Development Of UEGO Sensor Controller

Since the vehicle emission regulations are becoming increasingly stringent and lean burn technology has been widely used in the engine domain, the common switching-type EGO sensor cannot meet the needs of wide range air-fuel ratio control, it is an inevitable trend to take linear Universal Exhaust Gas Oxygen (UEGO) Sensor instead of EGO. The UEGO sensor, which is a kind of controllable sensor, only works properly with an exclusive controller, and the controller affects the static and dynamic performance of the sensor. This thesis focuses on the control method and system design of the UEGO sensor controller.Firstly, the pump current module is modeled by PEM based on open-loop experiment data, and then the digital PID controller is used and the PID parameters are tuned by internal-model method.A hardware system is developed on dSPACE platform, which includes temperature detecting and heating circuits, Nernst voltage and pump current measurement circuits and pump current drive circuits. The software is developed based on Simulink modules. Static and dynamic experiments have been done on a reconstructive Xiali carburetor engine testbed. The limiting current platform and static characteristic curve are presented. Comparing the output of designed controller and Horiba air-to-fuel ratio analyzer MEXA-700λin dynamic tests, it shows that the controller responses the sudden changed air-fuel ratio accurately and with a good dynamic performance.In addition, the hardware system based on DSP is designed, which integrates power supply manage part, sinusoidal signal generating circuit, input and output analog channels, as well as man-machine interfaces and communication interface. It establishes a good platform for the automotive air-fuel ratio control applications.