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Research

  • Benchmark Comparison of Commercially Available Systems for Particle Number Measurement

    Year: 2013

    Author: Nicolo Cavina, Luca Poggio, Fabio Bedogni, Vincenzo Rossi, Luca Stronati

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    Measurement of particle number was introduced in the Euro 5/6 light duty vehicle emissions regulation. Due to the complex nature of combustion exhaust particles, and to transportation, transformation and deposition mechanisms, such type of measurement is particularly complex, and regression analysis is commonly used for the comparison of different measurement systems.

    This paper compares various commercial instruments, developing a correlation analysis focused on PN (Particle Number) measurement, and isolating the factors that mainly influence each measuring method. In particular, the experimental activity has been conducted to allow critical comparisons between measurement techniques that are imposed by current regulations and instruments that can be used also on the test cell. The paper presents the main results obtained by analyzing instruments based on different physical principles, and the effects of different sampling locations and different operating parameters.

    The main instruments that have been critically analyzed during this project are: Horiba MEXA 2000 SPCS Particle Counter installed on a CVS tunnel; AVL APC 489 installed directly on the exhaust gas flow; AVL Smart Sample 478 GEM 140 (Mini CVS tunnel) + AVL APC 489; Cambustion DMS 500 installed directly on the exhaust gas flow; AVL MicroSoot Sensor 483 installed directly on the exhaust gas flow. The tests have been carried out on a prototype vehicle equipped with a GDI engine, both under steady-state conditions and during the New European Driving Cycle (NEDC), while comparing the effects of different dilution factors, different engine calibration datasets, and different positions of the various instruments.

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  • Thermal Management Strategies for SCR After Treatment Systems

    Year: 2013

    Author: Nicolo Cavina, Giorgio Mancini, Enrico Corti, Davide Moro, Matteo De Cesare, Federico Stola

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    While the Diesel Particulate Filter (DPF) is actually a quasi-standard equipment in the European Diesel passenger cars market, an interesting solution to fulfill NOx emission limits for the next EU 6 legislation is the application of a Selective Catalytic Reduction (SCR) system on the exhaust line, to drastically reduce NOx emissions.

    In this context, one of the main issues is the performance of the SCR system during cold start and warm up phases of the engine. The exhaust temperature is too low to allow thermal activation of the reactor and, consequently, to promote high conversion efficiency and significant NOx concentration reduction. This is increasingly evident the smaller the engine displacement, because of its lower exhaust system temperature (reduced gross power while producing the same net power, i.e., higher efficiency).

    The proposal of the underlying work is to investigate and identify optimal exhaust line heating strategies, to provide a fast activation of the catalytic reactions on SCR. The main constrain is to limit the potential fuel consumption increase, and possibly to even increase global efficiency, and the chosen application is a small EU5-compliant diesel engine.

    After an initial investigation, the research has been focused on main combustion control parameters, rather than on post-oxidation processes associated with late injections, in an effort to reduce eventual fuel penalties. The effect of each relevant engine control parameter has been analyzed on the test bench, observing the results in terms of exhaust system temperature and fuel efficiency. After this preliminary identification phase, different calibration strategies have been tested on the vehicle, executing several NEDC cycles. The most relevant comparisons are illustrated and critically discussed in the paper.

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  • Innovative Techniques for On-Board Exhaust Gas Dynamic Properties Measurement

    Year: 2013

    Author: Nicolo Cavina, Alberto Cerofolini, Enrico Corti, Fabrizio Ponti, Matteo De Cesare, Federico Stola

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    The purpose of this paper is to present some innovative techniques developed for an unconventional utilization of currently standard exhaust sensors, such as HEGO, UEGO, and NOx probes. In order to comply with always more stringent legislation about pollutant emissions, intake-exhaust systems are becoming even more complex and sophisticated, especially for CI engines, often including one or two UEGO sensors and a NOx sensor, and potentially equipped with both short-route and long-route EGR. Within this context, the effort to carry out novel methods for measuring the main exhaust gas dynamic properties exploiting sensors installed for different purposes, could be useful both for control applications, such as EGR rates estimation, or cost reduction, minimizing the on-board devices number.

