Design of Launch Vehicle Flight Control Systems Using Ascent Vehicle Stability Analysis Tool
A launch vehicle represents a complicated flex-body structural environment for flight control system design. The Ascent-vehicle Stability Analysis Tool (ASAT) is developed to address the complicity in design and analysis of a launch vehicle. The design objective for the flight control system of a launch vehicle is to best follow guidance commands while robustly maintaining system stability. A constrained optimization approach takes the advantage of modern computational control techniques to simultaneously design multiple control systems in compliance with required design specs. “Tower Clearance” and “Load Relief” designs have been achieved for liftoff and max dynamic pressure flight regions, respectively, in the presence of large wind disturbances. The robustness of the flight control system designs has been verified in the frequency domain Monte Carlo analysis using ASAT.
Higher order subparametric elements for large deflection analysis of plates
Abstract A family of higher-order subparamctric elements has been developed for large deflection analysis of flat plates of any geometric shapes subjected to lateral loading. The formulation procedure for these elements with 17–25 nodes involving in-plane as well as bending displacements with subparametric transformation is described and the derivation of the tangential stiffness matrix based on the classical von Karman nonlinear large deflection theory is presented. The Newton-Raphson scheme with modification is used. Several numerical examples of skewed slabs and circular plates are worked out and the results are compared with available data given by other research workers. It is found that these higher-order elements are simple, versatile, economical and convenient to use and give accurate results for large deflection analysis of plates.
Pareto optima of isostatic trusses
Abstract Multicriterion optimization of elastic stress limited isostatic trusses is considered and a numerical method for determining the Pareto optimal set of the problem is developed. The weight of the structure and some chosen nodal displacements are taken as design criteria, and member areas are used as design variables. The corresponding bicriterion problem with weight and one displacement in the objective function is solved exactly, and this result is used as a basis of the proposed method. By introducing certain parameters, each joined with one displacement criterion, the Pareto optimal solutions of the general problem may be obtained with any accuracy. Two examples are given to illustrate the method.