Consequences of modular controller development for automotive powertrains: a case study

A modular controller structure for automotive powertrains has certain benefits. These include improved productivity through module reuse, seamless integration of new features, transparent removal of obsolete features, and module sharing across powertrain platforms. Modular architecture also potentially reduces the complexity in the design and calibration process, in that controller modules for different subsystems are developed independently. Due to the fact that the automotive powertrain system contains many highly interactive sub-systems, it is not clear that a modular controller development process can yield acceptable feedback controller performance with respect to emissions, fuel economy, and drivability. In this paper, we describe the engineering design issues associated with a decentralized development process, and the impact that the resulting decentralized controller has upon the dynamic response of the feedback system. We describe the possible detrimental consequences of subsystem interaction, and the potential of coordinated, multivariable feedback for alleviating these limitations. Control of a spark ignition engine incorporating variable camshaft timing is used as a case study