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Summary: This paper deals with the reachable set estimation for the continuous‐time switched nonlinear positive systems with impulse, disturbance, and mixed time‐varying delays under the average dwell time switching. Based on a method developed in positive systems, sufficient conditions are established such that all solutions of the system converge exponentially to a ball. Both the bound of the reachable set and the convergence rate are determined explicitly. Compared with the existing result, the average dwell time given in this paper is less conservative. Finally, numerical examples demonstrate the effectiveness of our results. [ABSTRACT FROM AUTHOR]

This paper proposed a robust deadbeat predictive current control (PCC) of the permanent magnet linear synchronous machine (PMLSM) with an extended state modeling (ESM) based Kalman filter (KF) for both the state and disturbance estimation. First, the disturbance dynamics of the PMLSM electrical subsystem is analyzed in detail and then the ESM is constructed as considering the disturbance as a higher order integrator motivated by the main idea of the extended state observer. Second, the KF for the current prediction with reduced noises and the disturbance estimation due to the parameter variation is designed combining with the ESM. Furtherly, the robust PCC is introduced with the ESM-based KF. Finally, the parameter tuning for the ESM-based KF is discussed with the discrete simulation and then the experimental results are given under the single current closed loop and the double cascade position-current loop with linear-varying parameter. Both the simulation and experimental results verify the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents a technique for developing a sliding mode controller (SMC) using the state model of wheel mobile robot (WMR). The control scheme which consists of a controller and a disturbances observer can eliminate system uncertainties, disturbances, and unknown wheel slips. To successfully implement the sliding mode tracking controller algorithm, first, the transformation is utilized to convert the kinematic and dynamic models to an equation of state, and then create a controller based on Lyapunov function. Subsequently, a disturbance observer is formulated based on a stable sliding surface, followed by the development of an adaptive sliding mode control (ASMC) for the system. Moreover, to verify the efficacy of the given strategy, simulations have been performed under the aforementioned disturbance conditions. Finally, the simulation results show that chattering effect is eliminated, and the impact of disturbances is also diminished, thus proving the viability and correctness of the proposed control algorithm. [ABSTRACT FROM AUTHOR]

In this paper, two robust model‐free adaptive control (RMFAC) methods are proposed for a nonlinear flapping wing micro air vehicle (FWMAV) subject to measurable and unmeasurable wind disturbances. Firstly, a novel disturbance‐related full‐form dynamic linearization technique (DFFDL) is developed to transform the FWMAV with measurable disturbances into a dynamic linearization data model. Then, a DFFDL based RMFAC method is designed based on the obtained data model for the FWMAV to suppress the wind disturbances. Next, the stability analysis shows that the system output tracking error converges into a bounded range. And the above result is extended to the case of unmeasurable disturbances. Finally, the simulation comparison results demonstrate the effectiveness of two proposed RMFAC methods. [ABSTRACT FROM AUTHOR]

Human activities have often altered sediment dynamics in rivers, leading to aquatic habitat degradation. The dominant paradigm in fish–sediment interactions focuses on excessive fine sediments as indicators of habitat and water quality degradation. In contrast, geomorphologists have provided frameworks linking altered sediment dynamics to much broader and more complex changes to channel morphology and stream habitats across spatial scales.In this paper we use an interdisciplinary approach with historical and contemporary channel morphology and fish community datasets to examine how altered sediment dynamics have affected stream fish community evolution in the Bayou Pierre, Mississippi, U.S.A.Erosional process regimes have advanced upstream consistent with models of knickpoint propagation and channel evolution, leaving most of the catchment in a state of increased sediment transport and local sediment deficits. Fish communities in modern samples have less α and β diversity and fewer habitat specialist taxa than in historical samples.Whole‐community analysis via non‐metric multidimensional scaling found a strong gradient of homogenisation towards a fauna comprised of small‐bodied taxa adapted to large rivers.Comparisons of community and geomorphic change on this gradient found that reaches that transitioned between process regimes had more community change, and that local habitat factors relating to advanced channel evolution were strongly positively related to total community change.These results demonstrate that a catchment‐scale geomorphic analysis provided a strong tool for understanding fish community change on a decadal scale. Our findings further demonstrate concordant ecological responses to a complex sequence of disturbances and suggest that a broader view of sediment dynamics offers a rich toolkit for ecological analyses. [ABSTRACT FROM AUTHOR]

