System identification of a 6 m² kite power system in fixed-tether length operation

The traction force of a kite system can be utilized for extracting energy from high-altitude wind. This paper discusses a system identification algorithm derived to obtain real-time governing equations for the kite system based on real-flight data, obtained from a 6 m² kite power system developed in Kyushu University as an airborne wind energy project. The paper presents the system set-up, the design, the experimental results, a system identification algorithm, and the parameters identified for the kite used. The current stage of the project considers the kite application as a fixed-tether length system with a ground kite control unit. The control strategy is designed to work as a hardware-in the-loop to keep receiving the data and controlling the kite in real time. The experimental tests employed are divided into four distinct ones, and the data of the kite’s attitude, position, and tension forces are recorded. The tension forces resulted from these tests are presented for different wind speeds and flight modes. Ultimately, a novel system identification algorithm that evaluates the correlation between the tension force and the kite’s rolling angle over the four tests is applied, thereby enabling to study the kite behavior as a preliminary step for the achievement of autonomous flight.