Mu-synthesis based cascaded robust controller design for exact linearizable dynamical systems

Model-based controllers for nonlinear systems require the adequate knowledge of plant parameters in order to produce nominal performance and stability. Moreover, external disturbances can also interfere with reference tracking performance. The paper presents a robust controller synthesis method for a class of nonlinear systems. It merges two state-of-the-art approaches, namely exact linearization by state feedback, and mu-synthesis which is known from linear robust control theory. The resulting architecture is cascaded, where the outer loop contains the robust, linear two-degrees-of-freedom (2DoF) controller, which has better disturbance rejection properties compared to its serial compensator counterpart. Two examples (the second being a 2DoF robotic arm) are used to illustrate the control design procedure, which is then validated by simulations.