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This paper presents a feedback control method to analyze Marx's law of the tendential fall in the rate of profit which is the most important Marx's theory of capitalism. The law states that the rate of profit would tend to decline in the long run as a result of technological progress. In this paper, we set the composition of capital to be accumulated next year as a control input which is designed to increase the profit rate in the next year. Then we present certain conditions for which the control input to increase the rate of profit eventually decreases it, that is to say, the effort of capital to increase the rate of profit leads to its decrease on the contrary. [ABSTRACT FROM AUTHOR]

This paper presents a cell optimal equalizing control method for Lithium-Ion battery pack formed by many cells connected in series in order to extract the maximum capacity, maintain the safe operation requirements of pack, and prolong the cells cycle life. Using the active cell to cell equalizing method, the energy levels of two adjacent cells will be equalized based on the principle of the bidirectional Cuk converter with the pulse width modulation (PWM) control variables. The strategy to determine the optimal PWM variables is based on the solution of nonlinear optimal problem with the state of charge (SoC) feedback satisfying the constraints of the SoC levels, amplitude of charge/discharge current, equalizing currents, and control variables. The nonlinear optimal problem is solved by appying the sequential quadratic programming (SQP). Experimental optimal cell equalizing control results for Lithium-Ion battery pack with 7 Samsung 22P 18650 battery cells connected in series with charge/discharge alternately scenarios show that the cell optimal equalizing control proposed is quite effective and satisfied all the desired operation requirements of pack in the practice. [ABSTRACT FROM AUTHOR]

The author considers the problem of positional control of a group of several quadrocopters. The main goal is to transfer this group from a given initial position to a given target position at a fixed time interval, provided that at each intermediate time the quadcopters must be in a small neighborhood of a fixed smooth curve in space. A centralized group control scheme is used. A feature of the problem being solved is the complex, non-linear mathematical model used here, which describes the movement of each individual aircraft. The main goal is to develop computationally efficient algorithms for the approximate search for feedback control, which allow one to cope simultaneously with nonlinear dynamics, pointwise restrictions on control parameters, as well as state constraints arising in connection with group motion (in particular, due to the requirements of pairwise non-collision of the quadrocopters). To construct such algorithms, modifications of the methods of ellipsoidal calculus are used. [ABSTRACT FROM AUTHOR]

We investigate the dynamics of a thin liquid film that is placed atop a heated substrate of very low thermal conductivity. The direct numerical simulation of the stationary long-wave Marangoni instability is performed with the system of coupled partial differential equations. These equations were previously derived within the lubrication approximation; they describe the evolution of film thickness and fluid temperature. We compare our results with the early reported results of the weakly nonlinear analysis. A good qualitative agreement is observed for values of the Marangoni number near the convective threshold. In the case of supercritical excitation, our results for the amplitudes are described by the square root dependence on the supercriticality. In the case of subcritical excitation, we report the hysteresis. For relatively high supercriticality, the convective regimes evolve into film rupture via the emergence of secondary humps. For the three-dimensional patterns, we observe rolls or squares, depending on the problem parameters. We also confirm the prediction of the asymptotic results concerning the nonlinear feedback control for the pattern selection. This article is part of the theme issue 'New trends in pattern formation and nonlinear dynamics of extended systems'. [ABSTRACT FROM AUTHOR]

EMS maglev train uses the active control system to maintain the levitation stability, time delay is widespread in control system. However, the existing maglev dynamics studies rarely consider the effect of time delay, so these analysis results cannot directly guide the engineering design. This paper starts from a theoretical analysis of the levitation stability of a single electromagnet levitation system to obtain the theoretical critical value for the time delay. Then the model is gradually extended to a complete vehicle model and a vehicle-girder coupling dynamics model to find the time delay engineering critical values for the complex coupling system. In order to seek ways to reduce the influence of time delay on the dynamic responses, this paper analyzes the influence regularities of the running speed and control parameters on the dynamic response under the effect of time delay. The result shows that the theoretical critical value of the time delay is equal to the ratio of the differential coefficient and proportional coefficient of the PID controller. For a complex maglev system, the engineering critical value is less than the theoretical critical value. Higher running speeds lead to time delay having a more obvious effect on the maglev system's dynamic responses. Selecting the smaller proportional coefficient and appropriate differential coefficient for the levitation control system can expand the stability region and reduce the influence of time delay on the maglev system. This analysis is helpful and meaningful to the understanding of the EMS vehicle system stability, and helpful to explore the reason of violent coupled vibration in actual engineering. [ABSTRACT FROM AUTHOR]

Optimal regional control problem for a class of semilinear time-fractional diffusion systems with distributed feedback in a bounded domain is solved in the paper. For this purpose, we first discuss the well-posedness of the considered system and the differentiability of the control-to-state mapping. The existence of optimal controls for the studied optimal regional control problem is then proved. By using fractional-order system's duality theory to generalize the Hilbert uniqueness method, we present an approach on exploring the explicit expression of the optimal control formulae for associated optimal regional control problems. Moreover, to make the controllers implementation simpler and more precise, a particular case when the distributed controller is a kind of Sakawa-type is also investigated. Finally, we present a numerical example to illustrate the efficiency of our proposed approach. [ABSTRACT FROM AUTHOR]

