Sinusoidal Current Signal Research Articles

Flexi-EIT: A Flexible and Reconfigurable Active Electrode Electrical Impedance Tomography System.

Electrical Impedance Tomography (EIT) systems have shown great promise in many fields such as real-time wearable healthcare imaging, but their fixed number of electrodes and placement locations limit the system's flexibility and adaptability for further advancement. In this article, we propose a flexible and reconfigurable EIT system (Flexi-EIT) based on digital active electrode (DAE) architecture to address these limitations. By integrating a reconfigurable number of up to 32 replaceable DAEs into the flexible printed circuit (FPC) based wearable electrode belt, we can enable rapid, reliable, and easy placement while maintaining high device flexibility and reliability. We also explore hardware-software co-optimization image reconstruction solutions to balance the size and accuracy of the model, the power consumption, and the real-time latency. Each DAE is designed using commercial chips and fabricated on a printed circuit board (PCB) measuring 13.1 mm × 24.4 mm and weighing 2 grams. In current excitation mode, it can provide programmable sinusoidal current signal output with frequencies up to 100 kHz and amplitudes up to 1 mA p-p that meets IEC 60601-1 standard. In voltage acquisition mode, it can pre-amplify, filter, and digitize the external response voltage signal, improving the robustness of the system while avoiding the need for subsequent analog signal processing circuits. Measured results on a mesh phantom demonstrate that the Flexi-EIT system can be easily configured with different numbers of DAEs and scan patterns to provide EIT measurement frames at 38 fps and real-time EIT images with at least 5 fps, showing the potential to be deployed in a variety of application scenarios and providing the optimal balance of system performance and hardware resource usage solutions.

A Closed-Loop Signal Conditioning Scheme for Core-Less Planar LVDT

In this paper, we present an efficient signal conditioning scheme for a previously developed planar core-less Linear Variable Differential Transformer. The stationary coils are excited with variable amplitude complementary sinusoidal current signals through a Howland source using a closed loop controller in such a way that the moving coil voltage is maintained close to zero. The ratio of the difference to the sum of the amplitudes of the applied voltages is taken as the output, which is proportional to the moving coil position. The highlight is that any external interference can be detected by monitoring the null voltage, which allows taking remedial measures like switching of operating frequency. Tests on a prototype sensor with this scheme implemented shows improvement in positioning performance by more than one order of magnitude under strong interference near the operating frequency. Other benefits include insensitivity to variations in the forward path gain and better update rate. The new scheme also retains the characteristics of tolerance to vertical displacement, good linearity and high resolution previously expounded.

Sensor fault diagnosis technique applied to three-phase induction motor drive

This paper conducts research on sensor fault diagnosis for a three-phase induction motor drive (IMD) in steady-state operation. An improving diagnostic technique based on the integration algorithm of the sinusoidal current signal is proposed for detecting and locating faulty current sensors in the induction motor drive. The IMD integrated a proposed fault detection-isolation (FDI) system is investigated for operating characteristics when sensor failures occur. The faulty sensor needs to be accurately identified and quickly isolated from the control system. Then the estimated signal will be used to replace the fault signal to retain the IMD stability. MATLAB/Simulink software will be applied to simulate the speed-torque characteristics of the IMD system as well as sensor failures occurring during operation. The performance of the proposed method will be evaluated through the accuracy and timeliness in each fault case corresponding to each sensor.

Sinusoidal Current Signal-Based Fire Detection System with Automatic Address Assignment

In this paper, a novel sinusoidal current signal-based fire detection system is proposed with automatic address assignment. The system model employs a conventional power line to embed fire information, i.e., the address, rather than using an additional communication line. At the transmitter, different frequencies of the sinusoidal current signal are combined and transmitted through a power line. At the receiver, fast Fourier transform (FFT) is applied to distinguish the frequency bins, which can represent the addresses of fire detectors. The proposed system model is implemented and the numerical results are presented in terms of measurements.

