Nonlinear System Identification of an All Movable Fin with Rotational Freeplay by Subspace-Based Method

To interpret the nonlinear system identification of multi-degree-of-freedom vibrating structures with freeplay, an estimation procedure based on subspace method in time domain is developed in this paper. Two types of freeplay, namely, central freeplay and offset freeplay, are estimated. Besides, the frequency response function matrices of the underlying linear system and overlying linear system are identified. By considering an all movable fin from a portion of a supersonic flutter test platform containing freeplay on the rigid rotating motion, two series of numerical experiments are applied for demonstration. Results show that the proposed approach indicates a high and reliable recognition of freeplay regions and the nominal linear system. The limitations of the method in this study are also discussed.