Search

Spark-ignited engines equipped by a three-way catalyst require a precise control of the air fuel ratio fed to the combustion chamber. A stoichiometric mixture is necessary for the proper working of the catalyst in order to meet the legislation requirement. A critical part of the air fuel ratio control is the feed-forward compensation of the fuel dynamics. Conventional strategies are based on a simplified model of the wall-wetting phenomena whose parameters are stored in off-line computed look-up tables. Unfortunately, errors in the parameters calibration over the whole engine map deteriorate the control performances in terms of emissions. In this paper an automatic procedure for a rapid and efficient identification of the wall-wetting parameters is presented. The whole procedure has been experimentally tested on a vehicle by using a test bench. Using the identified parameters values, a significant reduction in the air fuel ratio excursion has been achieved during rapid throttle transients with respect to the same vehicle equipped by a commercial ECU with resident engine maps computed by traditional calibration activity. Moreover, the algorithm can be also on-line used to improve air-fuel ratio control performances.

Spark-ignited engines equipped by a three-way catalyst require a precise control of the air fuel ratio (A/F) fed to the combustion chamber. A stoichiometric mixture is necessary for the proper working of the catalyst in order to meet the legislation requirement. A critical part of the A/F control is the feed-forward compensation of the fuel dynamics. Conventional strategies are based on a simplified model of the wall-wetting phenomena whose parameter values (the well known X and \tau_f in the Aquino's model) are stored in off-line computed look-up tables. Unfortunately, different factors such as aging of the engine components, wide range of possible fuels, errors in the parameters calibration over the whole engine map deteriorate the control performances in terms of emissions. In this paper, we present a strategy for the slow on-line adaptation of the wall-wetting dynamics. In particular the algorithm detects when parameter mismatch occurs and then uses a least squares method to perform the adaptation. The aim is to reduce temporary lean (rich) excursions during fastaccelerations (decelerations), and obtain a good compensation during rapid throttle transients. The whole procedure was designed and tested by numerical simulations based on experimental data.

We present a PDE model of three-way catalytic converters used on commercial gasoline-powered vehicles. In order to speed-up simulation times, we developed a fast integration algorithm based partly on a `method of lines' space-discretization, partly on the `met hod of characteristics' for `quasi linear' hyperbolic PDEs, the separation being allowed by a two time scale analysis of the system.

In this paper we investigate about the possibility of an idle-speed control law, simple enough for real-time applications. Our design approach takes explicitly into account the presence of finite time delays between manifold pressure and spark advance inputs and the resulting torque output. Effectiveness and robustness of the control scheme are shown through computer simulations.

A key point in three-way catalytic converter modeling problems is the definition of a possible chemical scheme able to represent the catalyzed process inside the converter, especially during transients. The lack of precise kinetic measurements during the transient thermal phase makes hard the choice of the kinetic expressions and, overall, of the chemical parameter values. To solve this problem here we propose the use of neural networks (NN) to model the reaction kinetics since a NN structure can provide enough degrees of freedom to capture all the significant features of the real system. Since the NN is embedded into the overall TWC dynamics, it cannot be trained through one of the standard method and some difficulties arise when dealing with the parameter tuning of this model, that are circumvented using a genetic algorithm (GA). A comparison between simulations and experimental data highlights that encouraging results can be obtained using a quite simple NN structure, with reasonable training time.

HEVES is a simulator for hybrid electric vehicle under the Matlab/Simulink software platform. The simulator library allows one to compose and to simulate a large class of vehicle configurations and to test the desired control strategy. Each block of the library is constructed by exploiting its static or dynamic model and a suitable dialog box allows the user to select the main parameters of the model. Some simulation results for the classical series and parallel configurations are presented.

On-board fault diagnosis is a crucial point for the automotive industry. Recently, new on-board diagnostic system requirements (OBD II) have been enforced on California vehicles and this new legislation will become stricter and stricter from the year 2000 and beyond. Such requirements will be extended in Europe in the n ext few years. In fact, the government regulations will impose to monitor vehicles emissions and alert the driver if the exhaust after-treatment system is not properly working. To meet these specifications, sophisticated diagnostic algorithms have to be developed. This paper presents a fault detection strategy on the automotive exhaust after-treatment system in order to fulfil the above mentioned OBD II. This algorithm, based on simple control-oriented models of the three-way catalytic converter and the oxygen sensor, is simple enough for real time applications. The overall strategy has been tuned and validated on the basis of experimental data.

