SI-HCCI Mode Transitions Without Open-Loop Sequence Scheduling: Control Architecture and Experimental Validation

Abstract

This paper describes a model-based feedback control method to transition from spark ignition (SI) to homogeneous charge compression ignition (HCCI) combustion in gasoline engines. The purpose of the control structure is to improve robustness and reduce calibration complexity by incorporating feedback of the engine variables into nonlinear model-based calculations that inherently generalize across operating points. This type of structure is sought as an alternative to prior SI-HCCI transition approaches that involve open-loop calibration of input command sequences that must be scheduled by operating condition. The control architecture is designed for cam switching type SI-HCCI mode transition strategies with practical two-stage cam profile hardware, which previously have only been investigated in a purely open-loop framework. Experimental results on a prototype engine show that the control architecture is able to carry out SI-HCCI transitions across the HCCI load range at 2000 rpm engine speed while requiring variation of only one major set point and three minor set points with operating condition. These results suggest a noteworthy improvement in controller generality and ease of calibration relative to previous SI-HCCI transition approaches.

SI–HCCI Mode Transitions Without Open-Loop Sequence Scheduling: Online Parameter Adaptation

“…[16], which play a central role in all of the nonlinear model-based calculations of the controller in Ref. [1] for both SI and HCCI mode (including the p im reference derivation). The parameter update problems will be formulated in the linear parametric model framework where the model estimate e z of the quantity z can be expressed as…”

“…Note that for all control loops in the architecture of Ref. [1], the model predicted quantity e z that is necessary for parameter updating is straightforward to generate from its corresponding model inverse calculation by simply running the calculation forward with the solved control input.…”

“…In a previous paper [1], a model-based feedback control architecture for spark ignition to homogeneous charge compression ignition (SI-HCCI) combustion mode transitions was developed. This control approach was shown to be capable of carrying out SI-HCCI transitions at multiple operating conditions while requiring calibration of only simple set points and controller gains.…”

“…The controller model of Ref. [1] was shown to fit a wide range of SI and HCCI data in Ref. [16]; however, accuracy may decrease as the engine ages and conditions are extrapolated outside those in the model parameterization.…”

“…This paper aims to improve the performance and robustness of the model-based control architecture of Ref. [1] by using transient SI-HCCI feedback to adaptively tune the combustion model parameters in an online parameter update scheme. The controller thus makes use of transient data not only for immediate corrective output feedback action, but also for improving model-based control calculations for successive transitions.…”