Eigensensitivity Analysis in Variable Geometry Trusses

摘要

This work presents a procedure for estimating the variation of natural frequencies and vibration modes of VGTs during their movement, making it unnecessary to recalculate them at all positions but just for a small number thereof. It is possible to efficiently use modal superposition techniques with it, thus avoiding costly dynamic analysis based on direct integration techniques. Furthermore, it allows direct knowledge of the contribution of each mode in the structure movement, which is of special interest in VGT design. To model the variations of frequencies and modes throughout VGT evolution, linear estimation has been used, which obtains natural frequencies and vibration modes in a new position from their values in a previous position. For this, the derivatives of the natural frequencies and vibration modes are calculated in relation to the nodal coordinates for a reference position. Subsequently, a first-order series is developed around this position to obtain a precise estimation in the new position.