José de Oliveira

Estresse: diagnóstico dos policiais militares em uma cidade brasileira

OBJETIVOS: Diagnosticar a ocorrencia e a fase de estresse em policiais militares da Cidade de Natal, Brasil, alem de determinar a prevalencia de sintomatologia fisica e mental. METODO: Estudo descritivo, com corte transversal. Foi investigada uma amostra de 264 individuos extraida de uma populacao de 3 193 militares do Comando de Policiamento da Capital. Os dados foram coletados entre junho de 2004 e janeiro de 2005 utilizando-se o Inventario de Sintomas de Stress para Adultos de Lipp. Foi determinada a presenca de estresse, a fase de estresse (alerta, resistencia, quase-exaustao, exaustao), a prevalencia de sintomas fisicos e mentais e a relacao entre estresse e unidade policial, posto policial, sexo, habito de beber, fumo, escolaridade, estado civil, idade, tempo de servico e faixa salarial. RESULTADOS: A proporcao de policiais sem sintomas de estresse foi de 52,6%, enquanto que 47,4% apresentaram sintomatologia. Dos 47,4% com estresse, 3,4% encontravam-se na fase de alerta, 39,8% na fase de resistencia, 3,8% na fase de quase-exaustao e 0,4% na fase de exaustao. Sintomas psicologicos foram registrados em 76,0% dos policiais com estresse, e sintomas fisicos, em 24,0%. Das variaveis investigadas, a unica que apresentou relacao com estresse foi o sexo (P = 0,0337), sendo as mulheres as mais afetadas. CONCLUSAO: Os niveis de estresse e de sintomas nao indicaram um quadro de fadiga critico. E recomendavel uma acao preventiva por parte da organizacao policial, que poderia incluir a aplicacao de um programa de diagnostico, orientacao e controle do estresse.

Model-based predictive direct speed control applied to a Permanent Magnet Synchronous Motor with trapezoidal back-EMF

This paper presents an investigative work about the application of State Space Model-Based Predictive Control in a three-phase Permanent Magnet Synchronous Motor with trapezoidal back-electromotive force, for speed control. Such motor is utilized in the white goods appliances industry and also in automotive and medical applications, among others, especially due to its high efficiency and long life cycle. The predictive control methods present a differential in the driving performance for industrial applications, mainly by enabling the imposition of constraints. In this work, a linear prediction model identified with a Least Mean Squares algorithm is used with the State-Space predictive control approach. Such predictive method is interesting for industrial applications for being easy to tune and, in addition to the imposition of constraints, allowing ponderation between tracking performance and spent energy. The utilization of constraints is discussed for the predictive algorithm in this work. There are satisfactory simulated and experimental results that show advantages in using the mentioned control method to drive the Permanent Magnet Synchronous Motor.

Analysis of predictive control for boost converter in power factor correction application

This work presents a boost converter design methodology for active power factor correction, using finite control set model-based predictive control (FCS-MPC) for current control. Moreover, an external proportional integrative (PI) voltage control loop design methodology is explained. This paper also compares the conventional PI current control with MPC current for this application, both in transient load disturbance condition and in steady state different load conditions. The results in rated operation are compared with IEC 61000-3-2 international standard, which establishes limits for current harmonics rms values. The design methodology shows itself effective, with results near to the expected. Both controllers presented advantages and disadvantages, many of them exhaustively discussed in this work.

Evaluation of constrained and unconstrained SESSMPC applied in five-phase PMSM

This work presents a comparative analysis of a successively evaluated state space model-based predictive control approach used to drive a five-phase permanent magnet synchronous motor. It is presented a five-phase motor modelling and control theoretical basis main concept, including the prediction model preparation, as well unconstrained and constrained formulations. Both formulations are used and compared to drive the motor, in the simulation results. The results satisfactorily demonstrate the advantages of the model-based predictive control to drive this motor, specially due to the constraints treatment.

