PID control and PI state estimation for complex networked systems: a survey

The integration of networked systems with control and state estimation presents a variety of challenges, a prominent one being the performance degradation of data communication due to network-enhanced complexities. Due to their multi-loop architectures, proportional-integral-derivative (PID) controllers and proportional-integral (PI) observers provide superior design flexibility and reliability compared to their proportional-type counterparts. Therefore, it is of significant interest to explore the issues of PID control and PI state estimation for complex networked systems, particularly in mitigating the adverse effects of imperfect data transmission on system performance. This paper presents a comprehensive bibliographical review addressing PID control and PI state estimation problems for networked systems. Initially, the concept of network-induced complexity is introduced in detail according to its engineering background, characteristics, and representative research frameworks. Subsequently, the discussion focuses on PID control and PI state estimation issues under various performance indicators. Finally, we conclude the paper by delineating prospective research avenues and challenges pertaining to PID control and PI state estimation in the realm of complex networked systems.