Electrical Feedback Research Articles

Feedback traps for virtual potentials.

Feedback traps are tools for trapping and manipulating single charged objects, such as molecules in solution. An alternative to optical tweezers and other single-molecule techniques, they use feedback to counteract the Brownian motion of a molecule of interest. The trap first acquires information about a molecule's position and then applies an electric feedback force to move the molecule. Since electric forces are stronger than optical forces at small scales, feedback traps are the best way to trap single molecules without 'touching' them (e.g. by putting them in a small box or attaching them to a tether). Feedback traps can do more than trap molecules: they can also subject a target object to forces that are calculated to be the gradient of a desired potential function U(x). If the feedback loop is fast enough, it creates a virtual potential whose dynamics will be very close to those of a particle in an actual potential U(x). But because the dynamics are entirely a result of the feedback loop-absent the feedback, there is only an object diffusing in a fluid-we are free to specify and then manipulate in time an arbitrary potential U(x,t). Here, we review recent applications of feedback traps to studies on the fundamental connections between information and thermodynamics, a topic where feedback plays an even more fundamental role. We discuss how recursive maximum-likelihood techniques allow continuous calibration, to compensate for drifts in experiments that last for days. We consider ways to estimate work and heat, using them to measure fluctuating energies to a precision of ±0.03 kT over these long experiments. Finally, we compare work and heat measurements of the costs of information erasure, the Landauer limit of kT ln 2 per bit of information erased. We argue that, when you want to know the average heat transferred to a bath in a long protocol, you should measure instead the average work and then infer the heat using the first law of thermodynamics.This article is part of the themed issue 'Horizons of cybernetical physics'.

Electrical Control of Effective Mass, Damping, and Stiffness of MEMS Devices

We propose the use of electrostatic force feedback to control the effective mass, damping, or stiffness of micro electro mechanical system (MEMS). Our analysis suggests that if feedback force is proportional to sensed displacement, velocity, or acceleration of a MEMS proof mass, then feedback can be used to increase or decrease the apparent stiffness, damping, or mass of the system. Such feedback might be used to compensate the process variations, packaging stress, thermal drift, and damping. Prior efforts by others include position or velocity-based feedback for modifying frequency, bandwidth, quality factor, or sensitivity of resonators. However, we present a comprehensive means of controlling the response of MEMS. We develop an analytical steady-state MEMS model that includes feedback forces and circuit delay, and we develop a stability model. Our analytical models are verified using numerical simulations that include circuit delay, electrical feedback delay, and noise. Our results support the realization toward performance-on-demand MEMS (PODMEMS).

Methods of evaluating cognitive performance of products digital interface

Effective evaluation of cognitive performance is one of complex issue in product’s usability study. This paper proposed a comprehensive evaluation method for cognitive performance of product digital interface based on task decomposition, and extricated three objective indicators including brain electric feedback negativity, reaction timecorrect rate, which are easily to be measure,through operant behavior and cognition brain wave., so as to realize comprehensive evaluation of cognitive performance of product digital interface. Through example verification, it shows it can realize objective evaluation of “perceptibility, understanding, judgment” of digital interface based on these three indicators, respectively, and thus realize comprehensive evaluation of cognitive performance of product digital interface and explore a new ideal for evaluation of cognitive performance of product digital interface.

Interplay among distinct Ca2+ conductances drives Ca2+ sparks/spontaneous transient outward currents in rat cerebral arteries.

