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Technical Paper

Fuzzy Knock Control of Diesel-Dual-Fuel Engine

Knock behavior in diesel-dual-fuel (DDF) engine is more complex, more severe, and different than those of traditional engines. We investigate a type of diesel-dual-fuel engines, where CNG is multipoint-injected at the intake ports as main fuel and diesel is directly injected in smaller amount, mainly for ignition purpose, resulting in lower fuel cost. Because of the mixed behaviors between the spark ignited and compression ignited engines, a more sophisticated control system is needed to properly control knock in the DDF engine. In this paper, a novel control system based on fuzzy logic is presented to regulate knock intensity at an appropriate level. The control system comprises a fuzzy controller and a fuzzy decision maker. The fuzzy controller controls several pertaining actuators using rule-base from human experience, while the fuzzy decision maker adapts the magnitude of each actuator action to various operating points.
Technical Paper

Quantitative Feedback Control of Air Path in Diesel-Dual-Fuel Engine

In this paper, we investigate a multivariable control of air path of a diesel-dual-fuel (DDF) engine. The engine is modified from a CI engine by injecting CNG in intake ports. The engine uses CNG as its primary fuel and diesel as its secondary fuel, mainly for initiation of combustion. The modification is economically attractive because CNG has lower price than diesel and the modification cost is minimal. However, for DDF engine, control of the air path becomes more difficult because the engine now has combined characteristics of the CI and the SI engines. The combined characteristics come from the fact that diesel is still directly injected into cylinders (CI engine) while CNG is injected at the intake ports (SI engine.) In pure CI engine, throttle is normally fully opened for maximum air intake, while EGR valve is actively actuated to obtain low emissions. In pure SI engine, however, throttle is an active actuator, driven by pedal.
Technical Paper

Gain-Scheduling Integrator-Augmented Sliding-Mode Control of Common-Rail Pressure in Diesel-Dual-Fuel Engine

Accurate common-rail pressure control is vital to good engine performance and low emission. Injection strategy of diesel-dual-fuel engine varies more greatly with speed and load than its diesel engine predecessor, and so does the common-rail pressure set point. Along with this swift set point change, other control challenges exist; they are speed-and-load variation, model uncertainty, sensor noise, actuator nonlinearity, and pressure disturbance from injection. Traditional control such as the PID was proved to be only marginally effective because of the swift set point change. We proposed integrating an integrator-augmented sliding-mode control with gain scheduling and feed-forward term. The sliding-mode control has fast action and is low sensitive to model uncertainty and disturbance. The augmented integrator ensures zero steady-state error. The gain scheduling handles the speed-and-load variation. The feed-forward term helps with the actuator nonlinearity.
Technical Paper

Air-Fuel Ratio Regulation with Optimum Throttle Opening in Diesel-Dual-Fuel Engine

Accurate air-fuel ratio control is required for good engine performance and low emission in diesel dual fuel engine. Two actuators directly affect the ratio are the air throttle and the EGR valve. Maximum air throttle opening is favorable to minimize pumping loss, and the EGR valve opening should follow closely the values in a well-tuned map to minimize emission. In the past, the two actuators were either controlled separately or simultaneously to achieve the air-fuel ratio set point without much consideration on the actuators' opening positions. We proposed a logic that alternated between actuating the air throttle and the EGR valve to maintain optimum air throttle opening. Since each actuator was controlled one at a time, the overall control system was simplified, yet any advanced controller could be applied to increase the accuracy of each actuator.
Technical Paper

Robust Common-Rail Pressure Control for a Diesel-Dual-Fuel Engine Using QFT-Based Controller

Despite promising future, the diesel-dual-fuel engine, with diesel as pilot and natural gas as main, abounds with challenges from high NOx emission and knock especially at high speed and low load. To cope with these challenges, variation of common-rail pressure provides another desirable degree of freedom. Nevertheless, crippling with complicated dynamics, pressure wave inside the transporting rail, disturbance from varying of injections, engine speed variation, and actuator limitation, common-rail pressure control has relied on the simple PID to deliver only marginally satisfactory result. Some attempts to achieve better control have resulted in either too complicated or not too robust control system. We devise a controller from the quantitative feedback theory.