In today’s fast moving world, automobiles are facing challenges in terms of having to survive road accidents, increasing traffic, bad road-conditions and high/express ways. Brake systems play a vital role in controlling the vehicle speed while avoiding road accidents. The conventional brake systems consist of basically an actuator, transmission and frictional parts. This system is difficult for manipulated control by the driver during emergency and panic braking situations. In particular road and environmental conditions, it requires certain skill to have safe and effective brake control, which is always not possible from all drivers. Wheel locking is a predominant phenomenon during panic braking and this will cause vehicle skidding resulting in injuries and road accidents. In the case of a two-wheeler, being a single-track vehicle, skidding is one of the major causes for fatal road accidents due to loss in lateral balance. As the road safety regulations are becoming more stringent, the anti-lock brake systems (ABS) will replace the conventional brake systems in all road vehicles to avoid accidents and to improve vehicle safety. Early ABS systems, developed in the last 100-years, use intermittent and cyclic brake pressure control by sensing the wheel speed or wheel-slip as one of the major control inputs. Regulating the brake pressure with a preset threshold value is another method. These ABS systems have used electronics, or hydraulics or pure mechanical control. However, such ABS are not widely used in two-wheelers and other low cost vehicles till now, because of several limitations identified as follows: High cost, power supply needed for its operation in the case of intermittent and cyclic brake control, susceptibility to failure in the electronics system, interference from RF signals (from cell-phones for example), uneasiness to drivers from pedal pulsations with pedal noise, heavier weight, increased vehicle vibrations and failure modes of wheels due to torsional vibrations. The present research work is carried out to develop a new mechanical ABS concept, which will address most of the above problems. During braking, the change in rider-input force will change wheel reactions. This change is made proportional to the change in rider input force only upto wheel locking. Such a principle is used to develop the new mechanical ABS. The new concept regulates the output force from the ABS, by sensing the dynamic wheel reactions with increase in rider-response. The ABS output force is regulated by one of the following ways: (a) Slipping-down the lever-ratio or (b) preventing the excessive brake input force. Based on the parameters like less number of parts, least weight, simplicity, reliability, efficiency, durability, time-response, etc., the second method (of preventing the excessive brake input force) has been chosen. Further a new concept of ABS interconnecting system is proposed for usage between the front and rear wheels of the vehicle. This interconnecting system will ensure that the two mechanical ABS systems function at any kind of braking-balance between the front and rear applications. An analytical vehicle model has been developed with several input parameters like mass, geometry, inertia, aerodynamic properties, frictions of road and bearing-supports, road gradients, etc. From this analytical model, the dynamic wheel reactions and limiting adhesion of each tyre for various braking conditions are determined and the results are used to design the mechanical ABS. The same analytical model is used to predict the brake performance like stopping distance, vehicle deceleration and the vehicle speed variation for ideal braking conditions. The new ABS is modelled in Pro-E using the inputs from the analytical model. To evaluate the concept, a functional proto-type is built and fitted on a motorcycle. The ABS is evaluated for its functionality and performance at different road (level surface, up-gradients and down gradients) and environmental conditions (dry and wet road conditions). Using the VBOX II, proximate sensors and load-cells fitted on the vehicle, the vehicle stopping distance, wheel slip and pedal force are measured. The results show that wheel locking does not occur under panic driving conditions, which is the primary objective. In addition, the results show a good agreement with the predicted stopping distance and vehicle deceleration from the analytical model. As there is good scope for this new mechanical ABS for use in two-wheelers and other low cost vehicles, further research is needed to make this system work in curvilinear motion & banked surfaces.

