Academic literature on the topic 'Tractors – Transmission devices – Control'

Service and repair of operating and servicing organizations are largely equipped with outdated, low-power, highly specialized bench equipment from former specialized enterprises and do not always meet the technical requirements of the manufacturer, especially for conducting quality control programs for the repair of powerful and modern tractors. These circumstances together reduce the reliability of the obtained diagnostic parameters and may lead to the risk of errors in determining the technical readiness of the repaired equipment, in particular, internal combustion engines, transmission units and chassis, hydraulic drive. (Research purpose) The research purpose is in developing a mobile control and diagnostic device for monitoring the power and fuel consumption of the internal combustion engine, as well as the quality of repair of hydrostatic transmission and hydraulic drive units. (Materials and methods) The article presents an analysis of scientific works on improving methods for diagnosing energy indicators of mobile agricultural machinery, as well as conducted extensive research on the use of axial plunger pumps and throttling the flow of liquid injected by them with a constant and variable cross-section throttle for engine braking. (Results and discussion) Authors developed an experimental model of a mobile control and diagnostic device and experimentally tested the methods for determining its parameters and control and diagnostic operations. (Conclusions) The use of the proposed mobile control and diagnostic device will eliminate excessive fuel consumption by tractors when reducing the effective power of their internal combustion engines below the permissible limits, and will also allow the diagnosis of hydrostatic transmission units in the conditions of agricultural and service enterprises and exclude the sending of serviceable units with unused resources for repair.

When testing agricultural machinery in order to determine its functional indicators, the ability to wirelessly transmit data between sensors, measuring and information systems are important. (Research purpose) To develop methods and create wireless digital devices for determining the functional indicators of agricultural tractors and machines with the ability to wirelessly transmit data to a remote control point in real time. (Materials and methods) The authors assumed that it was possible to determine the slipping of driving wheels using an inertial navigation system. It was found that in order to calculate real-time indicators obtained using wireless technologies, it was necessary to determine the characteristics of the input signals of discrete sensors on the side of the measuring system. (Results and discussions) The authors substantiated a method for determining the period of incoming signals of discrete sensors with an accuracy of 0.001 seconds for wireless information transmission. They proposed the design of a slipping sensor for an energy vehicle driving wheels, the main element of which is an inertial wheel position sensor. They developed a discrete signal input module and an inertial slipping sensor with the possibility of wireless data transmission based on a radio system with a carrier frequency of 433 megahertz. During field tests, it was found that the accuracy of determining slippage using the inertial wireless sensor IP-291 does not exceed 1 percent; the range of stable radio communication from the tested object to the test control center reaches 1000 meters; the current indicators obtained through digital radio communication did not differ from the indicators obtained in the tractor cab. (Conclusions) The authors worked out an effective system for wireless information transfer with the ability to calculate the performance of the tested equipment in real time.

The article considers the issues of digital modeling of dynamic processes in the transmissions of vehicles. The purpose of this research was to develop an algorithm for numerical mathematical modeling of dynamic processes in the transmissions of transport vehicles using modern digital software packages. The method includes a systematic approach to the study of dynamic processes during switching, based on modeling the operation of the gearbox together with the internal com-bustion engine (taking into account its dynamic, speed and load characteristics). The order of appli-cation of the MATLab – Simulink, Simscape software for numerical simulation of dynamic pro-cesses is considered. Using the fundamental blocks of these applications, models of physical com-ponents are created: the internal combustion engine, friction clutches, gearboxes, elastic shafts, damping devices, and tractor power transmission control systems. A digital model of the tractor transmission is created, its design scheme is given, and the initial characteristics are set. It was used to simulate dynamic processes in the tractor gearbox. The main attention in this paper is paid to the application of the proposed method for calculating the dynamic processes in the gearbox during gear changes under load with forward and reverse switching, including the simultaneous use of several friction clutches.

