Predictive Control of HCCI Engines Using Physical Models

Homogeneous Charge Compression Ignition (HCCI) is a promising internal combustion engine concept. It holds promise of combining low emission levels with high efficiency. However, as ignition timing in HCCI operation lacks direct actuation and is highly sensitive to operating conditions and disturbances, robust closed-loop control is necessary. To facilitate control design and allow for porting of both models and the resulting controllers between different engines, physics-based mathematical models of HCCI are of interest. This thesis presents work on a physical model of HCCI including cylinder wall temperature and evaluates predictive controllers based on linearizations of the model. The model was derived using first principles modeling and is given on a cycle-to-cycle basis. Measurement data including cylinder wall temperature measurements was used for calibration and validation of the model. A predictive controller for combined control of work output and combustion phasing was designed and evaluated in simulation. The resulting controller was validated on a real engine. The last part of the work was an experimental evaluation of predictive combustion phasing control. The control performance was evaluated in terms of response time and steady-state output variance

Experimental Evaluation of Predictive Combustion Phasing Control in an HCCI Engine using Fast Thermal Management and VVA

This paper presents experimental results on model predictive control of the combustion phasing in a Homogeneous Charge Compression Ignition (HCCI) engine. The controllers were based on linearizations of a previously presented physical model of HCCI including cylinder wall temperature dynamics. The control signals were the inlet air temperature and the inlet valve closing. A system for fast thermal management was installed and controlled using mid-ranging control. The resulting control performance was experimentally evaluated in terms of response time and steady-state output variance. For a given operating point, a comparable decrease in steady-state output variance was obtained either by introducing a disturban ce model or by changing linearization point. The robustness towards disturbances was investigated as well as the effects of varying the prediction and control horizons

Physical Modeling and Control of Low Temperature Combustion in Engines

The topic of this thesis is model-based control of two combustion engine concepts, Homogeneous Charge Compression Ignition (HCCI) and Partially Premixed Combustion (PPC), using physics-based models. The studied combustion concepts hold promise of reducing the emission levels and fuel consumption of internal combustion engines. A cycle-to-cycle model of HCCI, including heat losses to the cylinder wall, was derived. The continuous heat transfer between the cylinder wall and the gas in the cylinder was approximated by three heat transfer events during each cycle. This allowed the model to capture the main dynamics of the cylinder wall temperature while keeping the complexity of the resulting model at a tractable level. The model was used to derive model predictive controllers for the combustion phasing using the inlet air temperature and inlet valve closing timing as control signals. The resulting controllers were evaluated experimentally and achieved promising results in terms of set-point tracking and disturbance rejection. Additionally, the differences in performance between using a switched state feedback controller and a hybrid model predictive controller for controlling exhaust recompression HCCI were investigated. The dynamics of exhaust recompression HCCI vary significantly between certain operating points, and the model predictive controller produced smoother transients in both simulations and experiments. A continuous-time model of PPC was derived and implemented in the Modelica language. The model structure, a single-zone model, and implementation platform, JModelica.org, were chosen in order to allow for numerical optimization based on the model equations. The resulting framework allowed the calibration of the model parameters to be formulated as an optimization problem penalizing deviations between a measured pressure trace and that of the model. The calibrated model predicted the effects of variations in the injection timing with satisfactory accuracy

Modeling for HCCI Control

Due to the possibility of increased efficiency and reduced emissions, Homogeneous Charge Compression Ignition (HCCI) is a promising alternative to conventional internal combustion engines. Ignition timing in HCCI is highly sensitive to operating conditions and lacks direct actuation, making it a challenging subject for closed-loop control. This paper presents physics-based, control-oriented modeling of HCCI including cylinder wall temperature dynamics. The model was calibrated using experimental data from an optical engine allowing measurements of the cylinder wall temperature to be made. To further validate the model, it was calibrated against a conventional engine and linearizations of the model were used to design model predictive controllers for control of the ignition timing using the inlet valve closing and the intake temperature as control signals. The resulting control performance was experimentally evaluated in terms of response time and steady-state output variance

Physical Modeling and Control of Homogeneous Charge Compression Ignition (HCCI) Engines

Due to the possibility of increased efficiency and reduced emissions, Homogeneous Charge Compression Ignition (HCCI) is a promising alternative to conventional internal combustion engines. Ignition timing in HCCI is highly sensitive to operating conditions and lacks direct actuation, making it a challenging subject for closed-loop control. This paper presents results on model-based control of ignition timing and work output using a cycle-resolved physical model including cylinder wall temperature dynamics. The model was used to design model predictive controllers for simultaneous control of the ignition timing and the indicated mean effective pressure by varying the inlet valve closing and the intake temperature. The performance of the resulting controller was evaluated in simulation and two possible extensions were developed. An extended controller was validated on a real engine

Modeling and Model-Based Control of Homogeneous Charge Compression Ignition (HCCI) Engine Dynamics

The Homogeneous Charge Compression Ignition (HCCI) principle holds promise to increase efficiency and to reduce emissions from internal combustion engines. As HCCI combustion lacks direct ignition timing control and auto-ignition depends on the operating condition, control of auto-ignition is necessary. Since auto-ignition of a homogeneous mixture is very sensitive to operating conditions, a fast combustion phasing control is necessary for reliable operation. To this purpose, HCCI modeling and model-based control with experimental validation were studied. A six-cylinder heavy-duty HCCI engine was controlled on a cycle-to-cycle basis in real time using a variety of sensors, actuators and control structures for control of the HCCI combustion in comparison. The controllers were based on linearizations of a previously presented physical, nonlinear, model of HCCI including cylinder wall temperature dynamics. The control signals were the inlet air temperature and the inlet valve closing. A system for fast thermal management was installed and controlled using mid-ranging control. The resulting control performance was experimentally evaluated in terms of response time and steady-state output variance. For a given operating point, a comparable decrease in steady-state output variance was obtained either by introducing a disturbance model or by changing linearization point. The robustness towards disturbances was investigated as well as the effects of varying the prediction and control horizons. Increasing the horizons had a very limited effect on the closed-loop performance while increasing the computational demands substantially. As shown in the paper, modeling constitutes a necessary element for embedded networked control design applied to HCCI combustion engine design

Single-Zone Diesel PPC Modeling for Control

Partially premixed combustion (PPC) is a combustion concept with similarities to both Diesel and Homogeneous Charge Compression Ignition (HCCI) combustion. It provides a combustion mode with better controllability than HCCI without increasing the emissions of nitrogen oxides and soot to the level of traditional Diesel engines. The model described in this paper aims to describe the main features of Diesel PPC combustion within the closed part of an engine cycle. It is a single-zone model including heat losses to the cylinder walls as well as fuel evaporation losses. The simulation framework used allows optimization problems to be formulated based on the model equations. The overarching goal of this modeling is to be able to use the model explicitly for optimization