A combined first and second order sliding mode approach for position and pressure control of an electropneumatic system

The aim of this paper is to propose efficient multivariables controllers for an electropneumatic system. The considered system use two three-way proportional servodistributors. Generally, it is supposed that these two servodistributors are equivalent to one five-way proportional servodistributor when they are controlled with inputs of opposite signs. In this case, a monovariable control law can be established. However, with the system of two three-way servodistributors, it is possible to control two different trajectories. For example, it seems useful to control position and pressure without a degradation of the desired specifications. Due to uncertainties appearing in the modelization, robust controllers are necessary to ensure position and pressure tracking with high precision. For this, two control laws based on a combination of a first and second order sliding mode are proposed. The experiment results are presented and discussed.