Simplício Arnaud da Silva

Artificial Biometric Finger Driven by Shape-Memory Alloy Wires

This paper presents the design and testing of an artificial finger based partly on biomechanics. The prototype was manufactured in acrylonitrile butadiene styrene plastic using a rapid prototyping three-dimensional printer. The flexing of the finger was realized by Ni-Ti shape-memory alloy (SMA) wires with diameters of 0.3 mm, activated by resistive heating. The results obtained show the new prototype to be superior in performance, mainly in terms of angles of rotation of the phalanges, compared with some SMA fingers discussed in the literature.

A Carrier-Based PWM Technique for Capacitor Voltage Balancing of Single-Phase Three-Level Neutral-Point-Clamped Converters

In this paper is presented a PWM technique for single-phase neutral-point-clamped converters for capacitors voltage balancing. The technique is based on the injection of a common mode voltage signal into the sinusoidal modulating signals of the conventional carrier-based pulse width modulation. Although several strategies have been reported for such a problem by using the voltage signal injection, the proposed method is very simple with easy implementation. It is presented a set of equations to demonstrate how the injected voltage signal introduces a dc component on the neutral-point current, which can be controlled in order to allow the capacitors voltages balancing. Selected results have been used demonstrate the effectiveness of the proposed strategy.

Generalized Minimum Variance Control for Water Distribution System

This paper presents the project of an adaptive control system to modeling and controlling, in real time, a water distribution system. The controllers act in determining the turning speed of the motor/pump set and in the opening angle of control valves. An experimental workbench was set aiming at modeling and identifying parametrically a hydraulic network. The control system is a Generalized Minimum Variance self-tuning (GMV), whose parameters where real-time estimated by the recursive least squares (MQR) method according to the imposed inputs to the converter and the valves. The GMV aims at the pressure control in measuring points, which provided the reduction of energy and water in the workbench. Experimental results show the performance of adaptive control system and its ability to control the water distribution process.

An integration algorithm for induction motor stator flux estimation with DC offset compensation

This paper presents an integration algorithm for induction motor stator flux estimation. The proposed algorithm is able to solve the problems associated with pure integrators and operates over a wide speed range. The estimated and the actual stator flux are indirectly compared by using the estimated electromagnetic torque and the measured load torque.

Application of artificial vision as measurement validation tests on a robotic hand driven by shape-memory alloys

In this work, a robotic hand has been developed. This hand is driven by SMA (Shape Memory Alloy) wires. Some researches has showed the high rejection rate by the amputees using prosthetic upper limbs due to several problems, such as weight, high noise and need of anthropomorphism. In this context, it is presented the development of a robotic hand which is not driven by conventional actuators, in this case, SMA actuators. The mechanical structure of the robotic hand was designed using a computer program (CAD) and subsequently manufactured in ABS (acrylonitrile butadiene styrene) polymer by a rapid prototyping machine (3D printer). The robotic hand was instrumented with a bend sensor (also known as Flexsensor) to monitor the angles formed by each phalanx. The data presented, as the obtained angles, were quite satisfactory for this application. In order to corroborate the data presented by the bend sensor, a system was developed using a camera to procedure a non-contact measurement with image processing.

Automatic Directing System for Controlling the Vibration of Frame Structures in Any Horizontal Direction Using a Hybrid Mass Damper

AbstractThis paper presents a hybrid system for controlling wind-induced flexural vibration of a frame structure in any vertical plan. The system was implemented and tested in a prototype reduced-scale two-floor building, which had steel decks supported by four columns of aluminum. The actuator consisted of a direct current motor that slid on a rail placed on top of the structure. The displacement of the motor was synchronized with lateral displacements of the structure obtained from the deformations of the columns, which, in turn, were measured by strain gages. A proposed system to automatically adjust direction was incorporated to the actuator to position it at the plan in which the structure oscillates, thus enabling a single mass to be used to absorb vibration in any vertical plan. The fuzzy control technique was employed in this control system, which was shown to be adequate for attenuating vibration.

Controlador vetorial neural para mesa de coordenadas XY

Este trabalho apresenta uma nova estrategia de acionamento para uma mesa de coordenadas XY, denominada de Controle Vetorial Neural, utilizando uma rede neural multicamada (RNMC) atuando como controlador adaptativo direto, cujo algoritmo de aprendizagem se baseia na minimizacao do erro entre o vetor de posicao atualizado e o de referencia. Duas estrategias de controle sao mostradas. A primeira estrategia e baseada no uso de controladores de posicao neurais, independentes, para cada eixo e a segunda e apresentada como principal contribuicao deste trabalho e e baseada no uso do Controlador Vetorial Neural. A estrategia proposta e diferenciada dos conhecidos controladores de trajetoria por nao possuirem controladores independentes para cada eixo. A mesa de coordenadas XY, usada para validacao, e uma estrutura de dois graus de liberdade considerada como um manipulador de eixos desacoplados. Resultados experimentais e de simulacao mostram o desempenho superior do Controlador Vetorial Neural. Um menor tempo de processamento no uso de uma unica rede neural e uma vantagem adicional do uso do Controlador Vetorial Neural em relacao aos controladores independentes.

