Thèses sur le sujet « Active Braking »

This study is performed to identify the customer braking behaviors of Articulated haulers. The data files from the different customer sites are used to analyses the data. The braking definition for the braking event was created to identify the braking events by using of output braking pressure. Also the statistical features related to the vehicle were calculated for  identified braking events. Furthermore the braking events were classified according to the classification rules which were created based on calculated statistical features.The final results ( classification)  motivates and satisfies with the  aim of the project.

This thesis investigates the principle of integrated vehicle dynamics control through proposing a new control configuration to coordinate active steering subsystems and dynamic stability control (DSC) subsystems. The active steering subsystems include Active Front Steering (AFS) and Active Rear Steering (ARS); the dynamic stability control subsystems include driveline based, brake based and driveline plus brake based DSC subsystems. A nonlinear vehicle handling model is developed for this study, incorporating the load transfer effects and nonlinear tyre characteristics. This model consists of 8 degrees of freedom that include longitudinal, lateral and yaw motions of the vehicle and body roll motion relative to the chassis about the roll axis as well as the rotational dynamics of four wheels. The lateral vehicle dynamics are analysed for the entire handling region and two distinct control objectives are defined, i.e. steerability and stability which correspond to yaw rate tracking and sideslip motion bounding, respectively. Active steering subsystem controllers and dynamic stability subsystem controller are designed by using the Sliding Mode Control (SMC) technique and phase-plane method, respectively. The former is used as the steerability controller to track the reference yaw rate and the latter serves as the stability controller to bound the sideslip motion of the vehicle. Both stand-alone controllers are evaluated over a range of different handling regimes. The stand-alone steerability controllers are found to be very effective in improving vehicle steering response up to the handling limit and the stand-alone stability controller is found to be capable of performing the task of maintaining vehicle stability at the operating points where the active steering subsystems cannot. Based on the two independently developed stand-alone controllers, a novel rule based integration scheme for AFS and driveline plus brake based DSC is proposed to optimise the overall vehicle performance by minimising interactions between the two subsystems and extending functionalities of individual subsystems. The proposed integrated control system is assessed by comparing it to corresponding combined control. Through the simulation work conducted under critical driving conditions, the proposed integrated control system is found to lead to a trade-off between stability and limit steerability, improved vehicle stability and reduced influence on the longitudinal vehicle dynamics.

Advances in electronic technology have had a profound impact on the design and development of modern vehicle systems. These advances have provided the basis for a research into active vehicle control paradigm with the aim of improving vehicle safety and its dynamic performance. The vehicle stability control (VSC) concept has recently been born in response to such a research challenge. Its refinement is looking for an algorithm able of integrating vehicle dynamics control (IVDC) by way of coordinating the active front steering (AFS) system and direct yaw-moment control (DYC) system. Thus, when the vehicle is in the normal driving situation, the AFS system is involved for handling enhancement; however, as the vehicle reaches the handling limits, both the AFS and DYC systems are integrated to ensure the vehicle stability. Recent research into VSC has indicated that the IVDC concept may be able to enhance the handling and stability of ground vehicle by controlling the main two control objectives, yaw rate and body sideslip angle, effectively in severe cornering manoeuvres and the steady-state condition, and several control strategies have been investigated to design an IVDC system. However, most of these control methods have not been focused on improving the transient response for vehicle yaw rate and sideslip angle tracking controllers in the presence of vehicle dynamics uncertainties and external disturbance. Therefore, further improvement of the transient response for the tracking controllers is still the most needed research topics.
Thesis (Masters)
Master of Philosophy (MPhil)
Griffith School of Engineering
Full Text

Active safety systems for road vehicles have been improved considerably in recent years along with technological advances and the increasing demand for road safety. In the development route of active safety systems which started with introduction of digital controlled ABS in the late seventies, vehicle stability control systems have been developed which today, with an integration approach, incorporate ABS and other previously developed active safety technologies. ABS, as a main part of this new structure, still maintains its importance. In this thesis, a design methodology of an antilock braking system controller for four wheeled road vehicles is presented with a detailed simulation work. In the study, it is intended to follow a flexible approach for integration with unified control structure of an integrated active safety system. The objective of the ABS controller, as in the previous designs in literature, is basically to provide retention of vehicle directional control capability and if possible shorter braking distances by controlling the wheel slip during braking. iv A hierarchical structure was adopted for the ABS controller design. A high-level controller, through vehicle longitudinal acceleration based estimation, determines reference slip values and a low-level controller attempts to track these reference slip signals by modulating braking torques. Two control alternatives were offered for the design of the low-level controller: Fuzzy Logic Control and PID Control. Performance of the ABS controller was analyzed through extensive simulations conducted in MATLAB/Simulink for different road conditions and steering maneuvers. For simulations, an 8 DOF vehicle model was constructed with nonlinear tires.