A Study of the Nonlinear Thomson Effect Produced by Changing the Current in a Thermoelectric Cooler

Abstract This work describes the nonlinear Thomson effect produced by a transient current source powering a thermoelectric cooler. The electric effect of the capacitive impedance in the semiconductors was considered in the equations as a novelty term that naturally appears by solving the Boltzmann equation to find the mathematical form of the current density. Thus, considering the new term and heath energy balances, a one-dimensional mathematical model for a thermoelectric cooler (TEC) powered by a time-dependent current was developed, finding a new nonlinear Thomson effect in the heath transfer equations. To evaluate the impact of the nonlinear effect on the thermodynamic behavior of the thermoelectric cooler, a continuous, sinusoidal and square-pulse current conditions were simulated. The temperature profile, temporal evolution, and the effective coefficient of performance (COP) were calculated. The results revealed a new thermoelectric heat transfer in addition to the Thomson flow created by virtual junctions throughout the semiconductors caused by the instantaneous change of current. This fact was evidenced by three results: the shifting of the temperature mean value due to the peak current change 0.45 A is 1.68 K 1.68\hspace{0.1667em}\mathrm{K} and 2.56 K 2.56\hspace{0.1667em}\mathrm{K} to sinusoidal and square current supplies, respectively; it was determined that a TEC powered by a square-pulse current signal had greater effective efficacy, having more pronounced cold side supercooling temperature peaks compared to those powered by a constant sinusoidal current signal.

A Position Error Correction Method for Sensorless Control of Dual Three-Phase Permanent Magnet Synchronous Machines

In this article, an online rotor position error correction method is proposed to eliminate the impact of parameter mismatch in sensorless control for dual three-phase (DTP) permanent magnet synchronous machines drives. The rotor position error production mechanism is first derived and shows that the error changes with the trend of current variation when there is a parameter mismatch. Based on this mechanism, by injecting sinusoidal current signals with low frequency and small amplitude into both sets of three-phase windings, the presence of parameter mismatch and its level can be revealed from the corresponding sinusoidal responses of the estimated speed of sensorless observers, which do not depend on the inertia of the machine. Since the amplitudes of these responses decrease as the parameter mismatch level reduces, with the help of the least mean square algorithm, the parameters can be adaptively adjusted to the actual values, and the position error can be thus corrected. Moreover, with the extra freedom of DTP machines, the detrimental effects on torque production due to current signal injections can be eliminated through adjusting the phase between the two injected signals. The effectiveness of the proposed method has been validated through simulation and experimental results.

Investigation of 2DOF PID Controller for Physio-Therapeutic Application for Elbow Rehabilitation

The aim of this work is to evaluate the output of a two-degree of freedom (DOF) proportional integral derivative (PID) controller for controlling elbow flexion and extension on an upper limb rehabilitation robot of an existing model. Since the usage of upper limb rehabilitation is increasing dramatically because of human impairment, 2DOF has been proposed in this work as a suitable controller. The 2DOF PID controller offers set-point-weight features and, hence, is fast in removing disturbance from the system and ensuring system stability. Importantly, as the system parameters are unknown in this work, the black-box model approach has been taken into consideration, using the MATLAB System identification toolbox to estimate a model. The best-fitted estimated model is then coupled with the proposed controller in the MATLAB/Simulink environment that, upon successful simulation works, leads, finally, to the hardware implementation. Three different amplitudes of sinusoidal current signals, such as 0.3 amps, 0.2 amps, and 0.1 amps, are applied for hardware measurements. Considering patients’ physical conditions. In this work, the 2DOF controller offers a fast transient response, settling time, negligible tracking error and 0% overshoot and undershoot.