Limited by the difficulty of obtaining the exact stationary solution of Fokker-Planck-Kolmogorov (FPK) equation, the general control strategy for tracking a specified stationary probability density function have not been obtained till now. However, the feedback control for tracking a pre-specified stationary probability density function plays an important role in engineering or industrial systems. In this paper, a feedback control strategy of nonlinear stochastic dynamic system for accurately tracking a specified stationary probability density function without the requirement of exact stationary solution of Fokker-Planck-Kolmogorov equation is proposed. According to the probability conservation form of the Fokker-Planck-Kolmogorov equation, the stationary Fokker-Planck-Kolmogorov equation is split into a probability circulation flow (PCF) equation and a probability potential flow (PPF) equation. The control force is divided into probability circulation flow part and probability potential flow part accordingly. The probability circulation flow part of the control force is determined to satisfy the probability circulation flow term of the controlled system constructed from the target stationary probability density function. The probability potential flow part of the control force is obtained by solving the probability potential flow equation. A two-dimensional nonlinear stochastic system is carried out as an example. The control force is designed to track different types of target stationary probability density functions. Numerical results show that the proposed control strategy can accurately track the stationary probability density functionswithout the requirement of the exact solution of Fokker-Planck-Kolmogorov equation. The control efficiency can be regulated by the control parameter C. [ABSTRACT FROM AUTHOR]

In order to improve the accuracy of robot terminal pose tracking and the anti-interference performance of robot nonlinear motion path control, a nonlinear output feedback control method based on neural network is proposed. Construct the coordinate transformation matrix of the connecting rod, calculate the linear and angular velocity of the nonlinear motion of the robot, then calculate the sum of the kinetic energy of each connecting rod of the robot, and establish the motion equation of the robot. The structure of BP neural network is analyzed, and the motion equation is solved by BP neural network. Finally, a Fractional Order PID controller is designed and BP neural network is constructed to control the nonlinear motion equation of the robot to complete the output feedback control of the robot. The experimental results show that the end attitude tracking error of this method is the smallest, and it best fits the actual nonlinear trajectory of the robot. It shows that this method can accurately track the end posture of the robot, and can still effectively control the trajectory of the robot in the interference environment. [ABSTRACT FROM AUTHOR]

This paper studies the exponential stabilization of a Boussinesq system describing the two-way propagation of small amplitude gravity waves on the surface of an ideal fluid, the so-called Boussinesq system of the Korteweg–de Vries type. We use a Gramian-based method introduced by Urquiza to design our feedback control. By means of spectral analysis and Fourier expansion, we show that the solutions of the linearized system decay uniformly to zero when the feedback control is applied. The decay rate can be chosen as large as we want. The main novelty of our work is that we can exponentially stabilize this system of two coupled equations using only one scalar input. [ABSTRACT FROM AUTHOR]

Chemical reaction networks can be utilised as basic components for nucleic acid feedback control systems' design for Synthetic Biology application. DNA hybridisation and programmed strand-displacement reactions are effective primitives for implementation. However, the experimental validation and scale-up of nucleic acid control systems are still considerably falling behind their theoretical designs. To aid with the progress heading into experimental implementations, we provide here chemical reaction networks that represent two fundamental classes of linear controllers: integral and static negative state feedback. We reduced the complexity of the networks by finding designs with fewer reactions and chemical species, to take account of the limits of current experimental capabilities and mitigate issues pertaining to crosstalk and leakage, along with toehold sequence design. The supplied control circuits are quintessential candidates for the first experimental validations of nucleic acid controllers, since they have a number of parameters, species, and reactions small enough for viable experimentation with current technical capabilities, but still represent challenging feedback control systems. They are also well suited to further theoretical analysis to verify results on the stability, performance, and robustness of this important new class of control systems. [ABSTRACT FROM AUTHOR]

In the current paper, we demonstrate a new approach for an stabilization criteria for n-order functional-differential equation with distributed feedback control in the integral form. We present a correlation between the order of the functional-differential equation and degree of freedom of the distributed control function. We present two cases of distributed control function in the integral form. Such a case of stabilization control functions plays a very important role in physics, aeronautics, aerospace, ship navigation and traffic network control management. Structure of functional-differential equations is based on the symmetry properties. [ABSTRACT FROM AUTHOR]

Introduction: Intradialytic hypotension (IDH) remains one of the most frequent complications associated to hemodialysis (HD), frequently triggered by a reduction in absolute blood volume (ABV) not compensated by vascular refilling. A recently developed dilutional method allows routinary measurement of ABV and, by a simple algorithm, may turn blood volume monitor (BVM) guided UF (ultrafiltration) biofeedback into an ABV control, automatically adjusting UF rate to maintain ABV above a preset threshold. The aim of this study is to identify an individual critical ABV threshold and test the ability of an ABV feedback control to avoid IDH. Methods: We studied 24 patients throughout three consecutive midweek HD treatments. ABV and blood pressure (BP) were measured every 30 min and anytime the patient referred any symptoms to identify each patient's critical ABV (ABV at the time of hypotension). A fixed bolus dilution approach at the start of HD was used to calculate ABV. Then, patients were followed through three additional HD treatments and IDH development was analyzed. Findings: Seventy‐one treatments performed in 24 patients. ABV monitoring showed a constant decrease as HD treatment progressed. Thirteen IDH events were observed in eight different patients, with a mean systolic BP drop in IDH treatments of 37.38 ± 4.31 mmHg and a mean adjusted ABV at hypotension of 71.07 ± 14.88 mL/kg. Critical ABV was individually set in patients prone to IDH. As expected, ABV feedback control successfully maintained ABV over preset critical ABV. IDH events were avoided in 21 out of 22 treatments performed. ABV drop was successfully reduced, as well as SBP drop (despite similar UF than prior to ABV feedback control implementation). Discussion: ABV feedback control avoided IDH in 21 out of 22 treatments performed by maintaining blood volume above critical ABV, significantly reducing ABV variations without compromising prescribed UF. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) resonant sensors are small in size and have high sensitivity. However, the CNT resonators are susceptible to nonlinear effect. The existing methods to avoid the nonlinearity would decrease the quality factor of the resonator. Here, a novel method for reducing nonlinear effect and increasing quality factor for a CNT resonant mass sensor is proposed. Based on the circuit model and mechanics model of the CNT resonant mass sensor with two feedback loops, the nonlinear vibration equation of the CNT resonant mass sensor is deduced which includes the non-local effect and the feedback control effects. Using this equation, the amplitude–frequency characteristics of the CNT and its variation with size parameters and feedback gain are studied. A method of simulating the nonlinear effect and quality factor of the sensor through the VAR module of ADS is proposed, which provides a reference for simulating nonlinear effect of field effect transistor sensors by using computer-aided design tools. Results show that by tuning feedback gain, the nonlinear effect of the CNT resonant mass sensor could be reduced and its quality factor could be increased. Using the feedback control strategy provided in this paper, the CNT sensor can be in a linear vibration state with high quality factor in a low-vacuum environment by only adjusting the feedback modulation gain, avoiding the expensive and complex ultra-low-temperature system. [ABSTRACT FROM AUTHOR]

