Suspension settings for optimal ride comfort of off-road vehicles travelling on roads with different roughness and speeds

Abstract

This paper reports on an investigation to determine the spring and damper settings that will ensure optimal ride comfort of an off-road vehicle, on different road profiles and at different speeds. These settings are required for the design of a four stage semi-active hydro-pneumatic spring damper suspension system (4S 4 ). Spring and damper settings in the 4S 4 can be set either to the ride mode or the handling mode and therefore a compromise ride-handling suspension is avoided. The extent to which the ride comfort optimal suspension settings vary for roads of different roughness and varying speeds and the levels of ride comfort that can be achieved, are addressed. The issues of the best objective function to be used when optimising and if a single road profile and speed can be used as representative conditions for ride comfort optimisation of semi-active suspensions, are dealt with. Optimisation is performed with the Dynamic-Q algorithm on a Land Rover Defender 110 modelled in MSC.ADAMS software for speeds ranging from 10 to 50 km/h. It is found that optimising for a combined driver plus rear passenger seat weighted root mean square vertical acceleration rather than using driver or passenger values only, returns the best results. Results indicate that optimisation of suspension settings using one road and speed will improve ride comfort on the same road at different speeds. These settings will also improve ride comfort for other roads at the optimisation speed and other speeds, although not as much as when optimisation has been done for the openUP (July 2007) particular road. For improved ride comfort damping generally has to be lower than the standard (compromised) setting, the rear spring as soft as possible and the front spring ranging from as soft as possible to stiffer depending on road and speed conditions. Ride comfort is most sensitive to a change in rear spring stiffness.

Use of generated artificial road profiles in road roughness evaluation

“…Moreover, many studies on the design and analysis of vehicle suspensions are often based on the use of artificial profiles [6,7].…”

Comparison of different gas models to calculate the spring force of a hydropneumatic suspension

“…It also has 16 moving parts, 6 spherical joints, 8 revolute joints, 7 Hooke's joints and a motion defined by the steering driver. The model was modified by [17], [18] and [19] to add additional changes made to the test vehicle. Schematic diagrams of the front and rear suspension layouts are indicated in Figure 3 and Figure 4.…”

Longitudinal vehicle dynamics control for improved vehicle safety

“…An existing MSC.ADAMS/ View multi-body dynamics model that accurately captures the fully nonlinear vertical and lateral dynamics of the test vehicle has been developed by Uys et al [4]. The model is now expanded and experimentally validated to accurately capture the longitudinal dynamics.…”