Abstract
A precise control of the normalized air to fuel ratio in spark ignition engines is an essential task. To achieve this goal, in this work we take into consideration the time delay measurement presented by the universal exhaust gas oxygen sensor along with uncertainties in the volumetric efficiency. For that purpose, observers are designed by means of a super-twisting sliding mode estimation scheme. Also two control schemes based on a general nonlinear model and a similar nonlinear affine representation for the dynamics of the normalized air to fuel ratio were designed in this work by using the super-twisting sliding mode methodology. Such dynamics depends on the control input, that is, the injected fuel mass flow, its time derivative, and its reciprocal. The two latter terms are estimated by means of a robust sliding mode differentiator. The observers and controllers are designed based on an isothermal mean value engine model. Numeric and hardware in the loop simulations were carried out with such model, where parameters were taken from a real engine. The obtained results show a good output tracking and rejection of disturbances when the engine is closed loop with proposed control methods.
Highlights
The air to fuel ratio (AFR) control [1, 2] is one of the most important control problems for conventional gasoline engines
The AFR control is an important problem for the regulation of emissions, fuel economy, and output torque
This problem is exacerbated by the presence of environmental perturbations, nonlinear dynamics, and time delays involved in the combustion process
Summary
The air to fuel ratio (AFR) control [1, 2] is one of the most important control problems for conventional gasoline engines. The relationship between the cylinder geometric volume and the actual volume or air aspirated into the cylinder is defined as volumetric efficiency eV Another issue to consider is the time delay in the λ factor measurement provided by the Universal Exhaust Gas Oxygen (UEGO) sensor [5, 6], which is basically the time between the fuel injection and the burned gases reaching the UEGO sensor. (iii) To design a super-twisting observer for the nonmeasurable parameter eV For these purposes, the controller and the observer designs are based on an isothermal mean value engine model (MVEM) developed in the works by [14, 15].
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