Abstract
Keywords:Vehicle Dynamics, Ride and Handling, Chassis, Suspension, Steering.
Vehicle suspension test rigs (1) have been around for some time and are commonly used to understand the response of suspension system designs. Currently these responses are analysed separately for geometry (kinematics) and forces (compliance).
In real world situations these two factors combine to give an overall response of the vehicle's suspension system (2) with the vehicle body moving relative to the wheels causing geometry changes, and forces generated by the tyres creating a compliant response of the suspension system.
In the past the overall response has been studied using full vehicle model simulation packages that predict the overall response of the suspension system. These can be multi-body based (3) and use the individual component designs to predict the vehicle's response. Or parameter based (4) and use the overall system responses to predict the vehicle's response. It can take some time to generate enough data to build a full model of a vehicle.
This paper outlines a simple technique for quickly combining the rig based measurements of the kinematic and compliance responses for a vehicle undergoing a steady state cornering test. The technique involves making a basic estimation of the vehicle's lateral load transfer during cornering and using this to estimate the suspension system movement and forces generated by the tyres. These two estimations are then combined to give a total response of the suspension system.
The results from this basic technique are then compared with actual response data measured on a vehicle. The simple approximation is shown to give a valid estimation of the actual vehicle's total suspension system response. This total response would be difficult to predict by looking at the kinematic and compliant responses in isolation. And similarly looking at the total response it is difficult to understand the separate kinematic and compliant contributions.
The paper then goes on to apply this technique to several vehicles measured on a suspension testing rig. An estimation of how various suspension system designs achieve their predicted overall response is made. It can be seen from the results that by clever use of design, deficiencies in cheaper semi-linked axle suspension systems can be overcome. This is shown to make their responses closer to the desired response from more expensive independent multi-link suspension systems.