Abstract

This paper presents an efficient algorithm for the generation of quantitative feedback theory (QFT) bounds for plants with affinely dependent uncertainties. For a plant with m affinely dependent uncertainties, it is shown that whether a point in the complex plane lies in the QFT bound for a frequency-domain specification at a given frequency can be tested by checking if m2m1 one-variable quadratic equations corresponding to the edges of the domain box are all non-negative on the interval [0,1]. This test procedure is then utilized along with a pivoting procedure to trace out the boundary of the QFT bound with a prescribed accuracy or resolution. The developed algorithm can avoid the unfavorable trade-off between the computational burden and the accuracy of QFT bounds. Moreover, it is efficient in the sense that no root-finding and iterative procedures are required. Numerical examples are given to illustrate the proposed algorithm and its computational superiority.

1.
Horowitz
,
I. M.
, 1991, “
Survey of Quantitative Feedback Theory
,”
Int. J. Control
0020-7179,
53
(
2
), pp.
255
291
.
2.
Horowitz
,
I. M.
, 1992,
Quantitative Feedback Design Theory
,
QFT Publications
, Boulder, CO.
3.
Brown
,
M.
, and
Petersen
,
I. R.
, 1991, “
Exact Computation of the Horowitz Bound for Interval Plants
,”
Proc. 30th IEEE Conf. Dec. Contr.
, Brighton, England, pp.
2268
2273
.
4.
Fialho
,
I. J.
,
Pande
,
V.
, and
Nataraj
,
P. S. V.
, 1992, “
Design of Feedback Systems Using Kharitonov’s Segments in Quantitative Feedback Theory
,”
Proc. 1st QFT Symposium
, Dayton, Ohio, pp.
457
470
.
5.
Zhao
,
Y.
, and
Jayasuriya
,
S.
, 1994, “
On the Generation of QFT Bounds for General Interval Plants
,”
ASME J. Dyn. Syst., Meas., Control
0022-0434,
116
(
4
), pp.
618
627
.
6.
Longdon
,
L.
, and
East
,
D. J.
, 1979, “
A Simple Geometrical Technique for Determining Loop Frequency Response Bounds Which Achieve Prescribed Sensitivity Specifications
,”
Int. J. Control
0020-7179,
30
(
1
), pp.
153
158
.
7.
East
,
D. J.
, 1981, “
A New Approach to Optimum Loop Synthesis
,”
Int. J. Control
0020-7179,
34
(
4
), pp.
731
748
.
8.
Wang
,
G. G.
,
Chen
,
C. W.
, and
Wang
,
S. H.
, 1991, “
Equations for Loop Bound in Quantitative Feedback Theory
,”
Proc. 30th IEEE Conf. Dec. Contr.
, Brighton, England, pp.
2968
2969
.
9.
Chait
,
Y.
, and
Yaniv
,
O.
, 1993, “
Multi-input/Single-Output Computer-Aided Control Design Using the Quantitative Feedback Theory
,”
Int. J. Robust Nonlinear Control
1049-8923,
3
, pp.
47
54
.
10.
Yaniv
,
O.
, and
Chait
,
Y.
, 1993, “
Direct Control Design in Sampled-Data Uncertain Systems
,”
Automatica
0005-1098,
29
(
2
), pp.
365
372
.
11.
Chait
,
Y.
,
Borghesani
,
C.
, and
Zheng
,
Y.
, 1995, “
Single-Loop QFT Design for Robust Performance in the Presence of Non-Parametric Uncertainties
,”
ASME J. Dyn. Syst., Meas., Control
0022-0434,
117
(
3
), pp.
420
425
.
12.
Rodrigues
,
J. M.
,
Chait
,
Y.
, and
Hollot
,
C. V.
, 1997, “
An Efficient Algorithm for Computing QFT Bounds
,”
ASME J. Dyn. Syst., Meas., Control
0022-0434,
119
(
3
), pp.
548
552
.
13.
Saff
,
E. B.
, and
Snider
,
A. D.
, 1976,
Fundamentals of Complex Analysis
,
Prentice-Hall
, NJ.
14.
Bartlett
,
A. C.
,
Hollot
,
C. V.
, and
Huang
,
L.
, 1988, “
Root Locations of an Entire Polytope of Polynomials: It Suffices to Check the Edges
,”
Math. Control, Signals, Syst.
