Proton Exchange Membrane (PEM) fuel cells are becoming an increasingly important alternative to combustion engines as the fossil fuel reserves are depleted. Several papers have presented steady state analyses of the system, but few are known to present dynamic analysis of the flow and control of the hydrogen delivery process. This thesis presents the dynamic analysis of hydrogen delivery to a PEM fuel cell system. The hydrogen is delivered to the anode with use of an ejector for passive recirculation. The system to be studied consists of the manifolds, ejector, and pressure control valve. Models describing the elements of the anode delivery systems are formulated. The governing nonlinear equations are solved analytically and numerically, and the regimes of stable hydrogen delivery process are established. The linearized models are used for performance analysis and optimization of the hydrogen delivery process. The nonlinear model is used to improve the simulation of the dynamics of the PEM fuel cell system and validate the parameters at optimal linearized stability. Experiments are conducted to find the parameters used in the model, as well as validate the results. Both the linear and nonlinear models are implemented in Simulink and tested against the laboratory data from the PEM fuel cell system. The analysis showed that the models have the same time constant and dynamic behavior as the PEM system. The optimal parameters for stability and a faster response with no oscillations in the output are obtained. The redesigned valve and resulting dynamics of the PEM fuel cell system provides improved system performance.

Electro-hydraulic proportional flow valves are widely used in hydraulic industry. There are several different structures and working principles. However, flow valves based on the existing principles usually have some shortcomings such as the complexity of the system and additional energy losses. A concept for a two-stage poppet flow valve with pilot pressure drop – pilot spool opening compensation is presented, and the linear relationship between the pilot stage and main stage, the semi-empirical flow equation are used in the electronic flow controller. To achieve the accurate control of the outlet flow, the actual input voltage of the pilot spool valve is regulated according to the actual pilot pressure drop, the desired flow rate and the given input voltage. The results show that the pilot pressure drop – pilot spool opening compensation method is feasible, and the proposed proportional flow control valve with this compensation method has a good static and dynamic performance.

Other than mobile hydraulics and high voltage switchgears, Bucher Hydraulics is also involved in the less-known area of hydraulic lifts. In fact, Bucher Hydraulics did invent the electronically controlled lift valve in the 1970s. Since then, Bucher Hydraulics developed a wide line of products for hydraulic elevators, such as valves and power units. In 2012, this valve family included various sizes, pressure ranges, systems with constant motor speeds, inverter-driven motors, energy-efficient solutions with hydraulic counterweight, as well as customized solutions. As the common principle, all these solutions apply an electronic closed-loop control that uses a volumetric flow sensor and a proportional actuator. Since 2012, Bucher Hydraulics is substituting this valve family with a new generation, the iValve. Every iValve uses several self-teaching algorithms to adapt to its environment. Their on-board and cabinet electronics control solenoid currents and measure flow, pressure, and temperature. These features enable the iValve to self-monitor, to adapt to operating parameters, and to analyze and log information about itself and the attached system. This report on a highly specialized product is meant to provide inspiring insights.

A variabilidade é um problema presente na maioria das malhas de controle de processos industriais, trazendo prejuízo ao causar perda de produtividade e utilização excessiva de matéria prima e energia. Muitas vezes ela é causada pela presença do atrito em válvulas de controle, os atuadores mais usados em processos industriais. Há uma série de métodos propostos para diagnosticar as perturbações causadas pelo atrito nas válvulas, classificados em intrusivos e não-intrusivos. Neste trabalho, foram estudados dois métodos intrusivos. Eles foram aplicados de maneira automática em simulações computacionais, que foram realizadas em um sistema híbrido de teste (HIL) de uma planta de vazão, com dois níveis de atrito da válvula, e também em um ambiente inteiramente simulado, visando analisar o desempenho dos dois métodos. Os resultados obtidos com ambos os métodos foram satisfatórios, muito embora um dos métodos tenha confundido os efeitos gerados pelo atrito com os produzidos por má sintonia do controlador da malha. / The variability is a problem present on the most of control loops in industrial processes. It causes losses in plant productivity and in material and energy usage. Many times it is caused by the presence of friction in control valves, the most used actuator in industrial processes. There are many methods proposed to diagnose the disturbances caused by control valve friction, which are classified in intrusive and non-intrusive. In this work, two intrusive methods are studied. They were applied automatically by computer simulations that were performed in a hybrid test system (HIL) of a flow plant, with two valve friction levels. Additionally they were applied in a completely simulated environment, aiming at analyzing the performance of both methods. The results with the two methods were satisfactory, although one of the methods has not separated the effects generated by the friction from the ones produced by a bad tuning of the loop controller.

