Comparison of time delay processing methods in control system

Time delay exists in the actual control system and presents some difficulties in processing of transfer function for process control. Approximation for time delay is commonly used in control system. This paper analyses the effects of different approximation including Taylor, Pade and all-pole approximation for different orders closed loop system. Second order Pade approximation can fit the time delay in first-order closed-loop system. Taylor approximation cannot apply to the system with large time delay. First order all-pole approximation gets the smallest over shoot, adjusting time both in first and second-order large delay system.

I. Introduction

The variation of output and input in time delay is the same except that the initial response of output falls behind input with time Time delay transfer function is defined as is the delay time constant). In real control systems, time delay is common ^[1]–[4].