Lower Control Costs Research Articles

Novel Controller Design for Finite-Time Synchronization of Fractional-Order Nonidentical Complex Dynamical Networks under Uncertain Parameters

The synchronization of complex networks, as an important and captivating dynamic phenomenon, has been investigated across diverse domains ranging from social activities to ecosystems and power systems. Furthermore, the synchronization of networks proves instrumental in solving engineering quandaries, such as cryptography and image encryption. And finite-time synchronization (FTS) controls exhibit substantial resistance to interference, accelerating network convergence speed and heightening control efficiency. In this paper, finite-time synchronization (FTS) is investigated for a class of fractional-order nonidentical complex networks under uncertain parameters (FONCNUPs). Firstly, some new FTS criteria for FONCNUPs are proposed based on Lyapunov theory and fractional calculus theory. Then, the new controller is designed based on inequality theory. Compared to the general controller, it controls all nodes and adds additional control to some of them. When compared to other controllers, it has lower control costs and higher efficiency. Finally, a numerical example is presented to validate the effectiveness and rationality of the obtained results.

Amorphous bismuth and GO co-doped WO3 electrochromic film with fast-switching time and long-term stability.

The sol-gel process for fabricating electrochromic thin films is straightforward, offering advantages such as low cost and ease of compositional control. Herein we prepared GO-Bi-WO3 films with improved electrochromic performance using a simple sol-gel spin-coating method. The sample shows a fast-switching time (1.8 s for coloring and 1.8 s for bleaching), large optical modulation (85% at 630 nm), excellent stability (86.4% retention after 10 200 cycles), and high coloration efficiency (65.9 cm2 C-1). This work indicates the electrochromic performance of WO3-based films can be enhanced by incorporating GO, which provides an effective strategy for the rapid, safe, and efficient fabrication of electrochromic thin films.

Event-triggered impulsive observer with [formula omitted]-asymptotic gain for DC microgrids

This paper studies the problem of the state estimate of a class of DC microgrids with both disturbed states and disturbed outputs via event-triggered impulsive observer (ETIO). First, a mathematical model is established for such class of DC microgrids, and then the notion of impulsive observer including impulsive observer with K-asymptotic gain is proposed. Then, by using two Lyapunov-like functions, a scheme of event-triggered impulsive control (ETIC) via three layers of event-triggering conditions is designed for ETIO to track the state of the DC microgrid. And an algorithm is given for the implementation of ETIC in practice. The ETIC scheme is then extended to the sampling-based ETIC (S-ETIC) to reduce the calculation and improve the effectiveness of the ETIC. Both theoretical proofs and numerical simulations are given to show that the proposed ETIO via both ETIC and S-ETIC can track the state of the DC microgrid within K-asymptotic gain. Specifically, when the disturbance tends to zero, the tracking is accurate. Moreover, the simulation is given for comparisons between ETIO and other observers including the classic impulsive observer, Luenberger observer, sliding mode observer, and extended state observer. It is shown that the designed ETIO has advantages of lower impulse frequency, lower control cost, and smaller tracking error than the other observers.

The optimisation of public health emergency governance: a simulation study based on COVID-19 pandemic control policy

BackgroundThe outbreak of the COVID-19 pandemic sparked numerous studies on policy options for managing public health emergencies, especially regarding how to choose the intensity of prevention and control to maintain a balance between economic development and disease prevention.MethodsWe constructed a cost-benefit model of COVID-19 pandemic prevention and control policies based on an epidemic transmission model. On this basis, numerical simulations were performed for different economies to analyse the dynamic evolution of prevention and control policies. These economies include areas with high control costs, as seen in high-income economies, and areas with relatively low control costs, exhibited in upper-middle-income economies.ResultsThe simulation results indicate that, at the outset of the COVID-19 pandemic, both high-and low-cost economies tended to enforce intensive interventions. However, as the virus evolved, particularly in circumstances with relatively rates of reproduction, short incubation periods, short spans of infection and low mortality rates, high-cost economies became inclined to ease restrictions, while low-cost economies took the opposite approach. However, the consideration of additional costs incurred by the non-infected population means that a low-cost economy is likely to lift restrictions as well.ConclusionsThis study concludes that variations in prevention and control policies among nations with varying income levels stem from variances in virus transmission characteristics, economic development, and control costs. This study can help researchers and policymakers better understand the differences in policy choice among various economies as well as the changing trends of dynamic policy choices, thus providing a certain reference value for the policy direction of global public health emergencies.

The Event-Triggered Impulsive Controls for Quasisynchronization of the Leader-Following Heterogeneous Dynamical Networks.