O atrito é uma não-linearidade que geralmente produz o mau desempenho de um sistema mecânico com partes móveis. Neste trabalho, o elemento mecânico estudado é a válvula de controle de processos, que é o elemento final de controle mais empregado nas indústrias de processo. A presença de atrito na válvula eleva a variabilidade da malha de controle, gerando impacto em toda a cadeia produtiva da planta, devido, principalmente, ao aumento do consumo de energia e à rejeição de produto final fora de especificação. Desta forma, os estudos visando a redução de variabilidade passaram a ter uma importância econômica muito grande, pois causam impacto direto na lucratividade do negócio. Muitos estudos foram realizados visando diagnosticar, medir e compensar o atrito. Neste trabalho, se implementam técnicas propostas na literatura para compensação de atrito em válvulas de controle. Para avaliar seu desempenho, são apresentadas as conclusões obtidas nos experimentos e são propostas possíveis implementações futuras, seguindo esta linha de pesquisa. / Friction is a nonlinearity that generally produces bad performance of a mechanical system with moving parts. In this work, the studied mechanical element is the process control valve, which is the most used final control element in process industries. The presence of friction in control valves increases control loop variability, generating impact in all plant productive chain, due to the increase of energy consumption and rejection of end product that is out of specification. In such a way, we can see that the studies aiming variability reduction had started to have a great economic importance, due to its direct impact in business profitability. Many studies have been done aiming friction diagnosis, measurement and compensation. In this work, techniques that have been proposed on the literature for friction compensation in control valves are implemented. The conclusions obtained in the experiments are presented to evaluate the performance of the compensators and possible future implementations are proposed, following this research line.

O elemento final de controle mais usado nas malhas de processo na indústria é a válvula de controle. Portanto, é necessário assegurar que ela possua o melhor desempenho possível, a fim de assegurar um funcionamento satisfatório da malha de controle. Devido ao desgaste natural das partes móveis e o ressecamento das gaxetas, as válvulas apresentam atrito que insere oscilações na abertura da válvula e devido a seu comportamento não linear que diminui a eficiência do controle. A presença de oscilações nas malhas de controle aumenta a variabilidade das variáveis de processo, o desgaste dos componentes e o consumo de energia, além de provocar o desperdício de materiais. Por isto, no presente trabalho são estudados e implementados diferentes compensadores de atrito existentes na literatura, visando reduzir o efeito do atrito nas válvulas e, por sua vez as oscilações na variável do processo. Estes métodos são aplicados na Planta Piloto de Neutralização de pH do Laboratório de Controle de Processos Industriais (LCPI). O processo de neutralização de pH é não-linear e apresenta características variantes no tempo, as quais tornam mais complexo o controle do processo. Inicialmente foi feita a implementação dos compensadores em um software acadêmico (MATLAB®), devido à familiaridade que se tem com ele, o que facilitou um melhor entendimento dos métodos de compensação junto com o controlador PID no processo. Em uma segunda etapa, a fim de trazer os estudos a um ambiente mais prático, foram implementados os algoritmos de compensação de atrito em um sistema de controle industrial (ABB®). Nos dois casos se realizaram testes em modo servo e regulatório e se avaliaram os resultados obtidos usando o índice ITAE (Integral Time Absolute Error). Os resultados evidenciam que os compensadores conseguem diminuir a variabilidade na válvula de controle, sendo que o compensador CR2 apresentou o melhor desempenho para o modo servo e regulatório. / The most used final control element in process loops in the industry is the control valve. It must ensure that it has the best possible performance in order to guarantee a satisfactory operation of the control loop. Due of the natural wear of moving parts and drying gaskets, valves exhibit friction. This friction inserts oscillations in the valve opening and due to its non-linear behavior; this causes the efficiency to decrease. The presence of oscillations in the control loop increases the variability of the process variables, the component wear, energy consumption and cause a waste of materials. Therefore, in this work we studied and implemented different friction compensation methods that exist in literature, in order to reduce the effect of friction on the valves and in turn the oscillations in the process variable. These methods are applied in the Pilot Plant Neutralization pH of Industrial Process Control Laboratory (LCPI), the pH neutralization process is nonlinear and presents time-varying characteristics, these characteristics become the control process more complex. Initially, it was made the implementation of compensation methods in academic software (MATLAB®), due to the familiarity that already exist with it, which facilitated a better comprehension of the compensation methods with the PID controller in the process. In a second step, in order to bring the study to a more practical environment, the friction compensation algorithms were implemented in an industrial control system (ABB®). In both cases were performed tests inn servo and regulatory mode, and evaluated the results using the ITAE index (Integral Time Absolute Error). The results show that in general terms that the compensating methods showing a very satisfactory performance, with the compensator CR2 showed the best performance for the servo and regulatory mode.

