José Cabral

3 Axis Capacitive Tactile Sensor and Readout Electronics

A way to determine the force that is applied to an object, for example by a manipulator, consists in the use of capacitive pressure sensors, like the one presented in this article. The major problems when reading capacitive sensors are the parasitic capacitances between the wires that connect the sensing elements to the interface electronics. The present article describes a capacitive tactile sensor that measures the force in the three axis xx, yy, and zz) and its interface electronics, which consists in a technique that reduces substantially the parasitic capacitance effects. The readout electronics basically is constituted by a 40 kHz voltage source and a current to voltage converter that works as an ammeter. Despite some practical limitations in the complete elimination of the parasitic capacitances, caused by the output impedance of the voltage source and the input impedance of the ammeter, the present work demonstrates that the three axis capacitive tactile sensor and its readout circuit are valid concepts to be applied in the robotics field

Development of a 1 Mbps low power acoustic modem for underwater communications

Underwater wireless communication systems are becoming a priority in terms of research and technological development due to the increasing demand for exploring the oceans in areas such as pharmaceutical, oil, minerals, environmental and biodiversity. This demand is increasing exponentially with the need for high data rate and near-real-time communications. In this work an underwater low power acoustic modem to operate over tens of meters, achieving a maximum data rate of 1 Mbps, is presented. This solution allows for reprogramming the digital signal processing block enabling the use of different types of digital modulations in order to improve the modems performance. The system is based on a poly(vinylidene fluoride) PVDF ultrasonic emitter transducer which is capable of sending high quality signals needed for digital modulations with high symbol rates per carrier period. BPSK, BFSK and OOK modulations have been tested. The results registered were 3×10-3 BER with 1 Mbps OOK, 2.3×10-5 with 512 kbps and 1×10-8 with 256 kbps.

Scheduling Algorithms to support QoS and Service Integration in Sensor and Actuator Networks

In this paper we analyse and evaluate several Scheduling Algorithms that are candidates to support Quality of Service and Service Integration in Sensor and Actuator Networks. They should satisfy two main goals: to guarantee committed delays for time sensitive services, and to improve the network transmission efficiency. The algorithms are described and some results, obtained by simulation, are presented. The proposed Traffic Class Oriented Algorithm proved to be a good solution to meet the proposed objectives as well as to integrate traffic generated by Fieldbus devices and control applications in real communication networks.

SU-8 microfluidic mixer for use in lab-on-a-chip devices for biological fluids analyses

This paper describes an easy-to-fabricate and low-cost SU-8 microfluidic mixer suitable for enabling a mixing process based on diffusion. It is developed to be an integrated part of a lab-on-a-chip for measuring the concentration of four biomolecules in urine samples, by optical absorption. The design of the microfluidic system is based on computational fluid dynamics techniques. Mixing and reaction of the components of the process must be simulated by solving the flow and mass transport equation. A good design must guarantee the mixing of the reactants to assure an uniform mixture at the detection zone. The resulting design and the experimental results are supported by numerical simulations, which allow a reliable quantitative analysis of the concentrations after the mixing process. The reduced size, weight and the simultaneous measurement of more than one biomolecule concentration will improve the performance of biological fluids analyses in clinical laboratories and consequently the quality of the medical diagnostic.

Piezoelectric sensor for acoustic wave detection in anisotropic systems

This paper describes a seismic wave sensor, its readout electronics and data acquisition system. The seismic sensor is based on piezoelectric materials, which show the ability of transforming mechanical into electrical signals. In particular, the present sensor is based on a piezoelectric polymer, poly(vinilidene fluoride) as its main characteristics made it suitable for detecting the amplitude and frequencies involved in seismic events. After a general background on seismic events, waves and piezoelectric materials, the main steps on the sensor design and fabrication, the data acquisition system and the first test results are presented.

A System Architecture for Low Bit Rate Traffic Aggregation in Control Applications

This paper describes the results of research work aimed at providing an efficient solution to the aggregation of low bit rate traffic in control applications. It includes the proposal and analysis of an architecture that integrates terminal adapters and a concentrator connected to a remote control application through a communication network. The ATM technology was selected to implement the proposed system due to its properties of multiplexing efficiency and control of packet delay. Scheduling algorithms for the terminal adapter and concentrator have been developed in order to satisfy two main goals: to guarantee committed delays for time sensitive services, and to increase the network transmission efficiency. The results, obtained by simulation, show that the system performance complies with the requirements of the majority of control applications

High data rate acoustic modem for underwater aplications

The development of an underwater wireless communication systems is becoming a research and a technological priority due to the increasing demand for exploring the potential of oceans in fields such as pharmaceutics, oil, minerals, environmental and biodiversity. However, underwater wireless communications still fail to ensure high data-rate connections which support real time applications. In this work a low power high data-rate acoustic modem is presented, based on a piezoelectric poly (vinylidene fluoride) polymer as a transducer and a Xilinx Field Programmable Gate Array (FPGA) that can be programmed to work with different types of modulations. The system has been validated by the implementation of a full duplex point-to-point communication at 1 Mbps using On-Off Keying (OOK) modulation with a 1 MHz single carrier and it represents a major advance in the state of the art and a breakthrough in underwater acoustic communications, being the first to show the possibility to achieve data rates up to 1Mbps. It was successfully tested with a 1 Mbps rate, achieving a 3×10-3 Bit Error Rate (BER) using just 1.4 μW of power consumption per bit.

Design and Development of a Prototype Electrotherapy Device

This article describes a complete prototype system that can be used in electrotherapy treatments, that is, in medical treatments involving electric currents. The system is composed of two main blocks: the master and the slave. The Master block, whose main component is a CPU, controls the user interface. The Slave block, which is composed of a microcontroller and a wave generator, produces the appropriated voltages and currents compatible with the desired treatment. The whole system is powered by a 12 V power supply and the output signal voltage ranges between -100 V and 100 V. Despite the prototype being able of performing all the electrotherapy treatments in the low-medium frequency ranges, it was tested in aesthetic mesotherapy, namely in anticellulite, located anticellulite, antistretch, and antiflaccidity. In these treatments, the output signal is composed of an overlap of two frequencies: the first one is selected in the range of 1.2 kHz - 1.8 kHz and the second in the range of 0.07 Hz - 2 Hz. The system was tested in a clinical environment with real patients. It showed good results both in effectiveness of treatments and in terms of pain suffered by the patients.

Dilatometer for characterization of thermal expansion of ceramic samples

This article describe the design, fabrication steps and experimental results of a dilatometer that will be used to characterize ceramic samples in terms of thermal expansion. The basic idea is to heat a 25 mm ceramic sample up to 1000oC and register its dimension variations during the rising and the falling of the temperature. The device prototype consists in a master-slave structure since there are two control units: the high-level one (master) and a low-level one (slave). The highlevel control unit will be responsible for supporting the user interface, exchanging and processing the necessary information between the user and the low-level control unit. The low-level control unit main component is a microcontroller. It is responsible for acquiring data from the strain and temperature sensors and controlling the temperature of the samples. The experimental results show that the prototype is appropriate for dilatometry essays once the maximum error was 0.037% of full-scale.