Simulation Research on Defect Detection in Station Process Pipelines using Ultrasonic Guided Waves

COMSOL Multiphysics was used to establish an ultrasonic guided wave detection model of bend pipes to resolve the defect detection challenge presented by gas station process piping, analyzing the propagation characteristics of the ultrasonic guided wave in the pipeline and the influence of its detection defect signal according to different factors. The results showed that the T (0, 1) mode guided wave generated by the sinusoidal current signal at a frequency of 50 kHz propagated along the pipeline axis, displaying a high rate of corrosion defect detection in bend pipes. The intense defect echo signals at excitation frequencies of 30 kHz, 50 kHz, and 70 kHz are compared and analyzed, indicating that the optimal excitation frequency was between 50 kHz and 60 kHz for a pipe with an exterior diameter of 219 mm and a wall thickness of 8 mm. In addition, the echo signals in straight pipes and bend sections were compared and analyzed, showing that the bend characteristics affected defect detection and caused a deviation in the axial positioning of these flaws. Therefore, the larger the distance between the defects and the bend, the larger the deviation of the axial positioning of these defects.

A Fast Estimation of Initial Rotor Position for Low-Speed Free-Running IPMSM

Fast and reliable initial rotor position detection is essential for restarting sensorless permanent magnet synchronous motors (PMSMs) in free-running condition. In this article, a fast initial rotor position estimation method for low-speed free-running motor is proposed, which utilizes a combined sinusoidal current and square-wave voltage injection method. The sinusoidal current is imposed into the estimated d-axis to magnify the magnetic saturation effect. The amplitudes of the d-axis current caused by injected square-wave voltage are then accumulated. The large difference of the two integrated signals for positive and negative d-axis currents can be reliably used to identify the rotor polarity. Meanwhile, in low-speed free-running stage, the change of saturation degrees introduced by the injected sinusoidal signal does not affect the position estimation accuracy. Moreover, even if the sinusoidal current signal is injected in the incorrect d-axis, the resultant torque is small and unexpected rotation of the rotor is prevented. Its influence on the free-running motor is negligible, due to the combined injection with continuously online updated estimated rotor position by high-frequency square-wave voltage injection during the polarity identification process. Finally, the effectiveness of the proposed method is investigated on a 1.5 kW interior PMSM test platform.

Design of integrated test system for current/frequency conversion circuit

In order to quickly and accurately measure the performance parameters of the current/frequency conversion circuit (I/F conversion circuit) of inertial navigation system, an I/F conversion circuit test system is designed. Constant current signal, sinusoidal current signal and transient step current signal are provided to the measured system by a program-controlled constant current source. Through the designed frequency measurement circuit, the output frequency signal is measured accurately, the static, dynamic and transient responses of three kinds of I/F converter circuits are analyzed.

THE PHASE INDUCTION MOTOR STATOR EFFECTIVE CURRENT VALUE STARTUP MODE DEPENDENCE DETERMINATION

To determine the effective value of the stator current phase induction motor specialized techniques were developed. Phase current stator instantaneous values resulting arrays were obtained via an analog-to-digital converter L-Card. Phase stator current instantaneous arrays have been scanned from the original file by parsing. To implement the parsing string data used specialized Embarcadero Delphi class TParser. For obtaining average stator current values two algorithms were developed and presented. Obtaining extremums (minimums and maximums) of the sinusoidal signal were developed and presented. To make a measurement phase induction motor stator current used in current sensor Hall effect ACS712 Allegro 20A. To determine the phase stator effective current value based on instantaneous values of sinusoidal current signal array and filtering the output dataset was developed Windows application by using Embarcadero Delphi Community Edition IDE. An application interface is designed in the form of fixed windows. The time dependence between instantaneous values of stator phase current without and with filtering by using a digital filter presented here. Effective stator current value time dependence is given here. The analysis of the results is given. The results were compared with measurements by using the astatic voltmeter with accuracy measurements 0.5. For experimental investigations low power induction motor AIR56A4U3 was used. Three-dimensional dependences of electromechanical characteristics are given. The simulation results are presented in the form of graphs of the transient processes of the stator current of an induction motor. Theresults are plotted as graphs of the dependence of the current values of the stator phase current, which were calculated and investigated by using Microsoft Excel. Polynomial dependences of the current values of the stator phase current are also given in a form of Microsoft Excel diagram

Una fuente de corriente sinusoidal para aplicaciones de bioimpedancia basado en un algoritmo de control no lineal en tiempo discreto

