Turbocharging of gasoline engines has gained renewed popularity as a means to improve fuel economy and CO2 emissions. Modern engines have advanced technology actuators such as electronic throttle and variable valve timing, in addition to wastegate. Proper control of system actuators is critical to achieving the full benefit of this technology. This paper presents system analysis and control development for a turbocharged gasoline engine equipped with wastegate and electronic throttle. A nonlinear mean value model for the system is presented. The nonlinear model is linearized at multiple operating points and its behavior analyzed using the systems approach. A gain scheduled, decentralized controller is designed to track the intake manifold and boost pressures to meet transient, as well as steady state requirements. A multi-variable control approach is also considered to alleviate tradeoffs inherent in decentralized design.
This paper investigates active control of an aftertreatment system for a conventional spark ignition engine equipped with one or two three-way catalysts and two oxygen sensors. The control objective is to maximize the simultaneous conversion efficiencies of oxides of nitrogen and unburned hydrocarbons. Linear exhaust gas oxygen sensors are used to measure air-fuel ratio upstream and downstream of each catalyst. A series controller configuration is adopted. The upstream controller provides relatively rapid response to disturbances on the basis of measured feedgas air-fuel ratio, while the downstream controller uses the feedgas and post-catalyst air-fuel ratio measurements to compensate for the bias corrupting the feedgas air-fuel ratio measurement. The performance and robustness of the proposed control system in the face of noise and model uncertainty are first evaluated through extensive simulations. The control strategy is then experimentally verified in a dynamometer test cell and its performance compared with an existing proprietary controller that is based on the more common switching-type air-fuel ratio sensors.
A control oriented analysis of an anode recirculation system that uses an ejector with a variable throat area is presented for a PEMFC system. Two control issues addressed in this paper are (a) achieving desired recirculated flow to meet humidity control requirements, and (b) regulating anode pressure to protect the polymer membrane from deformation. To meet these objectives, a static feedforward controller using the variable throat area is applied to control the recirculation flow rate, while a proportional-integral controller is designed for anode pressure regulation. A dynamic system model comprising of a nonlinear static characterization of the ejector and dynamic representation of the anode recirculation flow path is developed for controller design and evaluation. Linear analysis is used to derive design guidelines for tuning the feedback controller and to analyze the interactions between the feedback and the feedforward controllers. Our analysis shows that the system characteristics are dependent on the operating condition of throat area of ejector. To meet the control objectives for different operating conditions, a gain scheduling scheme is proposed to adjust the feedback controller parameters and the performance is evaluated through simulations. Results for two representative conditions are included.
In this paper, the pressure difference between the anode and cathode compartments of a polymer electrolyte membrane (PEM) fuel cell stack is regulated along with the anode and cathode humidities using an anode recirculation system. The pressure regulation requirement stems from membrane safety considerations. The regulation of average humidities in the two compartments is a necessary (although not a sufficient) requirement for stack water management. Two actuators in the anode recirculation system are considered, namely the dry hydrogen flow and the anode back pressure valve. These actuators are adjusted using a static output feedback controller that relies on pressure and humidity measurements on the anode side of the fuel cell stack. As the water mass dynamics and the characteristics of the water transport through the PEM are significantly different between subsaturated conditions (water is present only in vapor phase) and saturated conditions (liquid water along with water vapor), we show that the performance of the static output feedback controller with a fixed set of gains for subsaturated condition deteriorates significantly under a saturated condition. A gain-scheduled controller is therefore developed to compensate for a water-vapor saturated cathode condition. Analysis and simulation provide insights on some of the design and implementation issues for the gain-scheduled output feedback system.
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