The control unit controls and monitors all functions and active components of the exhaust-gas aftertreatment system, such as the heating element, the exhaust flap and the dosing systems. The software that goes with it covers the control strategies required to comply with the respective emissions targets. No changes are made to the engine management system.
The data required for control purposes are transferred from the engine to the exhaust-gas aftertreatment control unit by means of a CAN interface. Sensors pick up readings for the temperature, pressure and the nitrogen oxide content in the exhaust gases. The control unit then uses these data to coordinate the actuators of the system as required, with the assistance of the operating strategy laid down in the software.
The operating strategy comprises two core components – particulate filter regeneration and the AdBlue® dosing strategy for NOx reduction – and ensures that the emissions limits laid down are complied with. What's more, an on-board diagnosis system (OBD) monitors those components and assemblies of the exhaust-gas aftertreatment system that are of relevance with respect to complying with the emissions limits.
The control unit sports the following interfaces:
CAN interface for transmitting the necessary engine data (exhaust mass flow, exhaust-gas temperature, load, engine speed, engine temperature, ambient temperature and, if available, nitrogen-oxide and residual-oxygen content)
Inputs for transmitting the measured values of the individual sensors
The software encompasses functions for the:
Strategy for diesel particulate filter regeneration and monitoring (including control of the exhaust flap, the heating element and the HCI)
SCR dosing strategy
Diagnosis of the operating principle of components connected