Effect of wheel geometry parameters on vehicle steering

In modern era, steerability and handling characteristics of the vehicle have become major aspects. Providing comfort to the driver by reducing steering effort without any compromise in steerability and handling of the vehicle is a major concern for automakers. Evaluating handling and steering characteristics of a vehicle in a virtual environment with the help of multi-body system packages saves product development time and cost. The main intention is to improve the steerability and handling of the vehicle by avoiding the steering pull and wheel wandering problems.

As per the specification of the selected vehicle Honda CR-V, a multi-body model of the SUV was built in ADAMS/CAR software. The SUV model was validated by comparing simulation results with the standard graphs from literature. Using this model, manoeuvres for different values of wheel geometry parameters, were simulated. The steering effort, steering wheel returnability and the lateral forces produced by the tires were obtained in order to predict the behaviour of the vehicle for different wheel geometry parameters.

It can be seen from the results that positive caster angles improve the steering wheel returnability but increase the steering effort. Negative caster angles reduce the steering effort but create wheel wandering problems. Higher Steering Axle Inclination (SAI) angles help in improving the steering wheel returnability and decreasing the steering effort as well. Negative camber angles help in producing higher lateral forces to improve the cornerability of the vehicle. Toe-in angles help in improving the straight-line stability where as toe-out angles help in improving the cornering. Negative scrub radius seem to have stabilising effect on vehicle handling.