Durch das I-FAS der TU Chemnitz wurde im Rahmen des AKTIV-Projektes eine Probandenstudie zur Akzeptanz von Systemausprägungen einer Aktiven Gefahrenbremsung (AGB) bei PKW durchgeführt. Unter Verwendung eines stehenden Hindernisses wurden sechs Systemausprägungen verglichen, die von den AGB-Partnern in zwei Versuchsträger implementiert wurden. Die sechs Systemausprägungen werden nahezu identisch bewertet, solange Probanden keine Vergleichsmöglichkeit zu anderen Systemausprägungen haben. Wenn es zu einem Fahrereingriff kommt, ist der Eingriffszeitpunkt des Fahrers unabhängig von der gefahrenen Systemausprägung.

[EN] Nowadays, there are many electronic products that incorporate elements and features coming from the research in the field of mobile robotics. For instance, the well-known vacuum cleaning robot Roomba by iRobot, which belongs to the field of service robotics, one of the most active within the sector. There are also numerous autonomous robotic systems in industrial warehouses and plants. It is the case of Autonomous Guided Vehicles (AGVs), which are able to drive completely autonomously in very structured environments. Apart from industry and consumer electronics, within the automotive field there are some devices that give intelligence to the vehicle, derived in most cases from advances in mobile robotics. In fact, more and more often vehicles incorporate Advanced Driver Assistance Systems (ADAS), such as navigation control with automatic speed regulation, lane change and overtaking assistant, automatic parking or collision warning, among other features. However, despite all the advances there are some problems that remain unresolved and can be improved. Collisions and rollovers stand out among the most common accidents of vehicles with manual or autonomous driving. In fact, it is almost impossible to guarantee driving without accidents in unstructured environments where vehicles share the space with other moving agents, such as other vehicles and pedestrians. That is why searching for techniques to improve safety in intelligent vehicles, either autonomous or manual-assisted driving, is still a trending topic within the robotics community. This thesis focuses on the design of tools and techniques for planning and control of intelligent vehicles in order to improve safety and comfort. The dissertation is divided into two parts, the first one on autonomous driving and the second one on manual-assisted driving. The main link between them is the use of clothoids as mathematical formulation for both trajectory generation and collision detection. Among the problems solved the following stand out: obstacle avoidance, rollover avoidance and advanced driver assistance to avoid collisions with pedestrians.
[ES] En la actualidad se comercializan infinidad de productos de electrónica de consumo que incorporan elementos y características procedentes de avances en el sector de la robótica móvil. Por ejemplo, el conocido robot aspirador Roomba de la empresa iRobot, el cual pertenece al campo de la robótica de servicio, uno de los más activos en el sector. También hay numerosos sistemas robóticos autónomos en almacenes y plantas industriales. Es el caso de los vehículos autoguiados (AGVs), capaces de conducir de forma totalmente autónoma en entornos muy estructurados. Además de en la industria y en electrónica de consumo, dentro del campo de la automoción también existen dispositivos que dotan de cierta inteligencia al vehículo, derivados la mayoría de las veces de avances en robótica móvil. De hecho, cada vez con mayor frecuencia los vehículos incorporan sistemas avanzados de asistencia al conductor (ADAS por sus siglas en inglés), tales como control de navegación con regulación automática de velocidad, asistente de cambio de carril y