Basically, to evaluate the operational performances of online auction is according to seller¡¦s transaction and investment in the auction website. Thus, how to maintain good relationship with the existing seller switching and attract new seller is the most attention and major care for auction service provider. However, there were few prior researches focused on the topic of online auction switching and examined from real case. In this study, we tried to develop a measuring model and explore the factors that relate to auction seller¡¦s switching. In July 2006, Yahoo! Kimo auction, the largest auction website in Taiwan, announced a new fee scheme which would charge 3 percent transaction handling fee on its sellers from Aug. 10. Many users expressed objection to the new charge scheme. During the same period, Ruten, a new joint venture auction website that combined eBay and Taiwanese portal operator PChome is nearly ready and makes some responding strategic approaches to attract new user. Many sellers of Yahoo! Kimo auction thought to switch auction provider. Base on the background, the study aim to explore auction seller¡¦s switching behavior through switching costs, including procedure costs, financial costs, and relational costs. Moreover, we examined how website quality, fee, anti-lock-in, and anti-switching affect switching intention and behavior. A total of 292 usable questionnaires were gathered through online surveys from auction discussion board and BBS. The data were analyzed by partial least squares (PLS) to test the hypotheses. We find that switching costs, website quality, fee have negative effect on seller¡¦s switching intention. Anti-lock-in and anti-switching have moderating effect in the model. According to the finding, we provide useful guidance for auction seller and auction service provider.

No description available.

This thesis contains the design and simulation test results for the implementation of a new all-wheel drive (AWD) torque vectoring (TV) control system. A separate algorithm using standard control methods is included in this study for a comparison. The proposed controller was designed to be applied to an AWD independent drive electric vehicle, however the main concepts can be re-purposed for other vehicle drive train configurations. The purpose of the control system is to assist the driver in achieving a desired vehicle trajectory whilst also maintaining stability and control of the vehicle. This is accomplished by measuring various real time parameters of the vehicle and using this information as feedback for the control system to act on. The focus of this thesis resides on the controller. Hence, this study assumes perfect observation of feedback parameters, therefore some uncertainties are not accounted for. Using feedback parameters, the control system will manage wheel slip whilst simultaneously generating a torque around the center of gravity of the vehicle by applying a torque differential between the left and right wheels. The proposed TV algorithm is simulated in MATLAB/Simulink along with another separate TV algorithm for comparison. Both algorithms are comprised of two main parts: a slip ratio controller applied to each wheel individually and stability controller that manages yaw rate and side slip of the vehicle. The new algorithm leverages the super twisting algorithm for the slip ratio controller and uses a fusion of a linear quadratic regulator with the integral term of a super twisting algorithm to implement the yaw rate and side slip controller. The other algorithm used for comparison derives its implementation for the slip ratio controller and yaw rate and side slip controllers from simple and standard first order sliding mode control methods. Both control algorithms were tested in three different main tests: anti-lock braking, sine dwell (SD) steering, and constant steering angle (CSA) tests. To increase the comprehensive nature of the study, the SD and CSA tests were simulated at 3 speeds (30,50, and 80 mph) and the steering angle parameter was varied from 2 to 24 degrees in increments of 2. The result of this study proves that the proposed controller is a feasible option for use in theory. Simulated results show advantages and disadvantages of the new controller with respect to the standard comparison controller. Both controllers are also shown to provide positive impacts on the vehicle response under most test conditions.

This work deals with the impact of selected electronic chassis systems of modern vehicles, their driving dynamics. The general aim of this work is to create the basic methodology for assessing casualties of the influence of these systems. The thesis is describing functions and effects antilock and stability systems on vehicle dynamics. Below are possible methods and systems for determining the influence on accident plot. As part of the study was performed measuring the impact of anti-lock system on the vehicle. The result of this work is the basic methodology to the analysis of road accidents involving vehicles with electronic chassis systems.

