Modeling and Control of a Kite on a Variable Length Flexible Inelastic Tether

This paper deals with the modeling of a tethered kite system. Such systems have the potential to generate power by driving a ground generator from winds at high altitude. To test the validity of controllers developed for the system, it is necessary to employ models of various sophistication. In this paper, the tether is modeled as a collection of point masses connected by inelastic rods. A simple procedure for efficiently determining the tension constraint forces is developed. The procedure used for deploying and retrieving the cable in the model is also presented. This entails the addition and subtraction of elements in the model. A simple feedback controller is derived to maneuver the kite in the cross-wind direction and for maintaining the tether tension at the desired level. The tether length is controlled to maintain the desired altitude of the kite. Numerical results demonstrate the effectiveness of the controller and efficiency of the tether model.