Lateral Tyre Force Distribution for Four-Wheel Steer-by-Wire Vehicles

In a four-wheel independent steering vehicle, all the tyres have the capability of being steered independently. The traditional steering assemblies are mechanically limited because their inner and outer wheel’s steering angles are interrelated which makes it difficult to extract the maximum possible traction from the ground. Such steering systems are unable to take the advantage of the load transfer which occurs during the cornering. This work proposes a novel method of lateral tyre force distribution between the inner and outer wheels by making use of load transfer during the cornering of the vehicle. The distribution is obtained by using a function which maps the lateral acceleration of the vehicle to the distribution of the forces between the wheels. The function can be tailored according to the requirements of the driving. The control strategy involves simple equations to allow for an easy hardware implementation. The simulations performed through numerical solution of vehicle dynamics model using the computer program in MATLAB/Simulink show an improvement in the cornering performance of the vehicle and a significant reduction in workload of tyres.