Journal of Control Theory and Applications 2007 5 (4) 397–403 DOI 10.1007/s11768-006-6113-0
Solutions to the generalized Sylvester matrix
equations by a singular value decomposition
Bin ZHOU, Guangren DUAN
(Center for Control Theory and Guidance Technology, Harbin Institute of Technology, Harbin Heilongjiang 150001, China)
Abstract: In this paper, solutions to the generalized Sylvester matrix equations AX − XF = BY and MXN −X =
T Y with A, M ∈ R
n×n
, B, T ∈ R
n×r
, F, N ∈ R
p×p
and the matrices N, F being in companion form, are established
by a singular value decomposition of a matrix with dimensions n × (n + pr). The algorithm proposed in this paper for
the euqation AX − XF = BY does not require the controllability of matrix pair (A, B) and the restriction that A, F
don’t have common eigenvalues. Since singular value decomposition is adopted, the algorithm is numerically stable and
may provide great convenience to the computation of the solution to these equations, and can perform important functions
in many design problems in control systems theory.
Keywords: Generalize Sylvester matrix equations; General solutions; Companion matrix; Singular value decompo-
sition
1 Symbols and notations
In this paper, we use B
T
and rank(B) to denote the trans-
pose and the rank of matrix B, respectively, and b
ij
is the
i-th row and j-th column of matrix B. I
p
is the p × p iden-
tity matrix, and 0 will be used as a r × s matrix when the
dimensions are evident from the context. The symbol ⊗ is
to denote the Kronecker product. We use A ∈ F
r×p
which
means that A is an r × p matrix in the field F .
We use col[A
i
]
q
i=p
to denote a matrix in the form of
col[A
i
]
q
i=p
= [
A
p
A
p+1
· · · A
q−1
A
q
],
and use row[A
i
]
q
i=p
to denote
row[A
i
]
q
i=p
= [col[A
T
i
]
q
i=p
]
T
.
Further, let A ∈ R
n×n
and B ∈ R
n×r
, we define the
so-called Krylov matrix with matrix pair (A, B) as follows:
Q
c
(A, B, k) = col[A
i
B]
k−1
i=0
.
2 Introduction
The general solution to the generalized Sylvester matrix
equation
AX − XF = BY, (1)
where A ∈ R
n×n
, B ∈ R
n×r
, F ∈ R
p×p
are known, is
closely related with many problems in linear control sys-
tems theory, such as eigenvalue assignment [1, 2], observer
design [3], eigenstructure assignment design [4, 5], con-
strained control [6], etc, and has been studied by many au-
thors (see [3, 5, 7] and the references therein). When the
matrix F is in Jordan form, an attractive analytical and
restriction-free solution with explicit freedom is presented
in [3]. To obtain this solution, one needs to carry out an
orthonormal transformation, compute a matrix inverse, and
solve a series of linear equation groups. Reference [5] pro-
poses two solutions to the matrix equation, also for the
case that the matrix F is in Jordan form. The first one
is in an iterative form, while the second is in an explicit
parametric form. To obtain the explicit solution proposed
in [5], one needs to carry out a right coprime factorization of
(sI − A)
−1
B (when the eigenvalues of the Jordan matrix F
are undetermined) or a series of singular value decomposi-
tion (when the eigenvalues of F are known). Generalization
of this explicit solution to a more general case is considered
in [4] and [7].
When the matrix F is in companion form, a very neat and
elegant general complete parametric solution to the gener-
alized Sylvester matrix equation (1) is proposed in [8]. The
solution is expressed in terms of the controllability matrix
of the matrix pair (A, B), a symmetric operator matrix, and
a parametric matrix in the Hankel matrix form. Such a result
can provide great convenience for many analysis and design
problems associated with the matrix equation (1). However,
this proposed solution has a disadvantage that when A and
F have common eigenvalues, the given solution may be not
complete. This is not convenient to use in some problems
Received 16 June 2006; revised 22 November 2006.
This work was supported by the Chinese Outstanding Youth Foundation (No.69925308) and Program for Changjiang Scholars and Innovative Research
Team in University.