A linear digital control design and stability analysis for time delay systems without linear approximation

Systems with time delays are present in many applications and considerable research efforts have been made for design and analysis of controllers for this class of systems. Since time delay itself is nonlinear in nature, various approximation techniques have been developed based on restrictive assumptions. A common approximation technique for time delay is by using the Pade rational polynomials which expresses time delay transfer function e^-ts in the form of numerator and denominator in s. In this paper, systems with time delay are investigated directly in discrete time domain. The time delay is modeled accurately without linear assumption and an augmented state space model is obtained. Control law is developed and closed loop stability is proven. An example is given to demonstrate the technique