Spinal cord injury (SCI) can cause paralysis of trunk and hip musculature that negatively impacts seated balance and ability to lean away from an upright posture and interact fully with the environment. Constant levels of electrical stimulation of peripheral nerves can activate typically paralyzed muscles and aid in maintaining a single upright seated posture. However, in the absence of a feedback controller, such seated postures and leaning motions are inherently unstable and unable to respond to perturbations. Three individuals with motor complete SCI who had previously received a neuroprosthesis capable of activating the hip and trunk musculature volunteered for this study. Subject-specific muscle synergies were identified through system identification of the lumbar moments produced via neural stimulation. Synergy-based calculations determined the real-time stimulation parameters required to assume leaning postures. When combined with a proportional, integral, derivative (PID) feedback controller and an accelerometer to infer trunk orientation, all individuals were able to assume non-erect postures of 30–40° flexion and 15° lateral bending. Leaning postures increased forward reaching capabilities by 10.2, 46.7, and 16 cm respectively for each subject when compared with no stimulation. Additionally, the leaning controllers were able to resist perturbations of up to 90 N, and all subjects perceived the leaning postures as moderately to very stable. Implementation of leaning controllers for neuroprostheses have the potential of expanding workspaces, increasing independence, and facilitating activities of daily living for individuals with paralysis.

The rate of profit is a key element for understanding the movement of capitalism such as technological progress and economic crisis. Even though capitalists seek larger profit rates, there exists a tendency of stagnating or falling profit rates. According to Marx, the rate of profit would tend to decline in the long run as a result of technological progress, termed the law of tendential fall in the profit rate. This article introduces a novel approach based on the discrete-time feedback control mechanism to elucidate Marx’s theory. Specifically, this study presents a mechanism and conditions to show how the effort to maximize the profit rate, implemented by designing an “appropriate” control law under the sampling of fiscal years, eventually leads to the gradual decrease in the rate of profit in the long run.

By using linear entropy, a discrete quantum logistic chaotic map is introduced and the dynamical evolution of the quantum radiation field interacting with the matter is studied by changing the independent parameters. Its typical effect is the chaotic property of the quantum optics and a quantum classical correspondence is obtained, and the chaos and the regular structure of phase space can be better revealed by using the coherence dynamics of phase space. In addition, an approach for fast adaptive synchronization of the discrete quantum maps is proposed. Results validate the effectiveness of the proposed scheme.

By taking into account third-order dispersion effects in the presence of feedback, we investigate the stability and nonlinear dynamic movements of waves created in microcavities and fiber cavities from numerical simulations of the extended Lugiato–Lefever equation. The current analysis emphasizes that third-order scattering, feedback strength, and feedback local and global components allow for the numerical observation of dissipative bound states of solitons and chaos with extended and antisymmetric interaction domains. In this regard, we demonstrate how the symmetry of the localized structural interactions is broken by the radiation that results from third-order dispersion.

To investigate the manoeuvring performance of a body-caudal fin robot fish, a numerical framework combining computational fluid dynamics and multi-body dynamics with a closed-loop control algorithm was established in this study. Within this framework, we modelled a body-caudal fin swimmer as a multi-body system with the shape of a NACA0012 hydrofoil. The manoeuvring performance was investigated by using different curvature magnitudes and distributions along the centre line (the curvature is defined by means of a curvature envelop function as part of the general body undulation equation). To characterize the turning performance, a new parameter named cost of manoeuvring (CoM) is proposed. This parameter provides a combined assessment of the turning radius, linear and angular velocity components, and power. It is found that when the body curvature is introduced, the swimmer switches from straight-line swimming to quasi-steady turning at a constant speed. Further investigations were conducted to study contributions of head and tail deformations on the turning performance by comparing predominantly head and tail curved envelopes. Results reveal that a tail-dominated envelope improves performance, whereas a head-dominated envelope has a negative effect.

This study examines the design and long-term implementation of a feedforward and feedback (FF–FB) mechanism in a control system for cement sulfates applied to all types of cement produced in two mills at a production facility. We compared the results with those of a previous controller (SC) that operated in the same unit. The Shewhart charts of the annual SO3 mean values and the nonparametric Mann–Whitney test demonstrate that, for the FF–FB controller, the mean values more effectively approach the SO3 target than the older controller in two out of the three cement types. The s-charts for the annual standard deviation of all cement types and mills indicate that the ratio of the central lines of FF–FB to SC ranges from 0.39 to 0.59, representing a significant improvement. The application of the error propagation technique validates and explains these improvements. The effectiveness of the installed system is due to two main factors. The feedforward (FF) component tracks the set point of SO3 when the mill begins grinding a different type of cement, while the feedback (FB) component effectively attenuates the fluctuations in the sulfates of the raw materials.

