Command Pulses Research Articles

Hardware-in-the-loop simulation to validate the fractional-order neuro-fuzzy power control of variable-speed dual-rotor wind turbine systems

New and efficient command strategies and algorithms are needed in the field of wind turbine energy generation to ensure power quality according to international standards. However, conventional linear strategies are still used to command doubly-fed induction generators (DFIGs). Thus, inadequate power quality is obtained, which can cause network-level disturbances. This Hardware-in-the loop (HIL) study presents a new command scheme for a DFIG-based dual-rotor wind turbine (DRWT) system. The new command is a combination of a neuro-fuzzy algorithm and fractional-order control that overcomes the declining power quality of the DFIG-DRWT system. The new strategy is based on using pulse width modulation to generate command pulses for the rotor-side converter of DFIG. In the designed command system, the reference value of the active power is determined using maximum power point tracking to provide efficient power conversion performance under different operating conditions. First, MATLAB software is used to implement the fractional-order neuro-fuzzy (FONF) control technique, and the behavior of the proposed strategy is studied in comparison to that of the traditional direct power command (DPC) technique. A comparison is performed in terms of the ripple minimization ratio, durability, overshoot, steady-state error, reference tracking, and current quality. The results of the comparison show the high performance of the FONF technique. Second, the FONF technique is implemented in HIL test using the dSPACE 1104 Card, where two different forms of wind speed are used to study the characteristics of the proposed strategy and confirm its effectiveness and performance in HIL test compared to DPC technique. The experimental results obtained in the two tests confirm the efficiency, effectiveness, and high performance of the proposed FONF technique compared to DPC technique in improving the energy system characteristics, and the simulation obtains the same results.

Improved Interleaved Single-Ended Primary Inductor-Converter for Single-Phase Grid-Connected System

The generation of electricity based on renewable energy sources, particularly Photovoltaic (PV) system has been greatly increased and it is simply instigated for both domestic and commercial uses. The power generated from the PV system is erratic and hence there is a need for an efficient converter to perform the extraction of maximum power. An improved interleaved Single-ended Primary Inductor-Converter (SEPIC) converter is employed in proposed work to extricate most of power from renewable source. This proposed converter minimizes ripples, reduces electromagnetic interference due to filter elements and the continuous input current improves the power output of PV panel. A Crow Search Algorithm (CSA) based Proportional Integral (PI) controller is utilized for controlling the converter switches effectively by optimizing the parameters of PI controller. The optimized PI controller reduces ripples present in Direct Current (DC) voltage, maintains constant voltage at proposed converter output and reduces overshoots with minimum settling and rise time. This voltage is given to single phase grid via Voltage Source Inverter (VSI). The command pulses of VSI are produced by simple PI controller. The response of the proposed converter is thus improved with less input current. After implementing CSA based PI the efficiency of proposed converter obtained is and the Total Harmonic Distortion (THD) is found to be . The dynamics and closed loop operation is designed and modeled using MATLAB Simulink tool and its behavior is performed.

Exploring the Coordination of Cardiac Ion Channels With Action Potential Clamp Technique.

The patch clamp technique underwent continual advancement and developed numerous variants in cardiac electrophysiology since its introduction in the late 1970s. In the beginning, the capability of the technique was limited to recording one single current from one cell stimulated with a rectangular command pulse. Since that time, the technique has been extended to record multiple currents under various command pulses including action potential. The current review summarizes the development of the patch clamp technique in cardiac electrophysiology with special focus on the potential applications in integrative physiology.

Self-learning current optimizing control for conventional stepping motor drive technique based on step pulses

The essential advantage of the conventional stepping motor drive technique bases on step command pulses is the ability of open-loop positioning. By ruling out the cost of a position sensor, stepping motors are preferred in low power positioning applications. However, machine developers also want to obtain high dynamics with these small and cheap stepping motors. For that reason, stepping motors are used at its limits as much as possible. A drawback of the open-loop control is the continuous risk of missing a step due to overload. Due to this uncertainty, robustness is a major issue in stepping motor applications. Until today, to reduce the possibility of step loss, the motor is typically driven at maximum current level or is over-dimensioned with results in low-efficiency. Therefore in this paper, a self-learning [Formula: see text]-controller optimizing the current is presented. Moreover, to allow broad industrial applicability, this technique is computationally simple, needs no mechanical or electrical parameter knowledge and take into account the unique character of stepping motors and their conventional drive technique based on step command pulses. The proposed algorithm is validated through measurements on a hybrid stepping motor.