Introduction. The process of shifting gears under load is one of the most complex types of dynamic process in the transmissions of transport, road and construction vehicles. Currently, the existing calculation methods do not fully reflect the features of the engine and automated gearbox interaction by switching stages under load using more than two friction clutches at the same time. The paper discusses the method of calculating the dynamic characteristics of the gearbox with the simultaneous use of both two and four friction clutches by shifting gears under load with forward and reverse switching. The authors present the results of the dynamic characteristics of the theoretical study of the automated gearbox with frictional stages’ switching under load and without breaking the power flow.Materials and methods. The main method was based on a system approach to the dynamic processes study and on the modeling of the gearbox operation together with the internal combustion engine. The authors took into account the regulatory, speed and load engine characteristics, resistive torque variation, rate of pressure rise in clutches by shifting to higher and lower gears. The paper performed theoretical modeling of processes using the MATLab package and the Simulink application. Using the main blocks of this application, the authors created models of physical components: an internal combustion engine, friction clutches, gear reducers, elastic shafts, damping devices and tractor power transmission control systems.Results. As a result, the authors obtained calculated data of the dynamic processes, variations in speed and rotational torque on the gearbox shafts; the load on the engine by shifting gears at different values of the start and finish time in switching on and off the gearbox friction controls. The paper presented the relevant graphs of the processes.Discussion and conclusions. The developed method of calculating the dynamic characteristics of the gearbox allows simulating workflows by shifting to higher and lower gears. This method takes into account both the parameters of the gearbox design and of the control actions: the rate of switching on the friction clutches; the time intervals of overlapping the “on and off” clutches. Therefore, in relation to the considered gearbox, the authors determine the values of the optimal time control commands of the friction by shifting.Financial transparency: the authors have no financial interest in the presented materials or methods. There is no conflict of interest.

Introduction. At present, stands with running drums are widely used for various types of tests. Power stands play a special role. Such stands take the mechanical power from the driving wheels of the car. This simulates the process of movement of the vehicle under operating conditions. Such equipment has various designs, principles of operation and performance. It is also used in tests that are different by purpose, development stages and types: research, control, certification, etc. Therefore, it is necessary in order to determine the traction-speed, fuel-efficient and environmental performance characteristics.Materials and methods. The paper provides the overview of the power stands with running drums, which are widespread on the domestic market. The authors carried out the analysis of the main structural solutions: schemes of force transfer between the wheel and the drum; types of loading devices; transmission layout schemes and features of the control and measuring complex. The authors also considered corresponding advantages and disadvantages, recommended spheres of application, demonstrated parameters and characteristics of the units’ workflow, presented components and equipment.Discussion and conclusions. The authors critically evaluate existing models of stands with running drums. Such information is useful for choosing serial models of stands and for developing technical tasks for designing or upgrading the equipment.

This study aims to develop and evaluate an automated manual transmission (AMT) for agricultural tractors with high efficiency and high convenience by using electric actuators. An AMT system to control manual-type shuttle gearboxes and transmissions for tractors is developed by adding a shuttle shifting actuator, a clutch actuator, and a control system to a conventional manual transmission (MT). The clutch actuator is designed using an electric motor and a reduction gear. The AMT control system is developed and experimental tests are conducted to evaluate the performance of the AMT. The results of the performance of the actuator position control demonstrate that the shuttle shifting actuator and clutch actuator are controlled appropriately, achieving a maximum overshoot of less than 5% and 0%, a settling time of less than 0.500 s and 1.50 s, and a steady-state error of less than 1% and 1%, respectively. The performance of the automatic forward and reverse control demonstrates a shift control time of less than 2.50 s and target revolutions per minute (RPM) reaching time of less than 3.00 s. Thus, AMT systems for tractors can be easily developed by applying shuttle shifting actuators, clutch actuators, and a control system to conventional manual transmissions.

Due to the complex working conditions of tractor and its frequent load fluctuation, it is difficult to analyze shift schedule through the traditional approach of building the mathematical model of power train. The paper will applied fuzzy control theory to the shift schedule. The control rules is determined based on the different operating states of tractor. Slip rate which is a important indicator to reflect tractor operation will be introduced as control parameters to research the control strategy of tractor’s powershift antomatic transmisson. The simulation result shows that the method can effectively avoid shift circulation and reduce the shift frequency, which improve the dynamic performance and fuel economy of tractors.

