Within the scope of control of uncertain systems, the problem of performance robustness, especially in the face of parametric uncertainty, has been increasingly recognized as a predominant issue of engineering significance in many design applications. Quantitative Feedback Theory (QFT), a frequency response-based method introduced by Horowitz, has been shown advantageous in many cases where performance specifications for such systems, in terms of hard constraints on closed loop response, are to be met. In this paper, these traditional QFT design criteria are contrasted with a relaxed, sensitivity-based formulation for single input single output (SISO) feedback systems. The advantage of the latter is a greater degree of mathematical commonality with alternative frequency domain methods, thus laying the groundwork for future benchmark studies in control design. The methodology is demonstrated by application to a lateral autopilot design problem for the C-135 aircraft, both to the traditional QFT design specifications as well as to the relaxed sensitivity based criterion.
[1]
I. Horowitz,et al.
Synthesis of feedback systems with large plant ignorance for prescribed time-domain tolerances†
,
1972
.
[2]
K. R. Krishnan,et al.
Frequency-domain design of feedback systems for specified insensitivity of time-domain response to parameter variation
,
1977
.
[3]
J. Freudenberg,et al.
Right half plane poles and zeros and design tradeoffs in feedback systems
,
1985
.
[4]
Osita D. I. Nwokah,et al.
Strong robustness in uncertain multivariable systems
,
1988,
Proceedings of the 27th IEEE Conference on Decision and Control.
[5]
Osita D.I. Nwokah,et al.
Algebraic and Topological Aspects of Quantitative Feedback Theory
,
1989,
1989 American Control Conference.
[6]
Osita D.I. Nwokah,et al.
Optimal Loop Synthesis in Quantitative Feedback Theory
,
1990,
1990 American Control Conference.