The uncertainty in the secondary path of active noise control (ANC) headphones affects the waterbed effect and stability of the feedback system. This study focuses on the uncertainty of the secondary path when real users wear headphones and proposes a new uncertainty constraint based on the measured results of the secondary path transfer function under different wearing conditions of a dummy head and limited subjects. This constraint and a cascaded second-order infinite impulse response filter with fixed coefficients are used to formulate a control strategic function, which is optimized using the Improved Grey Wolf Optimizer (IGWO) algorithm to obtain the optimal controller with better noise reduction performance. The proposed method and simulation model are validated based on the experimental test results. The results demonstrate that the safety factor and waterbed suppressing factor contained in the proposed uncertainty constraint ensure more stable noise reduction and effective suppression of the waterbed effect for new subjects without a priori data.

In the next decades, both space agencies and private competitors are targeting the lunar environment as a scientific and technological resource for future space missions. In particular, the confirmed existence of water-ice deposits in the vicinity of the poles (predominantly the south pole) makes polar or near-polar low lunar orbits attractive for the purpose of designing space missions that could search for suitable Lunar base sites. However, traveling very-low-altitude orbits is very challenging, as they are strongly perturbed by the Moon’s gravity field as well as third- and fourth-body effects due to the Earth and the Sun. Several studies demonstrate that these orbits are expected to impact the lunar surface in a few months. Therefore, the definition and implementation of an effective station-keeping strategy represents a crucial issue in order to extend satellites’ lifetime. In this paper, a feedback nonlinear control law is employed in order to perform corrective maneuvers aimed at keeping the state of the satellite within acceptable margins. The satellite is assumed to be equipped with a steerable and throttleable low-thrust propulsion system. The control law is based on the Lyapunov stability theory and does not require any reference path to track, with a considerable decrease in the computational cost. The proposed real-time control law includes control saturation, related to the maximum available thrust magnitude, and is developed employing modified equinoctial elements, in order to avoid singularities and extend its range of application. Finally, the strategy at hand is tested in the presence of all the relevant perturbations (i.e., harmonics of the selenopotential, third- and fourth-body effects) in order to show its effectiveness and efficiency.

To sustain good lower hybrid wave (LHW)–plasma coupling for long-pulse plasma operation, for the first time, coupling feedback control is designed and realized in EAST using a proportion integration differentiation method by choosing the reflection coefficient (RC) of LHW power as the reference for gas-puffing feedback, and including one pulse test and multi-pulse experiments. Experiments show that such feedback control can work correctly and maintains good LHW–plasma coupling effectively for a long time, suggesting the possibility of feedback control application on LHW–plasma coupling in long-pulse plasma. Furthermore, during the feedback control process of multi-pulse supersonic molecular beam injection (SMBI), the stored energy changes from 29 kJ to 58 kJ, and the energy confinement factor ( H _89 ) increases from 0.98 to 1.45, implying a positive effect of coupling feedback on plasma performance. Experiments between SMBI puffing and the gas puffing system, fed by a piezoelectric valve near the antenna, are further investigated, showing that the response time of the RC with SMBI is faster than that by the piezoelectric valve. In addition, SMBI puffing on the electron-drift side of the LHW antenna is a little quicker than that on the ion-drift side. Studies suggest that such feedback control is effective for long-pulse LHW–plasma coupling, and the gas puffing by SMBI on the electron-drift side of the LHW antenna could offer an effective way to sustain good LHW coupling in steady-state operation in the future. Further optimization will be continued at a later date.

This article aims to describe social influence by elucidating the cognitive, affective, and motivational processes that occur when an individual experiences an attempt at being influenced. We hypothesized that these processes are part of a feedback loop system in an individual. This loop involves the situation (input), a goal state (reference), a comparator, a selection mechanism, a feedback predictor, and an action (output). Each element can become the target of social influence, and different types of social influence can be classified and explained by how these elements are targeted. For instance, attempting to persuade another person with strong arguments targets the goal state of the affected individual, while coercion targets the selection mechanism, and violence targets the action. In summary, this article aims to categorize, order, and explain phenomena in social influence research using a feedback loop framework focusing on the influenced individual.

Atmospheric pressure plasma jets (APPJs) are increasingly used in plasma medicine and materials processing applications. Reproducible and effective operation of APPJs requires regulating the cumulative effects of plasma on a target substrate in the face of variabilities and exogenous disturbances. This article investigates spatial delivery of thermal effects - thermal dose - of plasma using a kHz-excited APPJ in helium translated over a dielectric substrate. A dose metric is presented for quantifying the cumulative, nonlinear thermal effects of plasma along the translation trajectory of the APPJ. An optimization-based feedback control strategy is proposed for real-time regulation of thermal dose delivery using spatial measurements of substrate temperature. Experimental investigation reveals that feedback control is crucial for achieving spatially uniform dose delivery.

