The super-twisting second-order sliding-mode algorithm is modified in order to design a velocity observer for vehicle using only the ABS sensors already placed in standard vehicles nowadays. The finite time convergence of the observer is proved and consequently the separation principle can be considered as avoided. The gains of the proposed observer are chosen very easily ignoring the system parameters. This observer is compared, using experimental data, to classical derivation methods and is proven robust despite the bad resolution of the encoders. Its robustness combined with a sliding mode estimation of the vehicle velocity allow us to reconstruct the wheel sleep. In this way, the observability problems are avoided by means of cascaded finite time converging observer instead of additional sensors. It can be shown that contact forces can also be estimated by this way. The finite time convergence of state observations in the same time as robustness and perturbation rejection allows to solve the problem of parameter identification using the equivalent control method (by retrieval of the rejected signal). The use of the equivalent control, which provides a linear regression model, allows to apply the classical parameter identification methods (RLS) to estimate the systems dynamic parameters like the tyre longitudinal equivalent stiffness and the effective wheel radius. The estimation scheme build up using a Second Order Sliding Mode observers and a Sliding Mode velocity estimator has been tested on experimental data (acquired with a P406 vehicle) and shown to be very efficient using only standard sensors. The actual results prove effectiveness and robustness of the proposed method. In our further investigations we consider also the case of complete vehicle in a road with changing adherence. The estimations produced online will be used to define a predictive control to enhance the safety.
Second order sliding-mode observer for estimation of vehicle dynamic parameters
International Journal of Vehicle Design ; 48 , 3/4 ; 190-207
2008
18 Seiten, 10 Bilder, 40 Quellen
Aufsatz (Zeitschrift)
Englisch
Second order sliding-mode observer for estimation of vehicle dynamic parameters
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