The time-triggered impulsive controls were widely used to study the collective behavior of homogeneous dynamical networks due to their low control cost, which was a bit conservative in the occupation of communication channels. This article addresses designing the event-triggered impulsive controls for the quasisynchronization, namely, a weak cooperative behavior with the synchronization error no more than a positive constant in the leader-following heterogeneous dynamical network, which thus can reduce the occupation of resources significantly. The centralized and distributed impulsive controls are designed to lead the followers to synchronize approximately to the leader within a nonzero bound, where the impulsive instants are triggered, respectively, by the global or local state-dependent conditions. Numerical results are put forward to verify the effectiveness of the proposed methods.

Distributed formation control of networked mobile robots from the Udwadia–Kalaba approach

AbstractIn this article, formation control of networked mobile robots is studied. Two control strategies for the leaderless case and the leader‐following case are developed from the Udwadia–Kalaba approach, respectively. Differing from the existing results about formation control, which focus on kinematic models of robots, this article considers dynamic models and obtained a lower‐cost control force. To improve the robustness of the communication network, two distributed formation controllers are designed by establishing distributed estimators. Different from the centralized controllers, the distributed controllers established here only require local information, thus save communication resources and improve system robustness. Finally, some numerical simulations are provided to demonstrate the proposed methods are effective and have lower control cost.

Dynamic analysis and bifurcation control of a delayed fractional-order eco-epidemiological migratory bird model with fear effect

In this paper, a new delayed fractional-order model including susceptible migratory birds, infected migratory birds and predators is proposed to discuss the spread of diseases among migratory birds. Fear of predators is considered in the model, as fear can reduce the reproduction rate and disease transmission rate among prey. First, some basic mathematical results of the proposed model are discussed. Then, time delay is regarded as a bifurcation parameter, and the delay-induced bifurcation conditions for such an uncontrolled system are established. A novel periodic pulse feedback controller is proposed to suppress the bifurcation phenomenon. It is found that the control scheme can successfully suppress the bifurcation behavior of the system, and the pulse width can be arbitrarily selected on the premise of ensuring the control effect. Compared with the traditional time-delay feedback controller, the control scheme proposed in this paper has more advantages in practical application, which not only embodies the advantages of low control cost and easy operation but also caters to the periodic changes of the environment. The proposed control scheme, in particular, remains effective even after the system has been disrupted by a constant. Numerical simulation verifies the correctness of the theoretical results.

Active Disturbance Rejection-Based Performance Optimization and Control Strategy for Proton-Exchange Membrane Fuel Cell System

In this paper, to maximize the net output power and realize better performance optimization and control of the oxygen excess ratio, a complete dynamic model of the proton-exchange membrane fuel cell system is developed and an active disturbance rejection control strategy is proposed. The active disturbance rejection control drives the uncertainties and perturbations of the system to an extended state, which is predicted and eliminated by real-time input–output data. The simulation results indicate that, compared with the proportion–integral–differential and fuzzy proportion–integral–differential control, the active disturbance rejection control strategy can effectively improve the control performance with a lower control cost and less wear on the compressor, and the integral absolute error of the oxygen excess ratio control is reduced by up to 50%. In addition, the output voltage is improved and the power generation efficiency of the proton-exchange membrane fuel cell under the active disturbance rejection-based oxygen excess ratio control is 1.84% and 0.95% higher than that of the proportion–integral–differential and fuzzy proportion–integral–differential control, respectively. Moreover, the proposed optimal-reference control strategy increases the net power by up to 1.85% compared with the fixed-reference control strategy.

A novel CO2-resistant dispersed particle gel for gas channeling control in low-permeability reservoirs

A novel CO2-resistant dispersed particle gel (CR-DPG) for gas channeling control was successfully prepared by shearing an organic–inorganic composite bulk gel. The basic properties, CO2-resistance characteristics, gas channeling control capacity and enhanced oil recovery potential were systemically investigated. The prepared CR-DPG particles were regular spheres, which could maintain a uniform dispersion during the injection process. The CO2 resistance test was carried out at 90 ℃ and CO2 pressure of 20 MPa. After the CO2 resistance test, the dispersion stability of CR-DPG decreased, and the particles coalesced to form large aggregates instead of degrading, exhibiting excellent CO2 resistance. Furthermore, the mechanical strength of the CR-DPG particles aged for different time was measured using atomic force microscope (AFM). Due to the silica gel particles, the CR-DPG particles retained high mechanical strength in the long-term experiment, which could maintain a high plugging effect for a long time during CO2 flooding. A fractured core flowing model was employed to investigate gas channeling control capacity and EOR potential of CR-DPG. The CR-DPG particles could migrate to fractures in-depth, in which particles coalesced to form large aggregates and adsorbed to mitigate gas channeling. In addition, CR-DPG had great potential for enhanced oil recovery by 10.4 %. This work provides an alternative material with a simple preparation process and low cost for gas channeling control in oilfields with CO2 flooding.