Driver behavior has a significant impact on vehicle fuel economy and emissions. Eco-driving refers to anything a driver can do to improve on-road fuel economy. The most common strategy used to promote eco-driving is an in-vehicle display that provides the driver with feedback about their fuel efficiency, typically in real-time.This policy brief summarizes findings from an extensive review and analysis of many studies of eco-driving feedback conducted to determine the average impact of feedback on fuel economy and improve understanding of what types of feedback are most effective. The study provides the most accurate estimate to-date of the average impact of in-vehicle feedback on fuel economy and summarizes the current state of knowledge regarding characteristics of eco-driving feedback interventions that determine effectiveness.View the NCST Project Webpage

Engine vibration and noise are one of the important factors that affect the comfort of drivers and passengers during driving, and active control technology of engine mounts can effectively realize dynamic adjustment of stiffness during low-frequency vibration and high-frequency vibration, reduce the vibration and noise generated by the engine under different working conditions and significantly enhance driving comfort. This paper uses control theories such as feedforward control and feedback control to design a fusion control strategy, and combines the suspension control model to form a suspension active control scheme. The control scheme is verified and optimized in laboratory and in actual vehicle. Test results show that the active control technology of engine mount has a significant control effect on engine vibration in various frequency bands, and the vibration amplitude of engine in a specific frequency band is reduced by more than 80%, which verifies the effectiveness of the method.

Combining Sterile and Incompatible Insect techniques can significantly reduce mosquito populations and prevent the transmission of diseases between insects and humans. This paper describes impulsive differential equations for the control of a mosquito with Wolbachia. Several interesting conditions are created when sterile male mosquitoes are released impulsively, ensuring both open- and closed-loop control. To determine the wild mosquito population size in real-time, we propose an open-loop control system, which uses impulsive and constant releases of sterile male mosquitoes. A closed-loop control scheme is also being investigated, which specifies the release of sterile mosquitoes according to the size of the wild mosquito population. To eliminate or reduce a mosquito population below a certain threshold, the Sterile insect technique involves mass releases of sterile insects. Numerical simulations verify the theoretical results.

Abstract Background Stimulation-driven exercise is often limited by rapid fatigue of the activated muscles. Selective neural stimulation patterns that decrease activated fiber overlap and/or duty cycle improve cycling exercise duration and intensity. However, unequal outputs from independently activated fiber populations may cause large discrepancies in power production and crank angle velocity among pedal revolutions. Enforcing a constant cadence through feedback control of stimulus levels may address this issue and further improve endurance by targeting a submaximal but higher than steady-state exercise intensity. Methods Seven participants with paralysis cycled using standard cadence-controlled stimulation (S-Cont). Four of those participants also cycled with a low duty cycle (carousel) cadence-controlled stimulation scheme (C-Cont). S-Cont and C-Cont patterns were compared with conventional maximal stimulation (S-Max). Outcome measures include total work (W), end power (Pend), power fluctuation (PFI), charge accumulation (Q) and efficiency (η). Physiological measurements of muscle oxygenation (SmO2) and heart rate were also collected with select participants. Results At least one cadence-controlled stimulation pattern (S-Cont or C-Cont) improved Pend over S-Max in all participants and increased W in three participants. Both controlled patterns increased Q and η and reduced PFI compared with S-Max and prior open-loop studies. S-Cont stimulation also delayed declines in SmO2 and increased heart rate in one participant compared with S-Max. Conclusions Cadence-controlled selective stimulation improves cycling endurance and increases efficiency over conventional stimulation by incorporating fiber groups only as needed to maintain a desired exercise intensity. Closed-loop carousel stimulation also successfully reduces power fluctuations relative to previous open-loop efforts, which will enable neuroprosthesis recipients to better take advantage of duty cycle reducing patterns.

We present a theoretical study of bladder cancer treatment with Bacillus Calmette-Guerin (BCG) and interleukin 2 (IL-2) using a system biology approach to translate the treatment process into a mathematical model. We investigated the influence of IL-2 on effector cell proliferation, presented as a distributed feedback control in integral form. The variables in the system of Ordinary Differential Equations (ODE) are the main participants in the immune response after BCG instillations: BCG, immune cells, tumor cells infected with BCG, and non-infected with BCG. IL-2 was involved in the tumor-immune response without adding a new equation. We use the idea of reducing the system of integro-differential equations (IDE) to a system of ODE and examine the local stability analysis of the tumor-free equilibrium state of the model. A significant result of the model analysis is the requirements for the IL-2 dose and duration, depending on the treatment regimen and tumor growth. We proved that the BCG+IL-2 treatment protocol is more effective in this model, using the spectral radius method. Moreover, we introduced a parameter for individual control of IL-2 in each injection using the Cauchy matrix for the IDE system, and we obtained conditions under which this system would be exponentially stable in a tumor-free equilibrium.

A mechanism has been proposed that utilizes the gyroscopic moment generated by tilting the rotation axis of a flywheel for stabilization control of unstable system. In this study, we investigate the effectiveness of feedback control which drives a gimbal mechanism to maintain the standing posture of an unstable structure such as a two-wheel vehicle. Although a simple feedback of posture angle enables a two-wheel structure to keep standing, both posture and gimbal continue shaking little by little. This is because the gimbal temporarily stays at a constant angle due to the action of Coulomb friction, and the system becomes unstable in the interim. We propose a method to estimate both the length of time when the motion of the gimbal stops and the amplitudes of the vibration of posture and gimbal. Here, we assume that the first-order mode poles obtained from the linearized model are complex numbers and that the second-order mode response converges immediately. From the experimental results, it is found that if the gimbal stays at a constant angle for a long time, the structure tends to fall over. We show that state feedback is necessary to realize to shorten the time when the gimbal stays at a constant angle and to reduce the amplitudes of oscillations at the same time.

