Identification of Properties of Nonlinear Joints Using Dynamic Test Data

This paper presents a general purpose technique for identifying (extracting) the dynamic properties of nonlinear joints using dynamic test data. No theoretical model is required, only experimental data are needed for the identification. Because no assumption on the properties of the nonlinear joints is made, the method is applicable for identifying almost any type of nonlinear joints. In the identification method, the nonlinear force at a joint is treated as an external force and the principle of multi-harmonic balance is employed. The force-response relationship of a nonlinear joint is then obtained. Various measurement errors in experimental data can affect the accuracy of identification. In this paper, efforts are also devoted to understanding how the accuracy of identification is affected by measurement errors. Techniques for improving the accuracy of identification are also discussed. The method is verified by experimental studies. The nonlinear properties of an impact joint and a friction joint have been successfully identified.