Many control algorithms for ABS systems have been proposed in the literature since the introduction of this equipment by Bosch in 1978. In general, one can divide these control algorithms into two different types: those based on a regulation logic with wheel acceleration thresholds that are used by most commercial ABS systems; and those based on wheel slip control that are preferred in the large majority of academic algorithms. Each approach has its pros and cons [Shida 2010]. Oversimplifying, one can say that the strength of the first ones is their robustness; while that of the latter ones their short braking distances (on dry grounds) and their absence of limit cycles. At the midpoint of this industry/academy dichotomy, based on the concept of extended braking stiffness (XBS), a quite different class of ABS control strategies has been proposed by several researchers (see, e.g., [Sugai 1999] and [Ono 2003]). This concept combines the advantages from both the industrial and academic approaches. Nevertheless, since the slope of the tyre characteristic is not directly measurable, it introduces the question of real-time XBS estimation. The first part of this thesis is devoted to the study of this estimation problem and to a generalization of the proposed technique to a larger class of systems. From the technological point of view, the design of ABS control systems is highly dependent on the ABS system characteristics and actuator performance. Current ABS control algorithms on passenger cars, for instance the Bosch ABS algorithm, are based on heuristics that are deeply associated to the hydraulic nature of the actuator. An interesting observation is that they seem to work properly only in the presence of a specific delay coming from the hydraulic actuation [Gerard 2012]. For brake systems that have different delays compared to those of hydraulic actuators, like electric in-wheel motors (with a smaller delay) or pneumatic trailer brakes (with a bigger delay), they might be no longer suitable [Miller 2013]. Therefore, adapting standard ABS algorithms to other advanced actuators becomes an imperative goal in the automobile industry. This goal can be reached by the compensation of the delays induced by actuators. The second part of this thesis is focused on this issue, and to the generalization of the proposed technique to a particular class of nonlinear systems. Throughout this thesis, we employ two different linearization techniques: the linearization of the error dynamics in the construction of model-based observers [Krener 1983] and the linearization based on restricted state feedback [Brockett 1979]. The former is one of the simplest ways to build an observer for dynamical systems with output and to analyze its convergence. The main idea is to transform the original nonlinear system via a coordinate change to a special form that admits an observer with a linear error dynamics and thus the observer gains can be easily computed to ensure the observer convergence. The latter is a classical method to control nonlinear systems by converting them into a controllable linear state equation via the cancellation of their nonlinearities. It is worth mentioning that existing results for observer design by error linearization in the literature are only applied to the case of regular time scalings ([Guay 2002] and [Respondek 2004]). The thesis shows how to extend them to the case of singular time scalings. Besides, the thesis combines the classical state feedback linearization with a new method for the input delay compensation to resolve the output tracking problem for restricted feedback linearizable systems with input delays.

No description available.