When a quantum system is sent through a noisy channel, it is usually disturbed. At the same time, the system undergoes decoherence and tends to lose some delicate quantum features. For a particular basis, the coherence of the state changes. Otherwise, if the system is not disturbed, its state might retain all of coherence. As quantum noisy channels lead to both disturbance and decoherence, it is natural to ask about the relation between disturbance and decoherence. Recently, a trade-off relation for coherence and disturbance has been presented by Sharma and Pati (2018 Phys. Rev. A 97 062308). In this paper, with entangled photon pairs and linear optics, we experimentally verify this trade-off relation for a single-qubit system undergoing various noisy channels. Our experimental results agree with the theoretical predictions and provide a quantitative understanding of the relation between quantum channels and resources. [ABSTRACT FROM AUTHOR]

After the separation of the Continental Europe power system on 8th January 2021 in two synchronous zones, the electric power system of BiH (EPS BiH) shows a significant increase in frequency and voltages and oscillations of active and reactive power. The paper discusses the operation of protective devices in the BiH power system when the system was operating at high frequencies and voltages and had oscillations of active and reactive power. As a consequence of this behaviour in the EPS BiH there was activation of distance protections (DP) in substation (SS) 220/110 kV Prijedor 2 and overhead transmission lines (OHL) 220 kV Prijedor 2 - Međurić and OHL 220 kV Prijedor 2 - Sisak were disconnected. This was followed by activation of generator protections (reverse power protection and under-excitation protection) and outages of generator units in Hydro Power Plant (HPP) Salakovac, Thermal Power Plant (TPP) Kakanj, HPP Mostar, HPP Bočac, HPP Peć Mlini and HPP Jajce 2. [ABSTRACT FROM AUTHOR]

Disturbances can alter the structure and function of ecosystems. In stream ecosystems, changes in discharge and physicochemistry at short, intermediate, and long recurrence intervals can affect food webs and ecosystem processes. In this paper, we compare pH regimes in streams at La Selva Biological Station, Costa Rica, where episodic acidification frequency across the stream network varies widely due to buffering from inputs of bicarbonate‐rich interbasin groundwater. To examine the effects of acidification on ecosystem structure and function, we experimentally increased the buffering capacity of a headwater stream reach and compared it to an unbuffered upstream reach. We compared these reaches to a naturally buffered and unbuffered reaches of a second headwater stream. We quantified ecosystem structural (macroinvertebrate assemblages on leaf litter and coarse woody debris) and functional responses (leaf litter and coarse woody debris decomposition rates, and growth rates of a focal insect taxon [Diptera: Chironomidae]). Non‐metric multidimensional scaling and analysis of similarity revealed that macroinvertebrate assemblages were relatively homogenous across the four study reaches, although the naturally buffered reach was the most dissimilar. Ecosystem function, as measured by chironomid growth rates, was greater in the naturally buffered reach, while decomposition rates did not differ across the four reaches. Our results indicate that biological assemblages are adapted to pH regimes of frequently acidified stream reaches. Our experiment informs the effects on structure and function at short time scales in streams that experience moderate acidification, but larger magnitude acidification events in response to hydroclimatic change, as projected under climate change scenarios, may induce stronger responses in streams. [ABSTRACT FROM AUTHOR]

This paper presents a stochastic stable control protocol for heterogeneous vehicle platoon subject to communication topologies change, external disturbance, and information delay. First, a random vehicle platoon system composed entirely of several pure electric vehicles is built. The random variation of data transmission link among the platoon in a natural traffic environment is considered and molded by the Markov chain combined with the directed graph method. The influence of delays and discrete data in wireless communication, road slope, and air resistance on the vehicle platoon is also considered by introducing the external interferences and equivalent information delays. Additionally, to ensure the vehicle platoon’s inner-vehicle stability, the variable-gain distributed controller is proposed based on the Markovian jumping system stability theory and $ H_\infty$ control. Finally, the $ \mathcal {L}_{2}$ stochastic string stability is defined to attenuate perturbations as they propagate through the platoon. Simulation studies about a vehicle platoon under four communication topologies random switching with two different control methods are provided to verify the theoretical result. It is shown that, compared to traditional platoon robust control, it is possible to achieve the vehicle platoon’s stability even if in the continuous mutation of unstable topologies by using the proposed control approach. [ABSTRACT FROM AUTHOR]