This paper proposes a new transmission scheme of hydromechanical continuously variable transmission (HMCVT) for tractors. The HMCVT has 4 working ranges in each of the front and rear directions. The speed characteristic and the torque characteristic of HMCVT are theoretically derived. On the basis of HMCVT power flow direction, the Крейнeс formula is used to calculate the transmission efficiency. Then, the image analysis method is used to study the influence of parameters on the transmission efficiency of HMCVT, and the main influencing factors are found. The results of theoretical derivation demonstrate that, by coordinating control of the HST displacement ratio and the engagement conditions of shifting clutches, the stepless speed regulation of HMCVT at the tractor speed of 0–50 km/h can be realized. The proposed HMCVT has the ability to continuously transmit and change torque over all working ranges. The overall transmission efficiency of HMCVT is at a high level. To verify the theoretical derivation, Amesim simulation software is used for the modeling and simulation of HMCVT. The simulation results are consistent with the theoretical analysis results. Therefore, the HMCVT proposed in this paper has the advantages of compact structure and high transmission efficiency, and it is suitable for matching tractors.

In this work, a power-split continuously variable transmission (CVT) used in high-power tractors is considered. Power-split CVTs are characterized by the combination of a traditional discontinuous mechanical transmission and a continuously variable transmission. This provides, at the same time, smooth variations of the transmission ratio and high efficiency of the overall transmission system. The CVT considered in this paper is a hydrostatic power-split unit conceived for top-power agricultural tractors. The goal of this paper is to present a case study on the design and tuning of the control system structure for this type of CVT. This structure consists of three main parts: a servo controller on the internal current of the valve of the hydraulic transmission; a servo controller on the hydraulic transmission ratio; a synchronizer which coordinates the hydraulic and the mechanical parts of the CVT. The design, tuning and testing of this set of automatic controllers is presented.

The standard of the organization directed on increase of efficiency and quality of monitoring procedure of emissions of harmful substances of the fulfilled gases of diesels of the capital repaired tractors and self-propelled farm vehicles which are in operation, intended for work and working in the conditions of unlimited and limited air exchange is developed — and establishes norms of emissions of harmful substances with the fulfilled gases, means of their definition, at control and bench tests of tractors and the agricultural cars. Technical characteristics of the fuel and engine oil intended for test of the diesel are defined. Modern control devices are optimized and techniques of tool control of the maintenance of CO, CH and NOx in the fulfilled gases of diesels of page are the agricultural cars.

The main tasks of power electronics in power transmission and distribution systems is to process and control the flow of electric energy by supplying voltages and currents in a form that is suitable for user loads. In recent years, the field of power electronics has experienced a large growth. Electric utilities expected that by the year 2000 over half of the electrical load may be supplied through power electronic systems. In order to take advantage of this highly developed technology a number of detailed modelling procedures and simulation facilities are needed. The work in this thesis is concentrated on modelling, control and design of various power electronic based models for use within transmission and distribution systems. The overall objective is to provide effective methods and tools for assessing the impact of the latest technology based on power electronic devices in the reinforcement of power system networks. The thesis clarifies modelling and control of various variable speed drive models, such as the six-step, PWM and vector control and gives a detailed account of the systematic derivation of equations that are necessary for the dynamic and transient analysis of a multi-machine multi-node power system with associated adjustable speed drives. Simulation of Flexible AC Transmission Systems (FACTS) models has also been developed for a number of devices including: the SVC (Static Var Compensator), the STATCON (Static Condenser) and the UPFC (Unified Power Flow Controller). The methodologies for development of the models are described and a number of case studies are included in order to give a broad overview of the applications and to prove the usefulness of the results. The last part of the thesis includes simulation, control and design of Custom Power Devices for use within distribution system architectures. It starts with a complete control system strategy for the modelling of a solid-state switch and continues with the modelling of a Dynamic Voltage Restorer model, using an innovative control system. The creation of the power electronics models library provides several opportunities for future developments, which are discussed in the concluding sections of the thesis.

