Adaptive air–fuel ratio control scheme and its experimental validations for port‐injected spark ignition engines

Abstract

To maintain the stoichiometric air-fuel ratio (AFR), this paper presents a model-based adaptive AFR control scheme for port-injected spark ignition engines. The utilized mean-value model in control design accounts for the impingement and the evaporation process of the injected fuel on the walls and calculates on the uncertainties in the dynamics of the intake manifold and crankshaft rotation. A fueling controller with adaptive update laws is derived for estimating the uncertain parameters related to inaccuracies in air flow and fuel delivery into the cylinders and engine torque production, which is implemented by utilizing engine speed, manifold pressure and temperature, air mass flow rate at the throttle, and the universal exhaust gas oxygen (UEGO) sensor information, without knowledge of the fuel flow mass. Theoretical analysis shows that the proposed strategy is able to regulate the AFR against the parameter uncertainties. Moreover, both simulation and experiment on an engine test bench demonstrate the capability of the adaptive controller to recover the performance and robustness properties of the control system in the presence of various operating conditions and uncertainties including air path and fuel path perturbations and load torque disturbance as well.

Adaptive air-fuel ratio control for spark ignition engines with time-varying parameter estimation

“…A considerable portion of fuel will be trapped on the manifold wall. The issue is known as the 'wall-wetting' phenomenon, where the deposited fuel is usually called 'fuel film' or 'fuel puddles' in the literature [3,14,15]. An empirical equation of the fuelling dynamics [15] is given as…”

“…In this paper, we reformulate the error dynamics of (9) in order to simplify the control design and to reduce the number of adaptive parameters in comparison to [3]. Considering that the control input …”

“…stoichiometric AFR (14.67 for petrol) will maximize the steady-state conversion efficiency [3] [4]. Moreover, the combustion of the air-fuel mixture in the chamber will deliver optimum thermal efficiency and engine performance provided that the AFR is controlled in a narrow window near the stoichiometric value [5].…”

“…To deal with parameter uncertainties, adaptive control methods have been presented for a port-injection SI engine which accounts for the effect of the trapped fuel on the intake manifold wall [3]. A simplified adaptive controller was proposed which shows both simplicity and robustness under the certain conditions [10].…”

Air-fuel-ratio control of engine system with unknown input observer

“…Moreover, the engine torque generation and the stringent requirement for fuel economy also require that the AFR value should be recovered to its ideal value when engines are operated in various dynamic scenarios [2]. To achieve this objective, a common way is to control the fuel mass flow that is injected into the cylinder to fit the air mass flow entering the cylinder; this can be implemented using appropriate control for the fuel injector [3]. For this purpose, the AFR control design needs to take into account the engine modelling uncertainties, sensor noise, external loads and the fuel film effects [4,5].…”