A Novel Interleaved Parallel Cascaded Three-Level PFC With Low Inductance Volt-Second and Low Common-Mode Noise

Interleaved parallel cascaded multilevel technology is an attractive approach for converters to achieve high efficiency, high-power density, and high modularity. In this letter, a novel single-phase interleaved parallel cascaded three-level (IPC-TL) power factor correction (PFC) converter is proposed. It is formed by cascading two interleaved parallel totem-pole PFC cells. The proposed topology exhibits the merits of lower inductance volt-second and inductor current ripples, lower common-mode noise, and lower control cost, compared with the traditional IPC-TL topology. A laboratory-scale experimental prototype is developed to verify the effectiveness of the proposed topology.

Phase Synchronization for Helix Enhanced Wake Mixing in Downstream Wind Turbines

Wind farm controllers such as the Helix approach have shown potential in increasing plant power production through wake mixing. The concept suggests that actuating the upstream turbines’ blade pitching with a specific periodic signal can induce a helix-shaped wake, thereby alleviating wind velocity deficit on downstream turbines. Wake mixing initiation by downstream turbines may also be shown advantageous for power production; however, little to no attention has been given to such an approach. Similar wake mixing is expected to be achievable at lower control costs if the downstream turbine can benefit from the periodic component already present in the wake of the upstream turbine. Such a hypothesis is studied in this work by designing a minimal control scheme where the wake acting on the downstream turbine is simulated by a periodic input disturbance. A Kalman filter is proposed for incoming input disturbance phase estimation using SCADA data. The reconstructed phase information allows synchronization of the downstream control action with the periodic input disturbance by means of a phase synchronization wake mixing controller. The periodic component was estimated with a minimal root-mean-square error and the resulting control action was in phase with the input disturbance and demonstrated satisfactory performance even with a small phase perturbation. Future work will include applications in a high-fidelity wind turbine model and wind tunnel studies.

Actuator Selection for Dynamical Networks with Multiplicative Noise

We propose a greedy algorithm for actuator selection considering multiplicative noise in the dynamics and actuator architecture of a discrete-time, linear system network model. We show that the resultant architecture achieves mean-square stability with lower control costs and for smaller actuator sets than the deterministic model, even in the case of modeling uncertainties. Networks with multiplicative noise may fail to be mean-square stabilizable by any small actuator set, leading to a failure of a cost-based greedy algorithm. To account for this, we propose a multi-metric greedy algorithm that allows actuator sets to be evaluated effectively even when none of them stabilize the system. We illustrate our results on networks with multiplicative noise in the open-loop dynamics and the actuator inputs, and we analyze control costs for random graphs of different network sizes and generation parameters.

A Coordination Optimization Method for Load Shedding Considering Distribution Network Reconfiguration

Load shedding control is an emergency control measure to maintain the frequency stability of the power system. Most of the existing load shedding methods use the extensive form of directly cutting off the outlet of the substation, featuring low control accuracy and high control cost. A network reconfiguration technique can adjust the topology of the distribution network and offers more optimization space for load shedding control. Therefore, this paper proposes a reconfiguration–load shedding coordination optimization scheme to reduce the power loss caused by load shedding control. In the proposed method, a load shedding mathematical optimization model based on distribution network reconfiguration is first established. The tie switches and segment switches in the distribution network are used to perform the reconfiguration of the distribution network, and the load switches are adopted to realize the load shedding. To improve the solving efficiency of the model, a solving strategy that combined a minimum spanning tree algorithm with an improved genetic algorithm is trailed to address the nonlinear and nonconvex terms. The application of the proposed method and model are finally verified via the IEEE 33 bus system, and the advantages in reducing the loss cost and the number of outage users are accordingly proven.