Distinct Ca2+ channels work in a coordinated manner to grade Ca2+ spark/spontaneous transient outward currents (STOCs) in rat cerebral arteries. The relative contribution of each Ca2+ channel to Ca2+ spark/STOC production depends upon their biophysical properties and the resting membrane potential of smooth muscle. Na+ /Ca2+ exchanger, but not TRP channels, can also facilitate STOC production. Ca2+ sparks are generated in a voltage-dependent manner to initiate spontaneous transient outward currents (STOCs), events that moderate arterial constriction. In this study, we defined the mechanisms by which membrane depolarization increases Ca2+ sparks and subsequent STOC production. Using perforated patch clamp electrophysiology and rat cerebral arterial myocytes, we monitored STOCs in the presence and absence of agents that modulate Ca2+ entry. Beginning with CaV 3.2 channel inhibition, Ni2+ was shown to decrease STOC frequency in cells held at hyperpolarized (-40mV) but not depolarized (-20mV) voltages. In contrast, nifedipine, a CaV 1.2 inhibitor, markedly suppressed STOC frequency at -20mV but not -40mV. These findings aligned with the voltage-dependent profiles of L- and T-type Ca2+ channels. Furthermore, computational and experimental observations illustrated that Ca2+ spark production is intimately tied to the activity of both conductances. Intriguingly, this study observed residual STOC production at depolarized voltages that was independent of CaV 1.2 and CaV 3.2. This residual component was insensitive to TRPV4 channel modulation and was abolished by Na+ /Ca2+ exchanger blockade. In summary, our work highlights that the voltage-dependent triggering of Ca2+ sparks/STOCs is not tied to a single conductance but rather reflects an interplay among multiple Ca2+ permeable pores with distinct electrophysiological properties. This integrated orchestration enables smooth muscle to grade Ca2+ spark/STOC production and thus precisely tune negative electrical feedback.

Electrical tuning of mechanical characteristics in qPlus sensor: Active Q and resonance frequency control

We present an electrical feedback method for independent and simultaneous tuning of both the resonance frequency and the quality factor of a harmonic oscillator, the so called “qPlus” configuration of quartz tuning forks. We incorporate a feedback circuit with two electronic gain parameters into the original actuation-detection system, and systematically demonstrate the control of the original resonance frequency of 32 592 Hz from 32 572 Hz to 32 610 Hz and the original quality factor 952 from 408 up to 20 000. This tunable module can be used for enhancing and optimizing the oscillator performance in compliance with specifics of applications.

Electric Hydraulic Power Steering System Design Based on Electric Motor Coach of Mixed H2/H∞ Control

The Electric motor coach has become the focus of attention for its energy saving and green non-polluting, but it also poses a new challenge to feedback aspects of steering system and steering feeling. To enhance high-speed handling road sense, this article suggested using genetic algorithm to optimize mixed H2/H∞ system for boosting steering feeling control ability of hydraulic power steering system of electric motor coach based on analyzing electric hydraulic power steering system and feedback torque mathematical model of steering wheel. Simulation result showed that the accumulative error between torque feedback of steering wheel and wheel load torque is obviously reduced after optimization, and the feedback feeling of drivers to road sense has been strengthened.

Characterization, modeling, and control of Ni-Ti shape memory alloy based on electrical resistance feedback

The use of shape memory alloy actuators has steadily increased within the fields of aerospace, robotics, and biomedical engineering due to their superior properties compared to other actuation systems. Position control of shape memory alloy actuators is difficult due to the highly non-linear behavior but has been well studied using numerous approaches. Electrical resistance can be used to estimate strain in shape memory alloy actuator wire due to a correlation between the two parameters. Previous models of this correlation are subject to one or more drawbacks such as being limited to a single applied load, not accounting for hysteresis effects, or applying only to a specific actuator size. This article presents a stress–strain–resistance model that accounts for varying applied load, major and minor hysteresis effects and is normalized in terms of actuator geometry. Results of simulation and a simple position control experiment are demonstrated, validating the performance of the model. Furthermore, a correlation between the model and an augmented version of the Liang and Rogers model is also presented.

What goes on behind closed doors?