We present an idle-speed controller designed through an optimal LQ technique taking into account during the design phase the presence of a finite time delay between variations in the manifold pressure and in the produced torque. Effectiveness of the scheme and its robustness to underestimation of the delay are shown through computer simulations.

In this paper we treat the problem of constructing Lyapunov functions for systems which are, by assumption, exponentially stable. The construction we present results in a larger set of functions than those obtainable by previously known methods. A useful property of the suggested Lyapunov functions is that they preserve information on the rate of exponential convergence of the system. Some possible applications are presented

This paper is concerned with the analysis and comparison of nonlinear phenomena in current and voltage controlled boost, buck and buck-boost DC/DC converters. The study is carried out by using three different discrete time maps: the stroboscopic map, the S-switching map and the A-switching map, which are obtained by different samplings of the state variables. The construction of a general A-switching map is outlined. Under realistic assumptions on the switching frequency, simplified closed form maps are presented. The use of a certain Jacobian matrix for the analytical detection of some bifurcations is proposed. Routes to chaos exhibited by the three converters are discussed and compared via numerical experiments.

The problem of induction motor state estimation and control without AC current measurements is considered. A state observer is designed by using a suitably reformulated output equation of the motor dynamic model. A field oriented control scheme and a decoupling controller with two independent current control loops is also presented. The proposed scheme is suitable for series hybrid electric vehicles, so as confirmed by simulations carried out with Matlab/Simulink.

A hierarchical structure for the tasks of the electronic control units devoted to automotive engine control is proposed. The architecture, at its highest level of abstraction, is divided into three parts: the driver interpreter, the engine controller, and the actuator controller. The lower hierarchical structure of the actuator controller block is detailed and applied to the case of an equivalent single cylinder engine. The implementation of the proposed architecture is shown to be compliant with the function block approach of the proposed IEC 1499 international standard.

We illustrate the complete analytical solution to an optimal design problem of transistor devices characterized by state and control constraints and nonconvex Hamiltonian. We ascertain its optimality through a field theorem. This shows the usefulness of optimal control in the area of bandgap engineering for semiconductors.

In this paper we treat the problem of constructing Lyapunov functions for systems which are, by assumption, exponentially stable. The construction we present results in a larger set of functions than those obtainable by previously known methods. A useful property of the suggested Lyapunov functions is that they preserve information on the rate of exponential convergence of the system. Some possible applications are presented.

A robust tracking control system has been presented. The model, affected by bounded parameter uncertainties, has a structure often encountered in the analysis of complex mechanical systems. The continuous nonlinear control law which has been proposed (and which is an approximation of discontinuous laws) ensures the attractiveness of a certain region of the state space, while leaving the possibility of choosing the rate of convergence toward any ball of ultimate boundedness or just a decoupled structure of the controller. The method of analysis and design merges ideas of the VSC and Lyapunov approaches. Some of those ideas have been developed here and enriched for the tracking problem.

Two observer structures for estimating the state of a system with delayed outputs are presented. The first one only guarantees the convergence of the estimation error when the output delay is unitary. The second, and more complex one, enables the designeT. to arbitrarily specify the dynamics of the reconstruction error for every output delay. Moreover it realizes a saving in number of operation that must be performed on-line to obtain state estimates, especially in large scale systems. Hence it seems to be particularly well suited for applications in low cost microprocessor-based control systems.

The problem of optimal output feedback is addressed in the context of controlling uncertain systems. The objective is to control a possibly high-order uncertain system with a compensator of low order. The compensator formulation precludes the use of direct feedback of the plant output and uses an observer canonical form to represent the compensator dynamics. Similarly to the case of observer design, a two-step design procedure is proposed. A robust design assuming full state feedback is performed, followed by compensator design using an approximate loop-transfer recovery method. >

The design of a dynamic positioning system for a multiplymoored vessel with active winches and thrusters is presented. The proposed positioning system is based on the Kalman filter and linear optimal control. Its peculiarity is that it contains a scheme which allocates dynamically the control forces between moorings and thrusters. The allocation policy tries to minimize the energy of the control by maintaining the average propeller thrust near to zero. The efficacy of the scheme is illustrated by numerical simulations.

