An algorithm for mildly nonstationary mission synthesis (MNMS)

An important technical problem associated with the design, development and testing of vehicle subsystems is the definition of the operating conditions faced in use. Determining vibration missions is critical in the field of automotive NVH because numerous components are nonlinear, providing different vibratory behaviour depending on the nature of the input excitation used. An example of a nonlinear vehicle component is the person/ seat system. Seat transmissibility measurements in the vertical direction typically show a softening system behaviour, with the principal resonance shifting to lower frequencies as the excitation amplitude at the base of the seat rises [4]. Industrial testing methods such as those applied to seats often work around the problem of nonlinearity by using several test signals [3], each one selected to represent a specific road surface which was found through experience to excite important vehicle and subsystem resonances. Determining these mission signals has often been a matter of trial and error.