Purpose The purpose of this paper was to evaluate the impact of a competition-based intervention combining high-resolution electricity feedback, incentives, information and prompts on college dormitory residents’ energy consumption and participation in demand response events. The authors also investigated changes in individual-level pro-environmental behaviors and examined psychosocial correlates of behavior change. Design/methodology/approach Residents of 39 suites in a freshman residence hall competed against one another to reduce energy consumption and win prizes as part of a three-week competition. Feedback was provided in near real-time at the suite-level via an interactive touch-screen kiosk. Participants also completed baseline and follow-up surveys. Findings Electricity use among all suites was approximately 6.4 per cent lower during the competition period compared to baseline, a significant reduction. Additionally, participants reported engaging in various pro-environmental behaviors significantly more frequently during the competition relative to baseline. Changes in pro-environmental behavior were associated with changes in level of group identification and perceived social norms. Practical implications In three weeks, dormitory residents saved 3,158 kWh of electricity compared to baseline – the equivalent of more than 3,470 pounds of carbon dioxide emissions. The findings provide evidence that real-time feedback, combined with incentives, information and prompts, can motivate on-campus residents to reduce energy consumption. Originality/value The authors contribute to a limited body of evidence supporting the effectiveness of dorm energy competitions in motivating college students to save energy. In addition, the authors identified individual-level behavioral and psychosocial changes made during such an intervention. University residential life planners may also use the results of this research to inform student programming.

Performance of a microbial fuel cell-based biosensor for online monitoring in an integrated system combining microbial fuel cell and upflow anaerobic sludge bed reactor

A hybrid system integrating a microbial fuel cell (MFC)-based biosensor with upflow anaerobic sludge blanket (UASB) was investigated for real-time online monitoring of the internal operation of the UASB reactor. The features concerned were its rapidity and steadiness with a constant operation condition. In addition, the signal feedback mechanism was examined by the relationship between voltage and time point of changed COD concentration. The sensitivity of different concentrations was explored by comparing the signal feedback time point between the voltage and pH. Results showed that the electrical signal feedback was more sensitive than pH and the thresholds of sensitivity were S=3×10−5V/(mg/L) and S=8×10−5V/(mg/L) in different concentration ranges, respectively. Although only 0.94% of the influent COD was translated into electricity and applied for biosensing, this integrated system indicated great potential without additional COD consumption for real-time monitoring.

Shape memory alloy wire for self-sensing servo actuation

This paper reports on the development of a straightforward approach to realise self-sensing shape memory alloy (SMA) wire actuated control. A differential electrical resistance measurement circuit (the sensorless signal conditioning (SSC) circuit) is designed; this sensing signal is directly used as the feedback for control. Antagonistic SMA wire actuators designed for servo actuation is realized in self-sensing actuation (SSA) mode for direct control with the differential electrical resistance feedback. The self-sensing scheme is established on a 1-DOF manipulator with the discrete time sliding mode controls which demonstrates good control performance, whatever be the disturbance and loading conditions. The uniqueness of this work is the design of the generic electronic SSC circuit for SMA actuated system, for measurement and control. With a concern to the implementation of self-sensing technique in SMA, this scheme retains the systematic control architecture by using the sensing signal (self-sensed, electrical resistance corresponding to the system position) for feedback, without requiring any processing as that of the methods adopted and reported previously for SSA techniques of SMA.

Design and Fabrication of a Special Purpose Winding Machine for ELM Control Coils of JET

Under the India-European Union collaboration, the Institute for Plasma Research had successfully completed an engineering initiative aimed at developing a “special purpose winding machine” (SPWM) appropriate for winding 1:1 prototype edge-localized mode (ELM) coils of the Joint European Torus (JET). The typical 1:1 prototype ELM coil winding pack is composed of eight layers of 6.35-mm square cross-section CuCrZr conductors being wound in a saddle configuration having eight turns per layer with strict tolerance requirements. Such an SPWM has been designed and developed with Indian industry complying with the complex shape and tolerance requirements of the ELM coils. The SPWM developed is primarily composed of a feeding conductor spool with appropriate tensioning mechanisms, straightening and shaping units, cleaning unit, insulation unit, press forming units and rotating turn table mandrel, and rotation and synchronization arrangements with electrical control and feedback elements. The SWPM has been successfully demonstrated with winding for both types of 1:1 prototype ELM control coils of JET within a tolerance of ±3 mm. The design consideration for SPWM, critical subsystems of SPWM and their operation principle, winding methodology, and application articulated arm coordinate measuring machine for inspection of winding pack have been discussed in this paper.