In Singapore, there is an increasing need for independence from manpower within the Building and Construction (B&C) Industry. Prefabricated Prefinished Volumetric Construction (PPVC) production is mainly driven by benefits in environmental pollution reduction, improved productivity, quality control, and customizability. However, overall cost savings have been counterbalanced by new cost drivers like modular precast moulds, transportation, hoisting, manufacturing & holding yards, and supervision costs. The highly modular requirements for PPVC places additive manufacturing in an advantageous position, due to its high customizability, low volume manufacturing capabilities for a faster manufacturing response time, faster production changeovers, and lower inventory requirements. However, C3DP has only just begun to move away from its early-stage development, where there is a need to closely evaluate the process parameters across buildability, extrudability, and pumpability aspects. As many parameters have been identified as having considerable influence on C3DP processes, monitoring systems for feedback applications seem to be an inevitable step forward to automation in construction. This paper has presented a broad analysis of the challenges posed to C3DP and feedback systems, stressing the admission of process parameters to correct multiple modes of failure. [ABSTRACT FROM AUTHOR]

A displacement-velocity feedback control method is proposed to enhance the isolation performance of a quasi-zero-stiffness vibration isolator (QZS-VI). Time delay is considered in the controlled QZS-VI system. First, the steady-state solutions are obtained using the averaging method and validated by a numerical method. The jump phenomenon and frequency island phenomenon can occur, and a stability analysis is implemented. Then, the effects of the time delay and feedback gain on the frequency response and stability of solutions are analyzed in detail. Then, the force transmissibility is defined to evaluate the isolation performance of the controlled QZS-VI system. The results show that the time delay mainly affects the stability of the controlled system and weakly influences the isolation performance. The proposed displacement-velocity feedback control method can effectively suppress the vibration in the resonant region without affecting the performance in the isolation region. Finally, the vibration control effect is illustrated by the concept of an equivalent damping ratio. [ABSTRACT FROM AUTHOR]

While autoregulative adaptation is a common feature of living tissues, only a few feedback-controlled adaptive biomaterials are available so far. This paper herein reports a new polymer hydrogel platform designed to release anti-inflammatory molecules in response to the inflammatory activation of human blood. In this system, anti-inflammatory peptide drugs, targeting either the complement cascade, a complement receptor, or cyclophilin A, are conjugated to the hydrogel by a peptide sequence that is cleaved by elastase released from activated granulocytes. As a proof of concept, the adaptive drug delivery from the gel triggered by activated granulocytes and the effect of the released drug on the respective inflammatory pathways are demonstrated. Adjusting the gel functionalization degree is shown to allow for tuning the drug release profiles to effective doses within a micromolar range. Feedback-controlled delivery of covalently conjugated drugs from a hydrogel matrix is concluded to provide valuable safety features suitable to equip medical devices with highly active anti-inflammatory agents without suppressing the general immunosurveillance. [ABSTRACT FROM AUTHOR]

Chronic sensorineural hearing loss (SNHL) is characterized by an increase in hearing thresholds at basic speech frequencies, which implies deterioration of auditory speech feedback control and, as a result, changes of speech characteristics. A hypothesis was tested that such deterioration can manifest itself in an increase of F0, F1, F2 formants of speech vowel in patients with moderate and moderately severe postlingual SNHL. Recordings of elicited speech were performed for young and middle age women (36–59 years): 7 women speakers with moderate SNHL who did not use hearing aids; 5 women speakers with moderately severe SNHL who were hearing aids users but were not using them during the recordings; a control group of 12 normally hearing women speakers. An assessment of F0, F1 and F2 of stressed vowels [a], [i], [u] and calculations of vowels' centralization indices—vowel space area, vowel formant centralization ratio and the second formant ratio (F2i/F2u), were performed. All the studied spectral indices in groups of patients with postlingual SNHL were similar to those in the control group, no statistically reliable differences were revealed. [ABSTRACT FROM AUTHOR]

This paper studies N-species Lotka–Volterra cooperation models with feedback controls and continuous delays. Several conditions for the global attractiveness, permanence and periodic solution of the model are obtained by applying the integral inequality techniques, comparison principle and Lyapunov–Razumikhin method. Finally, a numerical example is also carried out to validate the feasibility and practicability of our proposed results. [ABSTRACT FROM AUTHOR]

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Digital twins, as a rising concept in many industry sectors, have tremendous potential for engineering dynamics. Their practical applications, however, are hindered by the lack of near real-time system identification and control design methods. This paper establishes and implements a framework of digital twins in engineering dynamics based on the latest advances in the field of data-driven equation identification. It consists of a preprocessing step and a circular step; the former includes an initial identification of the digital twin (i.e., an integral variational equation) from discrete data captured from a practical physical twin and an initial design of feedback control to intervene in the physical and digital twins simultaneously; the latter includes the detection of system variation and the rapid update of the digital twin and control strategy. Two typical examples, i.e., a Duffing oscillator and a slender straight beam with time-varying force along its axis, are adopted to illustrate the application and efficacy of the established framework, with the different control objectives of suppressing deterministic/stochastic responses and improving system stability. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM), an enabler of Industry 4.0, recently opened limitless possibilities in various sectors covering personal, industrial, medical, aviation and even extra-terrestrial applications. Although significant research thrust is prevalent on this topic, a detailed review covering the impact, status, and prospects of artificial intelligence (AI) in the manufacturing sector has been ignored in the literature. Therefore, this review provides comprehensive information on smart mechanisms and systems emphasizing additive, subtractive and/or hybrid manufacturing processes in a collaborative, predictive, decisive, and intelligent environment. Relevant electronic databases were searched, and 248 articles were selected for qualitative synthesis. Our review suggests that significant improvements are required in connectivity, data sensing, and collection to enhance both subtractive and additive technologies, though the pervasive use of AI by machines and software helps to automate processes. An intelligent system is highly recommended in both conventional and non-conventional subtractive manufacturing (SM) methods to monitor and inspect the workpiece conditions for defect detection and to control the machining strategies in response to instantaneous output. Similarly, AM product quality can be improved through the online monitoring of melt pool and defect formation using suitable sensing devices followed by process control using machine learning (ML) algorithms. Challenges in implementing intelligent additive and subtractive manufacturing systems are also discussed in the article. The challenges comprise difficulty in self-optimizing CNC systems considering real-time material property and tool condition, defect detections by in-situ AM process monitoring, issues of overfitting and underfitting data in ML models and expensive and complicated set-ups in hybrid manufacturing processes. [ABSTRACT FROM AUTHOR]

