Materials, technological status, and fundamentals of PEM fuel cells – A review

A review of high-temperature proton exchange membrane fuel cell (HT-PEMFC) system

There is a growing demand for low-power, small-size and ambulatory biopotential acquisition systems. A crucial and important block of this acquisition system is the analog readout front-end. We have implemented a low-power and low-noise readout front-end with configurable characteristics for Electroencephalogram (EEG), Electrocardiogram (ECG), and Electromyogram (EMG) signals. Key to its performance is the new AC-coupled chopped instrumentation amplifier (ACCIA), which uses a low power current feedback instrumentation amplifier (IA). Thus, while chopping filters the 1/f noise of CMOS transistors and increases the CMRR, AC coupling is capable of rejecting differential electrode offset (DEO) up to plusmn50 mV from conventional Ag/AgCl electrodes. The ACCIA achieves 120 dB CMRR and 57 nV/radicHz input-referred voltage noise density, while consuming 11.1 muA from a 3 V supply. The chopping spike filter (CSF) stage filters the chopping spikes generated by the input chopper of ACCIA and the digitally controllable variable gain stage is used to set the gain and the bandwidth of the front-end. The front-end is implemented in a 0.5 mum CMOS process. Total current consumption is 20 muA from 3V

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A 60 $\mu$ W 60 nV/ $\surd$ Hz Readout Front-End for Portable Biopotential Acquisition Systems

Technology and instrumentation for detection and conditioning of the surface electromyographic signal: state of the art.

Ubiquitous vital signs sensing using wireless medical sensors are promising alternatives to conventional, in-hospital healthcare systems. In this work, a wearable ECG sensor is proposed. This sensor system combined an appropriate wireless protocol for data communication with capacitive ECG signal sensing and processing. The ANT protocol was used as a low-data-rate wireless module to reduce the power consumption and size of the sensor. Furthermore, capacitive ECG sensing is a simple technique that avoids direct contact with the skin and provides maximum convenience to the user. In our work, small capacitive electrodes were integrated into a cotton T-shirt together with a signal processing and transmitting board on a two-layer standard printed circuit board design technology. The entire system has small size, is thin, and has low power consumption compared to recent ECG monitoring systems. In addition, appropriate signal conditioning and processing were implemented to remove motion artifacts. The acquired ECG signals are comparable to ones obtained using conventional glued-on electrodes, and are easily read and interpreted by a cardiologist.

A wireless wearable ECG sensor for long-term applications

AC coupling is essential in biopotential measurements. Electrode offset potentials can be several orders of magnitude larger than the amplitudes of the biological signals of interest, thus limiting the admissible gain of a dc-coupled front end to prevent amplifier saturation. A high-gain input stage needs ac input coupling. This can be achieved by series capacitors, but in order to provide a bias path, grounded resistors are usually included, which degrade the common mode rejection ratio (CMRR). This paper proposes a novel balanced input ac-coupling network that provides a bias path without any connection to ground, thus resulting in a high CMRR. The circuit being passive, it does not limit the differential dc input voltage. Furthermore, differential signals are ac coupled, whereas common-mode voltages are dc coupled, thus allowing the closed-loop control of the dc common mode voltage by means of a driven-right-leg circuit. This makes the circuit compatible with common-mode dc shifting strategies intended for single-supply biopotential amplifiers. The proposed circuit allows the implementation of high-gain biopotential amplifiers with a reduced number of parts, thus resulting in low power consumption. An electrocardiogram amplifier built according to the proposed design achieves a CMRR of 123 dB at 50 Hz.

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AC-coupled front-end for biopotential measurements

A second-order sliding mode strategy to control the breathing subsystem of a polymer electrolyte membrane fuel cell stack for transportation applications is presented. The controller is developed from a design model of the plant derived from open literature, and well suited for the design of second-order sliding mode strategies. Stability issues are solved using a super twisting algorithm. The resulting approach exhibits good dynamic characteristics, being robust to uncertainties and disturbances. Simulations results are provided, showing the feasibility of the approach.

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Sliding Mode Strategy for PEM Fuel Cells Stacks Breathing Control Using a Super-Twisting Algorithm

Grid connected wind energy conversion systems (WECS) present interesting control demands, due to the intrinsic nonlinear characteristics of windmills and electric generators. In this paper a direct adaptive control strategy for WECS control is proposed. It is based on the combination of two control actions: a radial basis function network-based adaptive controller, which drives the tracking error to zero with user specified dynamics, and a supervisory controller, based on crude bounds of the system's nonlinearities. The supervisory controller fires when the finite neural-network approximation properties cannot be guaranteed. The form of the supervisor control and the adaptation law for the neural controller are derived from a Lyapunov analysis of stability. The results are applied to a typical turbine/generator pair, showing the feasibility of the proposed solution.

Direct adaptive control of wind energy conversion systems using Gaussian networks

Fully differential amplifiers yield large differential gains and also high common mode rejection ratio (CMRR), provided they do not include any unmatched grounded component. In biopotential measurements, however, the admissible gain of amplification stages located before dc suppression is usually limited by electrode offset voltage, which can saturate amplifier outputs. The standard solution is to first convert the differential input voltage to a single-ended voltage and then implement any other required functions, such as dc suppression and dc level restoring. This approach, however, yields a limited CMRR and may result in a relatively large equivalent input noise. This paper describes a novel fully differential biopotential amplifier based on a fully differential dc-suppression circuit that does not rely on any matched passive components, yet provides large CMRR and fast recovery from dc level transients. The proposed solution is particularly convenient for low supply voltage systems. An example implementation, based on standard low-power op amps and a single 5-V power supply, accepts input offset voltages up to /spl plusmn/500 mV, yields a CMRR of 102dB at 50 Hz, and provides, in accordance with the AAMI EC38 standard, a reset behavior for recovering from overloads or artifacts.

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A novel fully differential biopotential amplifier with DC suppression

Introducing Fuel Cells.- Basics of PEM Fuel Cells.- Fundamentals of Sliding Mode Control Design.- Assessment of SOSM Techniques Applied to Fuel Cell Control.- Control-oriented Modelling and Experimental Validation of a PEMFC Generation System.- SOSM Controller for the PEMFC Generation System: Design and Implementation.- Closing Remarks.

Miguel Angel Mayosky

Papers

AC-coupled front-end for biopotential measurements

Sliding Mode Strategy for PEM Fuel Cells Stacks Breathing Control Using a Super-Twisting Algorithm

Direct adaptive control of wind energy conversion systems using Gaussian networks

A novel fully differential biopotential amplifier with DC suppression

Sliding-Mode Control of PEM Fuel Cells