Design and Automation of a vertical electrospinning system for manufacturing nanofibers

The objective of this research consists of the design, construction and automation of the electrospinning mechatronic system to obtain nanofibers. As a first stage, the structure of the electrospinning mechatronic system and the distribution, injection and manifold system were designed and built. In the second stage, the open-loop control system was outlined and implemented. It is made up of: control, isolation stage, and the plant. In the first element, the LabView interface and ATMega2560 microcontroller were used to manipulate the variables of the injection speed and distribution of the solution, the speed of the nanofiber collector and the height between the capillary tube and the collector, the magnitude of the temperature and humidity from the environment, also, the graphic interface was developed, the second element consists of isolating the control and power stage in addition to amplifying the command signals and enabling the correction elements, the third element receiving the signals from the power stage to perform the action and produce a change in the controlled variables in the process. With this prototype, it is intended to obtain nanofibers from different polymer solutions for use in the area of catalysis and biomaterials.

Design and Development of Non-Linearly Controlled Class-D Audio Amplifier

A systematic and simple approach to develop a 20 W audio frequency range switch mode amplifier is presented in this paper. A non-linear sliding mode (SM) technique-based low cost analog controller enables the realized amplifier to deliver highly linear and efficient operation throughout the audio frequency spectrum. The theoretical aspects and practical limitations in the design and realization of subsystems, such as the signal conditioning stage, power stage and sliding mode controller, are considered, while the viable solution is also stated and justified. The hardware realization scheme is also elaborated, based on which the laboratory prototype is fabricated. Hardware results with a 4 Ω resistive load are given on which the performance of the amplifier is evaluated. The total harmonic distortion (THD) below 1% and 73% efficiency at peak load make the amplifier well suited for high quality audio application.

Variable DC Approach in Fuel cell And Battery Powered Marine Power Systems: Control of The Fuel Cell Power Converter

Previously, the Variable DC approach concept was proposed for operation of hybrid fuel cell and battery powered marine vessels. The concept was shown to provide significant efficiency improvement, and consequently improved hydrogen fuel savings. However, although the general concept and the control of battery DC/DC converter has been detailly described in previous works, the operation of fuel cell DC/DC converter in different Variable DC approach control modes has not been presented. This paper proposes a fuel cell DC/DC converter control system specifically designed for operation in the three Variable DC approach control modes. The functionality of the proposed fuel cell DC/DC converter and the Variable DC approach in general is verified using a hardware-in-loop test setup consisting of virtual power stage models and real converter controllers. The system is shown to function well in both normal operating conditions and various fault conditions.

Two Stages of Speech Envelope Tracking in Human Auditory Cortex Modulated by Speech Intelligibility

The envelope is essential for speech perception. Recent studies have shown that cortical activity can track the acoustic envelope. However, whether the tracking strength reflects the extent of speech intelligibility processing remains controversial. Here, using stereo-electroencephalogram (sEEG) technology, we directly recorded the activity in human auditory cortex while subjects listened to either natural or noise-vocoded speech. These two stimuli have approximately identical envelopes, but the noise-vocoded speech does not have speech intelligibility. We found two stages of envelope tracking in auditory cortex: an early high-γ (60-140 Hz) power stage (delay ≈ 49 ms) that preferred the noise-vocoded speech, and a late θ (4-8 Hz) phase stage (delay ≈ 178 ms) that preferred the natural speech. Furthermore, the decoding performance of high-γ power was better in primary auditory cortex than in non-primary auditory cortex, consistent with its short tracking delay. We also found distinct lateralization effects: high-γ power envelope tracking dominated left auditory cortex, while θ phase showed better decoding performance in right auditory cortex. In sum, we suggested a functional dissociation between high-γ power and θ phase: the former reflects fast and automatic processing of brief acoustic features, while the latter correlates to slow build-up processing facilitated by speech intelligibility.

Analysis of Efficient FPGA Based Pid Controller For Dc-Dc Buck Boost Converter Using Hardware Co-Simulation Setup

Converters are widely used in smart grid applications where multilevel dc voltage source are required in a system. There are few critical challenges in existing converters such as low efficiency, slow response time, large circuit size due to more number of switches subsequently poor quality of PWM signal. Moreover, a separate converter is required for each source used in the circuit. In this work, we proposed and analyse an efficient FPGA based PID controller using Hardware Co-simulation for DC-DC Buck Boost Converter. We have successfully integrated two different sources of energy which are being fed to the power stage. The control of this converter topology is implemented by using FPGA kits Virtex5 and Virtex7. Furthermore, efficiency of both kits is compared and analysed. The proposed converter has high efficiency, fast response time and compact size due to least number of switches as compared to conventional topology of such converters.

Supercapacitor Assisted Hybrid PV System for Efficient Solar Energy Harnessing

In photovoltaic (PV) systems, maximum power point (MPP) is tracked by matching the load impedance to the internal impedance of the PV array by adjusting the duty cycle of the associated DC-DC converter. Scientists are trying to improve the efficiency of these converters by improving the performance of the power stage, while limited attention is given to finding alternative methods. This article describes a novel supercapacitor (SC) assisted technique to enhance the efficiency of a PV system without modifying the power stage of the charge controller. The proposed system is an SC—battery hybrid PV system where an SC bank is coupled in series with a PV array to enhance the overall system efficiency. Developed prototype of the proposed system with SC assisted loss circumvention embedded with a DC microgrid application detailed in the article showed that the average efficiency of the PV system is increased by 8%. This article further describes the theoretical and experimental investigation of the impedance matching technique for the proposed PV system, explaining how to adapt typical impedance matching for maximum power transfer.