A modified graphical based tuning and performance analysis of second order LADRC using frequency domain technique for SISO systems

This paper proposes a simplified frequency based tuning method for Second-order Linear Active Disturbance Rejection Control (SLADRC). By employing a 2-DOF structure for the controller, the challenge of optimizing numerous tuning parameters for complex systems is addressed. By considering the phase margin (PM) as one of the design specifications, an admissible region is mapped onto the Nyquist plot to identify the permissible bound for gain crossover frequencies (ωgc), from the known system frequency points. Distinct controllers with unique performance characteristics can be designed within the comprehensive set of design specifications (PM and ωgc). Subsequently, the optimal tuning parameter values are determined by identifying the design specifications that yield the desired response and the minimum ITSE. Two distinct approaches are proposed for selecting suitable design specifications: an iterative method and a heuristic-based method. These approaches rely on graphical analysis of time-domain performance metrics and robustness analysis using the disk margin. While the heuristic approach offers faster computation, the iterative method generally provides more accurate results. The reliability and versatility of the proposed tuning technique are validated on five distinct benchmark systems. The systems with time delay and unstable dynamics explains the detailed tuning procedure in performance study. In comparative study, time delay with integrating system, pure integrating system and nonminimum phase with higher order systems are considered, provides equivalent performance with reduced computational effort. Additionally, it is experimentally verified through a real-time speed control of a rotary servo system, achieving an ITSE of 16.2 and a disk margin of 1.332, confirming its practical applicability.