Electrochemical Performance of Li2TiO3//LiCoO2 Li-Ion Aqueous Cell with Nanocrystalline Electrodes

A challenge in developing high-performance lithium batteries requires a safe technology without flammable liquid electrolytes. Nowadays, two options can satisfy this claim: all-solid-state batteries and aqueous-electrolyte batteries. Commercially available Li-ion batteries utilize non-aqueous electrolytes (NAE) owing to a wide potential window (>3 V) that achieves high energy density but pose serious safety issues due to the high volatility, flammability, and toxicity of NAE. On the contrary, aqueous electrolytes are non-flammable, low-toxic, and have a low installation cost for humidity control in the production line. In this scenario, we develop a new aqueous rechargeable Li-ion full-cell composed of high-voltage cathode material as LiCoO2 (LCO) and a safe nanostructured anode material as Li2TiO3 (LTO). Both pure-phase LTO and LCO nanopowders are prepared by hydrothermal route and their structural and electrochemical properties are studied in detail. Simultaneously, the electrochemical performances of these electrodes are tested in both half- and full-cell configurations in presence of saturated 1 mole L−1 Li2SO4 aqueous electrolyte medium. Pt//LCO and Pt//LTO half-cells deliver high discharge capacities of 142 and 133 mAh g−1 at 0.5 C rate with capacity retention of ~95% and 94% after 50 cycles with a Coulombic efficiency of 98.25% and 99.89%, respectively. The electrochemical performance of a LTO//LCO full cell is investigated for the first time. It reveals a discharge capacity of 135 mAh g−1 at 0.5 C rate (50th cycle) with a capacity retention of 94% and a Coulombic efficiency of 99.7%.

An Adaptive Control of A Stepper Motor Drive Using a Hysteresis Current Control Approach

Stepper motors are widely used in industrial and consumer applications due to their low cost, great dependability, and capability for open-loop control. Open-loop has a straightforward design, but it has a low step objective, a big torque wave, and low energy productivity. A new sensorless speed control structure based on hysteresis current regulator is proposed in order to work on the exhibition without increasing equipment costs. It does not convert currents between a-b and d-q coordinates using Park and inverse Park transformations, in contrast to the traditional sensorless speed control. The dynamic performance of the hysteresis current controller is excellent. It has been extensively studied and used in inverter fed drives and voltage source inverters. This approach provides quick dynamic performance and incorporates the virtual rectifier stage's line modulation methodology into the overall modulation. The outcomes of the simulation and experiment show that the suggested plan is efficient and workable. Through experimentation and evaluation of the suggested controller's speed and position tracking capabilities, MATLAB/Simulink simulation (R2020a) is used to confirm its efficacy.

A self-vibration-control tensegrity structure for space large-scale construction

Tensegrity is a very attractive structure due to its unique advantages of self-equilibrium, lightweight, small compression volume, and low control cost. However, both the shape and the dynamic behavior of tensegrity are susceptible to environmental change, which has limited the development of the structure in high-accuracy applications. We develop a self-vibration-control tensegrity structure for the space large-scale construction that requires high accuracy and shape retention ability. In the control algorithm, a wave spectrum element method is established first for the dynamic, wave, and power flow analysis of the self-vibration-control tensegrity structure, and the relationship between the global displacement response and the local traveling waves is revealed quantificationally. Then, the power flow vibration control method, which has great robustness and adaptability to the environment, is established using both centralized control strategy and distributed control strategy. Eventually, some numerical simulations and experimental investigations are carried out. The result shows that the vibration of the self-vibration-control tensegrity structure can be effectively suppressed in a wide frequency region. The result of this study can also be applied to other fields.

Large‐Scale Synthesis of Nanostructured Carbon‐Ti4O7 Hollow Particles as Efficient Sulfur Host Materials for Multilayer Lithium‐Sulfur Pouch Cells

AbstractApplications of advanced cathode materials with well‐designed chemical components and/or optimized nanostructures promoting the sulfur redox kinetics and suppressing the shuttle effect of polysulfides are highly valued. However, in the case of actual lithium‐sulfur (Li−S) batteries under practical working conditions, one long‐term obstacle still exists, which is mainly due to the difficulties in massive synthesis of such nanomaterials with low cost and ease of control on the nanostructure. Herein, we develop a facile synthesis of carbon coated Ti4O7 hollow nanoparticles (C−Ti4O7) using spherical polymer electrolyte brush as soft template, which is scalable via utilizing a minipilot reactor. The C−Ti4O7 hollow nanoparticles provide strong chemical adsorption to polysulfides through the large polar surface and additional physical confinement by rich micro‐ & mesopores and have successfully been employed as an efficient sulfur host for multilayer pouch cells. Besides, the sluggish kinetics of the sulfur and lithium sulfide redox mechanism can be improved by the highly conductive Ti4O7 via catalyzation of the conversion of polysulfides. Consequently, the C−Ti4O7 based pouch cell endows a high discharge capacity of 1003 mAh g−1 at 0.05 C, a high‐capacity retention of 83.7 % after 100 cycles at 0.1 C, and a high Coulombic efficiency of 97.5 % at the 100th cycle. This work proposes an effective approach to transfer the synthesis of hollow Ti4O7 nanoparticles from lab‐ to large‐scale production, paving the way to explore a wide range of advanced nanomaterials for multilayer Li−S pouch cells.