We provided a framework of a mathematical epidemic modeling and a countermeasure against the novel coronavirus disease (COVID-19) under no vaccines and specific medicines. The fact that even asymptomatic cases are infectious plays an important role for disease transmission and control. Some patients recover without developing the disease; therefore, the actual number of infected persons is expected to be greater than the number of confirmed cases of infection. Our study distinguished between cases of confirmed infection and infected persons in public places to investigate the effect of isolation. An epidemic model was established by utilizing a modified extended Susceptible-Exposed-Infectious-Recovered model incorporating three types of infectious and isolated compartments, abbreviated as SEIIIHHHR. Assuming that the intensity of behavioral restrictions can be controlled and be divided into multiple levels, we proposed the feedback controller approach to implement behavioral restrictions based on the active number of hospitalized persons. Numerical simulations were conducted using different detection rates and symptomatic ratios of infected persons. We investigated the appropriate timing for changing the degree of behavioral restrictions and confirmed that early initiating behavioral restrictions is a reasonable measure to reduce the burden on the health care system. We also examined the trade-off between reducing the cumulative number of deaths by the COVID-19 and saving the cost to prevent the spread of the virus. We concluded that a bang-bang control of the behavioral restriction can reduce the socio-economic cost, while a control of the restrictions with multiple levels can reduce the cumulative number of deaths by infection. [ABSTRACT FROM AUTHOR]

California is the world's biggest producer and exporter of almonds. Currently, the sweeping of almonds during the harvest creates a significant amount of dust, causing air pollution in the neighboring urban areas. A low-dust sweeping system was designed to reduce the dust during the sweeping of almonds in the orchard. The system includes a feedback control system to control the sweeper brushes' height and their angular velocity by adjusting the forward velocity of the harvester and the brushes' rotational speeds to avoid any extra overlapping sweeping, which increases dust generation. The governing kinematic equations for sweepers' angular velocity and vehicle forward speed were derived. The feedback controllers for synchronizing these speeds were designed to optimize brush/dust contact to minimize dust generation. The sweepers' height controller was also designed to stabilize the gap between the brushes and the orchard floor and track the road trajectory. Controllers were simulated and tuned for a fast response for agricultural applications with less than a second response delay. Results showed that the designed system has acceptable performance and generates low amounts of dust within the acceptable range of California ambient air quality standards. [ABSTRACT FROM AUTHOR]

In this study, visual recognition with a charge-coupled device (CCD) image feedback control system was used to record the movement of a coplanar XXY stage. The position of the stage is fedback through the image positioning method, and the positioning compensation of the stage is performed by the image compensation control parameter. The image resolution was constrained and resulted in an average positioning error of the optimized control parameter of 6.712 µm, with the root mean square error being 2.802 µm, and the settling time being approximately 7 s. The merit of a long short-term memory (LSTM) deep learning model is that it can identify long-term dependencies and sequential state data to determine the next control signal. As for improving the positioning performance, LSTM was used to develop a training model for stage motion with an additional dial indicator with an accuracy of 1 μm being used to record the XXY position information. After removing the assisting dial indicator, a new LSTM-based XXY feedback control system was subsequently constructed to reduce the positioning error. In other words, the morphing control signals are dependent not only on time, but also on the iterations of the LSTM learning process. Point-to-point commanded forward, backward and repeated back-and-forth repetitive motions were conducted. Experimental results revealed that the average positioning error achieved after using the LSTM model was 2.085 µm, with the root mean square error being 2.681 µm, and a settling time of 2.02 s. With the assistance of LSTM, the stage exhibited a higher control accuracy and less settling time than did the CCD imaging system according to three positioning indices. [ABSTRACT FROM AUTHOR]

In this paper, a systematic method to suppress transonic buzz with feedback is presented. A trailing edge control surface in the form of part-span flap was used only to modify and control the unsteady aerodynamic loading on the wing. The flap rotation was used to provide feedback, which consisted of a weighted linear combination of the amplitudes of the principal modes of the structure, referred to as the control law. A linear, optimal feedback control law, that is synthesized systematically based on pseudo-spectral time domain analysis, may be used in principle, to assess its capacity to actively suppress the buzz in the transonic flow domain by using a servo-controlled control surface to modify the unsteady, nonlinear aerodynamic loads on the wing. Thus, it is essential that a set of feasible control laws are first constructed. In this paper, this is done by applying the doublet-lattice method. Restrictions, such as near-zero structural damping in the flap mode, were imposed on the aeroelastic model to facilitate the occurrence of transonic buzz. The feasible set of control laws were then assessed using the nonlinear transonic small disturbance theory and an optimum control is selected to suppress the buzz. The essential differences of the behaviour of the closed-loop system in nonlinear transonic flow, when compared to the applications of linear optimal control in linear potential flow, are presented and discussed. [ABSTRACT FROM AUTHOR]

