Session: 04-04: Integrated Smart Systems

Paper Number: 91443

91443 - Hinged Tile-Based Air Surface for Morphing Windshield Cowling 

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 and design the windshield cowling to resist wind loads, an air surface model is aggregated from multiple instances of a unit curling model of a single hinge system with a membrane connecting the two protrusions. The unit curling model is derived from first principles with additional phenomenological terms and is validated experimentally with single hinge prototypes with average errors of 6.2% across scales over wide ranges of torques and hinge angles in the curling and straightening directions. The aggregated air surface model incorporates the geometry and torque equilibrium of the unit curling model and predicts the deflected shape of air surface prototypes under load with average errors of 13%. The validated model enables a scalable dimensionless design space visualization for general curling applications against loads. The design plots are applied to the requirements of a windshield cowling. The resulting design is validated by building and testing 1) a morphing air surface segment demonstrating 80 MPH wind retention force and 2) 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.

Presenting Author: Tiantian Li University of Michigan