The main stream of the Tarim River in China is typical of ecologically sensitive areas that have been heavily disturbed by human activities; as such, the monitoring of the quality of its eco-environment constitutes an important task for researchers. By using GlobeLand30 data and applying the disturbance degree model and revised ecosystem service value (ESV) model, the study presented in this paper undertook a quantitative estimation of the effects of the disturbance impacts of human activities on the eco-environment of this area in the period of 2000 to 2020. The main conclusions are as follows: (1) disturbance index values, which reflect disturbance to the local ecosystem by human activities, increased over the study period. Further, cultivated land experienced the largest increase, which, in turn, brought about the most significant disturbance to the eco-environment. High disturbance index values presented a patchy distribution in the west of the main stream of the Tarim River and formed bands and dots in the east; the area of land characterized by high and moderate disturbance index values increased, with growth areas taking on a scattered distribution of patches, bands, and dots without significant spatial continuity. (2) The total ESV increased, indicating the quality of the eco-environment improved. The increase of cultivated land offset the increase in ESV, which counteracted the effects of ecological governance measures. Areas with high ESV values were mainly located in the western and central parts of the study area, while low values were found in the middle east and east. Areas with higher increases in ESV were mainly located in the western and the western part of the middle reaches and took on a zonal distribution, while areas of decrease followed a scattered distribution, presenting as dots or patches. Using the quantitative analysis methods and high-resolution remote sensing data to evaluate the changes in the eco-environment was considered as the innovation of this study, and the findings are useful in exploring the influence of human activities on ecosystems and evaluating the eco-environment in the minor watershed of an arid area. This piece of quantitative research contributes to the task of monitoring eco-environmental changes using remote sensing techniques in ecologically sensitive areas. [ABSTRACT FROM AUTHOR]

Purpose: No-till (NT) and fertilization are common land management practices in agricultural production systems to increase soil quality and crop yield. No-till can be reversed to tillage (termed tillage reversal, TR, in this paper) due to changes in management objectives. Materials and methods: The impact of NT, TR, and TR plus nitrogen (N) fertilization (TRN) treatments on the composition and structure of bacterial communities in a Gray Luvisol was studied in west-central Alberta, Canada. Results and discussion: The structure of bacterial communities was not affected by the TR treatment (compared with NT). The TRN treatment increased the relative abundance of some bacterial taxa groups, e.g., Gemmatimonadetes, Thermoleophilia and Solibacteres, that have chemolithotrophic nitrifying functions as compared with the TR treatment. The decreased relative abundance of some bacterial taxa groups, such as Alphaproteobacteria, Deltaproteobacteria, Spartobacteria, and Planctomycetia that have denitrifying functions, would change the soil's denitrification function in the TRN as compared to the TR treatment. There were more dominant bacterial taxa groups, and the bacterial community had greater inter-annual variations in the TRN than in the NT and TR treatments. Moreover, the function of bacterial communities was affected by the TRN as compared to the NT and TR treatments, based on the predicted metagenomes. Conclusions: We conclude that when TR was applied to the soil with long-term N fertilization, which eliminates N limitation, altered soil bacterial community structure and function over TR applied to the studied Gray Luvisol without long-term N fertilization. Findings from our study have important implications for improving land management practices through tillage and N fertilization to enhance the soil's function and quality in agroecosystems. [ABSTRACT FROM AUTHOR]

