Alternative Trim Analysis Formulations for Vehicles with Redundant Multi-Axis Control Surfaces

摘要

Conventional trim optimization problem formulations can produce poor results for vehicles with redundant multi-axis control surfaces. Trimming these vehicles requires solving the nonlinear equations of motion for their roots or equilibrium points. The hybrid wing-body vehicle has many redundant elevons and tends to result in an underdetermined system. As a consequence, there may be an infinite number of deflection combinations that satisfy the same moments. Challenges associated with using conventional trim optimizations with this type of vehicle are demonstrated, followed by two alternative approaches to relieve these problems. Control allocation techniques are integrated into the conventional approach to reduce the number of variables and attempt to make the problem more convex. A reformulation of the trim optimization from root seeking to drag minimization was also explored. These alternative methods were judged on how often they converged, trimmed drag and thrust, and commanded deflections.