Combined Sensitivity–Complementary Sensitivity Min–Max Approach for Load Disturbance–Setpoint Trade-off Design
ABSTRACT An approach to proportional-integrative-derivative controller tuning based on a simple plant model description, first order
plus time delay, is presented. The approach is based on the formulation of an optimal approximation problem in the frequency
domain for the sensitivity transfer function of the closed loop. The inclusion of the sensitivity function allows for a disturbance
attenuation specification. The solution to the approximation problem provides a set of tuning rules that constitute a parameterized
set that is formulated in the same terms as in  and includes, a third parameter that determines the operating mode of the
controller. This factor allows one to determine a tuning either for step response or disturbance attenuation. The approach
can be seen as an implicit 2-degree-of-freedom controller because by using one parameter, the operating mode (servo/regulation)
of the control system is determined as well as the appropriate tuning of the controller.
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ABSTRACT: In this paper, a simple PI controller design method is proposed which can achieve user-specified gain and phase margins if they are suitable, or otherwise the automatically adjusted alternatives for performance enhancement. Unlike reduced-order model-based tuning methods, exact margins, once specified or adjusted, can be accomplished regardless of the process order and damping nature. The response of the closed-loop system using the proposed design is hence more predictable than those using model-based methods when performance specifications are given in gain and phase margins. The proposed method is based on finding the intersections between two graphs that are plotted using the frequency response of the process. The given gain and phase specifications can be achieved if intersections can be found, and each intersection corresponds to one solution. Suggestions are provided on how to modify the specifications for achieving satisfactory responses for cases where there are no solution or when the specifications can be met but poor responses result. Simulation examples are given to show the usefulness of the method.Automatica. 01/1998;
Article: A course in H 1 control theory
- Industrial & Engineering Chemistry Process Design and Development. 04/2002; 25(1).