The Contextuality-by-Default approach to determining and measuring the (non)contextuality of a system of random variables requires that every random variable in the system be represented by an equivalent set of dichotomous random variables. In this paper we present general principles that justify the use of dichotomizations and determine their choice. The main idea in choosing dichotomizations is that if the set of possible values of a random variable is endowed with a pre-topology (V-space), then the allowable dichotomizations split the space of possible values into two linked subsets (“linkedness” being a weak form of pre-topological connectedness). We primarily focus on two types of random variables most often encountered in practice: categorical and real-valued ones (including continuous random variables, greatly underrepresented in the contextuality literature). A categorical variable (one with a finite number of unordered values) is represented by all of its possible dichotomizations. If the values of a random variable are real numbers, then they are dichotomized by intervals above and below a variable cut point. [ABSTRACT FROM AUTHOR]

This paper presents an optimal tracking control of engine valve timing for an electro-hydraulic variable valve actuator utilizing the adaptively estimated supply pressure that is the main source for valve timing variation. The system supply pressure is online estimated through a model-guided adaptive estimator with one-step prediction capability. The estimation model consists of a static guidance model, an in-event valve model, and a one-step prediction model. Using the estimation model, the adaptive estimator generates a nominal estimation with accelerated convergence, estimates the pressure residual error using in-event dynamics, and provides one-step forward pressure prediction along with the resulting pressure fluctuation. The linear quadratic tracking (LQT) control is used to track the desired valve timing based on an event-by-event valve model, where the adaptively estimated pressure variation is used as the feedforward control in the LQT control to improve the tracking accuracy and a Kalman filter is used to estimate the system states for the LQT state feedback control. The parameter estimation and control algorithms are validated through both the simulation and test bench studies by comparing different estimation and control schemes. Both the steady-state and transient operational conditions are investigated, and the effectiveness of the proposed adaptive LQT valve timing control is demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, design and development of fault-tolerant control (FTC) is investigated for linear systems subject to loss of effectiveness and time-varying additive actuator faults as well as an external disturbance using the fault-hiding approach. The main aim of this approach is to keep the nominal controller and to design a virtual actuator that is inserted between the faulty plant and the nominal controller in order to hide actuator faults and disturbances from the nominal controller, and consequently the performance of the system before and after the occurrence of actuator faults is kept to be the same. The proposed adaptive virtual actuator does not require a separated fault detection, isolation and identification (FDII) unit and both state and output feedback cases are considered. An illustrative example is given to demonstrate the effectiveness of the proposed adaptive virtual actuator in both cases. [ABSTRACT FROM AUTHOR]

The state-energy-constrained controller design for uncertain semi-state systems and its application in mechanical system control is studied in this paper. The objective is to get a sampled-data-based controller, with which the system is state-energy-constrained in a finite-time interval and has a given anti-disturbance performance. First, by adopting the matrix convex sets and data sampling, a sampled-data-based model for uncertain semi-state systems is obtained. Second, by considering those state-energy-constraints in real systems, the finite-time stability theory is utilized in the system analysis, and some sufficient conditions are achieved for uncertain semi-state systems with sampled data to be stabilizable. If these conditions are solvable, the sampled-data-based state-feedback controller can be gotten, such that the controlled system has an H-infinite performance, and the state energy is constrained in a finite-time interval. Finally, the obtained theorem is used to control some mechanical systems, and the results show that the controller obtained by the theorem in this paper can effectively attenuate the vibration of those mechanical systems and constrains their state-energies in a finite-time interval. [ABSTRACT FROM AUTHOR]

This paper describes a design scheme for terminal sliding mode controllers of certain types of non-linear dynamical systems. Two classes of such systems are considered: the dynamic behavior of the first class of systems is described by non-linear second-order matrix differential equations, and the other class is described by non-linear first-order matrix differential equations. These two classes of non-linear systems are not completely disjointed, and are, therefore, investigated together; however, they are certainly not equivalent. In both cases, the systems experience unknown disturbances which are considered bounded. Sliding surfaces are defined by equations combining the state of the system and the expected trajectory. The control laws are drawn to force the system trajectory from an initial condition to the defined sliding surface in finite time. After reaching the sliding surface, the system trajectory remains on it. The effectiveness of the approaches proposed is verified by a few computer simulation examples. [ABSTRACT FROM AUTHOR]

