TY - JOUR
T1 - Approximation of explicit model predictive control using regular piecewise affine functions : an input-to-state stability approach
AU - Genuit, B.A.G.
AU - Lu, L.
AU - Heemels, W.P.M.H.
PY - 2012
Y1 - 2012
N2 - Piecewise affine (PWA) feedback control laws defined on general polytopic partitions, as for instance obtained by explicit MPC, will often be prohibitively complex for fast systems. In this work we study the problem of approximating these high-complexity controllers by low-complexity PWA control laws defined on more regular partitions, facilitating faster on-line evaluation. The approach is based on the concept of input-to-state stability (ISS). In particular, the existence of an ISS Lyapunov function (LF) is exploited to obtain a priori conditions that guarantee asymptotic stability and constraint satisfaction of the approximate low-complexity controller. These
conditions can be expressed as local semidefinite programs (SDPs) or linear programs (LPs), in case of 2-norm or 1,inf-norm based ISS, respectively, and apply to PWA plants. In addition, as ISS is a prerequisite for our approximation method, we provide two tractable computational methods for deriving the necessary ISS inequalities from nominal stability. A numerical example is provided that illustrates the main results.
AB - Piecewise affine (PWA) feedback control laws defined on general polytopic partitions, as for instance obtained by explicit MPC, will often be prohibitively complex for fast systems. In this work we study the problem of approximating these high-complexity controllers by low-complexity PWA control laws defined on more regular partitions, facilitating faster on-line evaluation. The approach is based on the concept of input-to-state stability (ISS). In particular, the existence of an ISS Lyapunov function (LF) is exploited to obtain a priori conditions that guarantee asymptotic stability and constraint satisfaction of the approximate low-complexity controller. These
conditions can be expressed as local semidefinite programs (SDPs) or linear programs (LPs), in case of 2-norm or 1,inf-norm based ISS, respectively, and apply to PWA plants. In addition, as ISS is a prerequisite for our approximation method, we provide two tractable computational methods for deriving the necessary ISS inequalities from nominal stability. A numerical example is provided that illustrates the main results.
U2 - 10.1049/iet-cta.2010.0709
DO - 10.1049/iet-cta.2010.0709
M3 - Article
VL - 6
SP - 1015
EP - 1028
JO - IET Control Theory & Applications
JF - IET Control Theory & Applications
SN - 1751-8644
IS - 8
ER -