System identification of a mechanical system with impacts using model reference adaptive control

A single degree of freedom mechanical spring-mass system was considered where the motion of the mass is constrained by an adjustable rigid impact stop. A model reference adaptive control algorithm combined with interspike interval techniques was used to consider the viability of identifying system parameters when impacts are present. The unmodified adaptive control algorithm destabilizes during vibro-impact motion, so three modified control algorithms were tested experimentally. The first, the gain reset, was found to be of limited use and system identification could not be successfully carried out. The second and third used a gain pause strategy. The second algorithm used acceleration triggering and represented an improvement on the gain reset method. The third approach used displacement triggering and was found to be partially successful in identifying system parameters in the presence of vibro-impact motion.