Global exact tracking for uncertain multivariable linear systems by output feedback sliding mode control

This paper presents a solution to the problem of global exact output tracking for uncertain multivariable linear plants with non-uniform arbitrary relative degree using output feedback sliding mode control. The key idea to overcome the relative degree obstacle is to generalize our previous hybrid estimation scheme to a multivariable version by combining, through switching, a standard linear lead filter with a nonlinear one based on robust exact differentiators, achieving uniform global exponential practical stability and exact tracking.