Jonathan Hagena

Review of hardware-in-the-loop simulation and its prospects in the automotive area

Hardware-in-the-loop (HIL) simulation is rapidly evolving from a control prototyping tool to a system modeling, simulation, and synthesis paradigm synergistically combining many advantages of both physical and virtual prototyping. This paper provides a brief overview of the key enablers and numerous applications of HIL simulation, focusing on its metamorphosis from a control validation tool into a system development paradigm. It then describes a state-of-the art engine-in-the-loop (EIL) simulation facility that highlights the use of HIL simulation for the system-level experimental evaluation of powertrain interactions and development of strategies for clean and efficient propulsion. The facility comprises a real diesel engine coupled to accurate real-time driver, driveline, and vehicle models through a highly responsive dynamometer. This enables the verification of both performance and fuel economy predictions of different conventional and hybrid powertrains. Furthermore, the facility can both replicate the highly dynamic interactions occurring within a real powertrain and measure their influence on transient emissions and visual signature through state-of-the-art instruments. The viability of this facility for integrated powertrain system development is demonstrated through a case study exploring the development of advanced High Mobility Multipurpose Wheeled Vehicle (HMMWV) powertrains.

Engine-in-the-Loop Testing for Evaluating Hybrid Propulsion Concepts and Transient Emissions - HMMWV Case Study

This paper describes a test cell setup for concurrent running of a real engine and a vehicle system simulation, and its use for evaluating engine performance when integrated with a conventional and a hybrid electric driveline/vehicle. This engine-in-the-loop (EIL) system uses fast instruments and emission analyzers to investigate how critical in-vehicle transients affect engine system response and transient emissions. Main enablers of the work include the highly dynamic AC electric dynamometer with the accompanying computerized control system and the computationally efficient simulation of the driveline/vehicle system. The latter is developed through systematic energy-based proper modeling that tailors the virtual model to capture critical powertrain transients while running in real time. Coupling the real engine with the virtual driveline/vehicle offers a chance to easily modify vehicle parameters, and even study two different powertrain configurations. In particular, the paper describes the engine-in-the-loop study of a V8, 6L engine coupled to a virtual 4x4 HighMobility Multipurpose Wheeled Vehicle (HMMWV). The results shed light on critical transients in a conventional powertrain and their effect on NOx and soot emissions. Next, the conventional HMMWV powertrain is replaced with a parallel hybrid electric configuration and two power management strategies are examined. Comparison of the conventional and hybrid propulsion options provides detailed insight into fuel economy – emissions tradeoffs at the vehicle level.

Instructional Use of a Single-Zone, Premixed Charge, Spark-Ignition Engine Heat Release Simulation

Modeling and computer simulation of an internal combustion engines operating processes offers a valuable tool for enhancing our understanding of real physical phenomena and contributes significantly to optimizing and controlling the engines operation to meet different objectives. This paper illustrates the use of engine modeling in the educational setting through the development and use of a single-zone, premixed charge, spark-ignition engine heat release simulation. The paper begins by describing the operation of an engine. A heat release simulation is then discussed in depth, and a description is given of how it can be used to offer an understanding of thermodynamic fundamentals in an internal combustion engine. In particular, a comprehensive examination of the thermodynamic properties of the engine working fluid and in-cylinder gas-to-wall heat transfer demonstrates the need for accurate physical—chemical sub-models when performing a high-fidelity heat release analysis. Overall, this study demonstrates the power of such an engine simulation tool in an educational setting.

Engine-in-the-loop study of the stochastic dynamic programming optimal control design for a hybrid electric HMMWV

This paper presents a Stochastic Dynamic Programming (SDP) methodology for automatic generation of an implementable hybrid control strategy, and addresses engine soot emissions during controller development by using an advanced Engine-In-the-Loop (EIL) setup. Coupling the real engine with the virtual driveline/vehicle enables application of fast analysers to characterise the impact of transients on engine emissions. The benefits of using the EIL for establishing driveability and soot emissions constraints, and subsequent application of the constraints for refining the SDP strategy is demonstrated through a study of a virtual parallel-hybrid system for the High-Mobility Multipurpose Wheeled Vehicle with a V8 6L engine.

In-cylinder reduction of PM and NOx emissions from diesel combustion with advanced injection strategies

The effect of advanced injection strategies, including pilot- and post-injections, on reducing pollutants from diesel combustion is investigated through a synergistic approach combining experiments and Computational Fluid Dynamics (CFD) simulations. It is shown experimentally that pilot injections have the potential to reduce NOx and particulate matter emissions simultaneously when the timing of the pilot is selected appropriately. To gain further understanding of the combustion and emissions formation mechanisms from multiple injection events, a CFD analysis is performed to model in-cylinder processes. Results show that benefits of pilot injection stem from improved fuel-air mixing and the reduction of the amount of diffusion combustion. Furthermore, CFD analysis demonstrates that post injection can accelerate the soot oxidation process if the injection timing and the amount of fuel are suitably selected, while simultaneously reducing NOx by reducing the amount of fuel in the main event and lowering peak combustion temperatures.

Volterra series estimation of transient soot emissions from a diesel engine

This paper describes the development of a Volterra series model for predicting transient soot emissions from a diesel engine with fuel flow rate and engine speed as the two inputs to the model. These two signals are usually available as outputs of the power management controller in diesel hybrids. Therefore, an accurate offline estimation of the transient soot emissions using these signals is instrumental in optimizing the control strategy for both fuel economy and emissions. In order to develop the model, transient soot data are first collected by Engine-in-the-loop experiments of conventional and hybrid vehicles. The data are then used to construct a third-order multiple-input single-output (MISO) Volterra series to successfully model this system. Parametric complexity of the model is reduced using proper orthogonal decomposition (POD), and the model is validated on various datasets. It is shown that the prediction accuracy of transient soot, both qualitatively and quantitatively, significantly improves over the steady-state maps, while the model still remains computationally efficient for systems level work.

Cycle-by-Cycle Air-to-Fuel Ratio Calculation During Transient Engine Operation Using Fast Response CO and CO2 Sensors

Stringent engine emission regulations highlight the importance of proper engine control during transient operation. In recent years, fast emissions analyzers that measure CO and CO2 simultaneously have allowed for fast air-to-fuel ratio (AFR) calculation under steady-state engine operation. However, using a steady-state methodology to calculate AFR under transient conditions can lead to significant data interpretation errors. This research introduces an experimental cycle-by-cycle AFR calculation routine developed for transient operation using cycle-resolved CO2 and CO analyzers. Need for the new technique arises when the composition of recycled exhaust gases vary significantly from expected post-combustion products corresponding to the true in-cylinder AFR. This condition commonly occurs when AFR is changed from one cycle to the next. The peak difference between the new method and traditional methods is demonstrated to be in the range of 0.1 relative air-to-fuel ratio points, or approximately 10%. These results are for low dilution conditions where the new method should show minimal difference as compared to traditional methods. If residual gas fraction levels were increased the difference in corrected to uncorrected results would become even greater, motivating the use of the new method in high-dilution engines.Copyright