PID control schemes have been widely used in most of process control systems represented by chemical processes for a long time. Indeed, they are easy for most of engineers in many industries to understand and for a various systems to use, whose properties are obscure. However, conventional PID control schemes have not been so available for the systems of which system parameters and the time delays are unknown. The purpose of this paper is to consider advanced PID control schemes in discrete-time systems with unknown time delays. Two control schemes, that is, compound PID control systems with a local feedback compensator and a pre-compensator, are proposed, and they are extended to explicit-type self-tuning PID control shemes. Furthermore, these methods are applied to a pressure control system in order to show the effectiveness of them.