Search results for "frequ"
showing 10 items of 2272 documents
Controlling muscular force by functional electrical stimulation using intelligent PID
2015
Functional Electrical Stimulation (FES) appears as a way of extremely promising research today to solve numerous pathology connected to the deficiencies of the nervous system. It is usually used for the rehabilitation of people with neurological disorders. Generally, skeletal muscles are activated by using Constant Frequency Trains (CFTs) with a fixed amplitude and inter-pulse duration. In addition, the systems of electrical stimulation do not adapt the parameters stimulation to obtain a desired force response during the rehabilitation session. The purpose of this study is to adapt automatically the stimulation parameters to the force desired by the clinician with an intelligent PID control…
Feasibility of Body-centric Systems by Using passive textile RFID tags
2012
Recent progresses in the design of wearable RFID-tag antennas stimulate the idea of passive body-centric systems, wherein the required power to drive the wearable tags is directly scavenged from the interrogation signal emitted by the reader unit. While active body-centric links have been extensively investigated, the feasibility of passive systems is still questionable, due to the poor sensitivity of the tags and due to the modest reading distances. This paper describes a systematic measurement campaign involving low-profile wearable textile tags in the UHF RFID band. It was demonstrated that both on-body and off-body links are affordable, with a power budget fully compliant with the avail…
Green Data Centres providing ancillary services to power grid
2015
This work investigates the possibility for a Data Centre to provide services to the Grid. In particular, the paper simulates a sudden shift of frequency because of a power decrease and estimates how a real-life Data Centre can contribute the secondary frequency regulation.
EEMD based analysis of vehicle crash responses
2015
The vehicle crash is a complex process with nonlinear large deformation of structures. The analysis of the crash process is one of the challenges for all vehicle safety researchers. In this paper, the Ensemble Empirical Mode Decomposition (EEMD) method is applied in the analysis of crash responses in order to achieve some meaningful results. With the help of EEMD, the crash responses are decomposed into a trend signal and some high frequency fluctuations. By studying the load path of vehicle design, each component is corresponding to the structure of vehicle body. Consequently, some parameters of vehicle crash model can be identified. A frontal crash of Toyota Yaris is employed for demonstr…
Bearing fault detection for drivetrains using adaptive filters based wavelet transform
2017
Predicting a localized defect on a rolling bearing during the degradation process before a complete failure is crucial to prevent system failures, unscheduled downtimes and substantial loss of productivity. During this process, impulses associated with the fault are weak, nonstationary or time-frequency varying, and contaminated by noises, which render the problem of extracting these impulses very difficult. This work investigates the effectiveness of common signal processing techniques on predicting incipient faults, e.g. Fast Fourier transform, Short-Time Fourier transform, Wavelet transform. It was found that an adaptive filter is required to enhance and reconstruct the signals during th…
Hammerstein Model-Based Robust Control of DC/DC Converters
2007
This paper deals with model-based robust control of DC/DC power electronic converters. The converter is modelled by means of its static characteristic and a few continuous-time linear and time-invariant (LTI) models corresponding to contiguous ranges of duty-cycle. The model appears as a Hammerstein model in which the values of the parameters of the LTI part depend on the actual duty-cycle operating range. This suggests to describe the converter as an uncertain system to be controlled using robust control techniques. Frequency domain approach is used for describing the nominal model and the uncertainty. In view of applying robust control, identification of the LTI models is performed by mea…
Temporal Dispersion Characterization of Over-Building Propagation Applied to Iso-Frequency Repeaters
2009
This letter presents the results of a measurements campaign carried out at 2050 MHz with the aim of characterizing the time dispersion of multipath propagation when the transmit and receive antennas are placed near and situated on rooftops or mounted on masts. The measurements were taken in four separate locations within the urban area of Madrid, Spain. From the measured data, the root mean square (RMS) value of the delay spread and the delay interval that characterize the time dispersion propagation of the environment under study are analyzed. An average power delay profile (PDP), representative of the time dispersion, is proposed so as to extrapolate these results to other similar environ…
Experimental characterization of series arc faults in AC and DC electrical circuits
2014
This paper presents an experimental characterization of the arc fault phenomenon, for both AC and DC systems, focusing the attention on series arcs. The aim of the study is to find some current characteristics, which can be significant for the purpose of arc detection. The arcing current signal is analyzed in both time and frequency domain. For the AC analysis, the test conditions are chosen in accordance with the “unwanted tripping tests” and the “operation inhibition tests” reported in the Standard UL 1699. The DC study is carried out on the currents waveforms acquired during some on-field tests on a PV plant. Starting from the study herein presented, the authors have found that is it pos…
Diagnosis of mechanical unbalance for double cage induction motor load in time-varying conditions based on motor vibration signature analysis
2013
This paper investigates the detectability of mechanical unbalance in double cage induction motor load using motor vibration signature analysis technique. Rotor imbalances induce specific harmonic components in electrical, electromagnetical, and mechanical quantities. Harmonic components characteristic of this category of rotor faults, issued from vibration signals analysis, are closely related to rotating speed of the rotor, which complicates its detection under non-stationary operating conditions of the motor. Firstly, experimental results were performed first under healthy and mechanical load unbalance cases, for different load levels under steady-state operating conditions to evaluate th…
Development of a Coupling System for Medium Voltage Power Line Communication in the CENELEC A Frequency Band
2016
In this paper the performances of a new power line communication (PLC) coupling system for medium voltage (MV) smart grids are investigated in the CENELEC A frequency band (i.e. 3 - 95 kHz). The new coupling solution is based on the use of the capacitive divider of the voltage detecting system (VDS) as PLC coupler to the MV network. According to IEC 61243-5, VDS are worldwide used to reveal the presence of the mains voltage to ensure the safety of the operators. A proper interface circuit has been invented and patented to couple the PLC signal through the VDS. In this way no dedicated MV PLC coupler is required, thus avoiding the related costs of the coupler, of its installation, and those …