adelantamiento, aparcamiento automático o aviso de colisión, entre otras prestaciones. No obstante, pese a todos los avances siguen existiendo problemas sin resolver y que pueden mejorarse. La colisión y el vuelco destacan entre los accidentes más comunes en vehículos con conducción tanto manual como autónoma. De hecho, la dificultad de conducir en entornos desestructurados compartiendo el espacio con otros agentes móviles, tales como coches o personas, hace casi imposible garantizar la conducción sin accidentes. Es por ello que la búsqueda de técnicas para mejorar la seguridad en vehículos inteligentes, ya sean de conducción autónoma o manual asistida, es un tema que siempre está en auge en la comunidad robótica. La presente tesis se centra en el diseño de herramientas y técnicas de planificación y control de vehículos inteligentes, para la mejora de la seguridad y el confort. La disertación se ha dividido en dos partes, la primera sobre conducción autónoma y la segunda sobre conducción manual asistida. El principal nexo de unión es el uso de clotoides como elemento de generación de trayectorias y detección de colisiones. Entre los problemas que se resuelven destacan la evitación de obstáculos, la evitación de vuelcos y la asistencia avanzada al conductor para evitar colisiones con peatones.
[CAT] En l'actualitat es comercialitzen infinitat de productes d'electrònica de consum que incorporen elements i característiques procedents d'avanços en el sector de la robòtica mòbil. Per exemple, el conegut robot aspirador Roomba de l'empresa iRobot, el qual pertany al camp de la robòtica de servici, un dels més actius en el sector. També hi ha nombrosos sistemes robòtics autònoms en magatzems i plantes industrials. És el cas dels vehicles autoguiats (AGVs), els quals són capaços de conduir de forma totalment autònoma en entorns molt estructurats. A més de en la indústria i en l'electrònica de consum, dins el camp de l'automoció també existeixen dispositius que doten al vehicle de certa intel·ligència, la majoria de les vegades derivats d'avanços en robòtica mòbil. De fet, cada vegada amb més freqüència els vehicles incorporen sistemes avançats d'assistència al conductor (ADAS per les sigles en anglés), com ara control de navegació amb regulació automàtica de velocitat, assistent de canvi de carril i avançament, aparcament automàtic o avís de col·lisió, entre altres prestacions. No obstant això, malgrat tots els avanços segueixen existint problemes sense resoldre i que poden millorar-se. La col·lisió i la bolcada destaquen entre els accidents més comuns en vehicles amb conducció tant manual com autònoma. De fet, la dificultat de conduir en entorns desestructurats compartint l'espai amb altres agents mòbils, tals com cotxes o persones, fa quasi impossible garantitzar la conducció sense accidents. És per això que la recerca de tècniques per millorar la seguretat en vehicles intel·ligents, ja siguen de conducció autònoma o manual assistida, és un tema que sempre està en auge a la comunitat robòtica. La present tesi es centra en el disseny d'eines i tècniques de planificació i control de vehicles intel·ligents, per a la millora de la seguretat i el confort. La dissertació s'ha dividit en dues parts, la primera sobre conducció autònoma i la segona sobre conducció manual assistida. El principal nexe d'unió és l'ús de clotoides com a element de generació de trajectòries i detecció de col·lisions. Entre els problemes que es resolen destaquen l'evitació d'obstacles, l'evitació de bolcades i l'assistència avançada al conductor per evitar col·lisions amb vianants.
Girbés Juan, V. (2016). Clothoid-based Planning and Control in Intelligent Vehicles (Autonomous and Manual-Assisted Driving) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/65072
TESIS

