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Research

  • Thermodynamic Analysis of Variable Valve Timing Infuence on SI Engine Efficiency

    Year: 2001

    Author: Davide Moro, Fabrizio Ponti, Gabriele Serra

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    The large number of mechanical, electro-magnetic and oleo-dynamic systems for variable valve actuation developed by automotive suppliers demonstrates the great interest that is being devoted to their potential application on internal combustion engines.
    In the paper, a possible strategy to realize an original engine load control by means of both intake and exhaust variable valve timing (VVT) is briefly presented and the thermodynamic analysis of the performance obtainable with this solution is carried out. The peculiarity of this strategy is that it is possible to directly recirculate the desired mass of exhaust gas with less limitation with respect to the external duct architecture. To highlight its potentiality this solution has been compared with two different engine architectures:
    a traditional Spark Ignition (SI) engine, where the load control is demanded to the throttle body;
    an engine equipped with a VVT system only on the intake valves, where the load control is performed by means of the well-known Early Intake Valve Closing (EIVC) strategy.
    The proposed engine load control technique shows a relevant efficiency increase at partial load, with respect to both throttled and EIVC engines. The obtained results are certainly overestimated, due to the theoretical thermodynamic approach used to compare the different engine architectures, but the relevant efficiency increase shown in the paper seems to leave a good possibility to find in real experimentation a still appreciable improvement with respect to a throttled engine.

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  • Fast Algorithm for On-Board Torque Estimation

    Year: 1999

    Author: Nicolò Cavina, Fabrizio Ponti, Giorgio Rizzoni

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    Electronic Throttle Control systems substitute the driver in commanding throttle position, with the driver acting on a potentiometer connected to the accelerator pedal. Such strategies allow precise control of air-fuel ratio and of other parameters, e.g. engine efficiency or vehicle driveability, but require detailed information about the engine operating conditions, in order to be implemented inside the Electronic Control Unit (ECU). In order to determine throttle position, an interpretation of the driver desire (revealed by the accelerator pedal position) is performed by the ECU. In our approach, such interpretation is carried out in terms of a torque request that can be appropriately addressed knowing the actual engine-vehicle operating conditions, which depend on the acting torques. Estimates of the torque due to in-cylinder pressure (indicated torque), as well as the torque required by the vehicle (load torque), must then be available to the control module. The estimation procedure should be at the same time sufficiently precise and fast in order to comply with the driver requests in real time. In this paper we present a signal processing procedure to estimate the cycle mean values of both the indicated and load torque, based on a frequency analysis of the engine block vibrations signal. The algorithm that has been developed tries to meet the precision and quickness requirements for on board implementation; this goal has been reached using only two frequency components of the engine block vibrations. The quality of the estimation methodology has been initially tested on an engine test cell, using a two cylinder small diesel engine and showing a good agreement between measurements and estimations, even under strong speed and load transients. The procedure is scheduled to be validated on-board a production vehicle.

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  • Air-Fuel Ratio Control for a High Performance Engine using Throttle Angle Information

    Year: 1999

    Author: Piero Azzoni, Giorgio Minelli, Davide Moro, Massimo Ceccarani, Giorgio Rizzoni

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    This paper presents the development of a model-based air/fuel ratio controller for a high performance engine that uses, in addition to other usual signals, the throttle angle to enable predictive air mass flow rate estimation.
    The objective of the paper is to evaluate the possibility to achieve a finer air/fuel ratio control during transients that involve sudden variations in the physical conditions inside the intake manifold, due, for example, to fast throttle opening or closing actions. The air mass flow rate toward the engine cylinders undertakes strong variation in such transients, and its correct estimation becomes critical mainly because of the time lag between its evaluation and the instant when the air actually enters the cylinders.
    The approach to research consists of the use of a fuel film dynamics model-based compensator and of an algorithm that estimates, before the intake stroke, the amount of air that will enter the cylinder, using the throttle position signal as a feed-forward information about the mean intake manifold pressure.
    The conclusion will show the possibility to enable some improvement in the air-fuel ratio control; experimental tests on-board the vehicle are in progress.

