Reduced-order partial-state feedback for robust nonlinear control using state-dependent scaling

This paper addresses reduced-order design of dynamic partial-state feedback controllers for uncertain nonlinear systems. The design objective is to achieve disturbance attenuation and global stabilization in spite of nonlinear static and dynamic uncertainties arising from various locations of the system. Since only a part of the plant state is measured and the reduced-order dynamic controller does not have the mechanism to rebuild the full state vector, the design problem is much harder than state-feedback and full-order observer/state-feedback design. The design problem is tackled by the pair of state-dependent scaling and diffeomorphism which are newly tailored to the reduced-order partial-state feedback successfully. The paper not only shows a state-dependent scaling characterization of controllers and an analytical solution, but also suggests numerical computation.