La traversée d’intersection constitue une tâche typique dans laquelle plusieurs affordances coexistent, l’une traduisant les possibilités de franchir l’intersection, l’autre traduisant les possibilités d’immobiliser le véhicule afin d’éviter une collision. En nous inspirant des travaux de Gibson et Crooks (1938), nous avons formalisé les affordances Field of Safe Travel (FST) et Minimum Stopping Zone (MSZ) en termes de temps critique pour réussir le franchissement d’intersection et l’immobilisation du véhicule, respectivement. Grâce à un dispositif de réalité virtuelle et un simulateur de conduite, nous avons testé la prise en compte de ces affordances par un agent engagé dans la tâche de référence à travers trois expérimentations. Les résultats, appuyés par notre modèle de prise de décision, montrent que le conducteur intègre non seulement l’affordance FST, mais aussi l’affordance MSZ, dans sa décision de franchir l’intersection. De plus, l’utilisation conjointe de ces deux affordances rend compte des régulations de vitesses produites par un agent devant réaliser la tâche de franchissement en présence d’un véhicule préprogrammée ou soumis au contrôle d’un autre agent. Ces différents résultats montrent que les agents prennent en compte les différentes possibilités qui leur sont offertes (affordances FST et MSZ) pour faire un choix adapté et réguler leur vitesse
Crossing an intersection is a typical task in which several affordances coexist, one offering the possibilities to safely cross the intersection (the main goal) and another offering the possibilities to stop the driving car to avoid a collision (the alternative goal). Based on Gibson and Crooks’ works (1938), we formalized the so-called Field of Safe Travel (FST) and Minimum Stopping Zone (MSZ) affordances in terms of critical time for safe crossing and for safe stopping, respectively. Using a virtual reality set-up with a driving simulator, three experiments have been designed to test the role of these two affordances on the decision-making and the regulation of action process. Our results, supported by a model of decision-making, reveal that drivers rely not only on the FST affordance, but also on the MSZ affordance, to choose to cross-or-not the intersection. Moreover, the joint use of these affordances is still observed when drivers have to control their velocity to perform the task when either a vehicle with a computed kinematic or a car driven by another agent is approaching. Put together, these results show that drivers take into account several possibilities for action offered by the environment (FST and MSZ affordances) to make a suitable choice and to control their speed when approaching an intersection

This thesis analyses driving dynamics of tractors and its dependence on their weight and age. In the beginning, brief history of tractor development and definition of basic concept of the tractor analysis is described. The thesis states procedures for obtaining magnitudes necessary for determining of driving dynamics. Experimental part describes the realized measurement on chosen sample of tractors and interprets measured values. Last part of the thesis contains evaluation of the measurement results.

碩士
國立臺北科技大學
車輛工程系碩士班
91
In a conventional active brake system, the hydraulic actuator is applied to actively operate a brake system. However, many accessories are needed in the brake system so that the system requires more space and more cost. This research will improve a conventional vacuum booster in a brake system so that drivers can switch the brake system between an active system and a conventional system. When the brake system is switched to the active system, a solenoid valve is used to change the pressure difference in the vacuum booster to control braking force. The proposed vacuum booster will use the pressure difference between intake manifold and atmosphere. This device is a highly nonlinear system and the sliding control will be used to design a controller for the braking force control. In this research, Matlab/Simulink will be used to simulate braking force control and the proposed system will be applied to the intelligent cruise control. Because only a solenoid valve is added to the original vacuum booster, the proposed system will not occupy any extra space and will not increase component cost. The proposed system will provide the sufficient braking force for intelligent cruise control, traction control, deceleration control, and hill holder.

The decreasing number of road accidents in Europe is correlated to the massive application of active safety systems on the vehicles. The evolution of advanced safety technologies, unfortunately does not apply also to Powered Two-Wheelers (PTWs). The raising trend of PTWs circulation in the streets has not been followed by an equal development of innovative active safety systems for those vehicles. The complex dynamics of PTWs slows down the design of new technologies and limits the possibility to find relevant solutions to address crucial aspects for road safety, as the vehicle stability under emergency situations. That points out the necessity to develop new advanced riding assistance systems able to enhance the riders and PTWs safety. Accordingly, the present work studies the potentialities of the current braking systems for PTWs application and describes the design of a new braking system. Relevant issues related to the development of the advanced braking system, as the real-time estimation of the vehicle speed and tire-road friction, are addressed. Fall detection parameters, used to control the stability of the vehicle during emergency maneuvers, are defined and verified by virtual and experimental data. The analysis of different aspects correlated to the braking dynamics of PTWs gave the possibility to define a new concept of braking force modulation applicable in case of loss of stability. Rationales, benefits and limitations of this new safety function, named Active Braking Control (ABC), are presented in detail. The virtual tests carried out to assess the potentialities of the system, demonstrated the effectiveness of the new braking force modulation strategy, in terms of improvement of vehicle stability and control.

