A QFT design methodology for feedback systems under input saturation

2000 ◽  
Author(s):  
W. Wu ◽  
S. Jayasuriya
Keyword(s):  
Design Methodology ◽  
Input Saturation ◽  
Feedback Systems

A New QFT Design Methodology for Feedback Systems Under Input Saturation

1999 ◽  
Vol 123 (2) ◽  
pp. 225-232 ◽  
Author(s):  
Wei Wu ◽  
Suhada Jayasuriya
Keyword(s):  
Robust Stability ◽  
Design Methodology ◽  
Design Method ◽  
Input Saturation ◽  
Function Technique ◽  
Feedback Systems ◽  
Robust Performance ◽  
Saturation Nonlinearity ◽  
Performance Requirements ◽  
And Performance

Presented in this paper is a design methodology for robust stability and robust performance for a large class of plants subject to an input saturation nonlinearity. Based on Horowitz’s 3-DOF linear design method, a more general form for the additional loop transmission around the saturating element is proposed to design the third degree of freedom Hs, for Type n plants, n⩾1. Robust stability is established with the circle criterion and the describing function technique, and robust performance is improved by imposing nonovershooting conditions. All stability and performance requirements are then transferred into frequency domain design bounds which are easily obtained using QFT design techniques. This procedure applies to all SISO, Type n, stable plants with uncertainties (parametric or nonparametric), and to marginally stable and conditionally stable plants as well.

Criteria for Recovery of Zero Initial Condition Responses of Unstable Plants Under Input Saturation

2000 ◽  
Author(s):  
Wei Wu ◽  
Suhada Jayasuriya
Keyword(s):  
Initial Conditions ◽  
Input Saturation ◽  
Input Sequence ◽  
Feedback System ◽  
Open Loop ◽  
Feedback Systems ◽  
Bounded Control ◽  
Analysis And Design ◽  
Study Results ◽  
Unstable Plant

Abstract In this paper, we consider the sufficient and/or necessary conditions under which responses of unstable plants with zero initial conditions would be bounded under step inputs. Several possible unstable pole patterns are examined, and corresponding criteria are derived. It is shown that an unstable plant can be stabilized to have bounded responses using an alternate step input sequence. Step inputs simulate the saturated inputs in a feedback system with bounded control, where the closed-loop stability of an unstable plant is really difficult to study. Results from this open-loop study may lend some insight into the analysis and design of such feedback systems under input saturation nonlinearities.

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