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The camless valve system is able to provide flexible engine-valve profiles (timing, duration, lift, etc.) to optimize the performance of internal combustion engines. To provide a precise valve profile of an electro-hydraulic variable valve actuator and achieve the desired engine performance, an optimal tracking controller for the valve-rising duration, a key valve profile parameter, is presented in this paper. An event-by-event nonlinear model, connecting the system supply pressure dynamics to the valve-rising duration, is developed and linearized along the desired valve-rising trajectory. Based on the trajectory linearization, a receding horizon linear–quadratic tracking (LQT) controller is designed along with a Kalman optimal state estimation. The equilibrium control resulted from the model linearization is used as the LQT feedforward control. The control performance is compared with that of baseline controllers through both simulation study and bench tests. The transient and steady-state validation results confirm the effectiveness of proposed control scheme. [ABSTRACT FROM AUTHOR]

Combustion phasing control is very important for internal combustion engines to achieve a high thermal efficiency with low engine-out emissions. Traditional open-loop map-based control becomes less favorable in terms of calibration effort, robustness to engine aging, and especially control accuracy for turbulent jet ignition (TJI) engines due to the increased number of control variables over conventional spark-ignition engines. In this paper, a model-based feedforward controller is developed for a TJI engine. A feedback controller is designed based on the linear quadratic tracking control with output covariance constraint. Since the TJI main-chamber combustion is influenced by the prechamber one, the proposed controller optimizes the control variables in both combustion chambers. The proposed feedforward and feedback controller reduces standard deviation of combustion phase by more than 22% over a group of baseline controllers through a series of dynamometer engine tests. [ABSTRACT FROM AUTHOR]

It is fairly challenging to achieve a smooth mode transition between spark ignition combustion and homogeneous charge compression ignition combustion for a spark ignition engine capable of homogeneous charge compression ignition, because their in-cylinder thermal and charge mixture properties are quite different owing to the distinct combustion characteristics. In this paper, a mode transition strategy between spark ignition combustion and homogeneous charge compression ignition combustion was developed over the entire transition boundary between the spark ignition mode and the homogeneous charge compression ignition mode, where the engine speed is between 1100 r/min and 2000 r/min and the corresponding load (the indicated mean effective pressure) is between 3.8 bar and 5.0 bar. During the combustion mode transition and steady-state homogeneous charge compression ignition operation the normalized air-to-fuel ratio of the engine was maintained between 1.0 and 1.3; the charge air was heated by a manifold charge cooler heated by the engine coolant, and a test gasoline fuel with a research octane number of 85 was used for all the experiments conducted. The mode transition strategy was experimentally validated on a spark ignition engine capable of homogeneous charge compression ignition equipped with electric variable-valve-timing systems, dual-lift valves and an electronic throttle control system. Because of the limitation on the electric variable-valve-timing response time, it takes 5–10 cycles of the engine, depending on the engine speed, to complete the mode transition. The throttle was opened step by step to its wide-open position for the transition from spark ignition to homogeneous charge compression ignition or closed directly to the target position for the transition from homogeneous charge compression ignition to spark ignition, where the hybrid combustion mode was employed with spark assistance to change gradually to the desired homogeneous charge compression ignition mode or spark ignition combustion mode respectively, by increasing or decreasing the percentage of homogeneous charge compression ignition combustion during the hybrid combustion operation. The experimental results show that the developed strategy is able to achieve a smooth combustion mode transition with the net mean effective pressure and the combustion phase fluctuations at the level of stable spark ignition and homogeneous charge compression ignition combustion. [ABSTRACT FROM AUTHOR]

A control-oriented engine model is often used in the hardware-in-the-loop (HIL) simulation environment for developing and validating the corresponding control strategies. For homogeneous charge compression ignition (HCCI) combustion, mixture heterogeneity should be considered in the control-oriented model to provide accurate combustion phase prediction. This paper describes a two-zone HCCI combustion model, where the in-cylinder charge is divided into the well-mixed and unmixed zones as the result of charge mixing. Simplified fluid dynamics is used to predict the residual gas fraction before the combustion phase starts, which defines the mass of the unmixed zone, during real-time simulations. The unmixed-zone size determines not only how well the in-cylinder charge is mixed, which affects the start of HCCI combustion, but also the resulting peak in-cylinder pressure and temperature during the combustion process. The developed model was validated in the HIL simulation environment. The HIL simulation results show that the proposed charge mixing and HCCI combustion model provides better agreement with the corresponding GT-Power simulation results than the previously developed one-zone model. [ABSTRACT FROM PUBLISHER]

The combustion mode transition between spark ignition (SI) and homogeneous charge compression ignition (HCCI) combustion of an internal combustion (IC) engine is challenging due to the distinct engine operating parameters over the two combustion modes and the cycle-to-cycle residue gas dynamics during the mode transition. The control problem becomes even more complicated for a multicylinder engine without camless variable valve actuators. This paper studies the combustion mode transition problem of a multicylinder IC engine equipped with dual-stage valve lift and electrical variable valve timing (VVT) systems. Hardware-in-the-loop (HIL) simulations were used as a tool to develop and validate the proposed control strategies. Based on the HIL simulation results, this paper shows that smooth combustion mode transition can be realized in a few engine cycles. During the mode transition, a model-based linear quadratic tracking strategy was used to track the desired engine manifold pressure through the engine throttle control to maintain the engine AFR in a desired range; the fuel quantity of individual cylinder was controlled via the iterative learning; and engine spark was maintained for the SI–HCCI (or spark assistant) hybrid combustions during the combustion mode transition. The HIL simulations demonstrated the effectiveness of the developed control strategies under both steady state and transient engine operating conditions. As a result, it is feasible to have a smooth combustion mode transition for an HCCI capable SI engine equipped with dual-stage valve lift and electrical VVT systems. [ABSTRACT FROM AUTHOR]

While the homogeneous charge compression ignition (HCCI) combustion has its advantages of high thermal efficiency with low emissions, its operational range is limited in both engine speed and load. To utilize the advantage of the HCCI combustion, an HCCI capable spark ignition (SI) engine is required. One of the key challenges of developing such an engine is to achieve smooth mode transition between SI and HCCI combustion, where the in-cylinder thermal and charge mixture properties are quite different due to the distinct combustion characteristics. In this paper, a control strategy for smooth mode transition between SI and HCCI combustion is developed and experimentally validated for an HCCI capable SI engine equipped with electrical variable valve timing (EVVT) systems, dual-lift valves, and electronic throttle control (ETC) system. During the mode transition, the intake manifold air pressure is controlled by tracking the desired throttle position updated cycle-by-cycle; and an iterative learning fuel mass controller, combined with sensitivity-based compensation, is used to manage the engine torque in terms of net mean effective pressure (NMEP) at the desired level for smooth mode transition. Note that the NMEP is directly correlated to the engine output torque. Experiment results show that the developed controller is able to achieve smooth combustion mode transition, where the NMEP fluctuation is kept below 3.8% during the mode transition. [ABSTRACT FROM AUTHOR]