Hinged Tile-Based Air Surface for Morphing Windshield Cowling

Abstract The gap between the windshield and hood provides an opening for windshield wipers to operate, but can be problematic at other times, 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 the simultaneous force/stroke generation, cannot perform two-way actuation, or fail to rigidly hold their position against varying loads such as wind. This paper introduces a useful curling air surface based on hinged T-shaped tiles that improves upon existing morphing technologies by adding straightening actuation to out-of-plane curling with large force and deflection, while also providing rigid position holding. An upper curling bladder encloses the hinged T-shaped tiles and pulls the T-protrusions together when vacuumed, causing the surface to curl. Lower straightening bladders span the hinge lines and pull the tiles flat when inflated. Through vacuum and inflation of the two bladders, the air surface covers and uncovers the gap against the wind load, and can hold its curled position rigidly using inter-tile hard stops. To predict the air surface performance, an air surface model is aggregated from multiple instances of a unit curling model that is derived from first principles with additional phenomenological terms. The validated model enables a scalable dimensionless design space visualization for general curling applications against loads, which is applied to design a windshield cowling. The resulting design is tested with its wind retention ability and built into a full-scale prototype windshield cowling operating on a sedan. This paper provides the technology concept and supporting model and design approach to more broadly apply this useful air surface architecture to applications in automotive (air dam, adaptive seating), aerospace (morphing wing), architecture (self-assembly shelters) and other domains.