Electronic instrumentation for the characterization of a rotary thermoelectric motor driven by shape memory alloy springs

The possibility of using Shape Memory Alloys (SMA) has been currently studied in development of actuators and thermoelectric motors. Generally, these devices use the SMA characteristics of high strain or force capability to produce the displacement and, in this case, the displacement is produced by supplying heat to the actuator element. Their applications are still limited to low speed, but, with the possibility of high torques. When they are used as a thermoelectric motor, the development of a suitable instrumentation becomes indispensable to drive and measure the electrical parameters and the motor motion. Based on that need, this paper presents the electronic instrumentation to characterize a thermoelectric motor grounded on shape changes in shape memory alloys. The prototype of the motor has been built using mini SMA springs as active elements. The geometry of the motor and the spring support base have been developed in ABS (Acrylonitrile Butadiene Styrene) polymer. A current amplifier circuit was designed to generate heat and, consequently, produce the motor displacement. The circuit was switched for pulse width modulation (PWM), which has produced the heating by Joule effect. The image technique has been used with a camera placed on the rotor shaft and the SMA actuator, for the strain and displacement measurement. A load cell has been used for the force measurement and a thermocouple for the temperature measurement, both properly conditioned. The electrical current and the potential difference have been measured on it, and so, the electrical resistance variation of the actuator was obtained. Thus, in order to consolidate the thermoelectric motor characterization, results of electrical resistance, force and displacement are presented as a function of heating temperature on the actuators. Furthermore, results of force related to strain and the motor shaft rotation in the time domain are also shown.

Detecting soil parameters from a small tracked vehicle

Tracked robots have been studied for years, to high-level applications, such as autonomous navigation in areas of difficult access and maneuvering strategies that allow better performance compared to other types of vehicles. The full operation of a robotic system depends on ensuring the functioning of all its parts, which can be divided hierarchically or functionality. There is a consensus that the kinematic model can be simplified for most analyzes. Likewise, the dynamic model is greatly simplified because of its complexity and uncertainty, but not allowing use of models that approximate the actual behavior. The dynamic approach proposed in this work includes a lateral drag force, causing the tracks moves in curvilinear, considering their non-linearity and strong coupling between the tracks. The traction performed by the vehicle is from electric DC motors. Also it is presented the implementation of a procedure for detecting parameters of the interaction between the tracks and the soil, by estimating the coefficients of kinetic and dynamic friction, from the measurement of current supplied to the engines while performing a maneuver.

ECONOMIA DE ENERGIA EM SISTEMAS DE BOMBEAMENTO: APLICAÇÃO DE UM SISTEMA FUZZY

This paper deals with the impact of variable speed drives on the power requirements and a system control performance of pumps. The investigation indicates that the adoption of Variable Speed Drives (VSD) reduces pump energy consumption in certain cases, reduces the pressure in the hydraulic networks and improves pump efficiency during most of the partial load conditions. The use of fuzzy system to provide new control functions that are outside the domain of traditional control is sought in this paper, where fuzzy control is likely to provide the greatest payoff. The development and application of a fuzzy control system for a pumping system, operating with variable rotational speed are presented to demonstrate the energy savings provided by the adoption of the PWM frequency inverter in an experimental system. The control system is responsible for maintaining the manometric height of the pump at an optimal value, eliminating any excess pressure at the critical point of the water distribution network. The results of the experiments show that the fuzzy systems are efficient and the control of the rotational speed resulted in a reduction of 35% in the consumption of electricity. Keywords: Fuzzy system, Water distribution system, Energy efficiency, Pressure control, Variable frequency drive. RESUMO Este artigo apresenta a influencia do uso de inversores de frequencia no consumo energetico de sistemas de bombeamentos e o desempenho de um sistema de controle para atuar nesses equipamentos. A pesquisa indica que a adocao de inversores reduz o consumo de energia em determinadas aplicacoes, reduz a pressao nas redes hidraulicas e melhora a eficiencia da bomba. O desenvolvimento e aplicacao de um sistema de controle Fuzzy para conjuntos motor-bomba operando com velocidade de rotacao variavel sao apresentados para demonstrar a economia de energia resultado da adocao do inversor de frequencia PWM em um sistema experimental. O uso deste sistema para condicoes de operacao que estao fora do dominio do controle tradicional e procurado neste trabalho, em que o controle Fuzzy e susceptivel de proporcionar maior retorno. O controlador e responsavel pela manutencao da altura manometrica da bomba em um valor otimo, eliminando qualquer excesso de pressao no ponto critico da rede de distribuicao de agua. Os resultados das experiencias mostraram que o sistema Fuzzy foi eficiente e o controle de velocidade de rotacao resultou numa reducao de 35% no consumo de eletricidade. Palavras-chaves: Sistema Fuzzy, Sistema de distribuicao de agua, Eficiencia energetica, Controle de pressao, Inversor de frequencia.