Modeling and Design of Hinged Tile-Based Curling Air Surface for Morphing Windshield Cowling

Abstract

Abstract The gap between the windshield and hood allows windshield wipers to operate, but causes problems gathering leaves and snow. Active morphing approaches provide an opportunity to create a windshield cowling that addresses this issue by covering the gap normally and actively curling out of the way to allow wiper operation. Most existing morphing techniques lack simultaneous large force/stroke generation, cannot perform two-way actuation, or fail to rigidly hold their position against varying loads such as wind. This article studies a novel curling air surface based on hinged T-shaped tiles that improve upon existing technologies by adding straightening actuation to out-of-plane curling with large force and deflection, while also holding position rigidly. Through vacuuming an upper curling bladder enclosing the tiles and inflating lower straightening bladders spanning the hinge lines, the air surface uncovers and covers the gap against wind loads and holds its curled position rigidly using inter-tile hard stops. An analytical surface model aggregated from multiple instances of a first principle unit curling model predicts the air surface performance. This model includes additional kinematic effects, extending the range of applicability, and additional bladder effect phenomenological terms to improve accuracy. The model is validated across scales and enables design space visualization, which is applied to design a windshield cowling. The resulting design is validated and demonstrated in a full-scale prototype. This article provides the technology concept, supporting model, and design approach to broadly apply this useful air surface to other morphing applications.