In this thesis the objective has been to investigate whether sliding mode controllers combined with sliding mode observers perform better compared to conventional classical control algorithms in the application of a hydraulic system.
In the thesis the backhoe loader of a Case Prestige 580 is used as load for the hydraulics, and is modeled as a 4 link robot manipulator.
In the thesis a sliding mode controller based on a modified Twisting controller is evaluated up against two linear reference controllers; a P-controller and a velocity feed-forward pressure compensated PI-controller. The sliding mode controller requires the velocity of the cylinder piston, and therefore two sliding mode observers are considered to estimate the velocity of the cylinder piston.
Three different load scenarios evaluate the three controllers. The first load scenario is a fast inertia move, the second load scenario imitates a progressive disturbance and the third load scenario a sudden disturbance.