| Two different technologies are demonstrated for a span-morphing wingtip: a linear controller for a pneumatic artificial muscle (PAM) actuator, and a passive 1-D morphing skin. A generic PAM system incorporating a single PAM working against a nonlinear spring is described in a Simulink model, which is validated using experimental data. A linear PID controller is then incorporated into the model. Frequency responses are obtained by both simulation and experiment, and the ability to track relatively high frequency control inputs is demonstrated. The morphing skin system includes an elastomer-fiber-composite surface layer that is supported by a flexible honeycomb structure, each of which exhibit a near-zero in-plane Poisson's ratio. Composite skin and substructure configurations are designed using analytical methods and downselected after experimental evaluation. A complete prototype morphing skin, mated to a PAM driven extension mechanism, demonstrates 100% uniaxial extension accompanied by a 100% increase in surface area. Out-of-plane deflections under surface pressures up to 200 psf (9.58 kPa) are reported at varying levels of area change. |