The paper develops finite-time consensus control for multi-agent systems by considering disturbances and input saturation. A new adaptive-terminal sliding mode control is suggested to solve consensus control within a finite time. Two cases are solved in the paper. In the first case, it is assumed that disturbances are with known upper. To achieve the consensus purpose within the finite time, in this case, the control inputs are designed based on terminal sliding mode technique by considering the input signal saturation. Also, the control inputs are modified to reduce the high dependency of reaching times to initial speeds. In the second case, the agents are subjected to disturbances with unknown upper bounds. To handle the problem, the control signals are acquired by combining the adaptive and terminal sliding mode methods. By considering saturation boundary and disturbances with unknown upper band, a new adaptive-terminal sliding mode method is designed to control the multi-agent system in reduced settling and reaching times. The proposed techniques efficiency is confirmed by numerical simulations. [ABSTRACT FROM AUTHOR]

It is well known the descriptor systems have a wide application field. Usually it appear as a mathematical model of a real problem, mainly the model that involves the input output relationship. It is well known that a descriptor linear system has an unique solution if the pencil matrix of the system is regular. However, there are some systems that are not regular. Moreover, even though the system is regular the solution can contain the noncausal behavior. Therefore, it is necessary to normalize the descriptor system so as it has well behavior. In this paper, we propose a feedback to normalize a discrete descriptor system under disturbance. Furthermore, we establish a sufficient condition in order for the discrete descriptor system under disturbance can be normalized positively. [ABSTRACT FROM AUTHOR]

This paper explores the similarity between the practice of art and the practice of the psychotherapist. Both demand a commitment to risk and a high tolerance of excitement. The artist goes into his studio and isn't sure what will happen. In the same way the therapist enters the consulting room and something completely unexpected happens. Both artists and therapists have been very highly trained but this training has to be put to one side, at least at the conscious level, for that training to be effective. This paper challenges the idea that artists are daydreamers, a charge which psychoanalysts have frequently leveled at them. The paper makes use of the early stages of psychosexual development, and in particular explores the role of orality and anality in the creative process. It is only by turning attention to the process that we can understand the result. [ABSTRACT FROM AUTHOR]

Overhead cranes are common industrial structures that are used in many factories and harbors. They are usually operated manually or by some conventional control methods, such as the optimal and PLC-based methods. The theme of this paper is to provide an effective all-purpose adaptive fuzzy controller for the crane. This proposed method does not need the complex dynamic model of the crane system, but it uses trolley position and swing angle information instead to design the fuzzy controller. An adaptive algorithm is provided to tune the free parameters in the crane control system. The ways to speed the transportation and reduce the computational efforts are also given. Therefore, the designing procedure of the proposed controller will be very easy. External disturbance, such as the wind and the hit, which always deteriorates the control performance, is also discussed in this paper to verify the robustness of the proposed adaptive fuzzy algorithm. At last, several experimental results with different wire length and payload weight compare the feasibility and effectiveness of the proposed scheme with conventional methods [ABSTRACT FROM PUBLISHER]

This paper presents a novel nonlinear control strategy based on a backstepping fuzzy adaptive approach to avoid chaos in a synchronous motor. In the controller design and stability proof, the parameter uncertainty and the system disturbance are taken into account. The matching condition is not satisfied in this model, and disturbances with an unknown upper bound are also exerted on the system. The disturbance and uncertainty are considered in one manifold with an unspecified upper bound. The system stability is verified using the Lyapunov method. The cuckoo optimization algorithm is employed to optimize the adaptive and backstepping control coefficients. [ABSTRACT FROM AUTHOR]

In this paper, a novel control approach is designed for surge instability in the compressor system using the finite-time adaptive sliding mode scheme. The primary novelty of this study lies in the development of a finite-time adaptive control for the surge instability avoidance in a compressor system in the presence of disturbance and uncertainty in the characteristic curve of the compressor and also throttle valve. The Lyapunov method is utilized to verify the finite-time stability of the closed-loop system. The performance of the presented method is compared against other methods in the literature through simulations in Matlab. The results suggest that our designed controller outperforms the existing ones in terms of surge avoidance and robustness against uncertainties and disturbances. [ABSTRACT FROM AUTHOR]