Emerging body-wearable sensor devices for continuous health monitoring are severely energy constrained and yet required to offer high communication reliability under fluctuating channel conditions. This thesis aims at investigating the opportunities and challenges in the use of dynamic radio transmit power control for prolonging the lifetime of such devices. We first present extensive empirical evidence that the wireless link quality can change rapidly in body area networks, and a fixed transmit power results in either wasted energy (when the link is good) or low reliability (when the link is bad). We then propose a class of schemes feasible for practical implementation that adapt transmit power in real-time based on feedback information from the receiver. We show conservative, balanced, and aggressive adaptations of our scheme that progressively achieve higher energy savings of 14%-30% in exchange for higher potential packet losses (up to 10%). We also provide guidelines on how the parameters can be tuned to achieve the desired trade-off between energy savings and reliability within the chosen operating environment. Finally, we implement and profile our scheme on a MicaZ mote based platform, demonstrating that energy savings are achievable even with imperfect feedback information, and report preliminary results on the ultra-low-power integrated healthcare monitoring platform from our collaborating partner Toumaz Technology. In conclusion, our work shows adaptive radio transmit power control as a low-cost way of extending the battery-life of severely energy constrained body wearable devices, and opens the door to further optimizations customized for specific deployment scenarios.

The current study compared the performance of six commonly used cursor devices (absolute touchpad, mouse, trackball, relative touchpad, force joystick, and displacement joystick) on three types of tasks (target acquisition, text editing, and graphics). Prior to these comparisons, each of the devices was optimized for display/control dynamics in independent experiments. A total of 30 subjects were used in the five optimization studies. For each device, the optimization experiment compared a range of control dynamics using a target acquisition task (i.e., positioning a cross-hair cursor over square targets of varying sizes and screen distances). An analysis of variance procedure was used to determine the best control dynamics, of the range studied, for each device. Performance was based on a time-to-target (TT) measure. A comparison of the six optimized devices was then performed on the three task environments. For the target acquisition, text editing, and graphics tasks, a total of 12, seven, and six subjects were required, respectively. For the target acquisition study, the six devices were compared on a task identical to the optimization task; that is, cursor positioning performance for various target sizes and distances. In addition to the TT dependent measure, bipolar scale and subjective rank data were also collected. The text editing task required subjects to perform document correction on the computer using each of the six devices, with cursor keys added as a baseline device. Task completion time (TCT), bipolar scale response, and subjective rank data were collected. For the graphics task, subjects were required to perform basic graphics editing tasks with the six devices. As with the text editing task, TCT, bipolar scale, and rank data were collected. Results indicated a wide variation in the cursor positioning performance of the devices on the three tasks. Without exception, the mouse and trackball performed the best of the six devices, across all tasks. In addition, these devices were most preferred. In general, the two joysticks performed worse on the target acquisition and graphics tasks than the two touchpads. On the text editing task, however, the rate—controlled joysticks performed better than the touchpads.
Ph. D.

The tractive force has to be interrupted during a gear-shifting operation in a manual vehicle transmission, leading into a decrease of speed while changing gears during the acceleration process. Therefore in a racing application, the shifting time has to be as short as possible so that the required performance of a racing car can be achieved. The following dissertation describes the development of a transmission control system to enable gear changes within a manual gearbox, which was designed for the Formula Student racing series. Various solutions were developed on the basis of reviewed literature, technical data of components and experiences of Formula Student teams. Following this, a comparison of the concepts by means of a utility analysis identified the pneumatic actuation of selector forks to be the most suitable concept. This was mainly due to the expected shifting time, the weight, and its advantageous energy supply requirement. After the selection of the actuators and the position sensors, the system was implemented into the drivetrain to check the tment and the technical feasibility. To draw conclusions regarding the shifting time and to prove the functionality of the system, an open test bench was constructed. Additionally, the hardware and software had to be developed to enable the test run. After the manufacturing and assembling of the test bench, the optimal settings for the test run were determined. By comparing the achieved shifting time of alternative solutions, an improvement in the driving performance of a Formula Student race car is probable.

