Second-order Dynamic Model Research Articles

An Input–Output Feedback Linearization Control Method Synthesized by Artificial Neural Network for Grid-Tied Packed E-Cell Inverter

In this article, a trained artificial neural network (ANN) input-output feedback linearization (IOFL) control strategy is proposed for a grid-connected nine-level packed E-cell (PEC9) converter under various operating variations. For the first time, a second-order dynamic model in d-q reference frame is developed for PEC9 converter. This model enforces the converter to employ IOFL-based proportional-resonance compensators for accurately contributing to current tracking enhancement, mitigation at the current ripple, and consequently, the capacitors dc voltages ripple. As another contribution, the current tracking ability of the proposed controller is much more promoted by decoupling the d-q dynamic components. Indeed, the effect of each proposed control component is fortified through decoupling feedback coefficients. In addition, as the third contribution, ANN as the complementary controller adapts the proposed IOFL-based controller coefficients to improve efficiency and stability of the whole control loop system, including the PEC9 capacitor voltages in unstable operation of load, grid, and dc source as well as in the presence of parameters mismatch and disturbances. To support the aforementioned contributions with more details, the closed-loop description and the dynamic model of the proposed controller-based PEC9 converter are utilized to present several stability evaluation processes in both time and frequency domains. This assessment process is accurately executed to confirm the stable performance of PEC9 when the errors of the PEC9 converter currents are changed as well as the decoupling feedback coefficients are varied. Finally, comparative dSPACE setup-based experimental and simulation results are attained to further verify the validity of the proposed control strategy under various operating conditions.

Design and experimental validation for nonlinear control of internal combustion engines with EGR and VVT

This paper presents a feedback control design scheme for internal combustion engines with the exhaust gas recirculation and the variable valve timing. A second-order nonlinear dynamical model is pr...

Adsorption of Acid Dye by Activated Carbon from Agricultural Solid Waste Leucona Leucocephala Seed Shell Waste: Kinetics, Equilibrium and Isotherm Study

Activated carbons from Leucaena leucocephala Seed Shell left over were generated accompanied by 10% phosphoric acid solution in the N2 atmosphere by chemical activation and their characteristics were investigated. SEM, FTIR and XRD analysis were used to analyse the characteristics of the triggered preparations. Isothermal models, namely the Freundlich and Langmuir representations, were the equilibrium studies carried out.. The equilibrium adsorption result was better suited to the isotherm model of Langmuir and its maximum monolayer adsorption potential for acid blue was 70.67 mg/g. Adsorption kinetics studies have shown that the best fit is provided by the pseudo second-order dynamic model. An intraparticle dispersion model demonstrated that the dissemination of the intraparticle was not a step of rate control. Studies of thermodynamics have shown that the sorption mechanism is spontaneous and exothermic in nature. The findings suggest that the seed shells of Leucaena leucocephala may be used as a possible adsorbent for Acid blue1 adsorption.

Optimized formation control of multi-agent system using PSO algorithm

<p>Formation Control (FC) is an important application for Multi-agent Systems (MASs) in coordinated control and especially for Unmanned Aerial Vehicle (UAV) which are widely used nowadays in military and civil sections. FC is mostly applied in conjunction with consensus algorithm. In this paper, a framework for an implementation of consensus FC that involves the decentralized type of network control is considered in order to achieve formation keeping, where the control of each vehicle is calculated dependent upon locally existed facts. The dynamic behavior of each vehicle agent is governed by its second-order dynamic model, and the networked mobile vehicle system is modeled by a directed graph. Then, Particle Swarm Optimization (PSO) is implemented for speeding up the convergence to the desired geometrical shape. Acceleration of the network while approaching the coveted shape is achieved and omissions of undesired swing that transpires through the acceleration is examined. The merits and effectiveness of the applied approach are demonstrated using two different examples.</p>

High Performance Both in Low-Speed Tracking and Large-Angle Swing Scanning Based on Adaptive Nonsingular Fast Terminal Sliding Mode Control for a Three-Axis Universal Inertially Stabilized Platform.

In order to improve the performance in the practical engineering applications including so called low-speed video tracking and large-angle swing scanning imaging at the same time for a three-axis universal inertially stabilized platform (UISP), we propose an adaptive nonsingular fast terminal sliding mode control (ANFTSMC) strategy subjected to the uncertain disturbances and input saturation constraints. First of all, a second-order dynamic model is established with uncertain disturbances and input saturation constraints. Secondly, a nonsingular fast terminal sliding mode controller (NTSMC) is constructed to ensure the system error converges to zero fast in a finite time; meanwhile, a novel reaching law based on a modified normal distribution function is designed to adjust the control gain. Thirdly, an adaptive control law is designed to online estimate the parameters of the lumped uncertain disturbances. Additionally, the stability of the control system is proved by Lyapunov theory. Finally, extensive comparative simulations and experiments are carried out, the results comprehensively show the effectiveness and superiority of the proposed control method, which can accelerate convergence, weaken the chattering, and has the better control accuracy and robust performance both in the low-speed tracking and large-angle swing scanning applications. Moreover, the exact dynamic model and the prior knowledge of the upper bounds of the disturbances are not required during the procedure of the controller design, which make it have more extensive application value in practical engineering.

