Thereare richtheories and designs for generalcontrolsystems, but
usually, they will not lead to PID controllers. Noting that the PID
controller has been the most popular one in industry for over ?fty
years, we will con?ne our discussion hereto PIDcontrolonly. PID
controlhasbeenanimportantresearchtopicsince 1950's, and causes
remarkable activities for the last two decades. Most of the existing
works have been on the single variable PID control and its theory and
design are well established, understood and practically applied.
However, most industrial processes are of multivariable nature. It is
not rare that the overall multivariable PID control system could fail
although each PID loop may work well. Thus,
demandforaddressingmultivariableinteractionsishighforsuccessful
applicationofPIDcontrolinmultivariableprocessesanditisevidentfrommajor
leading control companies who all rankedthe couplings of multivariable
systems as the principal common problem in industry. There have been
studies on PID control for multivariable processes and they provide some
useful design tools for certaincases. But itis notedthat the existing
worksaremainlyfor decentralized form of PID control and based on ad hoc
methodologies. Obvious, multivariable PID control is much less
understood and developed in comparison with the single variable case and
actual need for industrial applications. Better theory and design have
to be established for multivariable PID control to reach the same
maturity and popularity as the single variable case. The present
monograph puts together, in a single volume, a fairly comp- hensive,
up-to-date and detailed treatment of PID control for multivariable p-
cesses, from paring, gain and phase margins, to various design methods
and applications.
