Experimental and Analytical Evaluations of a Torsio-Elastic Suspension for Off-Road Vehicles

The ride performance potentials of a prototype torsio-elastic axle suspension for an off-road vehicle were investigated analytically and experimentally. A forestry vehicle was fitted with the prototype suspension at its rear axle to assess its ride performance benefits. Field measurements of ride vibration along the vertical, lateral, fore-aft, roll and pitch axes were performed for the suspended and an unsuspended vehicle, while traversing a forestry terrain. The measured vibration responses of both vehicles were evaluated in terms of unweighted and frequency-weighted rms accelerations and the acceleration spectra, and compared to assess the potential performance benefits of the proposed suspension. The results revealed that the proposed suspension could yield significant reductions in the vibration magnitudes transmitted to the operator's station. The field evaluations revealed that suspended vehicle could yield 35%, 43% and 57% lower frequency-weighted rms accelerations in the x -, y - and z -axis, respectively, compared to the unsuspended vehicle, when loaded. A 13-degrees-of-freedom model of the suspended vehicle was subsequently developed and validated using the measured data, which could serve as a design tool for deriving optimal suspension designs for a wide range of vehicles. The model results revealed reasonably good agreements with the measured vibration spectra. From the simulation results, it was further concluded that a reduction in the vertical stiffness of the torsio-elastic member would yield beneficial effects on the overall weighted vertical and pitch rms acceleration magnitudes.