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The disturbance obserber observes
a disturbance as one of the state elements of a
dynamical system. The observed disturbane includes
parameter variations of the system explicitly, and
allows direct estimation of parameter variations.
An estimation method for state quantities
of vehicle system based on the disturbance obserber
was proposed. Furthermore, a necessary and sufficient
design condition for the existence of disturbance
obserbers which estimate target variations was clarified
from the viewpoint of the obserbability of the expanded
system. This condition is used for determining sensors
necessary to measure the states corresponding to
parameter variations. Also the simple correlation
method is used to extract the parameter variations
from the observed disturbances including external
disturbances and noise. The proposed method was
applied to the estimation of the spring constant
of the tire in an active suspension system, and
proved effective by several numerical and experimental
results.
This method is also useful in detecting
the failure with parameter variations of the components
of the system.
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