Parameter Estimation and Control of Time Delay SISO Systems

The paper presents a relay feedback experiment for identification and model-based control of a class of time delay single-input single-output (SISO) systems. When a hysteresis relay is fed back to an unknown system, sustained oscillations are yielded at the system output around the setpoint broadly known as limit cycle. Based on limit cycle information and relay settings, a set of state space based explicit expressions is deduced for accurate identification of system dynamics in terms of first order plus time delay (FOPTD) and second order plus time delay (SOPTD) transfer function models. Following the system identification, a set of balanced tuning rules for a proportional-integral (PI) controller is suggested to achieve an enhanced closed loop transient performance. Numerical simulation of well known examples from literature and experimental results from level control system are illustrated for validation of the proposed identification and control schemes.