Anti-Disturbance Finite-Time Adaptive Sliding Mode Backstepping Control for PV Inverter in Master–Slave-Organized Islanded Microgrid

With the aim to solve the problem related to the power chattering and anti-disturbance performance of a photovoltaic (PV) inverter in master–slave-organized islanded microgrid, an anti-disturbance finite-time adaptive sliding mode backstepping (DFA-SMB) controller is designed in this paper. First, the topology and the second-order dynamic model of PV inverter are established based on constant DC voltage and constant reactive power control method. Subsequently, the backstepping method is adopted to perform the control of a high-order system. Moreover, a second-order sliding mode differentiator is used to realize the function of command-filter, solving the differential expansion problem caused by the derivation of virtual controller. Besides, the terminal sliding mode control (TSMC) is introduced into the q-axis controller and d-axis inner loop controller, increasing the robustness and reducing the convergence time of the system. Adaptive control and disturbance-observer (DO) are used to perform the adaptive estimation of model parameters and the observation of lumped disturbances, respectively, enhancing the dynamic characteristics of the controller. Finally, a master–slave-organized islanded microgrid with 100 kW PV array is established in MATLAB/Simulink. The results demonstrate that the proposed control method can effectively reduce power chattering and improve the anti-disturbance ability of the PV system.

Robust adaptive backstepping active control of compressor surge based on wavelet neural network

Surge active control can extend the stable operating range of the compressor. Most of the previous active control algorithms can only work on the basis that compression characteristics are known, which limits the engineering application of it. The robust control can alleviate the negative effects brought by uncertain system characteristics, however its designed control law is too conservative that active control can't give full play to its benefits. To overcome the weakness of the former active controllers, this paper comes up with the idea of active surge control, which assumes that the characteristics of the compression system are unknown. And it uses the wavelet neural network algorithm, a kind of algorithm with the nature of approaching any linear and nonlinear functions, to approach the unknown compressor steady-state characteristics asymptotically. Then, by applying backstepping on the second-order MG compressor surge dynamic model with CCV, a robust adaptive active controller of compressor surge is designed, which makes the control law effective to a larger extent, and greatly improve its performance in tracking and anti-interference. From the simulation results, it can be seen that the designed controller displays the strong robustness against un-modeled dynamics, flow and pressure disturbances, and in the meanwhile achieves near to zero asymptotical tracking error. The method proposed in this paper allows compressors to operate stably with high-pressure ratio and high-efficiency beyond the surge boundary, namely greatly expands its operating range. Thus, this paper has significant guidance for future development, theoretical research, and engineering application of surge active control of the compressor.

OPF-based under frequency load shedding predicting the dynamic frequency trajectory

The paper describes a centralized Under Frequency Load Shedding (UFLS) method, where load shedding decisions are based on the solution of an optimization problem. The proposed approach anticipates the evolution of the grid frequency trajectory by means of a system dynamic model. Moreover, the method is augmented by the equations derived from the Optimal Power Flow (OPF) problem allowing to constrain asymptotic values of node voltages and line currents. The proposed OPF-based method differs from traditional UFLS methods as it enables the user to compute the minimum amount of load to be shed and, at the same time, provides a feasible grid trajectory. The trajectory of the system frequency due to the contingency, and the subsequent load shedding, is predicted over the entire time horizon by means of a second-order dynamic model. The feasibility and applicability of the proposed method are assessed by means of numerical simulations carried out using a real-time simulator, where the time-domain full-replica model of the IEEE 39-bus system has been implemented. Two contingency scenarios are investigated and the performance of the proposed method is compared against the UFLS strategy recommended by the European Network of Transmission System Operators (ENTSO-E). The metrics used for such a comparison are the amount of energy not served, the frequency variation and the violation of the grid safety constraints.

First-Order Dynamic Modeling and Control of Soft Robots.

Modeling of soft robots is typically performed at the static level or at a second-order fully dynamic level. Controllers developed upon these models have several advantages and disadvantages. Static controllers, based on the kinematic relations tend to be the easiest to develop, but by sacrificing accuracy, efficiency and the natural dynamics. Controllers developed using second-order dynamic models tend to be computationally expensive, but allow optimal control. Here we propose that the dynamic model of a soft robot can be reduced to first-order dynamical equation owing to their high damping and low inertial properties, as typically observed in nature, with minimal loss in accuracy. This paper investigates the validity of this assumption and the advantages it provides to the modeling and control of soft robots. Our results demonstrate that this model approximation is a powerful tool for developing closed-loop task-space dynamic controllers for soft robots by simplifying the planning and sensory feedback process with minimal effects on the controller accuracy.

