Control effectiveness comparison of wheel loaders longitudinal vibrations by means of passive and active vibration stabilisers

When wheel loaders move with velocity higher than 10 km/h, they are subject to intense longitudinal vibrations. These vibrations are experienced particularly unpleasantly by an operator. Passive vibration stabilisers are used for controlling their intensity. They make outrigger's support more flexible so that outrigger's vibrations counteract the wheel loader's longitudinal oscillations when moving. Unfortunately, the effectiveness of passive stabilisers is insufficient and at present more effective alternative means are sought. One of the solutions for angular longitudinal vibrations includes the replacement of passive stabilisers with active stabilisers. Nevertheless, the possibility of active stabilisers’ use in minimising longitudinal vibrations requires a scientific assessment. Hence, this paper, meeting the needs, includes calculations, which allow for comparing the effectiveness of active and passive stabilisers in minimising the vibrations of a typical wheel loader. Active stabilisers, which are the subject of the study, worked based on state controller, whose synthesis was carried out on the basis of optimal control linear theory with square quality indicator. The calculations were conducted on linear models under stochastic road excitations. Stochastic excitations were defined by means of power spectral density of road's unevenness. Active stabiliser's effectiveness was analysed, both for a loader moving with an empty bucket, and for a loader transporting a 3-tonne load. In order to facilitate the analysis of the results obtained, vibrations minimising quality indicator was introduced, defined as a root of a vehicle longitudinal deflections power.