Cícero da Rocha Souto

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.

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.

Sistema de controle adaptativo aplicado a um sistema de distribuição de água com ênfase na eficiência energética

Esta pesquisa objetivou projetar um sistema de controle adaptativo para o modelamento e controle, em tempo real, de um sistema de distribuicao de agua. Os controladores atuaram no controle da pressao por meio da variacao da velocidade de rotacao do sistema de bombeamento e do ângulo de abertura de valvulas de controle. O sistema de controle e do tipo Variância Minima Generalizado (GMV) autoajustavel, cujos parâmetros foram estimados em tempo real pelo metodo dos minimos quadrados recursivo (MQR). Os ensaios realizados na bancada experimental apresentaram resultados satisfatorios, com um erro maximo no controle de pressao de 2,12% (0,42 mca) e uma reducao de 19,2% no consumo de energia eletrica para o sistema atuando na condicao mais desfavoravel.

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.

Development and characterization of an electric power generator using piezoelectric (PZT) subjected to base excitation

This paper presents the development and characterization of an electric power generator device using a piezoelectric material made of Lead Zirconate Titanate (PZT). The device was built like a mechanical structure in which were coupled eight piezoelectric cells subjected to cyclical loads of traction and compression, which work as electricity generator. For the experimental characterization, a system was mounted and instrumented to measure the acceleration and generated voltages. Initially numerical simulations were developed to guide the set of experimental actions. The simulated and experimental results obtained of the dynamics of the generator and the electric voltages generated are presented. The maximum power developed by the generator was 9.760 mW submitted to a base acceleration of 18.3 m/s² at a frequency of 60 Hz.

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.

Study of the stability of the NiTi wire applied to thermomechanical actuators

Shape memory alloys (SMA) have been the subject of several studies due to their excellent physical and mechanical properties. For this reason, a wire SMA is used in various applications as thermomechanical actuators that are subject to repeated thermal cycling in a range of temperatures and variable loads. The mechanical stability is a fundamental behavior that need to be understood to project well accurate actuators. Thus, the total recoverable strain must be constant under certain external conditions. In this research, an apparatus was built to monitor the recoverable strain in Ni-Ti SMA wire with differentiated thermomechanical training during prolonged thermal cycles under constant loads. Experimental results have shown that the recoverable strain decreases with cycling. In addition, an acceptable stabilization can be found for a specific condition of thermomechanical training and constant load.

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.

Characterization of thermoelectric cell for electric power generation

The thermoelectric effect has been studied in the world as an alternative source for electric power generation ranging from low to high levels of potencies. In particular, it has been studied the possibility of recovering thermal energy dissipated in the environment to generate levels of low potencies, but they are able to feed low-power electronic circuits with small thermoelectric generators. In this context, this paper presents a study of the behavior of the Seebeck effect in a Peltier cell for the purpose of electric power harvesting. For this study the Peltier cell was heated and cooled cyclically with a controlled thermal system and the response of electric power generation was registered. The heating and cooling were produced respectively by an electrical resistance and for a Peltier cell and were controlled by a Proportional-Integral controller (PI). With the obtained results it was possible to note the linearity of the thermoelectric effect relating the responses of electrical voltage produced by the cell with the temperatures applied to their faces. In this case, the voltage response performed proportional to the applied heat flux as expected.