The Humanoid Walking Robot (HWR) is a research platform for the study of legged and wearable robots actuated with Hydro Muscles. The fluid operated HWR is representative of a class of biologically inspired, and in some aspects highly biomimetic robotic musculoskeletal appendages showing certain advantages in comparison to more conventional artificial limbs and braces for physical therapy/rehabilitation, assistance of daily living, and augmentation. The HWR closely mimics the human body structure and function, including the skeleton, ligaments, tendons, and muscles. The HWR can emulate close to human-like movements even when subjected to simplified control laws. One of the main drawbacks of this approach is the inaccessibility of an appropriate fluid flow management support system, in the form of affordable, lightweight, compact, and good quality valves suitable for robotics applications. To resolve this shortcoming, the Compact Robotic Flow Control Valve (CRFC Valve) is introduced and successfully proof-of-concept tested. The HWR added with the CRFC Valve has potential to be a highly energy efficient, lightweight, controllable, affordable, and customizable solution that can resolve single muscle action.

A variabilidade é um problema presente na maioria das malhas de controle de processos industriais, trazendo prejuízo ao causar perda de produtividade e utilização excessiva de matéria prima e energia. Muitas vezes ela é causada pela presença do atrito em válvulas de controle, os atuadores mais usados em processos industriais. Há uma série de métodos propostos para diagnosticar as perturbações causadas pelo atrito nas válvulas, classificados em intrusivos e não-intrusivos. Neste trabalho, foram estudados dois métodos intrusivos. Eles foram aplicados de maneira automática em simulações computacionais, que foram realizadas em um sistema híbrido de teste (HIL) de uma planta de vazão, com dois níveis de atrito da válvula, e também em um ambiente inteiramente simulado, visando analisar o desempenho dos dois métodos. Os resultados obtidos com ambos os métodos foram satisfatórios, muito embora um dos métodos tenha confundido os efeitos gerados pelo atrito com os produzidos por má sintonia do controlador da malha. / The variability is a problem present on the most of control loops in industrial processes. It causes losses in plant productivity and in material and energy usage. Many times it is caused by the presence of friction in control valves, the most used actuator in industrial processes. There are many methods proposed to diagnose the disturbances caused by control valve friction, which are classified in intrusive and non-intrusive. In this work, two intrusive methods are studied. They were applied automatically by computer simulations that were performed in a hybrid test system (HIL) of a flow plant, with two valve friction levels. Additionally they were applied in a completely simulated environment, aiming at analyzing the performance of both methods. The results with the two methods were satisfactory, although one of the methods has not separated the effects generated by the friction from the ones produced by a bad tuning of the loop controller.

