MATLAB Simulation and Analysis of Effect of Stiffness to Damping Ratio and Variable Road Elevations on Vehicular Driving Comfort and Safety

Abstract

In this work, it is proposed that the use of variation in Tire Spring Length (Ls (Tire)), Suspension Spring Length (Ls (Suspension)) together with changes in Sprung Mass Acceleration (SMA), all as a function of Suspension Stiffness to Damping Ratio (k:c) and Road Elevation (E), will provide the required indicators to enable vehicle drive strategy and optimize autonomous vehicle automatic selection. MATLAB simulation is performed using three main k:c ratios (1, 20, 0.27) and three main road elevations (1, 3, 5) to achieve the stated objective of this work. It is shown through this work that there is a relationship between spring length variation for both tire and suspension, road elevation, and sprung mass acceleration, such that driving strategy can be optimized according to road profile and k:c ratio using these parameters and the intersection of points between tire spring length variation and suspension spring length variation as a function of time and road elevation. Criteria are established in this research for the design and operation of driving strategy, such that three points of selection are used to enable either comfort or handling mode driving strategy. The final findings confirmed that for better handling, the Spring Length Variation Ratio (SLVR) should be less than one, with a steady increase in SMA and a minimum number of intersections between the tire spring length variation curve and suspension spring variation length curve as a function of road elevation and time. The presented work suggested through Tables 6 and 7 criteria to enable design for mode switching of autonomous vehicles as a function of road conditions.