Induction motors are widely used in industrial processes. The malfunction of a motor may not only lead to high repair costs, but also cause immense financial losses due to unexpected process downtime. Since thermal overload is one of the major root causes of stator winding insulation failure, an accurate and reliable monitoring of the stator winding temperature is crucial to increase the mean time to catastrophic motor breakdown, and to reduce the extraordinary financial losses due to unexpected process downtime. To provide a reliable thermal protection for induction motors fed by motor control devices, a dc signal-injection method is proposed for in-service induction motors fed by soft-starter and variable-frequency drives. The stator winding temperature can be monitored based on the estimated stator winding resistance using the dc model of induction motors. In addition, a cooling capability monitoring technique is proposed to monitor the cooling capability of induction motors and to warn the user for proactive inspection and maintenance in the case of cooling capability deterioration. The proposed cooling capability monitoring technique, combined with the proposed stator winding temperature monitoring technique, can provide a complete thermal protection for in-service induction motors fed by motor control devices. Aside from online thermal protection during a motor's normal operation, the thermal protection of de-energized motors is also essential to prolong a motor's lifetime. Moisture condensation is one of the major causes to motor degradation especially in high-humidity environments. To prevent moisture condensation, a non-intrusive motor heating technique is proposed by injecting currents into the motor stator winding using soft-starters. A motor's temperature can be kept above the ambient temperature due to the heat dissipation, so that the moisture condensation can be avoided. To sum up, active stator winding temperature estimation techniques for induction motors under both operating and de-energization conditions are proposed in this dissertation for both thermal protection and optimizing the operation of a motor system. The importance of these proposed techniques lies in their non-intrusive nature: only the existing hardware in a motor control device is required for implementation; a motor's normal operation is not interrupted.

This thesis is devoted to the development of new models for a recently-implemented FACTS (flexible alternating current transmission system) device, the unified power flow controller (UPFC), and the control coordination of power systems with FACTS devices in steady-state operating mode. The key objectives of the research reported in the thesis are, through online control coordination based on the models of power systems having FACTS devices, those of maximising the network operational benefit and restoring system static security following a disturbance or contingency. Based on the novel concept of interpreting the updated voltage solutions at each iteration in the Newton-Raphson (NR) power-flow analysis as dynamic variables, the thesis first develops a procedure for representing the unified power flow controllers (UPFCs) in the steady-state evaluation. Both the shunt converter and series converter control systems of a UPFC are modeled in their dynamical form with the discrete time variable replaced by the NR iterative step in the power-flow analysis. The key advantage of the model developed is that of facilitating the process of UPFC constraint resolution during the NR solution sequence. Any relative priority in control functions pre-set in the UPFC controllers is automatically represented in the power-flow formulation. Although the developed UPFC model based on the dynamic simulation of series and shunt converter controllers is flexible and general, the number of NR iterations required for convergence can be large. Therefore, the model is suitable mainly for power system planning and design studies. For online control coordination, the thesis develops the second UPFC model based on nodal voltages. The model retains all of the flexibility and generality of the dynamic simulation-based approach while the number of iterations required for solution convergence is independent of the UPFC controller dynamic responses. Drawing on the constrained optimisation based on Newton’s method together with the new UPFC model expressed in terms of nodal voltages, a systematic and general method for determining optimal reference inputs to UPFCs in steady-state operation is developed. The method is directly applicable to UPFCs operation with a high-level line optimisation control (LOC) for maximising the network operational benefit. By using a new continuation technique with adaptive parameter, the algorithm for solving the constrained optimisation problem extends substantially the region of convergence achieved with the conventional Newton’s method. Having established the foundation provided by the comprehensive models developed for representing power systems with FACTS devices including the UPFC, the research, in the second part, focuses on real-time control coordination of power system controllers, with the main purpose of restoring power system static security following a disturbance or contingency. At present, as the cost of phasor measurement units (PMUs) and wide-area communication network is on the decrease, the research proposes and develops a new secondary voltage control where voltages at all of the load nodes are directly controlled, using measured voltages.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Ronald G. Harley; Committee Member: David G. Taylor; Committee Member: Deepakraj M. Divan; Committee Member: Ganesh Kumar Venayagamoorthy; Committee Member: Thomas G. Habetler. Part of the SMARTech Electronic Thesis and Dissertation Collection.

