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Report, 1993

Modelling and optimization of passive and adaptively controlled active cab suspensions on terrain vehicles, especially agricultural tractors

Hansson, Per-Anders


The main purpose of the work was to study the possibilities of using the cab suspension technique to improve the driver’s environment on an agricultural tractor. Two simulation models describing the frame-suspension-cab system were developed: A nonlinear model for studying the characteristics for suspensions with only small constrictions on the geometry and on the working principles of the elements, and a linear model which is a simplified description of the same system including more constraints, but more applicable when designing and studying performance particularly for active suspensions. The simulation models were validated against measurements made on a full-scale cab suspension. The influence of different passive suspension parameters on vibration damping capacity and the requirement for free space in the construction were investigated. Panicular emphasis was placed on the effects of passive non•linear suspension elements and varying locations of the elements. An optimization model, based on an evolution algorithm, was developed and used to optimize parameters in a passive suspension with different types of generally defined constraints. The development and analysis of LQG based active cab suspensions are described. The vibration damping characteristics of the suspensions are studied. The change in characteristics when the suspension’s configuration or design variables are changed is also studied. The results show that an active cab suspension based on linear state feedback must have time variant adaptive characteristics to be really useful. An adaptive active suspension controller based on LQG technique has been developed and studied. The principle for the adaptation is based on the parameters in the penalty matrices being varied so that the resulting controller always strives to make optimum use of the available travel space.


cab suspension; whole body vibrations; tractors; terrain vehicles; vehicle dynamics; nonlinear elements; modelling; simulation; optimization; validation; passive suspension; active suspension; adaptive active suspension; suspension systems; optimal control; optimal estimation

Published in

Rapport - Sveriges lantbruksuniversitet, Institutionen för lantbruksteknik
Publisher: Institutionen för lantbruksteknik, Sveriges lantbruksuniversitet

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