    In this work, a gray-box model for measuring the gas mass flow rate, based on standard NOx sensor operating parameters of its heating circuit, is analyzed. Its accuracy is then compared to the one of a similar model applied to the UEGO probe, presented in a previous paper, to on-board standard MAF and speed-density measurements, and to a simple pressure loss-flow characteristic model, whose robustness derives from the particular NOx probe location in the exhaust pipe. The comparison is performed for steady-state tests. The sensitivity to model input variables is also considered, that is gas temperature and pressure, leading to the introduction of a complementary physical model and besides describing an adaptive method for estimating exhaust gas static pressure, which is based on the pressure-current dependence of UEGO and NOx sensors.

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  • Development and Implementation of Hardware in the Loop Simulation for Dual Clutch Transmission Control Units

    Year: 2013

    Author: Nicolo Cavina, Davide Olivi, Enrico Corti, Giorgio Mancini, Luca Poggio, Francesco Marcigliano

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    A control oriented model of a Dual Clutch Transmission was developed for real time Hardware In the Loop (HIL) applications. The model is an innovative attempt to reproduce the fast dynamics of the actuation system maintaining a step size large enough for real time applications. The model comprehends a detailed physical description of hydraulic circuit, clutches, synchronizers and gears, and simplified vehicle and internal combustion engine sub-models; a stable real time simulation is achieved with a simplification of the model without losing physical validity. After an offline validation, the model was implemented in a HIL system and connected to the TCU (Transmission Control Unit) via two input-output boards, and to a load plate which comprehends all the actuators. The paper presents a selection of the several tests that have been performed for the development of the DCT controller: electrical failure tests on sensors and actuators, mechanical failure tests on hydraulic valves, clutches and synchronizers, and application tests comprehending all the main features of the control performed by the TCU, i.e. drive away and gear shift strategies, and interactions with the driver. Furthermore, the paper shows that the model is capable of reproducing the behavior of the real system during adaption procedures performed by the TCU under particular conditions, i.e. synchronizer position detection and clutch pressure characteristic detection. Being based on physical laws, in every condition the model simulates a plausible reaction of the system to the imposed failure or maneuver, as demonstrated by the possibility of performing a complete new software release test in fully automatic mode.

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  • Benchmarking Hybrid Concepts: On-Line vs. Off-Line Fuel Economy Optimization for Different Hybrid Architectures

    Year: 2013

    Author: Oliver Dingel, Nicola Pini, Igor Trivic, Joerg Ross, Nicolo Cavina, Alberto Cerofolini, Mauro Rioli

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    The recent advance in the development of various hybrid vehicle technologies comes along with the need of establishing optimal energy management strategies, in order to minimize both fuel economy and pollutant emissions, while taking into account an increasing number of state and control variables, depending on the adopted hybrid architecture.

    One of the objectives of this research was to establish benchmarking performance, in terms of fuel economy, for real time on-board management strategies, such as ECMS (Equivalent Consumption Minimization Strategy), whose structure has been implemented in a SIMULINK model for different hybrid vehicle concepts. The results obtained from these simulations have then been compared with those derived from a general purpose, off-line optimization technique, based on deterministic DP (Dynamic Programming), and capable of finding the numerical global optimum and of generating the optimal cycle-based control trajectory over a discretized multidimensional grid of the selected state and control variables. The paper investigates the structure of the DP problem and its interactions with the specific hybrid architecture, especially in terms of the most appropriate selection of state and control variables. The implications of the chosen modeling approach are also critically evaluated, searching for the best compromise between accurate simulation results and reliable comparisons between off-line and on-line optimization results.

    One of the outcomes is that the system model should be designed in order to be compatible with efficient DP techniques implementation, with the objective of obtaining robust optimal control policies while achieving acceptable computational costs.