[EN] This Thesis is focused on the development and implementation of efficient numerical methods for the acoustic modelling and design of noise control devices in the exhaust system of combustion engines. Special attention is paid to automotive perforated dissipative silencers, in which significant differences are likely to appear in their acoustic behaviour, depending on the temperature variations within the absorbent material. Also, material heterogeneities can alter the silencer attenuation performance. Therefore, numerical techniques considering all these features are required to guarantee the accuracy of the results. A literature review is carried out, mainly related to one-dimensional models, as well as to acoustic models for absorbent materials and perforated surfaces. However, plane wave model limitations make indispensable using alternative multidimensional methods. In addition, the possibility of using new acoustic elements is explored. These elements have as an objective being a potential alternative to the fibrous absorbent materials, which can have a negative impact on health. The Thesis considers the use of microperforated and sintered surfaces. The latter have, in some cases, a nearly constant acoustic impedance, whose value depends, among others, on the thickness and porosity of the plates. To avoid the limitations of plane wave models, a finite element (FE) approach is proposed for the acoustic analysis of dissipative silencers including a perforated duct with uniform axial mean flow and an outer chamber with a heterogeneous distribution of the absorbent material. On the other hand, property variations can be also produced by temperature gradients. In this case, a hybrid FE model has been derived for perforated dissipative silencers including: (1) Thermal gradients in the central duct and the chamber; (2) A perforated passage carrying non-uniform axial mean flow. A FE approach has been implemented to solve the pressure-based wave equation for a non-moving heterogeneous medium, associated with the chamber. Also, the governing equation in the central duct has been written and solved in terms of an acoustic velocity potential to allow the presence of an axially inhomogeneous flow. The coupling between both regions has been carried out by means of a perforated duct and its acoustic impedance, adapted here to include absorbent material heterogeneities and mean flow effects. It has been found that the presence of non-homogeneities can have a significant influence on the acoustic attenuation of a silencer and should be included in the theoretical models. Optimization techniques for industrial noise control devices are relevant, since they lead to the production of elements with better characteristics. Evolutionary algorithms are emergent techniques able to obtain a solution, even in those problems in which the traditional optimization have difficulties. Optimization techniques are combined with the FE method to achieve the maximum attenuation in the frequency range of interest. A multichamber silencer optimization problem is defined and several analyses are carried out to obtain the most suitable configuration for each application. Under certain assumptions of axial uniformity, several techniques have been considered to reduce the computational effort of a full 3D FE analysis for dissipative silencers with temperature gradients and mean flow. These are based on a decomposition of the acoustic field into transversal and axial modes within each silencer subdomain, and a matching procedure of the modal expansions at the silencer area changes through the continuity conditions of the acoustic fields. The relative computational efficiency and accuracy of predictions for the matching techniques are studied, including point collocation at nodes and Gauss points and also mode-matching with weighted integration. All of them provide accurate predictions of the attenuation and improve the computational cost of a FE calculation
[ES] Esta Tesis se centra en el desarrollo e implementación de métodos numéricos eficientes para el diseño y modelado de componentes de la línea de escape en motores de combustión interna. Merecen especial atención los silenciadores disipativos perforados de automóviles, ya que su comportamiento acústico puede sufrir variaciones importantes debidas a las variaciones de temperatura en el material absorbente, así como a las heterogeneidades de la fibra. Por tanto, se requieren técnicas numéricas que consideren estos casos para garantizar la precisión de los resultados. Se lleva a cabo una revisión bibliográfica que recoge los modelos de onda unidimensionales, así como modelos acústicos de materiales absorbentes y superficies perforadas. Sin embargo, las limitaciones de los primeros hacen indispensable el uso de modelos multidimensionales. Además se explora la posibilidad de usar nuevos elementos acústicos, cuyo objetivo es ser una alternativa potencial a los materiales absorbentes, que pueden tener un efecto negativo sobre la salud. La Tesis considera el uso de superficies microperforadas y sinterizadas. Estas últimas en algunos casos presentan una impedancia casi constante, cuyo valor depende, entre otras cosas, del espesor y la porosidad de las placas. Para evitar las limitaciones de los modelos de onda plana, se propone un enfoque en elementos finitos (EF) para el análisis acústico de silenciadores disipativos que incluyen un conducto con flujo medio axial uniforme y una cámara externa con una distribución heterogénea de material absorbente. Por otro lado, la variación de las propiedades también puede producirse por gradientes térmicos. En este caso, se propone una formulación híbrida de EF para silenciadores disipativos perforados que incluye: (1) Gradientes térmicos en el conducto central y la cámara; (2) Un conducto perforado que canaliza flujo medio axial no uniforme. Se ha implementado una formulación de EF para resolver la ecuación de ondas en términos