Impact of Implementation Imprecision on Sliding Mode Controller Design for Automotive Cold Start Emissions

Imprecisions from controller software implementation can substantially affect a controller’s performance for leading a physical plant to a desired behavior. In this paper, a discrete-time quasi-sliding mode approach is used to design a controller with improved robustness to software implementation imprecisions. The application of the controller is illustrated for automotive cold start hydrocarbon emissions. The designed controller shows more robustness with respect to implementation imprecisions including sampling, quantization and fixed-point arithmetic when compared to its continuous-time counterpart. In particular, the influence of the sampling time is investigated and a controller configuration with minimal computational requirements is proposed. Finally, the performance of the new controller is verified with real-time simulations.