Papers by Aurel Stoicescu
International Journal of Vehicle Design, Aug 4, 2014
This paper presents the motor vehicle velocity control that, under certain well–defined condition... more This paper presents the motor vehicle velocity control that, under certain well–defined conditions, ensures a minimum fuel consumption. To this purpose, a vehicle with a stepped mechanical transmission is considered, assuming that the gear is unchanged during the movement. The optimal control problem is formulated for different cases and solved by applying Pontryagin's maximum principle. Whenever there is a singular solution, it is shown to correspond to the uniform motion law. The optimal velocity controls include the following phases that may be combined in different ways: deceleration without engine shut–off (null engine power), strong decelerative braking, constant speed movement and full–throttle acceleration. Examples are presented by using the experimental data on engine fuel consumption. The stress falls on the significant reductions in fuel consumption that can be achieved compared to uniform motion.
In lucrare se studiază oscilaţiile de săltare ale autombilului cu suspensie pendulară. Se foloseş... more In lucrare se studiază oscilaţiile de săltare ale autombilului cu suspensie pendulară. Se foloseşte un model al acestui tip de suspensie fără a se presupune că deplasările în sistem sunt mici. Se ajunge la un sistem de ecuaţii diferenţiale neliniare, potrivit pentru studiul oscilaţilor la trecerea roţilor peste neregularităţi mari ale căii. Se fac aprecieri cu privire la precizia determinării rigidităţii şi amortizării suspensiei când automobilul nu se deplasează. Pentru ecuaţiile liniarizate se compară rezultatele obţinute cu cele corespunzătoare modelului uzual din literatură. Se constată că deformaţiile laterale ale pneurilor determinate de variaţia ecartamentului roţilor afectează confortul la oscilaţii şi ţinuta de drum ale automobilului. In the present paper the heave vibrations of an automobile are investigated in the case of a swing axle suspension. A model of this suspension type is used without considering the displacements as small. We obtain a non-linear system of the di...
În lucrare se prezintă studiul regimului optimal de frânare a unui automobil, care conduce la per... more În lucrare se prezintă studiul regimului optimal de frânare a unui automobil, care conduce la performanţe maxime de frânare. Pentru aceasta se aplică principiul de maxim al lui Pontreaghin, arătându-se că există o soluţie singulară a problemei. În cazul general, comanda optimală include comenzi de tip releu şi comanda singulară. Pentru un sistem uzual de frânare realizarea acestor comenzi este dificilă, astfel că deceleraţia maximă posibilă limitată de aderenţă este practic imposibil de obţinut. The paper presents the study of the optimal braking duty of an automobile that leads to the maximum braking performance. With this end in view one applies the Pontryagin's maximum principle. It is proved that there exists a singular solution of the problem. In the general case, the optimal control consists of relay type controls and singular control. This control is difficult to achieve by an usual braking system. Therefore, the maximum deceleration limited by adhesion is impossible of e...
In lucrare se prezintă metoda de proiectare optimală a arcurilor elicoidale din suspensia automob... more In lucrare se prezintă metoda de proiectare optimală a arcurilor elicoidale din suspensia automobilelor dupa criteriul masei lor minime. Pentru aceasta, la o rigiditate dată a arcului, sunt luate în considerare solicitarea corespunzătoare forţei maxime preluate de arc, solicitarea la oboseală, condţia de stabilitate la flambaj, restricţiile privitoare la indicele şi diametrul exterior ale arcului. Exemplul numeric tratat în lucrare permite să se tragă concluzii cu caracter mai general.
In lucrare se analizează restricţiile geometrice şi funcţionale ale trapezului de direcţie al aut... more In lucrare se analizează restricţiile geometrice şi funcţionale ale trapezului de direcţie al automobilelor, folosindu-se sistematic lungimile raportate ale elementelor acestuia. Se analizează în ce măsură funcţia de transmitere necesară a mecanismului poate fi realizată folosind la sinteza mecanismului metoda dezvoltării în serie Taylor a acestei funcţii. In the paper the geometrical and the operational constraints of an Ackermann steering linkage are analyzed by systematic using of the normalized lengths of the elements of the mechanism. One analyzes to what extent the necessary transmission function of the mechanism can be carried out when the synthesis of the mechanism is performed by method of the Taylor's series expansion.
The steering system of an automobile with a rigid steering axle (beam and steering knuckles hinge... more The steering system of an automobile with a rigid steering axle (beam and steering knuckles hinge-connected to the beam with king pins) comprises the steering mechanism which is represented by the steering trapezium otherwise known as Ackermann steering linkage. The analysis and synthesis of the Ackermann steering linkage has been tackled in numerous papers [1]. Although in these works the problem of solution finding which should lead to enough good approximation of the correct steering condition has been set, a rigorous approach to optimization has been undertaken only relatively recently. So, in [2] the optimization problem of a planar Ackermann linkage has been investigated by the method of increasing the degree of freedom of mechanism. It is supposed that the function which is generated by the mechanism should ensure positions which are as near as possible to certain chosen positions (design points). For the optimization of a planar Ackermann linkage in [3] a method is applied w...
In the paper a rigorous method for the determination of the minimum value of the rated power of t... more In the paper a rigorous method for the determination of the minimum value of the rated power of the motor as well as the selection of the gear ratios of an electric vehicle transmission so that to ensure a given acceleration time from rest to a certain vehicle velocity is presented. After the acceleration characteristic of an electric vehicle is examined, the rated power optimization problem is treated when there is a single-gear and a multi-gear transmission. Taking into account different constraints, including that relating to the adhesion limit of the driven wheels, one reaches a nonlinear programming problem with constraints. One investigates also the case when motor inertia is neglected. The numerical exemplifications allow drawing more general conclusions.
International Journal of Vehicle Design, 2002
ABSTRACT By taking into account the case of motor-vehicle with continuously variable transmission... more ABSTRACT By taking into account the case of motor-vehicle with continuously variable transmission (CVT), the paper presents the motor vehicle velocity control that ensures the minimisation of the following criteria: (1) acceleration time; (2) accelerating time for a given travelled distance; (3) accelerating index. As a preliminary the analysis of the motion equation of a motor vehicle with CVT and of the phase trajectories emphasises certain peculiarities of motion regimes. The optimal control problem is appropriately formulated for the three criteria and solved by applying Pontryagin's maximum principle. It is shown that for the three criteria there are singular solutions of the optimal control problem. In the case of the criterion (1), for usual values of the CVT ratios, the numerical computations prove that the singular phase trajectory almost coincides with the trajectory corresponding to the CVT ratio which provides the ideal traction hyperbole. In the case of the criterion (2), depending on the final conditions, there are two singular solutions. The first of them is nearly enough to the solution of the criterion (1) when the given travelled distance is, in general, more than 500 m. The latter solution is very close to the singular solution of the criterion (1). In the case of the criterion (3), the singular trajectory is similar to the first solution of the criterion (2). The paper analyses different variants of optimal trajectories pointing out control switching points.
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Papers by Aurel Stoicescu