de presión para el medio estacionario heterogéneo asociado a la cámara. Además, la ecuación asociada al conducto central, expresada en términos de potencial de velocidad acústica, permite la presencia de flujo axial no uniforme. El acoplamiento entre ambas regiones se ha realizado mediante un conducto perforado y su impedancia acústica y se ha adaptado para incluir la citada falta de homogeneidad. Se ha visto que las heterogeneidades pueden influir notablemente en la atenuación acústica de un silenciador, debiéndose incluir en los modelos teóricos. Las técnicas de optimización para componentes industriales de control de ruido son importantes, ya que producen elementos con mejores características. Los algoritmos evolutivos son técnicas emergentes capaces de obtener una solución, incluso cuando la optimización tradicional tiene dificultades. Las técnicas de optimización se combinan con el MEF para conseguir la máxima atenuación posible en el rango de frecuencias de interés. Se ha definido un problema de optimización de un silenciador multicámara y se han llevado a cabo varios análisis para obtener la configuración más adecuada para cada caso. Bajo ciertas hipótesis de uniformidad axial, se han considerado varias técnicas para reducir el coste computacional de un análisis 3D completo para silenciadores disipativos con gradientes de temperatura y flujo medio. Éstas se basan en la descomposición del campo acústico en modos axiales y transversales dentro de cada subdominio, y un procedimiento de acoplamiento de las expansiones modales en los cambios de sección del silenciador mediante las condiciones de continuidad de los campos acústicos. Se estudia la eficiencia computacional y precisión de las predicciones de las técnicas de acoplamiento, incluyendo colocación puntual en nodos y puntos de Gauss, así como ajuste modal. Todos ellos proporcionan predicciones precisas de la atenuación mejorando el coste
[CAT] Aquesta Tesi es centra en el desenvolupament i implementació de mètodes numèrics eficients per al disseny i modelatge de components de la línia d'escapament en motors de combustió interna. Mereixen especial atenció els silenciadors dissipatius perforats d'automòbils, ja que el seu comportament acústic pot patir variacions importants degudes a les variacions de temperatura en el material absorbent, així com a les heterogeneïtats de la fibra. Per tant, es requereixen tècniques numèriques que considerin aquests casos per garantir la precisió dels resultats. Es porta a terme una revisió bibliogràfica que recull els models d'ona unidimensionals, així com models acústics de materials absorbents i superfícies perforades. No obstant això, les limitacions dels primers fan indispensable l'ús de models multidimensionals. A més s'explora la possibilitat d'usar nous elements acústics amb l'objectiu que siguen una alternativa potencial als materials absorbents, que poden tenir un efecte negatiu sobre la salut. La Tesi considera l'ús de superfícies microperforades i sinteritzades. Aquestes últimes en alguns casos presenten una impedància gairebé constant. El seu valor depèn, entre altres coses, del gruix i la porositat de les plaques. Per evitar les limitacions dels models d'ona plana, es proposa un enfocament amb elements finits (EF) per a l'anàlisi acústic de silenciadors dissipatius que inclouen un conducte amb flux mig axial uniforme i una càmera externa amb una distribució heterogènia de material absorbent. D'altra banda, la variació de les propietats també es pot produir per gradients tèrmics. En aquest cas, es proposa una formulació híbrida d'EF per silenciadors dissipatius perforats que inclou: (1) Gradients tèrmics en el conducte central i la càmera; (2) Un conducte perforat que canalitza flux mig axial no uniforme. S'ha implementat una formulació d'EF per resoldre l'equació d'ones en termes de pressió per al medi estacionari heterogeni associat a la càmera. A més, l'equació associada al conducte central, expressada en termes de potencial de velocitat acústica, permet la presència de flux axial no uniforme. L'acoblament entre les dues regions s'ha realitzat mitjançant un conducte perforat i la seva impedància acústica i s'ha adaptat per incloure la esmentada falta d'homogeneïtat. S'ha vist que les heterogeneïtats poden influir notablement en l'atenuació acústica d'un silenciador i s'han d'incloure en els models teòrics. Les tècniques d'optimització per a components industrials de control de soroll són importants, ja que produeixen elements amb millors característiques. Els algoritmes evolutius són tècniques emergents capaces d'obtenir una solució, fins i tot quan l'optimització tradicional té dificultats. Les tècniques d'optimització es combinen amb el mètode d'elements finits (MEF) per aconseguir la màxima atenuació possible en el rang de freqüències d'interès. S'ha definit un problema d'optimització d'un silenciador multicàmera i s'han dut a terme diverses anàlisis per obtenir la configuració més adequada per a cada cas. Sota certes hipòtesis d'uniformitat axial, s'han considerat diverses tècniques per reduir el cost computacional d'una anàlisi 3D complet per silenciadors dissipatius amb gradients de temperatura i flux mig. Aquestes es basen en la descomposició del camp acústic en modes axials i transversals dins de cada subdomini, i un procediment d'acoblament de les expansions modals en els canvis de secció del silenciador mitjançant les condicions de continuïtat dels camps acústics. S'estudia l'eficiència computacional i precisió de les prediccions de les tècniques d'acoblament, incloent col·locació puntual en nodes i punts de Gauss, així com ajust modal. Tots ells proporcionen prediccions precises de l'atenuació millorant el cost computacional d'EF.
Sánchez Orgaz, EM. (2016). Advanced numerical techniques for the acoustic modelling of materials and noise control devices in the exhaust system of internal combustion engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64090
TESIS

