Analysis of suspension with variable stiffness and variable damping force for automotive applications

Lalitkumar Maikulal Jugulkar,Suresh Maruti Sawant,Shankar Singh

doi:10.1177/1687814016648638

Abstract

Passive shock absorbers are designed for standard load condition. These give better vibration isolation performance only for the standard load condition. However, if the sprung mass is lesser than the standard mass, comfort and road holding ability is affected. It is demonstrated that sprung mass acceleration increases by 50%, when the vehicle mass varies by 100 kg. In order to obtain consistent damping performance from the shock absorber, it is essential to vary its stiffness and damping properties. In this article, a variable stiffness system is presented, which comprises of two helical springs and a variable fluid damper. Fluid damper intensity is changed in four discrete levels to achieve variable stiffness of the prototype. Numerical simulations have been performed with MATLAB Simscape and Simulink which have been with experimentation on a prototype. Furthermore, the numerical model of the prototype is used in design of real size shock absorber with variable stiffness and damping. Numerical simulation results on the real size model indicate that the peak acceleration will improve by 15% in comparison to the conventional passive solution, without significant deterioration of road holding ability. Arrangement of sensors and actuators for incorporating the system in a vehicle suspension has also been discussed.

Highlights

Passive fluid shock absorber provides simple and effective solution for comfort and handling of the vehicle
Design and numerical simulation of a variable stiffness system have been presented in the article
Helical springs and adjustable fluid damper have been used in the prototype to vary the stiffness from 43.5 to 53.8 kN/mm

Summary

Introduction

Passive fluid shock absorber provides simple and effective solution for comfort and handling of the vehicle. Automobiles are designed to support maximum mass by calculating the suspension parameters (namely, stiffness and damping coefficient) It can be observed from equation (3) that the passive shock absorber will not give consistent performance as the sprung mass changes. Variable stiffness system has been developed that comprises of two controllable dampers.[2,14] Quarter car simulations on these systems indicate that peak acceleration will reduce to 70% to that of the passive system. The authors have reported about 36%–50% reduction in displacement transmissibility in comparison to the passive solution.[2,14] Gavin and Doke[17] have been studied response time of a control valve mechanism for variable stiffness vibration isolation system with numerical model. Eight different stiffness settings can be achieved with the prototype

Design considerations

Findings

Conclusion