Sinusoidal current sources are fundamental components of electronic equipment used in bioimpedance analysis and in electrical impedance tomography. Currently, these sources are mostly implemented as analog electronic systems. The aim of this paper is to present a new approach to current sources design based on discrete-time closed-loop control systems. The experimental results are obtained by implementing the current source in a system of analog and digital programmable blocks, and using as a controller a nonlinear difference equation proposed by the authors. This controller guarantees the convergence of the amplitude of the current flowing through the load, towards a user-desired level. This new control law does not require any parametric adjustment nor knowledge of the load . The developed device is able to produce a sinusoidal current signal of a frequency ranging from 100 Hz to 120 kHz and currents from 500 μA to 2 mA. The amplitude error of the current signal remained below 1% for tests performed with resistive-capacitive loads (Cole’s type loads). The output impedance is frequency dependent and ranges from 410 kW to 966 kW. The total harmonic distortion is less than 5%. All the proposed system is embedded in the mixed signal device PSOC 5LP, a shunt resistance being the only external component.

Development of Sonogel-Carbon based biosensors using sinusoidal voltages and currents methods

In this work, biosensors based on Sonogel-Carbon electrodes modified with poly(3,4-ethylenedioxythiophene) – tyrosinase biocomposite materials have been developed using sinusoidal voltages and currents methods The sinusoidal voltages method uses a sinusoidal voltage signal of a 50mHz fixed frequency and high amplitude superimposed on a direct current potential to modify the Sonogel-Carbon electrodes surface with the poly(3,4-ethylenedioxythiophene) – tyrosinase layer. A new preparation method involving the application of a sinusoidal current signal with fixed frequency and amplitude over a direct current has been developed as well. The experimental parameters of these methods have been optimized and selected in such a way to highlight the contribution of the sinusoidal component in the biosensors preparation. The advantages of the new preparation methods in terms of electrocatalytic and analytical efficiencies are presented. The analytical performances of the proposed biosensors towards benchmark analytes like dopamine, hydroquinone, and catechol have been investigated. The lowest limit of detection value of 7.10μM and a high sensitivity value of 0.0037μA/μM for dopamine determination were obtained with a biosensor prepared via the new sinusoidal currents method. The biosensors were successfully applied in the quantification of dopamine in pharmaceutical products.

Compact Optomagnetic Bragg-Grating-Based Current Sensor for Transmission Lines

A compact and practical optomagnetic current sensor intended to be used in power transmission lines is proposed in this paper. The novel sensor is able to retrieve the complete sinusoidal current signal, which is being carried by the line conductor through a fiber Bragg grating, which is attached to a magnetostrictive rod setup excited by dc and AC magnetic fields: a DC magnetic field created by a designed magnetic circuit in order to make the magnetostrictive material operate in its linear region; and an AC magnetic field generated by the current being monitored. Design stages and the proposed sensor configuration are showed in detail, and the assembled sensor head is tested using a power setup exclusively developed to simulate current magnitude levels in a transmission line. Measurement results are compared with those provided by a reference commercial probe, attesting the effectiveness of the novel current sensor, especially in terms of waveform distortion.

Detection of Eccentricity in Squirrel Cage Induction Motors by Finite Element Method

Finite Element method is used in this research work to detect eccentricity fault in squirrel cage induction motors. This paper is about the results obtained from the simulation part of the research on a real size motor. The simulation was done using FLUX software, which can solve the magnetizing partial differential equations of the rotor, stator and the air-gap by FEMM. In the primary stage of this research the focus is on two dimension mapping of the electromagnetic field of the motor by using FLUX-2D. The presented results in this paper show the effect of the eccentricity is traceable from the FEMM of the motor. At the later part of this paper, the results from the simulation part were tested against the analytical method for validation. In the analytical method the present research was concentrated on the stator current and sees how the original sinusoidal current signal is distorted after fault. At the final part of the paper a complete FFT analysis of the current and voltage were presented for two cases of static and dynamic eccentricity faults. The paper is concluded by showing the effectiveness of this research for eccentricity fault diagnoses.

