Traditionally, the term powertrain has been thought to include the engine, transmission, differential, and drive axle/wheel assemblies. With the advent of electronic controls, the powertrain also includes the electronic control system (in whatever configuration it has). In addition to engine control functions for emissions regulation, fuel economy, and performance, electronic controls are also used in the automatic transmission to select shifting as a function of operating conditions. Moreover, certain vehicles employ electronically controlled clutches in the differential (transaxle T/A) for traction control.
These electronic controls for these major powertrain components can either be separate (i.e., one for each component) or an integrated system regulating the powertrain as a unit.
This latter integrated control system has the benefit of obtaining optimal vehicle performance within the constraints of exhaust emission and fuel economy regulations. Each of the control systems is discussed separately beginning with electronic engine control. Then a brief discussion of integrated powertrain follows. This chapter concludes with a discussion of hybrid vehicle (HV) control systems in which propulsive power comes from an internal combustion engine (ICE) or an electric motor (EM) or a combination of both. The proper balance of power between these two sources is a very complex function of operating conditions and governmental regulations.
