LATERAL STABILITY AND HANDLING BEHAVIOUR OF THREE-WHEELED VEHICLES

Abstract

The three -wheeled vehicles are likely to see resurgence in their usage due to their advantages in being fuel efficient and relatively inexpensive. But any such possibility in a big way is hindered by their notoriety for unstable behaviour and overturning nature in turning maneuvers. The lateral stability and handling characteristics of road vehicles are very important to road safety and accident avoidance capabilities of vehicle-rider system. Therefore there is a clear need to study the stability behaviour and lateral dynamics of these vehicles. Two basic problems arise in vehicle handling. One is the control of the vehicle to a desired path and the other is the stability of the vehicle motion. Various parameters like stiffness of tyre, wind drag, suspension characteristics, caster trail etc. affect the stability and handling behaviour of vehicle. The vehicle model is represented by five rigid masses, and includes the effect of suspension, which has not been considered so far. Using nine degree of freedom mathematical model, lateral stability and handling behaviour of three-wheeled vehicle is analyzed. This work presents a detailed review of the existing literature in the above area. The equations of motion are developed using Lagrangian principle. The tyre forces and moments equations have been calculated by assuming first order lag characteristics. The damping ratios and damped natural frequencies of various modes of vehicle motion are evaluated by means of MATLAB software and modes of motion are studied. To find the handling behaviour, under-steering coefficient has been evaluated. The results are presented. Upon making various parametric studies, recommendations are made and conclusions drawn for improving the vehicles lateral stability and handling behaviour