 
Summary: 3rd
TEMPUSINTCOM Symposium, September 914, 2000, Veszprém, Hungary. 1
SOME REMARKS ON PADÉAPPROXIMATIONS
M.Vajta
Department of Mathematical Sciences
University of Twente
P.O.Box 217, 7500 AE Enschede
The Netherlands
email: m.vajta@math.utwente.nl
ABSTRACT
Padé approximations are widely used to approximate a deadtime in continuous control systems. It provides
a finitedimensional rational approximation of a deadtime. However, the standard Padé approximation
(recommended in many textbooks) with equal numerator and denominator degree, exhibits a jump at time
t=0. This is highly undesirable in simulating deadtimes. To avoid this phenomena we shall reconsider the
Padé approximation with different numerator degrees.
Keywords: Padé approximation, rational functions.
1. INTRODUCTION
There are many physical processes with deadtime. For example virtually all chemical processes involves
some time delay and all transport processes also exhibit deadtime [3,12]. Control systems with deadtime
are difficult to analyze and simulate. One of the reasons is that a closedloop control system with deadtime
