OBSERVER-BASED IDENTIFICATION OF NONLINEAR-SYSTEM PARAMETERS

This paper deals with an observer-based nonlinear system parameter ide ntification method utilizing repetitive excitation. Although methods f or physical parameter identification of both linear and nonlinear syst ems are already available, they are not attractive from a practical po int of view since the methods assume that all the system, x, and the s ystem input are available. The proposed method is based on a ''sliding observer'' and a feast-square method. A sufficient condition for the convergence of the parameter estimates is provided in the case of ''Li pschitz'' nonlinear second-order systems. The observer is used to esti mate signals which are difficult or expensive to measure. Using the es timated states of the system with repetitive excitation, the parameter estimates are obtained. The observer based identification method has been tested on a half car simulation and used to identify the paramete rs of a half car suspension test rig. The estimates of nonlinear dampi ng coefficients of a vehicle suspension, suspension stiffness, pitch m oment inertia, equivalent sprung mass, and unsprung mass are obtained by the proposed method. Simulation and experimental results show that the identifier estimates the vehicle parameters accurately. The propos ed identifier will be useful for parameter identification of actual ve hicles since vehicle parameters can be identified only using vehicle e xcitation tests rather than component testing.