O atrito é uma não-linearidade que geralmente produz o mau desempenho de um sistema mecânico com partes móveis. Neste trabalho, o elemento mecânico estudado é a válvula de controle de processos, que é o elemento final de controle mais empregado nas indústrias de processo. A presença de atrito na válvula eleva a variabilidade da malha de controle, gerando impacto em toda a cadeia produtiva da planta, devido, principalmente, ao aumento do consumo de energia e à rejeição de produto final fora de especificação. Desta forma, os estudos visando a redução de variabilidade passaram a ter uma importância econômica muito grande, pois causam impacto direto na lucratividade do negócio. Muitos estudos foram realizados visando diagnosticar, medir e compensar o atrito. Neste trabalho, se implementam técnicas propostas na literatura para compensação de atrito em válvulas de controle. Para avaliar seu desempenho, são apresentadas as conclusões obtidas nos experimentos e são propostas possíveis implementações futuras, seguindo esta linha de pesquisa. / Friction is a nonlinearity that generally produces bad performance of a mechanical system with moving parts. In this work, the studied mechanical element is the process control valve, which is the most used final control element in process industries. The presence of friction in control valves increases control loop variability, generating impact in all plant productive chain, due to the increase of energy consumption and rejection of end product that is out of specification. In such a way, we can see that the studies aiming variability reduction had started to have a great economic importance, due to its direct impact in business profitability. Many studies have been done aiming friction diagnosis, measurement and compensation. In this work, techniques that have been proposed on the literature for friction compensation in control valves are implemented. The conclusions obtained in the experiments are presented to evaluate the performance of the compensators and possible future implementations are proposed, following this research line.

In modern aircraft, one of the most difficult issues has been how to provide avionics with adequate cooling. Future versions of the fighter aircraft JAS 39 Gripen is equipped with new applications that have increased heat loads. In previous versions of the JAS 39 Gripen avionics was cooled by zero degree air and fuel, but in the next version a liquid loop will be installed to cool the new radar.The fluid in the liquid loop is cooled to proper temperature by pressurized bleed air from the engine which is cooled by ram air. The air to cool the avionics is produced the same way and this is a very expensive process for the airplane which lowers its performance. It is important to minimize the production of cooling air and therefore three new adjustable valves that provide various components of cooling air are installed in the next version of the JAS 39 Gripen. The cooled and pressure controlled air from the engine is distributed between different avionic shelves, each containing a set of components. Depending on the type of tasks performed and current flight mode of the aircraft the requirement of functions which should be active varies and therefore also the cooling demand to avionics. The first part of this thesis studies the overall priority of how the engine bleed shall be used. This part of the thesis results in a decision basis for the distribution of cooling air to be regulated in the absence of full cooling capacity. The amount of cooling which must be distributed to the radar is proportional to its developed power which varies widely depending on the radar’s operational mode. Since the pump which determines the liquid flow velocity operates at a constant speed is the regulation of cooling to the radar is controlled by varying the bleed air flow into the heat exchanger which cools the fluid and thus the temperature of the fluid has when it reaches the radar. This part of the thesis creates a control algorithm for controlling the airflow into the heat exchanger. The regulation keeps the fluid inlet temperature to the radar within the range of +25 ± 5 ˚ C and the gradient of the temperature less than 0.5° C per second. The PI-controller with the feed-forward filter succeeded in controlling the temperature of the liquid as it reached the radar within +25 ± 1° C, the temperature gradient requirement, 0.5° C per second, was also passed in all flight cases which were used to evaluate the controller. The PI-controller with feed-forward has a low convergence time and no static error. It also performs well when the measurement signals contain a lot of noise because of the controllers integrated low pass filter.   The three new adjustable valves saves 12 to 97 g/s of cooling air for the different valve positions studied in this thesis, this corresponds to 9 - 70% of the total amount of controllable air to the avionics. Since the production of cooling air is a costly process for the aircraft, the use of all 3 valves is recommended.