Over the last years, the development of new technologies and active safety systems for on-road vehicles contributed to mitigate the burden of road traffic crashes. This, unfortunately, did not fully apply to Powered Two-Wheelers (PTWs), for which the technological development was slowed down by their complex dynamics, smaller research interests and lower vehicle cost. Despite PTWs have one of the highest rates of crashes per kilometre travelled, their distribution is growing all over the world, thanks to their affordability and their agility in congested traffic environments, causing every year many crashes and fatalities. After the introduction of Antilock Braking System (ABS), which already showed its efficacy in preventing crashes, several studies indicated that Motorcycle Autonomous Emergency Braking (MAEB), which is the PTW derivative of the passenger car Autonomous Emergency Braking (AEB), is the most promising technology to mitigate PTW crashes among those currently in development. This technology, which deploys autonomously a braking action to reduce impact speed when an imminent collision is detected, was shown to be potentially effective and widely applicable in PTW crashes. However, to introduce such a system on standard PTWs, the riding conditions in which it can be applicable and its working parameters must be identified to maximise crash mitigation effects while not reducing PTW controllability and safety. This requires designing MAEB intervention in accordance with riders’ capabilities to manage the vehicle in pre-crash conditions. The present work aimed to investigate the real-world applicability of MAEB and its acceptability among end-users. The goal of this study was to identify pre-crash riding conditions and system intervention parameters which can make MAEB applicable in real-world crashes, accepted by end-users and effective in mitigating injuries. For this purpose, a field test campaign conducted within the EU founded PIONEERS project was carried out, involving 35 participants and two test vehicles provided with automatic braking devices able to simulate MAEB intervention in realistic riding conditions. The results of this field test campaign, analysed through different publications, indicate the safe applicability of MAEB in conditions representative of real-world riding. The designed MAEB working parameters resulted capable to reduce vehicle speed while guaranteeing the controllability of the PTW with limited effort required to the rider. The end-users who tested the system indicated good acceptability of MAEB encouraging its final development and its implementation on standard vehicles. Finally, the potential benefits of MAEB application in real-world crashes have been estimated through real-world crashes simulations, highlighting the relevant impact of MAEB in terms of injury and fatality mitigation potential.

碩士
國立臺灣師範大學
工業教育學系
102
This thesis mainly evaluates a brake regenerative system in electric vehicles (EVs) by using the Matlab/Simulink software package in order to recovering the optimal brake energy. The system consists of a high-power motor, a mechanical brake, lithium battery etc.. After the vehicle load information is sent to the vehicle dynamics model, the optimal brake control is conducted. We modeled the active and passive braking model based on the high-power motor dynamics. The rule-based control was used for the energy optimization. The regenerative energy was analyzed, and the optimal control model was verified and then modified. The active brake system activates the regenerative brake first, and then the mechanical brake compensates the rest of the energy. The passive energy uses the mechanical brake for the main brake power, while the regenerative brake compensates the rest. To accurately simulate the braking energy while driving, the real brake energy tested on the chassis dynamometer was compared to the model. The test brake energy was 13828 kJ, while the simulated one was 13670 kJ. The difference is only 1.14%, which indicates that the physical model can precisely emulated the vehicle brake operation. In order to comparing the effect of vehicle speed to the brake energy, three initial speeds (30 km/h, 60 km/h, and 90 km/h) and three braking time (10 sec., 20 sec., and 30 sec.) are set to be the braking conditions. Meanwhile, to simulate the normal driving, two driving cycles: FTP-75 and ECE40 are selected for the evaluation of brake regeneration. Simulation results show that with shorter braking time and higher initial speed, the regenerative brake recovers more energy. From the optimal energy recovery, the active brake system can recover 4.38% of total consumed energy, while the passive brake system recovers 0.24%. The active brake system recovers 18.25 times energy than the passive brake system.

碩士
國立暨南國際大學
電機工程學系
92
This thesis develops a nonlinear anti-lock braking system combined with active suspensions applied to a quarter-car model by employing nonlinear and adaptive backstepping design schemes. In driving emergency, a driver always reacts to exert great efforts to step on the brake pedal in order to stop the car immediately. If the braking torque is large enough to lock wheels, then the vehicle may solely slide on the road surface and must need more braking time and distance to stop. An anti-lock braking system is able to release the wheel-locking situation and assist the car to stop at shorter distance. Although the braking distance can be reduced by the control torque from disk/drum brakes, the braking time and distance can be further improved if the normal force generated from active suspension systems is considered simultaneously. Individual controller is designed for each subsystem and an integrated algorithm is constructed to coordinate these two subsystems. As a result, the integration of antilock braking and active suspension systems indeed enhances the system performance because of reduction of braking time and distance. In addition, variation of road conditions is usually known while driving a car. Hence, a nonlinear adaptive backstepping control scheme is employed for the design of our anti-lock braking system to guarantee that our controller has the ability to adapt for various road surfaces. Finally, some comparative simulations are given to illustrate the excellent performance of our integrated anti-lock braking system.