Ignition Energy Discharge of Oscillating Plasma Waveforms Under Atmospheric Conditions

Oscillating plasma ignition is a promising technique to produce larger initial ignition volume. In this study, an energy waveform analysis of oscillating plasma discharge is investigated. To suffice the industrial applications, the challenges of plasma generation and control platforms are first discussed in this work. A flexible modulation for oscillating plasma generation is established, with the measurements of discharge voltage, secondary current, and discharge current. The phase difference between voltage and current is a critical effect on the energy waveform of oscillating plasma. In relevance to the command pulse train, the energy waveforms corresponding to various plasma discharging events are analyzed, which include normal, arc, and void cases. High-speed imaging, simultaneous with the electrical waveform measurements, is applied to record the plasma formation. Under elevated background pressures, the ignition volume of oscillating plasma is suppressed, and fewer plasma streamers can be observed. The prolonged duration and increased voltage consistently demonstrated positive impacts on flame propagation. This research added a foundation for the plasma diagnostics under engine-like conditions with variations of pressure, temperature, gas composition, and flow pattern.

Position Accuracy Measurement and Error Compensation of Servo Electric Cylinder Test Platform

At present, the domestic electric platform mostly adopts semi-closed loop digital control, whose basic transmission form of the key components adopts rotary motor and trapezoidal screw (ball screw, roller screw), manufacturing precision and mechanical transmissions inevitably have assembly errors, pitch errors and gap errors. It is necessary to perform error analysis and compensation for high-precision electric cylinder platforms. In this paper, the above errors are further subdivided into linear error, nonlinear error, gap error, which is corresponded error measurement and compensation. The results show that the linear deviation of the measured position and deviation data of the forward and reverse strokes are linearly fitted by the least squares linear fitting method, and then the linear error compensation is performed by adjusting the command pulse amount. The average value of the linear proportional coefficient is taken as the average gap, and the gap error compensation is performed. After the cubic spline interpolation using as the nonlinear error compensation, which accords to GB/T17421.2-2000, the general rule of machine tool inspection Part 2: “the positioning accuracy of the numerical control axis and the determination of repeated positioning accuracy” calculated that the bidirectional positioning accuracy of the electric cylinder is increased from 0.1028 mm to 0.0245 mm, the bidirectional repeat positioning accuracy of the axis is increased from 0.0783 mm to 0.0249 mm, and the maximum backlash is reduced from 0.201 mm to 0.092 mm. These all meet the requirements of positioning accuracy and repeat positioning accuracy of 0.01 mm.

Load angle estimation for dynamic stepping motor motion applications

Stepping motors are well-suited for open-loop positioning tasks at low power. Every time the user sends a next pulse, the stepping motor driver excites the correct stator phases to rotate the rotor over a predefined discrete angular position. In that way, counting the step command pulses enables open-loop positioning. However, when the motor is overloaded or stuck, step loss occurs, and the relation between the expected rotor position and the actual rotor position is lost. Nowadays, the vast majority of the open-loop stepping motor methodologies do not detect this step loss. Especially for dynamically demanding applications where the stepping motor is used close to its operating boundaries, step loss is highly probable. Using a mechanical position sensor to detect and counteract step loss would increase the overall cost, the size of the machine, complexity of the system. Therefore in this paper, a dynamic sensorless load angle estimator based on the classical Transfer Function Analyzer (TFA) technique in the angular domain is presented. This load angle reflects the capability of the system to follow the position setpoint and gives an indication of the robustness against torque disturbances. The algorithm needs no tuning and can be used with the conventional full-, half- and micro-stepping algorithm. The estimation algorithm only needs one current and one voltage measurement and the electrical parameters of the stator winding to estimate the load angle. The proposed algorithm is validated through measurements on a hybrid stepping motor.

