A remark on sensor disturbance rejection of nonlinear systems

When disturbances enter sensors, the states of a plant cannot be precisely measured and the state feedback controllers are not implementable. Instead, the so-called measurement feedback controllers become interesting. For nonlinear systems, the output regulation theory is widely used for handling actuator and plant disturbances. This note gives a remark how the output regulation theory can be applied for sensor disturbances, and hence provides a novel measurement feedback design approach.