89 lines
2.5 KiB
Fortran
89 lines
2.5 KiB
Fortran
LOGICAL FUNCTION SB02OV( ALPHAR, ALPHAI, BETA )
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C
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C SLICOT RELEASE 5.0.
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C
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C Copyright (c) 2002-2009 NICONET e.V.
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C
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C This program is free software: you can redistribute it and/or
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C modify it under the terms of the GNU General Public License as
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C published by the Free Software Foundation, either version 2 of
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C the License, or (at your option) any later version.
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C
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C This program is distributed in the hope that it will be useful,
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C but WITHOUT ANY WARRANTY; without even the implied warranty of
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C MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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C GNU General Public License for more details.
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C
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C You should have received a copy of the GNU General Public License
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C along with this program. If not, see
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C <http://www.gnu.org/licenses/>.
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C
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C PURPOSE
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C
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C To select the unstable generalized eigenvalues for solving the
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C discrete-time algebraic Riccati equation.
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C
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C ARGUMENTS
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C
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C Input/Output Parameters
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C
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C ALPHAR (input) DOUBLE PRECISION
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C The real part of the numerator of the current eigenvalue
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C considered.
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C
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C ALPHAI (input) DOUBLE PRECISION
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C The imaginary part of the numerator of the current
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C eigenvalue considered.
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C
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C BETA (input) DOUBLE PRECISION
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C The (real) denominator of the current eigenvalue
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C considered.
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C
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C METHOD
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C
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C The function value SB02OV is set to .TRUE. for an unstable
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C eigenvalue (i.e., with modulus greater than or equal to one) and
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C to .FALSE., otherwise.
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C
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C REFERENCES
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C
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C None.
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C
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C NUMERICAL ASPECTS
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C
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C None.
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C
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C CONTRIBUTOR
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C
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C Release 3.0: V. Sima, Katholieke Univ. Leuven, Belgium, Sep. 1997.
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C Supersedes Release 2.0 routine SB02CX by P. Van Dooren, Philips
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C Research Laboratory, Brussels, Belgium.
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C
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C REVISIONS
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C
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C -
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C
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C KEYWORDS
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C
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C Algebraic Riccati equation, closed loop system, continuous-time
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C system, optimal regulator, Schur form.
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C
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C ******************************************************************
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C
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DOUBLE PRECISION ONE
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PARAMETER ( ONE = 1.0D0 )
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C .. Scalar Arguments ..
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DOUBLE PRECISION ALPHAR, ALPHAI, BETA
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C .. External Functions ..
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DOUBLE PRECISION DLAPY2
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EXTERNAL DLAPY2
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C .. Intrinsic Functions ..
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INTRINSIC ABS
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C .. Executable Statements ..
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C
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SB02OV = DLAPY2( ALPHAR, ALPHAI ).GE.ABS( BETA )
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C
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RETURN
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C *** Last line of SB02OV ***
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END
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