Abstract
Nonlinear EGR and VGT Control with Integral Action for Diesel Engines - A nonlinear multivariable control design with integral action is proposed and investigated for control of Exhaust Gas Recirculation (EGR) and Variable Geometry Turbine (VGT) in heavy duty Diesel engines. The main control goal is to regulate oxygen/fuel ratio and intake manifold EGR-fraction, and they are specified in an outer loop. These are chosen as main performance variables since they are strongly coupled to the emissions. An existing nonlinear control design based on feedback linearization is extended with integral action. In particular; the control design method utilizes a control Lyapunov function, inverse optimal control, and a nonlinear input transformation. Comparisons between different control structures are performed in simulations showing the following four points. Firstly, integral action is necessary to handle model errors so that the controller can track the performance variables specified in the outer loop. Secondly the proposed control design handles the nonlinear effects in the Diesel engine that results in less control errors compared to a control structure with PID controllers. Thirdly, it is important to use the input transformation and it is sufficient to use a control structure with PID controllers and input transformation to handle the nonlinear effects. Fourthly, the proposed control design is sensitive to model errors in the input transformation while a control structure with PID controllers and input transformation handles these model errors.
Highlights
Legislated emission limits for heavy duty trucks are constantly reduced
The primary emission reduction mechanisms utilized to control the emissions are that NOx can be reduced by increasing the intake manifold Exhaust Gas Recirculation (EGR)-fraction xegr and smoke can be reduced by increasing the air/fuel ratio [1]
This paper focuses on EGR and Variable Geometry Turbine (VGT) control
Summary
Legislated emission limits for heavy duty trucks are constantly reduced. To fulfill the requirements, technologies like Exhaust Gas Recirculation (EGR) and Variable. A model for a heavy duty Diesel engine is used in simulation for tuning and validation of the developed controller This Diesel engine model is focused on the gas flows, (see Fig. 1), and it is a mean value model with eight states: intake and exhaust manifold pressures (pim and pem), oxygen mass fraction in the intake and exhaust manifold (XOim and XOem), turbocharger speed (ωt), and three states (uegr, uegr, and uvgt) describing the actuator dynamics for the two control signals (uegr and uvgt). These states are collected in a state vector x:. Reference [6] proposes a single integral action, the integral action here is used in other way compared to [6] in order to track the performance variables λO and xegr
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