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This paper presents a nonlinear model for a hydraulic amplifier, a component of the governor in the speed control loop of hydroelectric power plants. The amplifier transforms the electrical signal of the controller into mechanical movement of the turbine components, including the switching characteristics. This model is used to propose, on the one hand, a Piecewise Affine (PWA) representation for the hydraulic amplifier, and, on the other hand, a methodology for estimating the model parameters using field measurements, which facilitates its practical implementation. This representation is referred to as semi-physical because the model parameters are closely related with the physical construction of the hydraulic amplifier components. Among the advantages of this PWA representation are the appropriate structuring for use in system identification methods, for estimating its parameters, and the existence of advanced control techniques that use this structure in controller design, thereby improving the load-frequency control performance. The paper concludes with a description of the results, including the parameters that were estimated by using the hydraulic amplifier model with PWA structure.

Power system transient analysis relies on the deployment of models with ever-increasing accuracy that represents the system's frequency-dependent components with respect to the phenomena being scrutinized. A key issue in this context is the construction of a model yielding passive properties for each system component. Such properties are commonly compromised by corrupting noise in measurements that serve as input to the computation of blackbox models. In addition, model passivity could be further compromised during parameter estimation. This paper undertakes the task of developing a proposal to build an optimization methodology based on linear matrix inequalities (LMI-based) which is intended for obtaining an optimal, passive, blackbox model for a $n$ -terminal power transformer. The resulting model can be further realized as a circuit representation in order to simulate the transformer dynamics in an Eletromagnetic Transient program (EMT type). The results derived from two operating power transformers are later provided to confirm how effective the procedure herein proposed is.

This article presents a novel approach to analysing a power transformer’s internal response to system transients. In this approach a hybrid modelling methodology is adopted which leverages the distinct advantages offered by both Black and Grey Box modelling techniques. The Black Box model of the transformer is used within the EMTP system study environment in order to take advantage of its mathematical flexibility and modelling accuracy. Transients derived from network switching operations within the study can then be used for injection tests within the Grey Box modelling environment. The Grey Box model, which is based upon the physical structure of the transformer, will facilitate analysis of the transformer’s internal voltage response to the external stimulus. A fundamental difference between the approach described in this paper and more traditional approaches is that it does not require prior knowledge of the internal geometry of the transformer. All of the modelling parameters are derived from external tests, nameplate details and an intrinsic understanding of common transformer design principles. This can be a distinct advantage since in most cases a transformer’s design specifications are not readily available outside of the laboratory due to the manufacturer’s intellectual property restrictions. A study of a gas insulated substation within a hydroelectric power plant in Brazil is used to demonstrate the proposed technique.

This paper presents practical results from the application of a new synthesis methodology based on model predictive control (MPC) applied to a three-wheeled omnidirectional mobile robot seeking to follow pre-established trajectories. The approach is based on the definition of an objective function with a finite future time horizon. The resulting optimization problem is declared in the form of linear matrix inequalities (LMIs). The closed loop stability of the system is guaranteed through constraints related to the non-increasing monotonicity of the objective function. Constraints are also implemented in the manipulated variables with the objective of adapting the control system to the physical limitations of the robot. Additionally, methods are described to handle the computational delay in the robot model and to adjust the control law to improve the global performance of the system.

The wireless power transfer can be useful in applications where the use of cables for powering remote devices are not suitable or even feasible. However, the transferred power is highly dependent on the relative position between the transmitter and receiver coils as well as other circuit parameters. The use of adaptive matching network in wireless power transfer system allows to track the maximum power transferred to the load while changing the magnetic coupling between the coils. By controlling both, the excitation frequency and matching capacitor at the primary side of the inductive link, the output power can be hold approximately constant over a large range of magnetic coupling coefficient. This paper presents an automatic compensation method for an inductive power transfer system. The proposed method monitors the magnitude and phase of the input current of the inductive link. Thus, the data is processed by a fuzzy logic controller actuating on the working frequency and on the matching capacitor in order to maximize the power transferred to the load. The proposed method can tolerate the movement of remote devices while charging processes.

