A universal nonlinear model for the dynamic behaviour of shock absorbers

TL;DR

This paper introduces a comprehensive nonlinear analytical model for hydraulic shock absorbers that captures complex effects like hysteresis and instabilities, validated against experimental data and adaptable to various designs.

Contribution

A universal first-principles-based nonlinear model for shock absorbers that accurately predicts dynamic behaviors across different architectures.

Findings

Model predicts nonlinear oscillations and hysteresis loops.

Results agree well with test bench measurements.

Model can be adapted to various shock absorber geometries.

Abstract

Modern hydraulic shock absorbers display a wealth of nonlinear effects such as hysteresis and instabilities at high flow rates. Despite their wide application in practically all vehicles, both on- and off-road, a universal analytical model that captures the essential shock absorber dynamics and compressibility effects for various common damper architectures is lacking. This paper presents such a model and derives its system of equations from first principles for dampers of monotube- and piggyback-type. By applying the model to a typical suspension configuration, all relevant system variables, such as pressure drop, shim stack deflection, and damping force, are computed. Nonlinear oscillations and hysteresis loops, which might prove dangerous during operation, can be predicted effortlessly. The results achieved with the mathematical model are validated and agree well with test bench measurements. Furthermore, the presented approach is shown to be easily modifiable to describe the physical processes within other hydraulic shock absorber geometries in use today.