Control para el voltaje de salida de un inversor multinivel de capacitores flotantes

Este artículo presenta el diseño de un controlador mediante la técnica de rechazo activo de perturbaciones para el seguimiento de la trayectoria de referencia para el voltaje de salida de un inversor multinivel de capacitores flotantes. Si en el modelo dinámico del convertidor se consideran las dinámicas de cada capacitor flotante y adicionalmente, las de los elementos pasivos del filtro de salida, el modelo resultante es de un orden alto, lo que dificulta su control. En este trabajo se emplea la modulación PS-PWM para mantener los voltajes en los capacitores flotantes en sus valores nominales y de esta manera poder generar un modelo dinámico simple, que resulta ser más fácil de controlar. Los resultados de simulación y experimentales, confirman que el controlador es robusto a perturbaciones provocadas por cambios en la carga, sin importar si son de tipo lineal o no lineal. Se realizó la construcción del prototipo experimental del sistema y se implementó el controlador y modulador en un FPGA y en la parte final se muestran los resultados obtenidos.

Efficient removal of tetrabromobisphenol A (TBBPA) using sewage sludge-derived biochar: Adsorptive effect and mechanism

Sewerage sludge-derived biochars (SSDBCs) with high adsorption capacity and excellent recyclability were synthesized to remove tetrabromobisphenol A (TBBPA) in aqueous system. Scanning electron microscopy, elemental mapping via energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the morphology, composition, and microstructures. The maximum adsorption capacity of SSDBCs was about 87.02 mg g−1 at 303 K and pH 7.5. The Langmuir isotherm demonstrated that the adsorption was mainly homogeneous and chemical processes. The kinetics of TBBPA removal well fitted the second-order dynamic model. Thermodynamic analysis showed that the adsorption was exothermic. The effect of π−π dispersive force and hydrogen bonding was proven as the main adsorption mechanism. Multiple cycle runs experiment revealed the excellent stability of recycled SSDBCs. This work provided a promising method of sludge resourceful treatment using an efficient, economic, cyclic, and convenient material for typical organic contaminant in the environment.

Efficient removal of arsenic (III) from aqueous solutions by new layered hydroxides (Ca–Fe–Cl LDHs)

A novel bimetallic layered hydroxide (Ca–Fe–Cl LDHs) was prepared for the removal of arsenic (III) (As (III)) from an aqueous solution. The materials were characterized by SEM, XPS, TGA, and FTIR to analyze this removal mechanism. The effects of pH, contact time, dosage, initial concentration, and coexisting anions on the removal of As (III) by Ca–Fe–Cl LDHs were explored. The results demonstrated that Ca–Fe–Cl LDHs exhibited good performance with a maximum adsorption capacity of 22.1 mg/g, and adding 1.26 g/L Ca–Fe–Cl LDHs can reduce the concentration of arsenic solution (0.4 mg/L) to below 0.01 mg/L, and the removal rate of As (III) was not affected within the pH range of 2 − 12. The Langmuir model and the pseudo second-order dynamics model could better fit the experimental data with R2 equal to 0.969 and 0.885, respectively. Coexisting ions, such as HPO4 2−, SO4 2−, CO3 2−, and NO3 −could inhibit material adsorption and reduce the removal efficiency of As (III). Under experimental conditions, the concentration of 0.01 M Na2CO3 solution was used for regeneration, and the efficiency of As (III) removal was maintained above 90% after 5 regenerations.

Closed-Loop Control for Trajectory Tracking of a Microparticle Based on Input-to-State Stability Through an Electromagnetic Manipulation System

Magnetic force-based manipulation has several advantages, including its minimally invasive feature and insensitivity to biological substances. Consequently, it has exhibited considerable potential in many medical applications, such as targeted delivery in precise medicine, in which microparticles are driven to the desired regions precisely in vivo. This study investigates an automated and accurate delivery of magnetic microparticles using a self-constructed electromagnetic coil system. After establishing a simplified second-order dynamic model of microparticles suspended in a fluidic environment, a visual-based automated controller that incorporates the concept of input-to-state stability (ISS) into fault-tolerant technique is developed. This controller enables microparticles to follow a desired trajectory under model uncertainties and environmental disturbances, and address the problem that the actual magnetic driving force may not reach the required value due to magnetic loss in the coil system simultaneously. Input constraint of the magnetic force provided by the system due to device capability is also considered in the fault-tolerant ISS-based controller design. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed approach.

