Stability and Control of a Morphing Vehicle

Abstract

Air vehicle design is a study in compromises. Aircraft configurations are optimized to perform at one point in their flight envelope at the expense of performance at off nominal flight conditions. Two wildly different missions require two wildly different vehicles or one vehicle that does not perform either mission optimally. Morphing refers to the ability of an aircraft to significantly change its aerodynamic configuration to meet disparate mission requirements or optimize its performance based on changing flight conditions. Accomplishing this goal relies on technologies that touch every area of aerospace engineering including shape changing structures, configuration optimization, and stability and control. Here, the latter of these will be addressed. A configuration is developed that is capable of significant configuration change. The bare airframe stability characteristics are determined using a vortex lattice code in each nominal configuration. An outer loop and guidance controller are developed to allow for autonomous flight in the Boeing Vehicle Swarm Test Lab (VSTL). The vehicle dynamics are augmented with inner loop controllers in the lateral and directional axes. A simple nonlinearity is introduced to represent a nonlinearity that may be present during configuration changes. An adaptive control scheme is employed to maintain stability and performance during the transition between the nominal configurations in the presence of the nonlinearity. Autonomous flight tests of static configurations were performed to validate the aerodynamic code and control design techniques.