The uncertainty and disturbance estimator (UDE) with a time delay filter has been widely used for inverter systems due to its satisfactory harmonic rejection performance. However, the control performance may be affected when the grid frequency fluctuates. In this article, a modified UDE (FUDE) is proposed to improve the grid frequency fluctuation adaptability of the $LCL$ grid-tied inverter systems, which contains a compound filter consisting of time delay, zero-phase low-pass, and high-pass filters. Compared with the traditional time delay UDE, it can offer a wider notch bandwidth at the selected frequencies. A dual-loop controller is built in the separate-structure-type UDE-based controller, containing an outer loop PR controller and an inner loop FUDE. The sufficient conditions for the system stability are obtained by the small-gain theorem. The comparison experiments of the dual-loop controller with the proposed FUDE and the conventional time delay zero-phase low-pass UDE are performed on a 2-kW experimental platform, and the results demonstrate the effectiveness of the proposed FUDE. [ABSTRACT FROM AUTHOR]

This paper concerns a stochastic optimal control problem with feedback Markov inputs. The problem is reduced to a deterministic optimal control problem for a Kolmogorov equation where the control for the deterministic problem is of open-loop type. The existence of an optimal control is proved for the deterministic control problem in a particular case. A maximum principle and some first order necessary optimality conditions are derived. Some examples and comments are discussed. [ABSTRACT FROM AUTHOR]

With the increase in the number of offshore power generation facilities and aquaculture ponds, demand for remotely operated vehicles (ROVs) to inspect underwater structures and conduct ecological surveys is increasing. Because ROVs are connected to a ground station on the water by a tether cable to enable the transmission of operating commands and images underwater, where radio communication is difficult, they can only operate within the range of the tether cable. To expand the operational range of ROVs, an autonomous surface vehicle (ASV)-ROV cooperative system, in which a tether cable is connected to an ASV and radio waves are used for remote operation from the autonomous vessel, is attracting attention. In a cooperative system, the tether cable must be managed on the ASV side, and the position and cable length of the ASV must be controlled to prevent the cable from pulling against or tangling with the ROV, which moves around underwater under the command of a human controller. We propose a method of controlling the position and cable length of the ASV using the information on the position of the ROV obtained from an underwater positioning device for an ASV-ROV cooperative system that we are also developing. In addition, we confirmed through simulations that the ASV and cable length follow target values even when the ROV moves along a complicated path. [ABSTRACT FROM AUTHOR]

A cable-driven parallel robot (CDPR) is a mechanism that controls the position and attitude of an object using multiple cables. We propose an underwater cable-driven parallel robot (UCDPR), which is a CDPR composed of multiple surface robots. A UCDPR is a type of mobile cable- driven parallel robot (MCDPR) that is composed of multiple mobile robots and is an underwater application of MCDPR, which has been used only on land and in the air. We describe the details of the operational scenario of the UCDPR, from landing on the water to executing a task. We also simulated numerically the stabilization phase required after landing on water and the trajectory tracking control phase required for underwater exploration and other tasks. In this numerical simulation, we used a high-gain feedback controller as the trajectory tracking controller to add robustness to the control system. As a result, a trajectory tracking control was realized within a tolerance tracking error range of 10-2 m underwater in the presence of a maximum current velocity of 0.8 m/s (= 1.5 knots), which is a control requirement. [ABSTRACT FROM AUTHOR]

Shell models of turbulence are representation of turbulence equations in Fourier domain. Various shell models are studied for their mathematical relevance and the numerical simulations that exhibit at most resemblance with turbulent flows. One of the mathematically well‐studied shell model of turbulence is called sabra shell model. This work concerns with two important issues related to shell model, namely, feedback stabilization and robust stabilization. We first address stabilization problem related to sabra shell model of turbulence and prove that the system can be stabilized via finite dimensional controller. Thus, only finitely many modes of the shell model would suffice to stabilize the system. Later, we study robust stabilization in the presence of the unknown disturbance and corresponding control problem by solving an infinite time horizon max‐min control problem. We first prove the H∞$$ {H}^{\infty } $$ stabilization of the associated linearized system and characterize the optimal control in terms of a feedback operator by solving an algebraic Riccati equation. Using the same Riccati operator, we establish asymptotic stability of the nonlinear system. [ABSTRACT FROM AUTHOR]

The paper focuses on the development of a new mission to explore Phobos using an anchored tether system located below the L1 Mars–Phobos libration point and deployed toward Mars at a length slightly greater than the distance from Phobos. The basic assumptions in terms of a planar circular restricted three-body problem are formulated. The motion equations are derived in polar coordinates relative to the anchor point of the tether system. For a constant-length tether, an energy integral, equilibrium positions, and phase portraits for various anchored point locations on the Phobos surface are found. Analytical formulas for the tether tension force are derived, and the influence of system parameters on this force is investigated for static and dynamic cases. To provide asymptotic Lyapunov stability of the tether in the vicinity of equilibrium positions, the feedback control is proposed. To validate the obtained results, numerical simulation of the space tether system controlled motion taking into account the eccentricity of the Mars–Phobos orbit using the equations in Nechvile's variables is performed. Results of this simulation confirm the results obtained earlier. Conclusions about the feasibility of the implementation of the suggested mission and features of the behavior of the tether system using the proposed feedback control are made. The results of this study can be used to enable many future missions throughout the solar system. [ABSTRACT FROM AUTHOR]