Development and Full-Scale Experimental Validation of a Rapid Prototyping Environment for Plant and Control Design of Airborne Wind Energy Systems

Abstract

Airborne wind energy systems present great promise for inexpensive, clean energy at remote locations, but have only been demonstrated through short-duration flights in very limited wind conditions. Because of the time and money that is required to implement full-scale airborne wind energy prototypes, convergence toward designs that achieve longer-duration flight in adverse weather has been slow. This paper presents an inexpensive rapid prototyping approach for improving the flight dynamics and control of airborne wind energy systems, which has been implemented and validated on Altaeros Energies most recent full-scale flight prototype. The approach involves the 3d printing of lab-scale water channel models of airborne wind energy lifting bodies, which enable prediction of dynamic flight characteristics, rapid iteration between the designs, identification of unknown or poorly known parameters, and improved control design. By applying this approach to its last prototype design cycle, Altaeros demonstrated robust operation in double the wind speeds sustained by its previous prototype (reaching a maximum of 21.2 m/s, with sustained 10–15 m/s winds), with demonstrably improved flight characteristics.

A case study in experimentally-infused plant and controller optimization for airborne wind energy systems

“…For the case study described herein, this was accomplished by 3d printing 1/100-scale ABS plastic models that were subsequently tethered and flown in the UNC Charlotte 1m × 1m water channel. The experimental setup is an extension of earlier work by one of the co-authors to study passive flight properties at University of Michigan in conjunction with Altaeros Energies, which is described in [15] and [16]. These references demonstrate the dynamic equivalence between key properties of the labscale and full-scale systems, where a more comprehensive equivalence study based on dimensional analysis is a topic of current investigation.…”

“…These references demonstrate the dynamic equivalence between key properties of the labscale and full-scale systems, where a more comprehensive equivalence study based on dimensional analysis is a topic of current investigation. The present experimental setup expands upon the setup of [15] and [16] through the incorporation of closed-loop control. Fig.…”

“…For the specific case study considered in this paper, we isolated our optimization to two very important system parameters, namely the center of mass position, x cm , and the trim pitch angle, θ sp , which have been shown in [15] and [16] to dramatically influence flight performance. Because experiments were run at 1/100-scale, in a water channel environment, it was important to consider non-dimensional parameters in the optimization.…”

“…2 to the Altaeros BAT, we introduce the basic model and controller structure that is used for numerical optimization, along with key variables. A more detailed description of the dynamic model is presented in [17] and [15].…”

“…The proposed technique, referred to as experimentally-infused optimization retains the simplicity of the dynamic model used for numerical optimization, reconciling differences between the model and reality through lab-scale experiments. Furthermore, the use of 3d printing technology to test 1/100-scale models in the water channel enables accurate characterization of important system characteristics (such as added mass effects, net buoyancy, and scaled inertial properties, along with general stability and damping characteristics) at orders of magnitude lower cost than a full-scale prototype, as further detailed in [15] and [16]. This paper presents a case study of experimentally-infused optimization on the Altaeros BAT, which focuses on two non-dimensional (and therefore scalable between the water channel and full-scale) parameters that are tightly interconnected, namely the trim pitch angle and the center of mass position.…”