Range-inertial estimation for airborne wind energy

An estimation approach is presented for an autonomous tethered kite system for the purpose of airborne wind energy generation. Accurate estimation of the kite state is critical to the performance of automatic flight controllers. We propose an estimation scheme which fuses measurements from range sensing, based on ultra-wideband radios, and inertial readings from an inertial measurement unit. Ranges are measured between a transceiver fixed to the moving kite body and a number of static range beacons scattered on the ground. Estimates are computed using the multiplicative extended Kalman filtering scheme with a sensor-driven kinematic process model using a quaternion representation of the kite attitude. Furthermore, we assume only approximate prior knowledge of the range beacon locations and consider the problem of estimating the kite state and localizing the range beacons simultaneously. We present results of the estimator tested within a simulation environment of an airborne wind energy system and compare performance to an existing estimation scheme based on tether-angles and tether-length measurements.