Robust maneuvering envelope estimation based on reachability analysis in an optimal control formulation
This paper discusses an algorithm for estimating the safe maneuvering envelope of damaged aircraft. The algorithm performs a robust reachability analysis through an optimal control formulation while making use of time scale separation and taking into account uncertainties in the aerodynamic derivatives. Starting with an optimal control formulation, the optimization problem can be rewritten as a Hamilton-Jacobi-Bellman equation. This equation can be solved by level set methods. This approach has been applied on an aircraft example involving structural airframe damage. Monte Carlo validation tests have confirmed that this approach is successful in estimating the safe maneuvering envelope for damaged aircraft.
Launch-pad Abort Flight Envelope Computation for a Personnel Launch Vehicle Using Reachability
The main limitation of existing computational tools for continuous system reachability problems is that, due to the exponential growth of the computation with the dimension of the continuous state space, the tools can be applied effectively to relatively low dimensional problems (typically 1-4 dimensions). In this paper we adopt a two time scale approach to extend the use of continuous system reachability tools to six dimensions, thus making them applicable to a number of interesting case studies in the area of aeronautics. To prove the effectiveness of our approach, we apply it in the launch-pad envelope computation for safe landing of the HL-20 Personnel Launch Vehicle (PLV). The mathematical model of the PLV that is used is a three degree of freedom (six state) nonlinear point mass model, modified to contain several state constraints for the final approach phase. The results show that it is feasible to do exacting computations with nonlinear continuous dynamics in higher dimensions, if one can exploit additional structure in the model (in our case, the separation into slow and fast dynamics).
Impaired Aircraft Performance Envelope Estimation
A methodology for estimating the flight envelope of impaired aircraft using an innovative differential vortex lattice algorithm tightly coupled with an extended Kalman filter is presented. The approach exploits prior knowledge about the undamaged aircraft parameters to reduce the order of the estimation problem. Point-mass flight dynamic model and a set of approximate analytical methods for structural analysis are used in the development. Estimated damage parameters are used to determine the aircraft aerodynamic, structural, structural dynamic, and aeroelastic parameters. These parameters are then used to estimate the aircraft performance envelope and maneuver limits. As conceptualized in the present work, this data is displayed to the pilot to aid in effectively managing the aircraft flight after impairment. The data can also be used for implementing safe maneuvering and landing guidance laws in the future.