Output feedback controller using the singular perturbation method in the presence of sensor noise

There have been literatures to reduce the effect of sensor noise. By introducing new gain scaling factor, one of them makes it possible to arbitrarily reduce the effect of sensor noise composed of zero-mean random signal, whereas the others cannot reduce the effect of sensor noise under the magnitude of noise. In order to utilize the controller using gain scaling factor, the controller has to be directly connected to plant. However, in practical system, many systems are classified into cascade system since there is actuator between plant and controller. In this paper, we propose an output feedback controller applied to the cascade system by retaining the advantage of the previous controller. More specifically, the controller is composed of two part; in first part, the controller transforms the cascade system to a singularly perturbed system, and then the second part makes the effect of sensor noise be arbitrarily small in the singularly perturbed system.