A Class-E driven inductive power delivery system covering the complete upper body

The design, simulation and implementation of a dedicated Class-E driver for inductive power transfer is presented. Whereas focus is placed on wireless endoscopy, other upper body monitoring applications can be powered simultaneously. The driver is developed to generate a sinusoidal current signal through a coil, for the generation of an alternating magnetic field at 1MHz with a field intensity of about 300μT. The volume within the coil, implemented in a Helmholtz configuration, wherein this magnetic field is guaranteed, allows to cover a volume up to ∼0.2m3. This is an improvement by a factor of 20 compared to previous work [1] and sufficiently large to cover the full upper body of patients. The magnetic field thereby generated, is adequate to provide up to 300mW of power to previously developed capsules, in all possible orientations. Patient safety and solutions to reduce parasitic influences are addressed briefly.

Sensorless Control of PMSM Based on Low-Frequency Current Signal Injection in the Direct Axis at Low and Zero Speed

A novel sensorless control method of permanent magnet synchronous motor (PMSM) based on low frequency (LF) current signal injection is proposed in this paper. A LF sinusoidal current signal is superimposed into the estimated d-axis, and the corresponding voltage response and current response are detected to estimate the rotor speed and the rotor position. This method doesn't rely on the non-ideal features but just the fundamental model of PMSM. As a result, the introduced method can be applied to not only IPMSM, but also to SPMSM. Theoretical analysis and simulation results are carried out. The simulation results indicate that the rotor position and speed can be obtained exactly at low and zero speed. The approach ensures good dynamic and static performances, and can realize accurate position servo control.

Sensorless Control of SPMSM Based on High-Frequency Current Signal Injection in the Direct Axis at Low and Zero Speed

A novel sensorless control method of surface-mounted permanent magnet synchronous motor (SPMSM) based on high frequency (HF) current signal injection is proposed in this paper. A HF sinusoidal current signal is superimposed into the estimated d-axis, and the rotor position can be demodulated after q-axis voltage is regulated, which is relative to error angle. Ultimately sensorless control can be achieved. Theoretical analysis and simulation validation are carried out. The simulation results indicate that the rotor position and speed can be obtained exactly at low and zero speed. The approach ensures good dynamic and static performances, and can realize accurate position servo control.

Sensorless Position Control of Permanent-Magnet Motors With Pulsating Current Injection and Compensation of Motor End Effects

The sensorless position control of permanent-magnet motors is successfully implemented by superimposing a high-frequency voltage signal on the voltage reference or adding a high-frequency current signal to the current reference. The former approach is usually preferred because of its simplicity, although the latter one may allow better performance. This paper presents a new algorithm for the sensorless control of low-saliency permanent-magnet synchronous motors based on high-frequency sinusoidal current signal injection into the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis. Different from the related literature, the position information is derived by analyzing the measured high-frequency currents. The amplitude of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis voltage reference is also exploited to improve performance. A proportional-integral (PI) controller plus a resonant term (PI-RES) is adopted to ensure the accurate tracking of both the dc and high-frequency components of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis current reference. The main advantages of the proposed approach are the increased accuracy and sensitivity with respect to the approach based on voltage injection, the insensitiveness to inverter nonlinearities that are compensated by the current regulation loop, the actual control on the injected current value, and the practical absence of acoustic noise. Experiments on a linear tubular permanent-magnet synchronous motor prototype have been carried out to verify the aforementioned advantages. This paper also presents a discussion of the parameters of the PI-RES.

Electrochemical modeling of single particle intercalation battery materials with different thermodynamics

Current–voltage relations of a single intercalation battery electrode particle were modeled with the step current, step voltage, linear sweep voltage, and sinusoidal current signals. A solid solution with constant diffusivity, a solid solution with variable diffusivity, and a phase transformation material were considered for their thermodynamic and kinetic evaluations based on the regular solution model and the generalized Poisson–Nernst–Planck equations. The numerical simulation results were compared with known, small-signal solutions and experimental data throughout the article.