Characterization of Root-Mean-Square Acceleration Errors in Flexible Structures Undergoing Vibration Testing

A methodology is described to evaluate the Root-Mean-Square (RMS) errors in acceleration response during the vibration testing of flexible structures like missile and rockets. Simulation studies are carried out on a free-free uniform beam to characterize the error estimations in the desired and achieved acceleration spectra at different locations of the structure. Equal and unequal desired spectra are also considered at different locations of the structure and individual error in the achieved spectrum, as well as overall error is computed. The simulation results are obtained for traversing a single input along the length of the structure with three control sensors at different locations. The variation of the force requirement at different locations of the control sensor and the normalized RMS error for each control sensor is computed. The investigations show that the force requirement is less when the control sensors are placed at the far ends of the structure. It is also observed that the force requirement is increased marginally for the increased number of control sensors, whereas the overall error between the desired and achieved spectrum is reduced with the increase in the number of control sensors.