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  • Engine and Load Torque Estimation with Application to Electronic Throttle Control

    Year: 1998

    Author: Piero Azzoni, Davide Moro, Fabrizio Ponti, Giorgio Rizzoni

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    Electronic throttle control is increasingly being considered as a viable alternative to conventional air management systems in modern spark-ignition engines. In such a scheme, driver throttle commands are interpreted by the powertrain control module together with many other inputs; rather than directly commanding throttle position, the driver is now simply requesting torque - a request that needs to be appropriately interpreted by the control module.
    Engine management under these conditions will require optimal control of the engine torque required by the various vehicle subsystems, ranging from HVAC, to electrical and hydraulic accessories, to the vehicle itself. In this context, the real-time estimation of engine and load torque can play a very important role, especially if this estimation can be performed using the same signals already available to the powertrain control module.
    In this paper we present two methods to estimate the instantaneous indicated torque, combustion by combustion, and the vehicle load torque; we also present some preliminary results. The first method is based on the reconstruction of the in-cylinder pressure based on the measured engine block vibration. The second one exploits a nonlinear estimation technique, in which the difference between the instantaneous measurement of crankshaft angular velocity and an estimate of the same velocity, based on a model of the engine, forms the input to a sliding-mode observer.
    Experimental results of both methods have been obtained in an engine test cell on a two-cylinder compression-ignition.

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  • Misfire Pattern Recognition in High Performance SI 12-Cylinder Engine

    Year: 1998

    Author: Davide Moro, Piero Azzoni, Giorgio Minelli

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    This paper presents an original procedure for misfire detection in a high-performance 12-cylinder engine, based on the analysis of the time periods between subsequent combustions. A detailed analysis of the misfire effects on the engine crank-shaft instantaneous speed is presented, then a misfire detection procedure is designed, based on the misfire pattern recognition. The capability of this methodology was then validated under the worst case condition of a random misfire in several tests performed with the vehicle running on a circular race-track, at low and high load, in different gear, under acceleration and during a normal urban cycle. The results obtained are very interesting because the misfire pattern recognition works well even during cut-off or gear shifts, avoiding false alarm due to the strong influence that these phenomena have on crank-shaft dynamics. In conclusion same considerations have been done about the procedure capability of detecting more than one misfire within the same cycle.

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  • Reconstruction of Formula 1 Engine Instantaneous Speed by Acoustic Emission Analysis

    Year: 1998

    Author: P. Azzoni, D. Moro, G. Rizzoni

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    This paper presents some results of a method aimed at extracting instantaneous engine speed information from acoustic emission measurements obtained from Formula 1 (F1) vehicles during a race. The results presented in the paper show that it is possible to reconstruct the instantaneous engine speed for an entire race, if desired, from available sound intensity measurements.
    The analysis method used in this work is applied to acoustic emission data recorded by the microphone of the in-car cameras mounted on F1 vehicles. The data analyzed in this paper were acquired during the 1998 Grand Prix of San Marino (Imola), and pertain to the performance of the Ferrari and McLaren-Mercedes vehicles. At the time of writing the paper, these are the two teams challenging one another for the driver and constructor championships. The analysis presented in the paper is based on data acquired in three different sections of the Imola circuit: the starting straightaway and two curves, to highlight the capabilities of the method.
    The result of the analysis demonstrates that it is possible to estimate a number of useful variables from sound measurements. These estimates are related to engine performance (e.g.: engine speed and its acceleration, top engine speed), to engine architecture (e.g.: gear ratios), to driving strategy (e.g.: shifting strategy) and to vehicle performance (tire adhesion, aerodynamic behavior).

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  • Misfire Detection in a High-Performance Engine by the Principal Component Analysis Approach

    Year: 1996

    Author: Piero Mario Azzoni, Davide Moro, Carlo Maria Porceddu-Cilione, Giorgio Rizzoni

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    The aim of this paper is to present the application of some signal processing and statistical analysis methods to the problem of detecting and isolating misfire occurrences in a twelve-cylinder high-performance engine. The method employed in this work is based on a measurement of engine angular velocity, processed in the frequency domain to extract a number of spectral components that are shown to be strongly affected by misfire events. These spectral components are then subject to a procedure known as Principal Components Analysis, in which the principal features of the angular speed waveform are extracted to generate individual cylinder misfire signatures. A clustering method is then implemented to permit the isolation of the cylinder responsible for the misfire. The paper briefly reviews the signal analysis method and presents experimental results supporting the validity of the approach.

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