On-Board Diagnostics

On-board diagnostics (OBD) is the continuous monitoring of all emission-relevant sensors and actuators of an engine system. The goal of this project is to develop and improve algorithms to accurately monitor the static and dynamic properties of these sensors and actuators over the whole lifetime.

Introduction

Increasingly stringent governmental regulations require engine systems to meet the emission legislation limits over their lifetime. To satisfy the regulations, several raw emission control systems and exhaust after-treatment systems are implemented, e.g. the transient full load soot limitation in Diesel engines using an exhaust oxygen sensor (see Figure 1). Fast and accurate sensors are a prerequisite for those control systems to work properly. However, especially the sensors in the exhaust path are exposed to a harsh environment, which can lead to sensor clogging. Particularly in Diesel engines the soot raw emissions can lead to clogging of the sensors placed in the exhaust pipe, e.g. the wide-range oxygen sensor (lambda sensor or air/fuel ratio sensor). Sensor clogging can lead to measurement errors such as offset and drift as well as slowed down sensor dynamics. Therefore, in compliance with the emission regulations, the static and dynamic properties of the sensors and actuators need to be monitored. Observed changes can be compensated using adaptive control techniques or might require the replacement of the defective sensor or actuator.