| A roll control mechanism is proposed for a jeep-type utility vehicle employing an active suspension with hydragas suspension units. Pressure changes within the unit alter the stiffness characteristics of the units, thereby influencing the roll dynamics of the vehicle with the objective to reduce body roll and to prevent tire lift-off in serious driving manoeuvres.; The nonlinear multibody model of the vehicle is based on Jourdain's Principle, also known as Kane's equations, employing velocity degrees of freedom. The nonlinear tire behaviour is appropriately modelled, including effects such as side-slip saturation, camber, and aligning torque. For the active hydragas units, a linear model validated by test results of an earlier research project is used.; The equations of motion of the vehicle including the active suspension unit must be linearized to be suitable for control development. A numerical finite difference technique is applied to obtain the sensitivities of the degrees of freedom with respect to state and control input changes. The controller is based on an optimal design. A linear quadratic regulator approach is adapted to accommodate nonzero reference signals for body roll.; The performance of the control strategy is evaluated by comparing computer simulations of the passive and the active vehicle employing an object-oriented simulation environment developed during the study. J-Turn and slalom scenarios are simulated. Results show up to a 50% reduction in vehicle body roll and an improved distribution of tire normal forces as long as tires are not saturated. |