Due to the continuous resources’ reduction and cost increase of conventional fossil fuel along with the global trend to decrease the greenhouse effect, clean energy production from renewable sources has been given a global great concern. Among renewable energy sources, wind energy conversion systems have received a worldwide notable attention. It is expected that more than 10% of the global electricity demand will to be generated by wind energy conversion systems by the year 2020. During their early implementation stage, wind turbines were to be disconnected during abnormal and fault conditions within the electricity grid it is connected to. Owing to the fact that current wind installations supply a significant portion of the load demand, disconnecting windfarms may lead to business interruption and discontinuity of power supply to the end user. As such, transmission line operators have developed strict grid codes that wind turbine generator must meet to maintain its connection to support the grid during various fault conditions. To comply with these codes, flexible AC transmission systems have been widely used with current wind energy conversion systems to modulate reactive and/or active power at the point of common coupling of the wind turbine generator and the grid. This book presents the applications of various flexible ac transmission system devices to wind energy conversion systems. Devices such as unified power flow controllers, superconducting magnetic energy storage and static synchronous compensator are covered in this book. Topologies, control systems along with case studies of the aforementioned devices are presented and discussed. This book will be useful for postgraduate research students, upper-division electrical engineering students and practicing engineers.

This chapter proposes a new hybrid MAC protocol for direct communication among M2M devices with gateway coordination. The proposed protocol combines the benefits of both contention-based and reservation-based MAC schemes. The authors assume that the contention and reservation portion of M2M devices is a frame structure, which is comprised of two sections: contention interval (CI) and transmission interval (TI). The CI duration follows p-persistent CSMA mechanism, which allows M2M devices to contend for the transmission slots with equal priorities. After contention, only those devices which have won time-slots are allowed to transmit data packets during TI. In the proposed MAC scheme, the TI duration follows TDMA mechanism. Each M2M transmitter device and its corresponding one-hop distant receiver communicate using IEEE 802.11 DCF protocol within each TDMA slot to overcome various limitations of TDMA mechanism. The authors evaluate the performance of the proposed hybrid MAC protocol in terms of aggregate throughput, average transmission delay, channel utility, and energy consumption.

The John Deere 7000 TEN series tractors represent a significant change in the transmission system compared to previous John Deere tractor models in this category. John Deere 7710 and 7810 series tractors are the first of the 7000 TEN series tractors offering an infinitely variable transmission (IVT). These tractors provide infinite vehicle speeds in the forward mode from 50 meters/hr to 40 km/hr or an optional 50 km/hr. Reverse mode provides infinite vehicle speeds from 50 meters/hr to 17 km/hr. The IVT provides performance improvements in several areas for unmatched operator convenience and control. The new IVT uses an electric signal to control the electro-hydraulic hydrostatic system with mechanical power train. The IVT represents a hydro-mechanical transmission system using electronics, hydraulics and mechanical systems’ integration to achieve the required performance. This paper describes the IVT system configuration, components, operation, characteristics and some of the engineering considerations dealt with in the development process. The overall IVT system truly represents a “drive-by-wire” mechatronic design.