Improved Event-Based Pi Controller for Limit Cycles Avoidance

One of the issues in designing event-based proportional-integral (PI) controller using aggressive tuning rules is the possible occurrence of limit cycles. To date, there is no adequate simple event-based PI controller technique able to explicitly use aggressive tuning rule. In this paper an improved simple event-based PI controller is proposed to address this issue. By analysing the discrete PI algorithm, an improved triggering condition is introduced. To test the effectiveness of the approach, extensive simulations are carried out by introducing the proposed method to process control under various sampling period, triggering limit, and different tuning rules namely, AMIGO, SIMC and One-Third tuning rules. The performances are evaluated based on two standard criteria: ability to imitate the time-triggered system and computation load reduction. The results show that the performance of the proposed method able to surpass others simple event-based PI controller approaches by giving a closest response to the time-triggered system, lowest computational load and able to avoid the limit cycles occurrences. It is envisaged that the proposed method can be useful in designing a simple event-based PI controller that compatible with any type of tuning rules.

Pendulum tuned mass dampers and tuned mass dampers: Analogy and optimum parameters for various combinations of response and excitation parameters

This study deals with the optimisation of pendulum tuned mass damper parameters for different types of excitations and responses of the host structure to which it is attached. The study considers force excitation and base excitation with different types of output quantities to be minimised on the host structure. It also considers both harmonic motion with H ∞ optimisation of the different transfer functions and random white noise excitation where the variance of the output signal is minimised, leading to H2 optimisation. Although a lot of work has been done on optimisation of tuned mass dampers, there exists in the literature only a few solutions for optimisation of the pendulum tuned mass dampers not covering all possible types of loads and output quantities. The analogy between the mass spring tuned mass damper and pendulum tuned mass damper presented in this study allows to use all the tuning rules developed for tuned mass dampers in the case of pendulum tuned mass dampers. In addition, the existing tuning rules for tuned mass dampers are extended to cases which were not previously solved in the literature for H2 optimisation and validated by comparing with numerical optimisation. Finally, a discussion is presented where the different tuning rules are compared, and the performance degradation is assessed when the wrong tuning rule is used. This is representative of the case where, for example, both wind and earthquake excitation exist on the structure, and the pendulum tuned mass damper is tuned for just wind excitation.

Tuning Rules for Active Disturbance Rejection Controllers via Multiobjective Optimization—A Guide for Parameters Computation Based on Robustness

A set of tuning rules for Linear Active Disturbance Rejection Controller (LADRC) with three different levels of compromise between disturbance rejection and robustness is presented. The tuning rules are the result of a Multiobjective Optimization Design (MOOD) procedure followed by curve fitting and are intended as a tool for designers who seek to implement LADRC by considering the load disturbance response of processes whose behavior is approximated by a general first-order system with delay. The validation of the proposed tuning rules is done through illustrative examples and the control of a nonlinear thermal process. Compared to classical PID (Proportional-Integral-Derivative) and other LADRC tuning methods, the derived functions offer an improvement in either disturbance rejection, robustness or both design objectives.