Current Reduction in Stepping Motor Applications using an Adaptive PI controller based on Linearized Dynamics

Stepping motors are used in numerous applications because of their low manufacturing cost and simple open-loop position control capabilities. The bulk of the widely used full-step open-loop stepping motor drive algorithms are driven at maximum current to avoid step loss. This non-optimal way of control leads to low efficiency. In order to use stepping motors in a more optimal way, closed-loop control is needed. A previously described sensorless load angle estimation algorithm, solely based on voltage and current measurements, is used to provide the necessary feedback without using a mechanical position sensor. In this paper, an adaptive PI controller which optimizes the current level based on the feedback of the estimated load angle is introduced. Although the current - load angle dynamics are highly non-linear, an adaptive PI controller with the settling time of the current reduction as design constraint is worth considering. Especially because few tuning parameters are required. The described method is complimentary to the popular methodology used to drive a stepper motor, which is based on step command pulses. Measurements validate the proposed approach.

Ca2 +-activated Cl− current is antiarrhythmic by reducing both spatial and temporal heterogeneity of cardiac repolarization

The role of Ca2+-activated Cl− current (ICl(Ca)) in cardiac arrhythmias is still controversial. It can generate delayed afterdepolarizations in Ca2+-overloaded cells while in other studies incidence of early afterdepolarization (EAD) was reduced by ICl(Ca). Therefore our goal was to examine the role of ICl(Ca) in spatial and temporal heterogeneity of cardiac repolarization and EAD formation.Experiments were performed on isolated canine cardiomyocytes originating from various regions of the left ventricle; subepicardial, midmyocardial and subendocardial cells, as well as apical and basal cells of the midmyocardium. ICl(Ca) was blocked by 0.5mmol/L 9-anthracene carboxylic acid (9-AC). Action potential (AP) changes were tested with sharp microelectrode recording. Whole-cell 9-AC-sensitive current was measured with either square pulse voltage-clamp or AP voltage-clamp (APVC). Protein expression of TMEM16A and Bestrophin-3, ion channel proteins mediating ICl(Ca), was detected by Western blot.9-AC reduced phase-1 repolarization in every tested cell. 9-AC also increased AP duration in a reverse rate-dependent manner in all cell types except for subepicardial cells. Neither ICl(Ca) density recorded with square pulses nor the normalized expressions of TMEM16A and Bestrophin-3 proteins differed significantly among the examined groups of cells. The early outward component of ICl(Ca) was significantly larger in subepicardial than in subendocardial cells in APVC setting. Applying a typical subepicardial AP as a command pulse resulted in a significantly larger early outward component in both subepicardial and subendocardial cells, compared to experiments when a typical subendocardial AP was applied.Inhibiting ICl(Ca) by 9-AC generated EADs at low stimulation rates and their incidence increased upon beta-adrenergic stimulation. 9-AC increased the short-term variability of repolarization also.We suggest a protective role for ICl(Ca) against risk of arrhythmias by reducing spatial and temporal heterogeneity of cardiac repolarization and EAD formation.

Sensorless load angle control for two-phase hybrid stepper motors

The widely used full-step open-loop stepping motor drive algorithms are characterised by a low torque/power ratio, large torque ripple and resonance problems. In order to use stepping motors in more demanding applications, closed-loop control is needed. In this paper, a previously described load angle estimation algorithm, solely based on voltage and current measurements, is used to provide the necessary feedback without using a mechanical position sensor. This paper introduces a novel closed-loop load angle controller which optimises the current level based on the estimated load angle. This approach is challenging as the current - load angle dynamics are highly nonlinear. However, in this research a linear model is proposed and used to tune a PI load angle controller. The controller reduces the current level to obtain the optimal load angle but does not change the way stepping-motor are driven by step command pulses. This results in a broad industrial employability of these algorithms. The proposed sensorless controller is validated trough both simulations and measurements.