This paper presents a new method using Fuzzy Logic for generating lightning warnings. This methodology uses information about the atmospheric electric field, the lightning dynamics around the interest site, and lightning distance information. This information was combined by Fuzzy Logic which had its membership functions optimized by Genetic Algorithms. In addition, the objective function was composed by multiple performance indicators proposed in this work. The proposed methodology was tested in a case study, generating lightning warning for an oil refinery. The results were compared with other methods and it was concluded that this new method shows up to be the most effective in generating lightning warnings.

The paper presents a methodology for state feedback MPC synthesis applied to the trajectory tracking control problem of a three wheeled omnidirectional mobile robot. The MPC design used here is based on a cost function developed over finite horizon and LMI framework. It is shown that MPC concepts well established for robot applications, for instance, the use of open loop predictions, receding horizon control, constraints manipulation, are preserved in this new formulation. The stability of the closed loop system is guaranteed by LMI conditions related with the cost function monotonicity. Simulation results of navigation are provided to demonstrate the performance of the proposed control strategy.

Automated test systems (ATS) are application-specific systems that help in enhancing reliability and productivity of testing activities in different stages of product development cycle and manufacturing. Different tests are necessary to anticipate and validate a product and its sub-systems performances along the development cycle. Moreover, in the production phase, quality control systems that perform up to 100% inspection may be present and the integration of test results with company's management systems may be required. In this paper, the design of ATS is analyzed under the light of design methodologies, which can basically be understood as procedures stating stages and intermediary results to discipline the development process of technical systems. Usually, design methodologies are presented as a set of prescribed actions and recommendations, kept with some degree of generality to allow their compatibility with a wide range of industrial products, based on different technology branches. In this paper, an adaptation of Pahl and Beitz's approach allowed the derivation of a reference model to ATS development. Proposed stages are explained considering ATS typical division, i.e.: physical system, hardware and software. The adapted methodology, in which prescriptions are made with an intermediary degree and directed to one particular kind of system, can make easier the design of a highly context-dependant kind of system, helping the design team to consider important aspects in decisions taken along the development process and keeping these decisions linked to the requirements defined in early stages. Through the use of the proposed methodology, shorter development cycles are expected, since less design loops tend occur in a higher-systematization environment.

The present work is focused on the study of indoor thermal comfort control problem in buildings equipped with HVAC (heating, ventilation and air conditioning) systems. The occupants’ thermal comfort sensation is addressed here by the well-known comfort index known as PMV (predicted mean vote) and by a comfort zone defined in a psychrometric chart. In this context, different strategies for the control algorithms are proposed by using an only-one-actuator system that can be associated to a cooling and/or heating system. The first set of strategies is related to the thermal comfort optimization and the second one includes energy consumption minimization, while maintaining the indoor thermal comfort criterion at an adequate level. The methods are based on the model predictive control scheme and simulation results are presented for two case studies. The results validate the proposed methodology in terms of both thermal comfort and energy savings.

This work is focused on developing control algorithms for hygrothermal process represented by mixed logical and dynamical models. An example is the closed newborn incubator. Such kind of system promotes a controlled micro-climate, with small heat transfer between the premature and the environment, leading to comfortable and healthful environment. This device can be represented by a piece-wise linear model having discrete values for the input signal range. A hybrid predictive control scheme is proposed for such a process. The algorithm can also be applied to different dynamic systems having the same characteristics and it is easy to be implemented in real-time environments. System identification results based on orthonormal basis functions for finding the set of linear transfer functions are discussed. Closed-loop control experiments, by using an actual laboratory pilot plant (full scale), are performed and presented to validate the proposed method.

The present work is focused on the study of indoor thermal comfort control problem in buildings equipped with heating systems. The occupants' thermal comfort sensation is addressed here by a comfort index known as PMV (Predict Mean Vote). In this context, two control algorithms are proposed by using only-one-actuator system associated to the heating system. The methods are based on the model predictive control scheme and on the improvement of the PMV index together with energy minimization. Simulation results - obtained by using the weather data file for the city of Curitiba, Brazil - for two case studies: i) variations between low and moderate occupants metabolic rates and ii) variations between moderate and high occupants metabolic rates are presented to validate the proposed methodology in terms of room air temperature, relative humidity and PMV control.

