Sensor selection and controller design method with application to turbocharged stoichiometric spark-ignited engine controls with low pressure EGR

Abstract

This paper describes and demonstrates a model-based sensor selection and controller design framework for robust control of air–fuel-ratio, air flow and EGR flow for turbocharged stoichiometric engines using low pressure EGR, waste-gate turbo-charging, intake throttling and variable valve timing. Model uncertainties, disturbances, transport delays, and sensor- and actuator-characteristics are considered in this framework. Based on the required control performance and candidate sensor sets, the framework synthesizes an H∞ feedback controller and evaluates the viability of the candidate sensor set through analysis of the singular structured value μ of the closed-loop system in the frequency domain. The framework can also be used to understand if relaxing the controller performance requirements enable the use of a simpler (less costly) sensor set. The sensor selection and controller co-design approach is applied here, for the first time, to turbo-charged engines using exhaust gas circulation. High fidelity GT-Power simulations are used to validate the approach. The computed optimal controllers were able to maintain the AFR within 14.7 ± 0.3, control the torque within 8.2% error and the EGR ratio within 1.2% error at different drive cycles with sensor inaccuracies and actuator dynamics.