Achieving Maximal Speed of Solution Exchange for Patch Clamp Experiments

BackgroundResolving the kinetics of agonist binding events separately from the subsequent channel gating processes requires the ability of applying and removing the agonist before channel gating occurs. No reported system has yet achieved pulses shorter than 100 µs, necessary to study nicotinic ACh receptor or AMPA receptor activation.Methodology/Principal FindingsSolution exchange systems deliver short agonist pulses by moving a sharp interface between a control and an experimental solution across a channel preparation. We achieved shorter pulses by means of an exchange system that combines a faster flow velocity, narrower partition between the two streams, and increased velocity and bandwidth of the movement of the interface. The measured response of the entire system was fed back to optimize the voltage signal applied to the piezoelectric actuator overcoming the spurious oscillations arising from the mechanical resonances when a high bandwidth driving function was applied. Optimization was accomplished by analyzing the transfer function of the solution exchange system. When driven by optimized command pulses the enhanced system provided pulses lasting 26 ± 1 µs and exchanging 93 ± 1% of the solution, as measured in the open tip of a patch pipette.Conclusions/SignificancePulses of this duration open the experimental study of the molecular events that occur between the agonist binding and the opening of the channel.

Rapid dopaminergic and GABAergic modulation of calcium and voltage transients in dendrites of prefrontal cortex pyramidal neurons

The physiological responses of dendrites to dopaminergic inputs are poorly understood and controversial. We applied dopamine on one dendritic branch while simultaneously monitoring action potentials (APs) from multiple dendrites using either calcium-sensitive dye, voltage-sensitive dye or both. Dopaminergic suppression of dendritic calcium transients was rapid (<0.5 s) and restricted to the site of dopamine application. Voltage waveforms of backpropagating APs were minimally altered in the same dendrites where dopamine was confirmed to cause large suppression of calcium signals, as determined by dual voltage and calcium imaging. The dopamine effects on dendritic calcium transients were fully mimicked by D1 agonists, partially reduced by D1 antagonist and completely insensitive to protein kinase blockade; consistent with a membrane delimited mechanism. This dopamine effect was unaltered in the presence of L-, R- and T-type calcium channel blockers. The somatic excitability (i.e. AP firing) was not affected by strong dopaminergic stimulation of dendrites. Dopamine and GABA were then sequentially applied on the same dendrite. In contrast to dopamine, the pulses of GABA prohibited AP backpropagation distally from the application site, even in neurons with natural Cl− concentration (patch pipette removed). Thus, the neocortex employs at least two distinct mechanisms (dopamine and GABA) for rapid modulation of dendritic calcium influx. The spatio-temporal pattern of dendritic calcium suppression described in this paper is expected to occur during phasic dopaminergic signalling, when midbrain dopaminergic neurons generate a transient (0.5 s) burst of APs in response to a salient event.

A New Algorithm of Generating Command Pulses for Numerical Controllers

This paper proposes a new algorithm of generating command pulses for numerical controllers. Differently from the presently used NC pulse generating method, pulse trains with automatically changed f...

Acidosis inhibits spontaneous activity and membrane currents in myocytes isolated from the rabbit atrioventricular node

Recent evidence from intact hearts suggests that the function of cardiac nodal tissue may be particularly susceptible to acidosis. Little is currently known, however, about the effects of acidosis on the cellular electrophysiology of the atrioventricular node (AVN). This study was conducted, therefore, to determine the effect of acidosis on the spontaneous activity and membrane currents of myocytes isolated from the rabbit AVN, recorded at 35–37 °C using whole-cell patch-clamp. Reduction of extracellular pH (pH e; from 7.4 to 6.8 or 6.3) produced pH-dependent slowing of spontaneous action potential rate and upstroke velocity, and reductions in maximum diastolic potential and action potential amplitude. Ionic current recordings under voltage-clamp indicated that acidosis (pH e 6.3) decreased L-type Ca current ( I Ca,L), without significant changes in voltage-dependent activation or inactivation. Acidosis reduced the E-4031-sensitive, rapid delayed rectifier current ( I Kr) tail amplitude at − 40 mV following command pulses to between − 30 and + 50 mV, and accelerated tail-current deactivation. In contrast, the time-dependent hyperpolarisation-activated current, I f, was unaffected by acidosis. Background current insensitive to E-4031 and nifedipine was reduced by acidosis. Measurement of intracellular pH (pH i) from undialysed cells using BCECF showed a reduction in mean pH i from 7.24 to 6.45 ( n = 17) when pH e was lowered from 7.4 to 6.3. We conclude that I f is unlikely to be involved in the response of the AVN to acidosis, whilst inhibition of I Ca,L and I Kr by acidosis are likely to play a significant role in effects on AVN cellular electrophysiology.