Investigation of The Effect of Vacuum Drying Conditions On Graphene Oxide Production

Graphene consists of sp2 hybridized carbon (C) atoms arranged in a honeycomb shape as single layer. Graphene oxide (GO) structures have importance over graphene, because of hydrophobic nature of graphene, non-adjustable band gap, complex production processes and its production costs. GO structures are generally synthesized using graphite or carbon sources which are similar compounds compare to graphene. GO consists of both sp2 and sp3 hybridized C atoms to which functional groups are attached at the top and bottom of the layer. The mechanical, electronical and thermal properties of GO structures can be controlled during the production phase thanks to these oxygen-containing functional groups in their structure. These functional groups consist of oxygen (O) and hydrogen (H) elements in the form of carbonyl, hydroxyl, carboxyl or epoxide and they are highly dependent on the production method. Among the various methods for producing GO structures, the Hummers method stands out with its low cost, time efficiency and ease of parameter control. In this study, GO production was carried out by improved Hummers method, which consists of steps such as mixing with strong acids and oxidizing agents, washing with water and drying. The drying process, which is the last stage of production, directly affects the physical and chemical properties of the final product. Thus, the type and the amount of functional groups in the structure may change according to the drying method applied. In this study, the effect of drying, which is one of the Hummers method production parameters, on the oxidation level of the GO structure was investigated. For this purpose, GO structures were dried at different vacuum levels and atmospheric conditions. The produced GO structures were characterized using X-Ray Diffractometry (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) devices. While XRD analysis showed the difference in phase structure, oxidation degree and interlayer distance between GO layers, FTIR analysis revealed the changes of functional groups in GO structures depending on drying conditions.

Dynamic Burst Actuation to Enhance the Flow Control Authority of Plasma Actuators

A computational study was conducted on flows over an NACA0015 airfoil with dielectric barrier discharge (DBD) plasma. The separated flows were controlled by a DBD plasma actuator installed at the 5% chord position from the leading edge, where operated AC voltage was modulated with the duty cycle not given a priori but dynamically changed based on the flow fluctuations over the airfoil surface. A single-point pressure sensor was installed at the 40% chord position of the airfoil surface and the DBD plasma actuator was activated and deactivated based on the strength of the measured pressure fluctuations. The Reynolds number was set to 63,000 and flows at angles of attack of 12 and 16 degrees were considered. The three-dimensional compressible Navier–Stokes equations including the DBD plasma actuator body force were solved using an implicit large-eddy simulation. Good flow control was observed, and the burst frequency proven to be effective in previous fixed burst frequency studies is automatically realized by this approach. The burst frequency is related to the characteristic pressure fluctuation; our approach was improved based on the findings. This improved approach realizes the effective burst frequency with a lower control cost and is robust to changing the angle of attack.

Transfer-Reinforcement-Learning-Based rescheduling of differential power grids considering security constraints

The power system rescheduling based on model-free methods has obvious defects in practical application, such as poor scenario transferability, long data training time, and waste of domain knowledge. To overcome the above defects, a transfer-reinforcement-learning-based rescheduling method of differential power grids considering security constraints is proposed. When constructing the Markov decision-making process of security-constrained rescheduling, both the off-limits of line power and node voltage are considered in the reward. The action space of deep reinforcement learning is narrowed by calculating the sensitivities of devices and mapped to control the active and reactive power regulating devices to reschedule active and reactive power simultaneously. According to the change degree of transfer object, the applications of transfer learning are divided into two scenarios. For the security-constrained rescheduling transfer scenario of different structures of the same power grid, a domain-adaption transfer learning method is formed, realizing good data adaptability after structure changes with the original model. Moreover, a policy-based transfer learning method is constructed for the security-constrained rescheduling transfer scenario of different power grids, enhancing the training speed and training effect of target power grid. Two standard systems and two actual power grids are utilized to verify the effectiveness of the method. For the actual power grids, the effects of the two scenarios are improved by 5.8% and 3.9% with transfer learning. Compared with other methods, this method not only has obvious advantages in transferability, but also has a shorter learning process and lower control cost.