PID controllers and their tuning for EGR and VGT control in diesel engines

A PID structure is proposed and investigated for coordinated control ofEGR-valve and VGT-position in heavy duty diesel engines. Control goals are tofulfill the legislated emission levels and safe operations of the engine and theturbocharger. These goals are achieved through regulation of the followingperformance variables: normalized air/fuel ratio lambda, intake manifoldEGR-fraction as well as turbocharger speed. A systematic tuning strategy for thePID controllers is also developed and the tuning rules and their performance issuccessfully illustrated on a demanding part of the European Transient Cycle.Further, it is demonstrated that the VGT-position to turbocharger speed loopdoes benefit from a derivative part in order to predict high turbochargerspeeds. This is due to the large time constant in the corresponding open-looptransfer function.