This work is focused on hygrothermal control problem of closed newborn incubators. Such incubator promotes a controlled micro-climate, with small heat transfer between the premature and the environment, which promotes a healthful environment. In this context, the main hygrothermal informations are temperature, relative humidity and partial vapor pressure where the last one is closed related with the water loss by transpiration. A model predictive control scheme for this problem is presented and real time closed-loop control examples validate the proposed method in such a context. The identification procedure, a need in model based control schemes, is based on the use Laguerre functions and the experiments are performed on a laboratory pilot plant (full scale) which was built to evaluate control algorithms in incubators.

This work is focused on temperature and humidity control problem of closed newborn incubators. Such incubator promotes a controlled micro-climate, with small heat transfer between the premature and the environment, leading to a healthful environment. In this context, a laboratory pilot plant (full scale) was built to evaluate control algorithms and this plant is presented here. Furthermore, some identification results based on the use of orthonormal basis functions are discussed and a control scheme is also proposed. This control law is based on multiple local models and predictive control ideas. Closed-loop control examples validates the proposed method.

This work is focused on indoor thermal comfort control problem in buildings equipped with HVAC (Heating Ventilation and Air Conditioning) systems. The occupants thermal comfort is addressed here by a comfort zone in the psychometric chart and the PMV (Predict Mean Vote) index. In this context, three control algorithms are proposed by using only-one-actuator system associated to a heating equipment. The methods are based on the model predictive control scheme and on the improvement of indices related to occupants thermal comfort sensation. Simulation results – obtained by using the weather data file for the city of Curitiba, Brazil – are presented to validate the proposed methodology in terms of room air temperature, relative humidity and PMV control.

This paper addresses the problem of closed-loop position control and trajectory tracking of nonholonomic unicycle-type mobile robots with visual-based navigation. The robot focused here has two coaxial wheels, each one driven by an independent DC-motor. The control problem is solved by a Nonlinear Model Based Predictive Controller (NLMBPC) which contains some modifications in order to deal with the system characteristics and improve its tracking behavior. Stability properties of the closed loop system are analyzed and a comparison with a linear MBPC is presented. An actual nonholonomic robot platform, the Khepera robot, is used to validate the proposed strategy.

This paper is focused on the problem of obtaining wide band transformer models for electrical power system transient simulation purposes. It is analyzed the use of orthonormal basis functions models in such context. A model structure selection strategy, based on the transformer properties, is discussed and the frequency-domain parameter estimation procedure is presented. Identification results, based on actual transformer frequency response data, are presented and discussed.

The present paper is focused on thermal comfort control for building occupants. Thermal comfort is addressed here by the use of PMV index for such measurement. Based on PMV, two predictive strategies characterized by having terminal constraints are proposed and compared. The first is based on generating a temperature set-point signal that optimizes the building (single zone) internal PMV value. The second includes the PMV model in the controller prediction computations, generating a non-linear PMV model having Wiener structure. In both cases, the linear part of the model is built by using Laguerre basis. Simulation results, conducted with actual climate data, illustrate the performance of the thermal comfort control algorithms.

In this paper, the mathematical model of a secondary system (fan-coil) of a HVAC equipment is described. This system was inserted into a computer code developed in Matlab/Simulink platform devoted to the analysis of buildings hygrothermal behavior and performance of closed-loop control systems. The model is presented in terms of state-space variables that represent the energy and mass balance for each component of the fan-coil. Results are presented in terms of a comparative analysis of the cooling coil temperature and external air ventilation rate effects on the room air psychrometrics state. Finally, the control system performance is presented for both temperature and relative humidity.Copyright © 2004 by ASME

For Electric Power System safety and stable operation, planning and analysis by using simulation environments are necessary. An important point for frequency stability analysis is, on one hand, an adequate representation of Load-Frequency Control (LFC) loops and, on the other hand, the design of advanced control strategies to deal with the power system dynamic complexity. Therefore, in this paper we propose to represent the group turbine/penstock, found in hydropower plants, in a Piecewise Affine (PWA) modelling structure. Based on such modelling, we also propose the use of a Hybrid Model Predictive algorithm to be use as a control law in LFC loops. Among the advantages of this PWA representation is the use of this model in the controller algorithm, thereby improving the Load-Frequency Control performance. Simulation results, on a 200 MW hydropower plant compares the performance of predictive control strategy presented with the classical PID control strategy in an isolated condition.