Depuis l'introduction du premier système ABS par Bosch, en 1978, de nombreux algorithmes de commande pour les systèmes ABS ont été proposés dans la littérature. En général, ces algorithmes peuvent être divisés en deux catégories : ceux basés sur une logique de régulation déterminée par des seuils sur l'accélération angulaire des roues et ceux basés sur la régulation du taux de glissement. Chaque approche a ses avantages et ses inconvénients. D'une manière simplifiée, on peut dire que le point fort du premier type est sa robustesse ; tandis que ceux du deuxième type sont leur courte distance de freinage (sur les terrains secs) et leur absence de cycles limite. Au milieu de cette dichotomie industrielle/académique, en se basant sur un concept appelé extended braking stiffness (XBS), une classe complètement différente de stratégies de commande pour l'ABS a été proposée par certains chercheurs. Ce concept combine les avantages des deux approches. Néanmoins, puisque l’XBS n'est pas directement mesurable, elle introduit la question de son estimation en temps réel. La première partie de cette thèse est consacrée à l'étude de ce problème d'estimation et à une généralisation de la technique proposée à une plus grande classe de systèmes. D'un point de vue technologique, la conception des systèmes de contrôle pour l'ABS est fortement dépendante des caractéristiques physiques du système et des performances de l'actionneur. Les algorithmes de commande actuels pour l'ABS sur les véhicules, par exemple l'algorithme ABS de Bosch, sont basés sur des approches heuristiques qui sont profondément liées à la nature hydraulique de l'actionneur. Ils ne fonctionnent correctement qu'en présence d'un retard spécifique associé à la nature hydraulique de l'actionneur. Pour les systèmes de freinage qui ont un retard différent de ceux des actionneurs hydrauliques, comme les moteurs-roues électriques par exemple (un retard plus court) ou les freins pneumatiques des semi-remorques (un retard plus grand), ils ne sont plus appropriés et ont un fonctionnement déficient. Par conséquent, l'adaptation des algorithmes standards de l'ABS pour d'autres actionneurs avancés devient un objectif primordial dans l'industrie automobile. Cet objectif peut être atteint par la compensation des retards induits par les actionneurs. La deuxième partie de cette thèse se concentre sur cette question, et à la généralisation de la technique proposée à une classe particulière de systèmes non linéaires.Tout au long de cette thèse, nous utilisons deux techniques de linéarisation différentes : la linéarisation de la dynamique d'erreur dans la construction des observateurs basés sur des modèles et la linéarisation basée sur le retour d'état restreint. La première est l'une des façons les plus simples pour synthétiser un observateur pour des systèmes dynamiques avec sortie et pour analyser sa convergence. L'idée principale est de transformer le système non linéaire original via un changement de coordonnées en un système différemment formalisé, qui admette un observateur avec une dynamique d'erreur linéaire et les gains de l'observateur peuvent donc être facilement calculés pour en assurer la convergence. Cette dernière est une méthode classique pour commander des systèmes non linéaires en les convertissant en une équation d'état linéaire contrôlable via l'annulation de leurs non-linéarités. Il convient de mentionner que les résultats existants pour la synthèse des observateurs par la linéarisation de l'erreur dans la littérature ne sont appliqués que pour le cas des changements réguliers de l'échelle de temps. Cette thèse explique comment les étendre aux cas des changements singuliers de l'échelle de temps. Par ailleurs, la thèse combine la linéarisation classique par retour d'état avec une nouvelle méthode de compensation du retard de l'entrée pour résoudre le problème de suivi de la sortie pour des systèmes linéarisables par retour d'état restreint avec des retards de l'entrée. / Many control algorithms for ABS systems have been proposed in the literature since the introduction of this equipment by Bosch in 1978. In general, one can divide these control algorithms into two different types: those based on a regulation logic with wheel acceleration thresholds that are used by most commercial ABS systems; and those based on wheel slip control that are preferred in the large majority of academic algorithms. Each approach has its pros and cons [Shida 2010]. Oversimplifying, one can say that the strength of the first ones is their robustness; while that of the latter ones their short braking distances (on dry grounds) and their absence of limit cycles. At the midpoint of this industry/academy dichotomy, based on the concept of extended braking stiffness (XBS), a quite different class of ABS control strategies has been proposed by several researchers (see, e.g., [Sugai 1999] and [Ono 2003]). This concept combines the advantages from both the industrial and academic approaches. Nevertheless, since the slope of the tyre characteristic is not directly measurable, it introduces the question of real-time XBS estimation. The first part of this thesis is devoted to the study of this estimation problem and to a generalization of the proposed technique to a larger class of systems. From the technological point of view, the design of ABS control systems is highly dependent on the ABS system characteristics and actuator performance. Current ABS control algorithms on passenger cars, for instance the Bosch ABS algorithm, are based on heuristics that are deeply associated to the hydraulic nature of the actuator. An interesting observation is that they seem to work properly only in the presence of a specific delay coming from the hydraulic actuation [Gerard 2012]. For brake systems that have different delays compared to those of hydraulic actuators, like electric in-wheel motors (with a smaller delay) or pneumatic trailer brakes (with a bigger delay), they might be no longer suitable [Miller 2013]. Therefore, adapting standard ABS algorithms to other advanced actuators becomes an imperative goal in the automobile industry. This goal can be reached by the compensation of the delays induced by actuators. The second part of this thesis is focused on this issue, and to the generalization of the proposed technique to a particular class of nonlinear systems. Throughout this thesis, we employ two different linearization techniques: the linearization of the error dynamics in the construction of model-based observers [Krener 1983] and the linearization based on restricted state feedback [Brockett 1979]. The former is one of the simplest ways to build an observer for dynamical systems with output and to analyze its convergence. The main idea is to transform the original nonlinear system via a coordinate change to a special form that admits an observer with a linear error dynamics and thus the observer gains can be easily computed to ensure the observer convergence. The latter is a classical method to control nonlinear systems by converting them into a controllable linear state equation via the cancellation of their nonlinearities. It is worth mentioning that existing results for observer design by error linearization in the literature are only applied to the case of regular time scalings ([Guay 2002] and [Respondek 2004]). The thesis shows how to extend them to the case of singular time scalings. Besides, the thesis combines the classical state feedback linearization with a new method for the input delay compensation to resolve the output tracking problem for restricted feedback linearizable systems with input delays.