Mid-ranging control for an automotive three-way catalyst outer loop

As government regulations force stringent automobile emission standards with graceful degradation under various hardware faults and operating environments, accurate feedback control of the engine air-to-fuel ratio has become a key enabler. We present an overview of the automotive three-way catalyst (TWC) control system and discuss challenges associated with development and implementation of a successful feedback controller, including plant and sensor nonlinearities - in use, as well as regulatory On-Board-Diagnostics induced faults, bandwidth restrictions, and constraints such as drivability and noise, vibration, and harshness (NVH) considerations. To meet these goals, we modify the conventional mid-ranging control structure for accurate control of the TWC subsystem while simultaneously adhering to drivability and NVH constraints. Vehicle test results are shown exhibiting the controller's capabilities with and without induced faults.