Hybrid control of a hydro-pneumatic tractor suspension

We consider the set-point regulation of a nonstandard hydro-pneumatic suspension architecture used in commercial tractors, which allows regulating both the stroke and the pressure in the suspension. The model reveals an affine dynamic comprising two single integrators whose actuation is performed by way of suitably switching constant input selections. We design the switching input using a hybrid representation, providing necessary and sufficient conditions for the global stabilizability. Two constructive hybrid control laws are proposed: the first one solves the stabilization problem, while the second can be used to suitably reduce the number of switches of the input, thereby limiting the aging of the actuators. Both control laws are tested in simulation and assessed in terms of performance and robustness in the presence of parametric uncertainties.