number of limitations:
The controller of the kite and of the ground-station do not communicate directly with each other. This makes it difficult to implement system optimizations that depend on synchronous changes of the control of the kite and the ground-station.
The control system does not adapt to changing wind conditions automatically.
At low elevation angles and on a short tether the GNSS position sensor is very inaccurate. This causes control problems.
The winch control loop is not yet implemented in C++ and thus very slow. This limits the average tether force to about 3000 N, even though the system can withstand 4000 N.
The kite control unit is running on batteries, which is limiting the max. flight time to 2-3 hours.
The flight trajectories are not yet optimized.
The control effort (power of the steering and depower motors) is not yet minimized.
The current research (2013/2014) is trying do address these issues. The most important step is to develop a software-in-the-loop test setup for kite-power system controllers. This requires the development of a kite-power system simulator that includes a model of the kite, the tether and the ground-station. This model shall be easily adaptable to new kites and ground-stations.
The second research area is the development of a reliable kite-power system-state estimator to overcome the problems with the GNSS position sensors. Angular sensors have been added to the ground-station that measure the azimuth and elevation angle of the tether directly. This information, together with the reel-out length of the tether and the tether force can provide an additional estimate of the kite position. The best way to merge the position and orientation data from the different sensors is currently under investigation.
The third research area is the development of a fast, adaptive controller for the ground-station. It shall control the reel-out speed such that the average reel-out force is maximized while keeping the maximal force beyond a given limit.