Life cycle assessment indicators of urban wastewater and sewage sludge treatment

The world is facing a water quality crisis resulting from continuous population growth, urbanization, land use change, industrialization, unsustainable water use practices and wastewater management strategies, among others. In this context, wastewater treatment (WWT) facilities are of vital significance for urban systems. Wastewater management clearly plays a central role in achieving future water security in a world where water stress is expected to increase. Life cycle assessment (LCA) can be used as a tool to evaluate the environmental impacts associated to WWTPs and improvement options. In this study, LCA is applied to compare the environmental performance of different scenarios for wastewater and sludge disposal in a WWT plant located in Southern Italy. The first scenario (BAU, Business As Usual) is based on the present sludge management performed within and outside the case-study plant: after mechanical treatment, dewatered sludge is transported by truck to a landfill for final disposal, while treated water is released to a river. The second scenario (B) assumes a partially circular pattern, with anaerobic fermentation of sludge to biogas, biogas use for electricity and heat cogeneration, integrated by additional thermal energy from previously recovered waste cooking oil (WCO), electricity and heat feedback to upstream WWT steps (including sludge drying), and final disposal of dried sludge to landfill and water to river. The third scenario (C) suggests an improved circular pattern with gasification of the dried sludge to further support heat and electricity production (with very small delivery of residues to landfill). The fourth scenario (D) builds on the third scenario in that the volume of treated wastewater is not discharged into local rivers but is partially used for fertirrigation of Salix Alba fields, whose biomass is further used for electricity generation. In doing so, the water P and N content decreases and so does the water eutrophication potential. Finally, a renewable scenario (E) is built assuming that the electricity demand of the WWT plant is met by a green electricity mix, for comparison with previous options. The most impacted categories in all scenarios result to be Freshwater Eutrophication Potential (FEP) and Human Toxicity Potential (HTP). Increased circularity through recycling in scenarios B and C reduces the process contribution to some environmental impact categories such as Global Warming Potential (GWP) and Fossil Depletion Potential (FDP), but does not provide significant improvement to FEP. Fertirrigation in scenario D lowers FEP by about 60% compared to the BAU scenario. Furthermore, HTP is lowered by almost 53%. Finally, other options are discussed that could be also explored in future studies to evaluate if and to what extent they could further improve the overall performance of the WWT plant.

Design and development of a new wireless EMG electrode with high voltage impulse notification feedback

This paper deals with the development of a new wireless EMG electrode ‘VAMPIRE-BAT/WASPS’ for man–machine interface that can not only stream up EMG signal in real-time, but also give electric stimulus feedback to human operator. The authors’ unique idea is ‘stimulus feedback nearby the actuation point’. Their statement is that human response may be faster if feedback is applied exactly on or nearby the point of actuation (i.e. muscle). Firstly, they introduce their new EMG electrode device and its technical details with performance test result. Then, they also show experiments and their results to verify effectiveness of the idea of stimulus feedback nearby the actuation point.

Biomechanical Energy Harvesting System With Optimal Cost-of-Harvesting Tracking Algorithm