碩士
國立暨南國際大學
電機工程學系
99
This thesis investigates the integration of various subsystems of an automobiles chassis. The specific focus of this research is the control design of anti-lock braking systems (ABS) combined with active suspension systems (ASS) applied to a half-car model. The performance objective for the integrated approach is defined as the reduction of longitudinal velocity in both braking time and braking distance. The braking distance not only can be decreased by supplying braking torque from driver stepping on the brake pedal, but also can be further improved if the normal force generated from ASS is considered in the meanwhile. Above all, a mathematical model of a half-car is established for the braking and suspension dynamics, and then the controllers designed by nonlinear backstepping scheme are developed to achieve our control objectives. Braking distance judgment and better braking performance capability are major skills required for a safe drive in all road conditions. The friction coefficient could be variant because of different road conditions, we so an appropriate proportion algorithm is proposed to make our controllers adapt various kinds of road conditions. For achieving maximum braking performance, fully applying suitable coordination between both front and rear brakes without locking either wheel must be considered and investigated. That is, individual controllers are developed for the subsystems and a governing algorithm is constructed to coordinate the controllers of these subsystems. Hence, a nonlinear controller designed by adaptive backstepping scheme is developed for ABS to guarantee that the controllers possess the potentials to adapt it self for uncertainty of vehicle mass.

In this study, various stability control systems are developed to remove the lateral instability of a conventional articulated steer vehicle (ASV) during the oscillatory yaw motion or “snaking mode”. First, to identify the nature of the instability, some analyses are performed using several simplified models. These investigations are mainly focused on analyzing the effects of forward speed and of two main subsystems of the vehicle, the steering system and tires, on the stability. The basic insights into the stability behavior of the vehicle obtained from the stability analyses of the simplified models are verified by conducting some simulations with a virtual prototype of the vehicle in ADAMS. To determine the most critical operating condition with regard to the lateral stability and to identify the effects of vehicle parameters on the stability, various studies are performed by introducing some modifications to the simplified models. Based on these studies, the disturbed straight-line on-highway motion with constant forward speed is recognized as the most critical driving condition. Also, the examinations show that when the vehicle is traveling with differentials locked, the vehicle is less prone to the instability. The examinations show that when the vehicle is carrying a rear-mounted load having interaction with ground, the instability may happen if the vehicle moves on a relatively good off-road surface. Again, the results gained from the analyses related to the effects of the vehicle parameters and operating conditions on the stability are verified using simulations in ADAMS by making some changes in the virtual prototype for any case. To stabilize the vehicle during its most critical driving condition, some studies are directed to indicate the shortcomings of passive methods. Alternative solutions, including design of different types of stability control systems, are proposed to generate a stabilizing yaw moment. The proposed solutions include an active steering system with a classical controller, an active torque vectoring device with a robust full state feedback controller, and a differential braking system with a robust variable structure controller. The robust controllers are designed by using simplified models, which are also used to evaluate the ability to deal with the uncertainties of the vehicle parameters and its variable operating conditions. These controllers are also incorporated into the virtual prototype, and their capabilities to stabilize the vehicle in different operating conditions and while traveling on different surfaces during the snaking mode are shown.

碩士
元智大學
資訊工程學系
106
In advanced driver assistance system (ADAS), non-timely braking action is one of the important issues because it makes drivers exposed to a terrible and dangerous driving environment. For this reason, predicting driver braking action early and accurately must appear up, which can lower the potential of unsafe driving behavior and provide drivers more time to react. In this paper, we have sensory fusion data source from inside and outside of the car and our proposed multi-layer deep learning architecture (CBL) to predict braking action, which consists of convolutional neural network (CNN) and bidirectional long short-term memory units (BL) while CNN is good at extracting driving characteristic and BL is useful for keeping time-series data. The result points that the CBL performs much better than the other two architectures: bidirectional LSTM (BL) and uni-LSTM (UL) based on the high accuracy and f-score, and it also shows leave-one-out cross validation for drivers and many interesting differences in the speed, turning and intersection from time -5s to 0s.