Space Vector PWM-DTC Strategy for Single-Phase Induction Motor Control

Single-phase induction motors are widely used in fractional and sub-fractional horsepower applications, mostly in domestic and commercial applications such as fans, refrigerators, air conditioners, etc., operating at constant speed or controlled by an on/off strategy which can result in poor efficiency and low-power factor. In terms of construction, these types of motors usually have a main and an auxiliary stator winding, are asymmetrical and are placed 90 degrees apart from each other. The rotor is usually the squirrel-cage type. The asymmetry presented in the stator windings is due to the fact that these windings are designed to be electrically different so the difference between the stator windings currents can produce a starting torque (Krause et al., 1995). Since it has main and auxiliary stator windings, the singlephase induction motor is also known as a two-phase asymmetric induction motor. In recent years, with the growing concern about low-cost operation and the efficient use of energy, the advance in motor drive control technology made it possible to apply these motors to residential applications with more efficiency. Different inverter topologies have been proposed to drive single-phase induction motors, providing ways to save energy. In dos Santos et al. (2010) different ac drive systems are conceived for multiple single-phase motor drives with a single dc-link voltage to guarantee installation cost reduction and some individual motor controls. In Wekhande et al. (1999) and Jabbar et al. (2004), Campos et al. (2007a) and Campos et al. (2007b), two topologies are considered. One is a Half-bridge inverter and the other is a three-leg inverter. The cost difference between the two topologies lays in the fact that the H-bridge inverter needs two large capacitors in the dc link rated for dc link voltage. Also, there is a need of two large resistors connected in parallel with the capacitors to balance the voltage of the capacitors. Despite the fact that the three-leg inverter has more switches, the development of power modules and the need for just one capacitor in the dc link have decreased the topology cost. Along with the reduced cost, a more efficient use of the dc link voltage is achieved. Besides the effort for developing more efficient driving topologies, many strategies to control single-phase motors have been proposed. In Jacobina et al. (1999), rotor-flux control, stator-flux control and direct torque control (DTC) (Takahashi and Noguchi, 1986) are analyzed. The main drawback of the two first strategies is that they use an encoder to obtain

Fault tolerant control for permanent magnet synchronous motor

This paper presents a fault tolerant control proposal for a single Open Phase Fault (OPF) in a three-phase Permanent Magnet Synchronous Motor (PMSM). The mathematical model of the motor under open single phase is presented and its disturb to current, flux and torque are evaluated. The presented method is based on the Finite Control Set Model Based Predictive Control (FCS-MPC), and it is compared to other fault tolerant Direct Torque Control (DTC) methods. All the tests are run with the same conditions and results show that FCS-MPC has a better performance than the methods presented in the literature.

Evaluation of Luminous Performance and Lifetime of CFL in the Regime of Intermittent Use

This paper presents a methodology to evaluate the luminous efficiency and lifetime of the CFL. The variables analyzed are voltage, current, ambience temperature, relative humidity and finally the luminous flux to check the variations of illuminance in time. Measurements were made in a real scenario, in this case the residences, considering that is more aggressive than the laboratory testing. The performance of CFL and other variables measured were related to the consumer profile, because the behavior and consumer knowledge define the usage of CFL. Then, the switching was analyzed due to that the determination of life varies depending on the switching cycles (on-off). Later, test standards used by other countries were analyzed and compared with the standards of Brazil, in order to verify whether tests related to switching cycles and useful lifetime are similar or completely different.

Computational Cost Evaluation Method to Embedded Digital Control Systems

This paper presents a method to evaluate the computational cost of a function in embedded systems. This method, which uses the Least Squares method, is useful to see the sample time choice feasibility, in control applications. In this work, the developed method is used to evaluate the computational cost of the model-based predictive control to speed control of a shunt direct current motor. The method was tested using two embedded devices allowing to find the correct sample time for each device evaluated.

Evaluation of constrained SESSMPC to drive a three-phase PMSM applied in washing machines

This work proposes a study about using the successively evaluated state space model-based predictive control to drive a permanent magnet synchronous motor. The objective of this paper is to show as the control constraints and the anticipative reference characteristics influence in the drive. Still, it is done a brief analysis about the improvement of the drive efficiency with the proposed control scheme. The obtained results present the validity of the proposed approach.

Differential evolution optimization applied in multivariate nonlinear model-based predictive control

Model-based Predictive Controllers belong to a class of digital controllers which are used in many industrial applications. Such controllers have the main advantages of dealing with optimization subject to constraints and multiple-input, multiple-output systems. The optimization of the control system behavior is based on an explicit mathematical prediction model of the plant. Usually, linear approaches are used for the prediction model. However, for nonlinear plants, linear models may limit the control loop performance or even cause instability. In this work, a Nonlinear Model Predictive Controller, with optimization based on a nonlinear model performed with a Differential Evolution algorithm, was tested for position control of a robotic arm model. Simulation results show that the utilized control algorithm was able to deal with multivariable nonlinear optimization in the presence of process constraints.