Biomechanical energy harvesting can provide an attractive alternative for powering portable electronics, such as laptops and mobile communication devices. This unique type of energy is particularly advantageous to those who do not have direct access to the utility grid for extended periods of time. This paper presents an innovative biomechanical energy harvesting system based on the regenerative braking concept applied to the human natural motion. To determine the optimal braking profile, previous studies used an offline procedure based on constant external load to determine the optimal braking profile. The new concept of this paper continuously optimizes the maximum amount of energy that can be extracted during human motion while minimizing the subject's effort (metabolic rate). This is achieved by an energy harvesting system equipped with a programmable braking profile and a unique power extraction algorithm, which adaptively changes the braking profile to obtain the optimal ratio of energy to effort. These are facilitated by a brushless dc generator that is connected to boost converter. A digital current-programmed control of the boost converter enables an adaptive torque variation according to biofeedback (the measure of effort) and electrical feedback. This paper focuses on the human knee joint as the energy source, since most of this joint's work during level walking is negative (muscles are acting as brakes). Since this paper is preliminary and more oriented to the novel concept of adaptive profile and optimal power extraction, the operation of the energy harvester is demonstrated on a full-scale laboratory prototype based on a walking emulator. Initial experiments on human subjects have been initiated and are also reported. The results exhibit ultimate power extraction capabilities as well as adaptation to the walking pattern.

On-Chip Magnetic Platform for Single-Particle Manipulation with Integrated Electrical Feedback.

Methods for the manipulation of single magnetic particles have become very interesting, in particular for in vitro biological studies. Most of these studies require an external microscope to provide the operator with feedback for controlling the particle motion, thus preventing the use of magnetic particles in high-throughput experiments. In this paper, a simple and compact system with integrated electrical feedback is presented, implementing in the very same device both the manipulation and detection of the transit of single particles. The proposed platform is based on zig-zag shaped magnetic nanostructures, where transverse magnetic domain walls are pinned at the corners and attract magnetic particles in suspension. By applying suitable external magnetic fields, the domain walls move to the nearest corner, thus causing the step by step displacement of the particles along the nanostructure. The very same structure is also employed for detecting the bead transit. Indeed, the presence of the magnetic particle in suspension over the domain wall affects the depinning field required for its displacement. This characteristic field can be monitored through anisotropic magnetoresistance measurements, thus implementing an integrated electrical feedback of the bead transit. In particular, the individual manipulation and detection of single 1-μm sized beads is demonstrated.

Hysteretic behavior induced by an electroacoustic feedback loop in a thermo-acousto-electric generator

An active control method of the spatial distribution of the acoustic field is applied in a thermo-acousto-electric generator. An auxiliary acoustic source is used to force the self-sustained thermoacoustic oscillation in order to control the thermoacoustic amplification. The auxiliary source consists of a loudspeaker, located inside the loop-tube close to the main ambient heat exchanger, and supplied with a delayed signal through an electric feedback loop, comprising a phase-shifter and an amplifier, connected to a reference microphone. Experiments are performed on a prototype engine working with air at a static gauge pressure of 5 bars. Experimental results demonstrate how it is possible to tune the acoustic oscillations in order to increase the global performance of the generator, compared to the case without control, as well as the existence of a hysteretic behavior induced by the electroacoustic feedback loop itself, which leads to a discrepancy between the onset heat input and the offset one.

Long-Term Frequency Stabilization of 10-GHz Quantum-Dash Passively Mode-Locked Lasers

This paper reports on the repetition frequency stability of InAs/InP quantum-dash-based mode locked lasers emitting in the 1.55-μm telecom window and of a long-term frequency stabilization schemes. We discuss the main noise sources that affect the frequency stability. In free running operation, quantum-dash-based mode locked lasers demonstrate an initial long-term stability of $\sim 10^{-7}$ . In order to improve it, we developed different approaches based on electrical feedback and optical feedback loops. The stabilization systems exploit the bias-dependent frequency drift and the optical feedback sensitivity to keep repetition frequency in lock for an extensive period of time with a stability of $1.5 \times 10^{-9}$ .