Dissertação de mestrado em Engenharia Eletrónica Industrial e de Computadores
Grande parte da energia elétrica consumida em todo o mundo está relacionada com o uso de motores elétricos, concretamente com o uso de motores de indução trifásicos em aplicações industriais. O acionamento destes motores por variadores eletrónicos de velocidade (VEVs) é uma solução relativamente recente, no entanto, já bastante utilizada na indústria. Por norma, os VEVs para motores de indução empregam uma ponte retificadora a díodos com o intuito de fornecer potência ao barramento CC a partir da rede elétrica. Apesar de este tipo de retificadores ser uma solução económica, estes contribuem para a degradação da qualidade de energia elétrica, dado que consomem correntes com elevado conteúdo harmónico que, por sua vez, provocam distorções na forma de onda da tensão e baixo fator de potência a montante do VEV. Além disso, não permitem inverter o fluxo de energia, tornando, por isso, inviável o processo de travagem regenerativa. Os conversores CA-CC ativos, ou retificadores ativos, surgem desta forma como solução aos problemas de qualidade de energia elétrica dos conversores CA-CC tradicionais, permitindo o consumo de corrente sinusoidal, com fator de potência unitário, o controlo da tensão ou corrente do barramento CC e um fluxo bidirecional de potência. Deste modo, a presente dissertação visa o estudo teórico, implementação e respetiva comprovação experimental de um acionamento eletrónico de velocidade variável, com conversor CA-CC ativo trifásico e conversor CC-CA trifásico do tipo fonte de tensão, para motores de indução. A solução proposta é capaz de permitir, para além do controlo da velocidade de rotação do motor, o arranque e paragem suave, a troca rápida de velocidade (na qual se inclui também a inversão do sentido de rotação), consumo de correntes sinusoidais, equilibradas e em fase com as tensões da rede elétrica e ainda a operação no modo bidirecional, viabilizando a injeção de energia à rede elétrica em processos de travagem ou inversão de velocidade do motor.
A large amount of the electricity consumed worldwide is related to the use of electric motors, specifically with the use of three-phase induction motors in industrial applications. The use of variable speed drives (VSDs) in these motors is a relatively recent solution, however, already widely used in the industry. Normally, the VSDs for induction motors employ a diode bridge rectifier in order to supply power to the DC-link from the electrical power grid. Although this type of rectifiers is an economical solution, they contribute to the degradation of the electric power quality, since they consume currents with high harmonic content that, consequently, cause distortions in the voltage waveforms and low power factor upstream the VSD. In addition, they do not allow the energy flow to be reversed, making the regenerative braking process impracticable. The active AC-DC converters, or active rectifiers, appear as a solution to the electrical power quality problems of traditional AC-DC converters, allowing a sinusoidal current consumption, with unitary power factor, voltage or current control of the DC-link and a bidirectional power flow. Thus, the present dissertation aims at the theoretical study, implementation and respective experimental verification of an electronic variable speed drive (VSD) for induction motors using a three-phase active AC-DC converter and a three-phase DC-AC converter of the voltage source type. Besides controlling the rotational speed of the motor, the proposed solution is capable of allowing the start and soft stop, quick speed changes (which also includes the reversal of the rotation direction), sinusoidal current consumption in phase with the power grid voltage and also the operation in bidirectional mode, making possible the injection of energy into the power grid in breaking processes or motor rotation reversal.
Este trabalho de mestrado está enquadrado no projeto de IC&DT “Quality4Power - Enhancing the Power Quality for Industry 4.0 in the era of Microgrids”, financiado pela Fundação para a Ciência e Tecnologia, com a referência PTDC/EEI-EEE/28813/2017.
Este trabalho de mestrado está enquadrado no projeto de IC&DT “DAIPESEV – Development of Advanced Integrated Power Electronic Systems for Electric Vehicles”, financiado pela Fundação para a Ciência e Tecnologia, com a referência PTDC/EEI‑EEE/30382/2017.