In this paper, we are concerned with the output feedback stabilisation for a cascade ODE-Heat system subject to boundary control matched disturbance. First, we design a avariable structure unknown input type observer by using the output of the system. Then, we transform the system into an equivalent target system by volterra integral transformation. By ADRC approach, we design a disturbance estimator to estimate the disturbance. The output feedback control is designed based on the observer and disturbance estimator. Finally, the existence of solution to the closed-loop system is proved and the stability is concluded. [ABSTRACT FROM AUTHOR]

This paper presents a modified approach based on symmetrical components in time domain for the detection and classification of various power-quality (PQ) disturbances. Single-phase PQ disturbance signal along with the two other ideal phases generated using phase-locked loop (PLL) is processed to find out the symmetrical components of all phases in time domain. Triggering points for PQ disturbances have been detected from the negative-sequence component of disturbance phase and have been easily classified from the signatures of the waveforms using the summation of the positive- and negative-sequence components. PQ disturbances, such as voltage sag, swell, interruption, harmonics, flicker, transients, notches, and spike present in a distribution system, have been investigated and are easily localized and segmented with this technique. Being a time-domain technique, it can be adopted for the online monitoring and assessment of the PQ disturbances. Simulated and real-time results are presented for a number of PQ disturbances to show the effectiveness of the proposed method for the PQ disturbances’ detection and classification. [ABSTRACT FROM PUBLISHER]

This paper clarifies the reason for the specific array structure and operation methods of a select gate lateral coupling (SGLC) cell array as well as its disturbance immunity. An SGLC cell is a type of single-poly embedded nonvolatile memory that does not require any additional masks and process steps for fabrication. It shows excellent features, such as high programming speed, small cell size comparable to that of SRAM, multitime programmable, and over-erase free characteristic. However, the reasons of its operation methods and cycling limitation have not yet been clarified. We investigated the cycling effect of two types of array structures based on the unit-cell operation method. In particular, in the forward read mode, because of drain-induced barrier lowering (DIBL) that is enhanced by trapped holes at the liner nitride, VT of a programmed cell significantly decreased with a relatively small number of program/erase (P/E) cycles, resulting in a narrower VT window. By adopting the reverse read mode with source-side programming, DIBL enhancement was suppressed and a stable VT window was maintained during P/E cycling. Furthermore, by measuring each disturb method that works with the SGLC cell array structure and the reverse read operation mode, we confirmed that an array size larger than 128-kB sectors is possible. [ABSTRACT FROM AUTHOR]

This paper presents the distributed cooperative tracking control of the multi-agent port-controlled Hamiltonian (PCH) systems that are networked through a directed graph. Controller is made robust against the parametric uncertainties using neural networks. Dynamics of the the proposed novel neural network tuning law is driven by both the position and the velocity errors owing to the information preserving filtering of the Hamiltonian gradient. In addition, the PCH structure of the closed-loop system is preserved and the controller achieves the disturbance attenuation objective. Simulations are performed on a group of robotic manipulators to demonstrate the efficacy of the proposed controller. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Many secondary deciduous forests of eastern North America are approaching a transition in which mature early‐successional trees are declining, resulting in an uncertain future for this century‐long carbon (C) sink. We initiated the Forest Accelerated Succession Experiment (FASET) at the University of Michigan Biological Station to examine the patterns and mechanisms underlying forest C cycling following the stem girdling‐induced mortality of >6,700 early‐successional Populus spp. (aspen) and Betula papyrifera (paper birch). Meteorological flux tower‐based C cycling observations from the 33‐ha treatment forest have been paired with those from a nearby unmanipulated forest since 2008. Following over a decade of observations, we revisit our core hypothesis: that net ecosystem production (NEP) would increase following the transition to mid‐late‐successional species dominance due to increased canopy structural complexity. Supporting our hypothesis, NEP was stable, briefly declined, and then increased relative to the control in the decade following disturbance; however, increasing NEP was not associated with rising structural complexity but rather with a rapid 1‐yr recovery of total leaf area index as mid‐late‐successional Acer, Quercus, and Pinus assumed canopy dominance. The transition to mid‐late‐successional species dominance improved carbon‐use efficiency (CUE = NEP/gross primary production) as ecosystem respiration declined. Similar soil respiration rates in control and treatment forests, along with species differences in leaf physiology and the rising relative growth rates of mid‐late‐successional species in the treatment forest, suggest changes in aboveground plant respiration and growth were primarily responsible for increases in NEP. We conclude that deciduous forests transitioning from early to middle succession are capable of sustained or increased NEP, even when experiencing extensive tree mortality. This adds to mounting evidence that aging deciduous forests in the region will function as C sinks for decades to come. [ABSTRACT FROM AUTHOR]