A three-fingered, touch-sensitive, metrological micro-robotic assembly tool

This article describes a metrological, robotic hand to manipulate and measure micrometer size objects. The presented work demonstrates not only assembly operations, but also positioning control and metrology capability. Sample motion is achieved by a commercial positioning stage, which provides XYZ-displacements for assembly of components. A designed and manufactured gripper tool that incorporates 21 degrees-of-freedom for independent alignment of actuators, sensors, and the three fingers of this hand is presented. These fingers can be opened and closed by piezoelectric actuators through levered flexures providing an 80 μm displacement range measured with calibrated opto-interrupter based, knife-edge sensors. The operational ends of the fingers comprise of a quartz tuning fork with a 7 μm diameter 3.2 mm long carbon fiber extending from the end of one tuning fork tine. Finger-tip force-sensing is achieved by the monitoring of individual finger resonances typically at around 32 kHz. Experimental results included are focused on probe performance analysis. Pick and place operation using the three fingers is demonstrated with all fingers being continuously oscillated, a capability not possible with the previous single or two finger tweezer type designs. By monitoring electrical feedback during pick and place operations, changes in the response of the three probes demonstrate the ability to identify both grab and release operations. Component metrology has been assessed by contacting different micro-spheres of diameters 50(±7.5) μm, 135(±20) μm, and 140(±20) μm. These were measured by the micro robot to have diameters of 67, 133, and 126 μm respectively with corresponding deviations of 4.2, 4.9, and 4.3 μm. This deviation in the measured results was primarily due to the manual, joystick-based, contacting of the fingers, difficulties associated with centering the components to the axis of the hand, and lower contact sensitivity for the smallest sphere. Finally, assemblies of spheres onto the edge of a razor blade plus assembly of spherical contact probes for micro-meter scale coordinate measurement applications are presented.

Householder engagement with energy consumption feedback: the role of community action and communications

The provision of energy consumption feedback on in-home displays (IHDs) has a prominent role in government strategies for domestic energy demand reduction. Research suggests that IHDs can support energy consumption reduction, but also that engagement with IHDs can be limited to men and is often short-term. In this paper, we draw on research carried out in Smart Communities, a two-year project in which electricity and gas consumption feedback played a key role. This study was distinctive because it was accompanied by a weekly email communications programme and was provided within the context of community action. Project findings suggest that, although by no means panaceas, approaches such as these can support long-term engagement with energy consumption feedback, including by women, and can support behaviour change.

Activation of endothelial IKCa channels underlies NO-dependent myoendothelial feedback

Agonist-induced vasoconstriction triggers a negative feedback response whereby movement of charged ions through gap junctions and/or release of endothelium-derived (NO) limit further reductions in diameter, a mechanism termed myoendothelial feedback. Recent studies indicate that electrical myoendothelial feedback can be accounted for by flux of inositol trisphosphate (IP3) through myoendothelial gap junctions resulting in localized increases in endothelial Ca2+ to activate intermediate conductance calcium-activated potassium (IKCa) channels, the resultant hyperpolarization then conducting back to the smooth muscle to attenuate agonist-induced depolarization and tone. In the present study we tested the hypothesis that activation of IKCa channels underlies NO-mediated myoendothelial feedback. Functional experiments showed that block of IP3 receptors, IKCa channels, gap junctions and transient receptor potential canonical type-3 (TRPC3) channels caused endothelium-dependent potentiation of agonist-induced increase in tone which was not additive with that caused by inhibition of NO synthase supporting a role for these proteins in NO-mediated myoendothelial feedback. Localized densities of IKCa and TRPC3 channels occurred at the internal elastic lamina/endothelial-smooth muscle interface in rat basilar arteries, potential communication sites between the two cell layers. Smooth muscle depolarization to contractile agonists was accompanied by IKCa channel-mediated endothelial hyperpolarization providing the first demonstration of IKCa channel-mediated hyperpolarization of the endothelium in response to contractile agonists. Inhibition of IKCa channels, gap junctions, TRPC3 channels or NO synthase potentiated smooth muscle depolarization to agonists in a non-additive manner. Together these data indicate that rather being distinct pathways for the modulation of smooth muscle tone, NO and endothelial IKCa channels are involved in an integrated mechanism for the regulation of agonist-induced vasoconstriction.