    The concepts that have been analyzed in this work are the following two parallel hybrid architectures: HEV (Hybrid Electric Vehicle), normally applied in current hybrid vehicles production, and HSF-HV (High Speed Flywheel Hybrid Vehicle), an interesting and promising hybrid mechanical solution. An example of the influence of the selected gear has also been investigated by implementing a multi-dimensional DP optimization routine. In order to perform this analysis, a general purpose DP MATLAB function, including specifically designed algorithms to avoid numerical interpolation issues that typically occur in constrained problems, has been modified to run any SIMULINK-based engine-vehicle model.

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  • Development of a Novel Approach for Non-Intrusive Closed-Loop Heat Release Estimation in Diesel Engines

    Year: 2013

    Author: Fabrizio Ponti, Vittorio Ravaglioli, Enrico Corti, Davide Moro, Matteo De Cesare

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    Over the past years, policies affecting pollutant emissions control for Diesel engines have become more and more restrictive. In order to meet such requirements, innovative combustion control methods have currently become a key factor. Several studies demonstrate that the desired pollutant emission reduction can be achieved through a closed-loop combustion control based on in-cylinder pressure processing. Nevertheless, despite the fact that cylinder pressure sensors for on-board application have been recently developed, large scale deployment of such systems is currently hindered by unsatisfactory long term reliability and high costs. Whereas both the accuracy and the reliability of pressure measurement could be improved in future years, pressure sensors would still be a considerable part of the cost of the entire engine management system. In the light of these remarks, and especially with regard to light duty applications, research is being conducted in order to develop non-intrusive methodologies for the extraction of relevant information about the combustion process.
    This work presents a methodology for heat release estimation through a proper analysis of the signals coming from a set of accelerometers and the engine speed sensor already present on-board. The presented algorithm is mainly composed of two steps: the first step is an open-loop pressure estimation based on a zero-dimensional model of the combustion process, while the second one consists in a closed-loop correction based on the analysis of the signals coming from the above mentioned sensors.
    This paper also reports the results obtained applying the whole estimation methodology to a light-duty turbocharged Common Rail Diesel engine.

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  • Automatic Combustion Phase Calibration With Extremum Seeking Approach

    Year: 2013

    Author: Enrico Corti, Giorgio Mancini, Claudio Forte, Davide Moro

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    Combustion control is assuming a crucial role in reducing engine tailpipe emissions and maximizing performance. The number of actuations influencing the combustion is increasing, and, as a consequence, the calibration of control parameters is becoming challenging. One of the most effective factors influencing performance and efficiency is the combustion phasing: for gasoline engines control variables such as Spark Advance (SA), Air-to-Fuel Ratio (AFR), Variable Valve Timing (VVT), Exhaust Gas Recirculation (EGR) are mostly used to set the combustion phasing.
    The optimal control setting can be chosen according to a target function (cost or merit function), taking into account performance indicators, such as Indicated Mean Effective Pressure (IMEP), Brake Specific Fuel Consumption (BSFC), pollutant emissions, or other indexes inherent to reliability issues, such as exhaust gas temperature, or knock intensity.
    Many different approaches can be used to reach the best calibration settings: Design Of Experiment (DOE) is a common option when many parameters influence the results, but other methodologies are in use: some of them are based on the knowledge of the controlled system behavior, by means of models that are identified during the calibration process.
    The paper proposes the use of a different concept, based on the extremum seeking approach. The main idea consists in changing the values of each control parameter at the same time, identifying its effect on the monitored target function, allowing to shift automatically the control setting towards the optimum solution throughout the calibration procedure. An original technique for the recognition of control parameters variations effect on the target function is introduced, based on spectral analysis.
    The methodology has been applied to data referring to different engines and operating conditions, using IMEP, exhaust temperature and knock intensity for the definition of the target function, and using SA and AFR as control variables. The approach proved to be efficient in reaching the optimum control setting, showing that the optimal setting can be achieved rapidly and consistently.

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  • Numerical Simulation of the Zefiro 9 Performance Using a New Dynamic SRM Ballistic Simulator

    Year: 2013

    Author: R Bertacin, F Ponti, E Corti, D Fedele, A Annovazzi

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