DYNAMIC MODAL TRUNCATION-RELAXATION

Mechanical systems including elastic bodies are considered. When equat ions governing motions of such systems are generated, use is frequentl y made of the assumed-mode theory to describe elastic deflections of e lastic bodies; and numerical integrations of these equations require a n a priori determination of the number of modes being assumed. Here, a method called dynamic modal truncation-relaxation is introduced, wher eby modes can be either truncated or relaxed at each integration step. The method is applied to a specific example, and a simulation code is constructed, showing that a significantly improved balance can be obt ained between simulation efficiency (i.e., execution time) and simulat ion accuracy, as compared with the balance obtained with an a priori c hosen number of modes. The method is useful when simulation run time i s of importance, e.g., when real-time simulations are performed in the context of control design; when many simulations have to be performed in the context of a parameter study; or when missions of a long durat ion have to be simulated rapidly, as in the design of a new course for a spacecraft already in motion.