K. Yi et K. Hedrick, OBSERVER-BASED IDENTIFICATION OF NONLINEAR-SYSTEM PARAMETERS, Journal of dynamic systems, measurement, and control, 117(2), 1995, pp. 175-182
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.