The authors treat the problem of robustness of output feedback controllers with respect to singular perturbations. Given a singularly perturbed control system whose boundary-layer system is exponentially stable and whose reduced order system is exponentially stabilizable via a (possibly dynamical) output feedback, they present a sufficient condition which ensures that the system obtained by applying the same controller to the original singularly perturbed control system is exponentially stable for sufficiently small values of the perturbation parameter. This condition, which is less restrictive than all those previously given in the literature, is always satisfied when the singular perturbation is due to the presence of fast actuators and/or sensors. Furthermore, it is claimed that, in the linear time-invariant case, if this condition is not satisfied then there exists an output feedback controller which stabilizes the reduced-order system but destabilizes the full-order system. >

Nonlinear phenomena in closed-loop pulsewidth modulated (PWM) DC/DC converters are analyzed. We introduce a new discrete time nonlinear map-the A-switching map-which is related to the asynchronous switchings, i.e., the changes of converter configuration occurring within the modulating period. This map is compared with the stroboscopic map, which is typically used in the study of DC/DC converters. Analytical conditions for the occurrence of periodic orbits and flip bifurcations are obtained. Moreover, necessary conditions for infinite local stretching on the phase space are derived. Finally, a possible explanation of the sudden jump to chaos exhibited by DC/DC converters is proposed. Analytical and numerical results can be applied to all fundamental DC/DC converter topologies. The case of the voltage-controlled buck converter is treated in detail.

A sufficient condition for the robust stability of a class of interval matrices is derived using the Lyapunov approach. The matrices considered have elements which are nonlinear functions of a vector of independent and bounded parameters. The robust stability condition requires that a quadratic form be positive definite in a finite number of conspicuous points of an enlarged parameter space. >

Atmospheric pollution caused by automotive vehicles is nowadays a very relevant and open problem. To limit the emissions level, the vehicles are equipped with a three way catalytic converter. Currently the largest amount of pollutants is produced during the warm-up phase when the the catalyst is not activated. In this work we propose a model-based active control strategy, based on an optimal approach, aimed to the fast heating of the catalyst while guaranteing the driver drivability requirements. The effectiveness of the control action is shown via Hardware-In-the-Loop experiments, where the performance of the actual control hardware has been tested in the loop. Here the actual plant is replased by the dSPACE Mid-Size Vehicle Simulator.

The development of real time control systems not only requires the design of control strategy, but also the search for tradeoffs between control specifications, supervision logics, tasks scheduling and plant dynamics or constraints. This is particularly true for automotive applications where mechanics and electronics are strongly tightened together. In this paper we present a modeling approach for the integrated simulations of both vehicle dynamics and functional behavior of the control systems. By exploiting Modelica features, it is ongoing the development of a library of reusable models that will allow to build and mimic the dynamic behavior of vehicles in any propulsive configuration with particular attention to the hybrid ones. Besides the physical components models a multi tasking electronic control unit (ECU) object oriented model, based on IEC 1131 standard, is also proposed to analyze pseudo parallel computing effect on control efficiency.

The stability robustness problem for a class of nominally linear systems subject to time-varying parameter uncertainty is dealt with. The allowable range of parameter variation is assumed to be a hyperrectangle in parameter space. The proposed robustness test, which is based on a Lyapunov approach, requires a finite number of positivity tests of a quadratic form in correspondence to some salient points in parameter space. >

Atmospheric pollution is an open problem that hits above all the cities. It is caused by different factors, as exhaust gas of the cars. To limit the emission level a three way catalytic converter is used to post-treat exhaust gases produced by combustion. The catalyst efficiency depends on the operating point; particularly during the warm-up phase the largest amount of pollutants is produced because the catalyst is not properly working. An appropriate control strategy is necessary during this phase in order to minimize dangerous emissions. In this paper, different innovative control strategies, designed for the warm-up phase, are presented. Firstly a simple controller, based on PI regulator, is compared with a more complex controller realized using the LQ technique. Finally, a secondary air injection on the exhaust manifold is considered and the two control strategies are implemented with this new control input.