Dynamics of four-wheel-steering vehicles
K. Spentzas2001, Forschung im Ingenieurwesen
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Abstract
In this paper we present an optimised 3 degreesof-freedom non-linear dynamic model of a four-wheelsteering (4WS) vehicle. As variables, we retain the lateral velocity V, the rolling velocity p and yaw velocity r. The front steer angle d f and rear steer angle d r are considered to be linear functions of the steering wheel angle h s and of dh s =dt, the proportionality parameters being k 1f , k 2f for d f and k 1r , k 2r for d r . The parameters k 1f , k 2f , k 1r , k 2r are optimised by use of the BOX mathematical algorithm. In a ®rst optimisation loop we minimise the sideslip angle b of the vehicle and in a second optimisation loop we assure, that the resultant (taken in the centre of gravity of the vehicle) of all the transversal forces F y applied on the wheels of the vehicle (reaction forces contained in the road plane), give a component F yx along the longitudinal axis of the vehicle, that takes a non negative value. This assures, that the motor of the vehicle will not waste fuel to overcome resistance forces originating from the steering system of the vehicle. A numerical application is also presented for a 4WS vehicle negotiating a curve at constant velocity. The results are compared to those obtained by two models frequently used in the literature. The comparison testi®es on the superiority of our model for the application presented here.
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