Design of Electronic Control for Diesel Engines

Abstract

The main drivers of engine development are fuel economy and very high emission standards that need tighter control of fuel injection during the highly transient automotive cycle. For long, the responsibility is surrogated by mechanical controllers to high speed digital controls that are electronic. The intimate control of injection pressure injection timing, rate of injection and most importantly the number of injection pulses per cycle are controlled by the ECU, not only for limiting the engine-out emissions or reducing fuel consumption, but also for control of noise and after-treatment system. This chapter gives an overview of common rail injection system and working of the electronic injector, listing their advantages. The features of electronic control unit (ECU) are air charge management, torque set-point function, torque limitation function, engine speed control, engine position management, metering unit control and pressure relief valve control as well as fault diagnostics and on-board diagnostics are discussed. The engine management system has inputs, outputs, sensors and actuators apart from sensors and the pedal module. In the latest on-board diagnostic requirements, there is a need for monitoring rationality of sensor signals and total functional failure are important for detecting total breakdown of the system (such as loss of after-treatment device, EGR cooler or charge air cooler) or a component, or loss of a component like the catalyst. Inducement strategies of low level, maximum vehicle speed and OBD disablement, and electronic control of after-treatment system and EGR as well as OBD I and OBD II needs are treated at the end of the chapter. The topics on development process of an ECU, hardware-in-loop, software-in-loop, verification on vehicle for series production, production code generation and closed loop control mechanism are briefly dealt with.