0932-4194,
1
(
1
), pp.
61
71
.
15.
Nataraj
,
P. S. V.
, and
Sardar
,
G.
, 2000, “
Computation of QFT Bounds for Robust Sensitivity and Gain-Phase Margin Specifications
,”
ASME J. Dyn. Syst., Meas., Control
0022-0434,
122
(
3
), pp.
528
534
.
16.
Nataraj
,
P. S. V.
, 2002, “
Computation of QFT Bounds for Robust Tracking Specifications
,”
Automatica
0005-1098,
38
(
2
), pp.
327
334
.
17.
Sardar
,
G.
, and
Nataraj
,
P. S. V.
, 1997, “
A Template Generation Algorithm for Nonrational Transfer Functions in QFT Designs
,”
Proc. 36th IEEE Conf. Dec. Contr.
, San Diego, pp.
2684
2689
.
18.
Nataraj
,
P. S. V.
, and
Sardar
,
G.
, 2000, “
Template Generation for Continuous Transfer Functions Using Interval Analysis
,”
Automatica
0005-1098,
36
(
1
), pp.
111
119
.
19.
Gutman
,
P-O.
,
Nordin
,
M.
, and
Cohen
,
B.
, 2007, “
Recursive Grid Methods to Compute Value Sets and Horowitz-Sidi Bounds
,”
Int. J. Robust Nonlinear Control
1049-8923,
17
(
2-3
), pp.
155
171
.
20.
Bailey
,
F. N.
,
Panzer
,
D.
, and
Gu
,
G.
, 1988, “
Two Algorithms for Frequency Domain Design of Robust Control Systems
,”
Int. J. Control
0020-7179,
48
(
5
), pp.
1787
1806
.
21.
Bailey
,
F. N.
, and
Hui
,
C.-H.
, 1989, “
A Fast Algorithm for Computing Parametric Rational Functions
,”
IEEE Trans. Autom. Control
0018-9286,
34
(
11
), pp.
1209
1212
.
22.
Bartlett
,
A. C.
, 1990, “
Nyquist, Bode, and Nichols Plots of Uncertain Systems
,”
Proc. American Contr. Conf.
, San Diego, pp.
2033
2036
.
23.
Fu
,
M.
, 1990, “
Computing the Frequency Response of Linear Systems With Parametric Perturbation
,”
Syst. Control Lett.
0167-6911,
15
(
1
), pp.
45
52
.
24.
Bartlett
,
A. C.
, 1993, “
Computation of the Frequency Response of Systems With Uncertain Parameters: A Simplification
,”
Int. J. Control
0020-7179,
57
(
6
), pp.
1293
1309
.
25.
Chen
,
J.-J.
, and
Chyi
,
H.
, 1998, “
Computing Frequency Responses of Uncertain Systems
,”
IEEE Trans. Circuits Syst., I: Fundam. Theory Appl.
1057-7122,
45
(
3
), pp.
304
307
.
26.
Shen
,
S.-K.
,
Wang
,
B.-C.
, and
Lee
,
T.-T.
, 1999, “
An Improved Algorithm for Computing the Boundary of Parametric Rational Functions
,”
IEEE Trans. Autom. Control
0018-9286,
44
(
1
), pp.
227
231
.
27.
Tan
,
N.
, and
Atherton
,
D. P.
, 2000, “
Frequency Response of Uncertain Systems: A 2q-Convex Parpolygonal Approach
,”
IEE Proc.: Control Theory Appl.
1350-2379,
147
(
5
), pp.
547
555
.
28.
Jia
,
Y.
, 2002, “
Computing the Frequency Response of Systems Affinely Depending on Uncertain Parameters
,”
IEE Proc.: Control Theory Appl.
1350-2379,
149
(
4
), pp.
311
315
.
29.
Nishioka
,
K.
,
Adachi
,
N.
, and
Takeuchi
,
K.
, 1991, “
Simple Pivoting Algorithm for Root-Locus Method of Linear Systems With Delay
,”
Int. J. Control
0020-7179,
53
(
4
), pp.
951
966
.
30.
Borghesani
,
C.
,
Chait
,
Y.
, and
Yaniv
,
O.
, 1995,
The Quantitative Feedback Theory Toolbox for MATLAB
,
The MathWorks
, MA.
You do not currently have access to this content.