Comparison of Low-complexity Controllers in Varying Time-delay Systems

Motivated by the recent developments in networked control systems and control over wireless, this paper presents a comparison of five control algorithms that are based on PID, IMC and fuzzy gain scheduling techniques and discusses their performance in varying time-delay systems. The low complexity of the proposed algorithms makes their use attractive in resource-constrained environments such as wireless sensor and actuator networks. The control system consists of a controller, a simple process and an output delay in the feedback loop. Three different delay models are considered in this framework; constant, random, and correlated random delay. In addition to presenting modifications to the control algorithms to better fit the varying time-delay systems a delay-robust tuning method is proposed, and the performance of various controllers is evaluated using simulation. The results show the benefits of adapting the controller parameters based on delay measurement if its amplitude is significant with respect to the time-constant of the process. Nevertheless, the PID algorithm used in the study also performs well in all scenarios, and this is achieved by its careful tuning.

[1]  L.M. Eriksson,et al.  PID Controller Tuning Rules for Varying Time-Delay Systems , 2007, 2007 American Control Conference.

[2]  Karl Johan Åström,et al.  Computer-Controlled Systems: Theory and Design , 1984 .

[3]  Xiaohong Nian.  Stability of linear systems with time-varying delays: an Lyapunov functional approach , 2003, Proceedings of the 2003 American Control Conference, 2003..

[4]  Jean-Chrysostome Bolot,et al.  Characterizing End-to-End Packet Delay and Loss in the Internet , 1993, J. High Speed Networks.

[5]  Mikael Johansson,et al.  Simple PID tuning rules for varying time-delay systems , 2007, 2007 46th IEEE Conference on Decision and Control.

[6]  Karl Johan Åström,et al.  PID Controllers: Theory, Design, and Tuning , 1995 .

[7]  Y. Tipsuwan,et al.  On the gain scheduling for networked PI controller over IP network , 2003, Proceedings 2003 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM 2003).

[8]  H.N. Koivo,et al.  Tuning of PID controllers for varying time-delay systems , 2004, Proceedings of the IEEE International Conference on Mechatronics, 2004. ICM '04..

[9]  Chung-Yao Kao,et al.  Simple stability criteria for systems with time-varying delays , 2004, Autom..

[10]  Bo Lincoln,et al.  Dynamic Programming and Time-Varying Delay Systems , 2003 .

[11]  Carlos E. Garcia,et al.  Internal model control. A unifying review and some new results , 1982 .

[12]  Heikki N. Koivo,et al.  Tuning of discrete-time PID controllers in sensor network based control systems , 2005, 2005 International Symposium on Computational Intelligence in Robotics and Automation.

[13]  Karl-Erik Årzén,et al.  A simple event-based PID controller , 1999 .

[14]  A.G. Alleyne,et al.  Closed-loop control over wireless networks , 2004, IEEE Control Systems.

[15]  Tamer Basar,et al.  Optimal control of LTI systems over unreliable communication links , 2006, Autom..

[16]  Johan Nilsson,et al.  Real-Time Control Systems with Delays , 1998 .

[17]  K. Åström,et al.  Revisiting the Ziegler-Nichols step response method for PID control , 2004 .