Inhibition of TASK1‐like channels by muscarinic receptor stimulation in rat adrenal medullary cells

The muscarinic receptor is known to be involved in the acetylcholine-induced secretion of catecholamines in the adrenal medulla (AM) cells of various mammals. The ionic mechanisms, however, have not been elucidated yet. Thus, we investigated the issue in acutely isolated rat AM cells with the perforated patch clamp method. Bath application of 30 muM muscarine induced depolarization with the consequent generation of action potentials or an inward current at negative membrane potentials. The muscarine-sensitive current instantaneously changed in amplitude upon application of command pulses without a time-dependent component, altered the polarity as a K(+)-electrode, and showed rectification of the Goldman-Hodgkin-Katz (GHK) type. The whole-cell current at -20 mV was inhibited by external H(+) ions with a concentration responsible for half inhibition of pH 7.09 and muscarine failed to induce a further inward current during exposure to a saline in which pH decreased to 6.5. A similar occlusion occurred in secretion when pH in muscarine-containing saline decreased to 6.6. RT-PCR, immunoblotting, and immunocytochemistry suggested that rat AM cells mainly express the TASK1 channel. This TASK channel in AM cells may directly sense a decrease in blood pH, which occurs during exercise. The muscarine action was mimicked by oxotremorine-methiodide, but not by oxotremorine. The present results indicate that activation of muscarinic receptors or a decrease in external pH in the rat AM cell induces secretion through the inhibition of TASK1-like channels.

Kinematic parameter calibration method for industrial robot manipulator using the relative position

A new calibration method for industrial robot system calibration on a manufacturing floor is presented in this paper. To calibrate the robot system, a laser sensor to measure the distance between robot tool and measurement surface is attached to the robot end-effector and a grid is established in the floor. Given two position command pulses for a robot manipulator and using the position difference between two command pulses, the relative position measurement calibration method will find the real robot kinematic parameters. The procedures developed have been applied to an industrial robot. Finally, the effects of the models used to calibrate the robot are discussed. This calibration method represents an effective, low cost and feasible technique for the industrial robot calibration in lab. projects and industrial environments.

CGMP Activates a pH-Sensitive Leak K+ Current in the Presumed Cholinergic Neuron of Basal Forebrain

In an earlier study, we demonstrated that nitric oxide (NO) causes the long-lasting membrane hyperpolarization in the presumed basal forebrain cholinergic (BFC) neurons by cGMP-PKG-dependent activation of leak K+ currents in slice preparations. In the present study, we investigated the ionic mechanisms underlying the long-lasting membrane hyperpolarization with special interest in the pH sensitivity because 8-Br-cGMP-induced K+ current displayed Goldman-Hodgkin-Katz rectification characteristic of TWIK-related acid-sensitive K+ (TASK) channels. When examined with the ramp command pulse depolarizing from -130 to -40 mV, the presumed BFC neurons displayed a pH-sensitive leak K+ current that was larger in response to pH decrease from 8.3 to 7.3 than in response to pH decrease from 7.3 to 6.3. This K+ current was similar to TASK1 current in its pH sensitivity, whereas it was highly sensitive to Ba(2+), unlike TASK1 current. The 8-Br-cGMP-induced K+ currents in the presumed BFC neurons were almost completely inhibited by lowering external pH to 6.3 as well as by bath application of 100 microM Ba(2+), consistent with the nature of the leak K+ current expressed in the presumed BFC neurons. After 8-Br-cGMP application, the K+ current obtained by pH decrease from 7.3 to 6.3 was larger than that obtained by pH decrease from pH 8.3 to 7.3, contrary to the case seen in the control condition. These observations strongly suggest that 8-Br-cGMP activates a pH- and Ba(2+)-sensitive leak K+ current expressed in the presumed BFC neurons by modulating its pH sensitivity.