In this paper, a new control method based on the linear matrix inequality is used to control the speed of a hybrid stepper motor. The proposed method is proved based on the Lyapunov criterion. The proposed method has a higher degree of freedom than conventional robust controllers, which can be used to better control the system. The proposed method also exhibits high robustness against the uncertainty of the hybrid stepper motor parameters as well as the applied disturbances. Also in this method, the effect of rapid changes in the reference speed of the hybrid stepper motor are considered so that the controller can have more effective tracking. The proposed control method is compared with the Self-tuning PI controller and PI (Ziegler-Nichols) controller in multiple scenarios considering the uncertainty of the parameters and different disturbances. The obtained results indicate that the proposed controller has a better performance against the disturbances and uncertainty of the parameters in comparison with the abovementioned controllers. It should be noted that the simulations have been performed in Matlab. [ABSTRACT FROM AUTHOR]

In this paper, the development of passivity‐based control (PBC) algorithms to stabilize an unmanned powered parachute aerial vehicle is presented. The equations of motion of the system are presented in both Lagrangian and Hamiltonian formalisms. The proposed controllers are based on the Hamiltonian function of the system and guarantee the parachute aircraft system stabilization. In the first control law a classic PBC strategy is proposed, and in the second, an interconnection and damping assignment‐passivity‐based control (IDA‐PBC) is chosen because of its inherent robustness against parametric uncertainty and unmodeled dynamics. The control objective is to reach a desired final position despite the initial launch conditions. Numerical simulations with variation in the parachute mass weight and in the presence of wind are carried out to validate our proposed schemes. [ABSTRACT FROM AUTHOR]

Demanding marine operations increase the complexity of manoeuvring. A highly accurate ship model promotes predicting ship motions and advancing control safety. It is crucial to identify the unknown hydrodynamic coefficients under environmental disturbance to establish accurate mathematical models. In this paper, the identification procedure for a 3 degree of freedom hydrodynamic model under disturbance is completed based on the support vector machine with multiple manoeuvres datasets. The algorithm is validated on the clean ship model and the results present good fitness with the reference. Experiments in different sea states are conducted to investigate the effects of the turbulence on the identification performance. Generalisation results show that the models identified in the gentle and moderate environments have less than 10% deviations and are considered allowable. The higher perturbations, the lower fidelity the identified model has. Models identified under disturbance could provide different levels of reliable support for the operation decision system. [ABSTRACT FROM AUTHOR]

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In this paper, a proxy-based sliding-mode control (PBSMC) approach is proposed for robust tracking control of a piezoelectric-actuated nanopositioning stage composed of piezoelectric stack actuators and compliant flexure mechanisms. The essential feature of the PBSMC approach is the introduction of a virtual coupling proxy, which is controlled by the sliding-mode controller (SMC) to track the desired position. Simultaneously, due to the virtual coupling, a proportional-integral-derivative (PID) controller on the other side of the proxy ensures the position of the end-effector of the stage to follow the position of the proxy. Therefore, the PBSMC guarantees the end-effector to track the desired trajectory. The advantages of the developed PBSMC lie in the facts that 1) the discontinuous signum function in the traditional SMC is omitted without any approximation. Hence, the output of the PBSMC is continuous, which does not suffer from the chattering phenomenon; and 2) the PBSMC laws are developed without having the necessity to include the nominal system model, hysteresis model or the state observer. Hence, the PBSMC provides a novel effective yet simple control method, which permits to avoid the lack of performances from PID and the chattering from SMC, and permits to combine the advantages from them. The stability of the closed-loop control system is proved through Lyapunov analysis. Finally, comparative studies are performed on a custom-built piezo-actuated stage. Experimental results show that the tracking errors of the PBCM are reduced by 74.22%, as compared to the traditional PID controller, with the desired sinusoidal trajectory under the 50-Hz input frequency, which clearly demonstrates the superior tracking performance of the PBSMC. [ABSTRACT FROM PUBLISHER]

