This paper presents an algorithm to design a robust servo controller for a controlled variable to follow the reference signal in the presence of disturbace, where the disturbances and the references are modelled by the outputs of free linear dynamical systems. The proposed one is modified Davison's procedure to clarify the robustness of the controlled system and is shown to be extended to a digital control easily.
In the second, the digital servo control system is designed based on the quadratic criterion function given to a continuous system and it is shown that the use of the higher order sample-hold circuit is desirable, and the remark for choice of the sampling interval based on the criterion function is also given.