Simulated and Experimental Results for a Hydraulic Actuator Controlled by two High-Speed on\off Solenoid Valves

AbstractResearch was completed to investigate the use of high-speed on\off valves in the control of a hydraulic actuator. This work was completed as part of efforts to improve the accuracy and smoothness of travel for a six-degree-of-freedom testing machine. A mathematical representation of the system was developed that correctly predicted experimental results when a single command pulse was sent to the valves. For experiments involving a series of pulses to the valves the simulated and experimental results generally agreed at lower duty cycles, however, at higher duty cycles there was some separation in the results due to assumptions made in the simulation.

Nitric Oxide Activates Leak K+ Currents in the Presumed Cholinergic Neuron of Basal Forebrain

Learning and memory are critically dependent on basal forebrain cholinergic (BFC) neuron excitability, which is modulated profoundly by leak K(+) channels. Many neuromodulators closing leak K(+) channels have been reported, whereas their endogenous opener remained unknown. We here demonstrate that nitric oxide (NO) can be the endogenous opener of leak K(+) channels in the presumed BFC neurons. Bath application of 1 mM S-nitroso-N-acetylpenicillamine (SNAP), an NO donor, induced a long-lasting hyperpolarization, which was often interrupted by a transient depolarization. Soluble guanylyl cyclase inhibitors prevented SNAP from inducing hyperpolarization but allowed SNAP to cause depolarization, whereas bath application of 0.2 mM 8-bromoguanosine-3',5'-cyclomonophosphate (8-Br-cGMP) induced a similar long-lasting hyperpolarization alone. These observations indicate that the SNAP-induced hyperpolarization and depolarization are mediated by the cGMP-dependent and -independent processes, respectively. When examined with the ramp command pulse applied at -70 mV under the voltage-clamp condition, 8-Br-cGMP application induced the outward current that reversed at K(+) equilibrium potential (E(K)) and displayed Goldman-Hodgkin-Katz rectification, indicating the involvement of voltage-independent K(+) current. By contrast, SNAP application in the presumed BFC neurons either dialyzed with the GTP-free internal solution or in the presence of 10 muM Rp-8-bromo-beta-phenyl-1,N(2)-ethenoguanosine 3',5'-cyclic monophosphorothioate sodium salt, a protein kinase G (PKG) inhibitor, induced the inward current that reversed at potentials much more negative than E(K) and close to the reversal potential of Na(+)-K(+) pump current. These observations strongly suggest that NO activates leak K(+) channels through cGMP-PKG-dependent pathway to markedly decrease the excitability in BFC neurons, while NO simultaneously causes depolarization by the inhibition of Na(+)-K(+) pump through ATP depletion.

Chloride Conductance Is Required for the Protein Kinase A and Rac1-dependent Phosphorylation of Moesin at Thr-558 by KCl in PC12 Cells

Moesin is a member of the ERM family, a family of cross-linkers between the plasma membrane and the actin cytoskeleton, which are known to be activated by phosphorylation. Previously, we reported the RhoA and Rho kinase-dependent phosphorylation of moesin at Thr-558 in hippocampal neuronal cells by glutamate. Here we studied the induction of moesin phosphorylation by KCl (60 mm) in PC12 cells. Moesin phosphorylation at Thr-558 was increased after 2 min of KCl treatment, peaked at 5 min, and returned to the basal level by 60 min. KCl also activated Rac1, but not RhoA, in PC12 cells, and KCl-induced moesin phosphorylation was suppressed in dominant negative Rac1 (N17 Rac1)-expressed cells. The inhibition of protein kinase A (PKA), known as an upstream kinase of Rac1, abolished Rac1 activation and moesin phosphorylation by KCl. Interestingly, the phosphorylation of moesin by KCl was independent of KCl-induced membrane depolarization and calcium influx but was dependent on KCl-induced chloride conductance. 60 mm KCl induced chloride conductance in PC12 cells, and pretreatment with Cl- channel blocker abolished Rac1 activation and moesin phosphorylation by KCl. These results suggest that the phosphorylation of moesin at Thr-558 in PC12 cells by KCl treatment is PKA- and Rac1-dependent and that KCl-induced chloride conductance is involved in the activation of this signaling system.