Disturbance is inevitable in product collaborative design (PCDSP), which has always posed a great challenge for enterprises making quick response. Thus, in the paper, a multi-objective rescheduling model and its solution algorithm are presented. Disturbance cases are analysed and dynamic scheduling procedure based on event-driven and lifecycle-driven is developed firstly. Then a multiobjective rescheduling model aiming to minimum the makespan and tardiness penalty is developed. As a solution, multi-objective dynamic adaptive scheduling algorithm (MODASA), based on bi-layer coding strategy, self-adaptive double point crossover and self-adaptive mutation, is proposed following closely. Finally, analytic results from a case of a wind turbine are used to illustrate the model and method proposed in this paper. Simulation results shows that the model and algorithm have full advantages in computing speed and precision. With the analysis, it can provide insight into ways of improving the strategic and operational decision making for enterprises. [ABSTRACT FROM AUTHOR]

This paper studies a distributed optimal tracking control method for nonholonomic mobile mechanical multi-agent systems under complex conditions such as input constraints, the presence of both kinematic and dynamic disturbances, and uncertain interconnections. Initially, novel feed-forward control inputs are proposed to transform the inherently separate systems of kinematics and dynamics into an equivalent integrated system. Successively, an online distributed L2-bounded optimal control algorithm is designed by utilizing adaptive dynamic programming and the theory of cooperative differential graphical games. In the algorithm, a single neural network instead of three for each agent is chosen, and the online weight-tuning laws for which are designed without identifying uncertain parameters directly or indirectly. Additionally, the optimal control and worst disturbance policies are synchronously updated in only one iterative loop. It is shown that during the convergence of the value functions to the approximate optimal values when the agents perform the algorithm, overall tracking and function approximation errors are uniformly ultimately bounded. Finally, as a successful application of the study, control of the wheeled mobile multi-robot system is discussed through simulations. [ABSTRACT FROM AUTHOR]

The disturbance at error sensors will degrade the performance of active noise control (ANC) systems, resulting in slow convergence and decreased noise reduction problems. This paper analyzes the disturbance effects on narrowband ANC (NANC) systems and proposes modified algorithm to enhance both the transient and steady-state performance. A delayless bandpass filterbank is designed to eliminate out-of-band disturbance in the generated individual error signals for updating the corresponding adaptive filters. The theoretical analysis and improved performance are verified by computer simulations using measured transfer functions from the experimental setup. [ABSTRACT FROM AUTHOR]

This paper studies the robust control problem for time-delay systems with complicated inherent nonlinearities and unknown disturbances. Based on the modified homogeneous domination method and by constructing the proper Lyapunov-Krasovskii (L-K) functional, output feedback controllers are successfully constructed to guarantee the boundedness of all the states of the closed-loop system. The convergence of the states is also realizable when the L2 norm of the disturbance exists. The presented method is also extended to solve the control problem of nonholonomic time-delay system. Simulation examples are given to show the effectiveness of the proposed theory. [ABSTRACT FROM AUTHOR]

This paper deals with a novel robust current control scheme for permanent magnet synchronous machine drives that improves the conventional cascade structure. The main idea is to substitute the commonly used decoupling network, which requires the precise knowledge of the system parameters in any working condition, with a more flexible and robust observer scheme. In particular, the traditional configuration is improved by means of two proportional-integral observers that allow the preservation of the desired drive performances even in the presence of disturbances and uncertainties. The increased robustness is achieved by maintaining the reliable basic scheme with a pure proportional controller in the forward path with advantages in terms of design and tuning. A genetic algorithm is used to optimize the controller and observer parameters. This multiobjective optimization leads to good stability and an overall enhanced performance of the drive above the operative range. The choice of the optimal solution is based on a novel fitness function that takes into account both dynamical features and disturbance rejection capabilities of the system. The effectiveness of the proposed control scheme compared with a standard proportional-integral control is verified by means of numerical simulations and experiments as well. [ABSTRACT FROM AUTHOR]