Optimal Frequency Control for Inverter-Based Micro-Grids Using Distributed Finite-Time Consensus Algorithms

This paper addresses the distributed frequency control and economic dispatch problem of micro-grid systems. The optimal frequency control problem is formulated considering both frequency regulation and generation cost minimization, by establishing an equivalent nonlinear second-order dynamic model. A distributed finite-time consensus protocol is proposed to solve the optimal frequency regulation problem based on the equivalent model. Despite the nonlinear dynamics, the system frequency converges to the nominal value and the economic dispatch is achieved both in finite time. It is proved that the equilibrium point of the closed-loop system is the unique optimal solution to the associated economic dispatch problem. Simulation results verify the theoretical analysis and demonstrate the effectiveness of the proposed control method.

Functionalized diatomite/oyster shell powder doped electrospun polyacrylonitrile submicron fiber as a high-efficiency adsorbent for removing methylene blue from aqueous solution: Thermodynamics, kinetics and isotherms

A novel diatomite/oyster shell (DS) powder doped polyacrylonitrile composite fiber adsorbent was fabricated via electrospinning technology and anion functionalization (fun-PAN/DS) was carried out with sodium hydroxide and sodium bicarbonate. The influences of different parameters such as solution pH, contact time, temperature and initial concentration on the adsorption of methylene blue (MB) were investigated in batch mode. The adsorption data showed that the removal rate of MB increased from 10.96% to 96.45% with the increase of pH value. The Freundlich isotherm model was found to be best depicting the adsorption of MB on fun-PAN/DS submicron fiber with a maximum capacity of 243.44 mg/g. The pseudo second-order dynamics model (R2 > 0.99) was more suitable for experimental data than other kinetic models. In the summary, fun-PAN/DS fiber with good physicochemical stability is an excellent material to be a high-efficiency adsorbent for removing methylene blue from aqueous solution.

Start-up timing behavior of single-loop oscillating heat pipes based on the second-order dynamic model

Oscillating heat pipes have the potential to combine with the grinding wheel to enhance heat transfer in grinding process to avoid thermal damage of workpiece and grinding wheel. Since the time of grinding process is short, it raises a requirement for a good start-up behavior of oscillating heat pipes inside grinding wheel. In order to understand the start-up behavior, a new method is proposed based on the second-order dynamic theory to represent and evaluate start-up process. Several parameters (i.e., rising and settling time, percent-overshoot) are defined to value quantitatively the start-up process. Accordingly, three start-up modes are discovered with respect to the evaporator temperature, which are over-damped, under-damped and transient start-up modes. The start-up behavior is discussed with both pure fluids and nanofluids. Results show that as the heating power increases, the start-up speed enhances, and over-damped start-up mode develops to under-damped or transition start-up mode. The start-up speed of DI water is faster at low heating power, while acetone and nano-diamond solution without dispersant show faster start-up speed at high heating power. This methodology will help to compare the start-up timing of the OHP experiments in literatures, providing a more robust way to analyze start-up data.

Selective removal mechanism of the novel Zr-based metal organic framework adsorbents for gold ions from aqueous solutions

A novel metal organic framework absorbent was synthesized by one step method using 2,2′-dithiodibenzoic acid as organic linker for efficient and selective recovery of Au(III) from aqueous solution. The adsorbent were detected by scanning electron microscope, X-ray diffraction and zeta potential instruments. Its performance was tested by batch experiments. The adsorption isotherm conforms to the Langmuir model, demonstrating that the adsorption process is the uniform monolayer adsorption. The kinetic model is well fitted to the pseudo second-order dynamics model. The maximum adsorption capacity was 1119 mg/g at pH = 2. High temperatures can promote the absorption process. The five adsorption and desorption cycles indicate that the adsorbent has good repeatability for Au(III) adsorption. It could selectively adsorbed Au(III) from wastewater. The adsorption derivefromchelation and reduction. The DFT and XPS results show that Au(III) is mainly adsorbed on the adsorbent by coupling with the S atom. These results indicate that it has a high potential to remove Au(III) from industrial wastewater.

Migration and Transformation of Ofloxacin by Free Chlorine in Water Distribution System

This study investigated the degradation kinetics and product generation of ofloxacin (OFL) in the pipe network under different pipe materials, flow rate, pH, free chlorine concentration and temperature. The experiments done in the beaker and pipe network were compared. The results showed that the reaction rate of OFL chlorination with free chlorine increased with the increase of the free chlorine concentration in the pipe network and deionized water, and the degradation efficiency of OFL in the pipe network was higher than that in the deionized water, satisfying the second-order dynamics model. The degradation rate under different pHs was: neutral > acidic > alkaline. The influence of the flow rate is not significant while the influence of the pipe materials and temperature is obvious. The degradation rate of OFL increased with the increase of the temperature, indicating that the OFL degradation was an endothermic process. A liquid chromatograph-mass spectrometer (LC-MS) was used to detect the chlorination intermediates, and the results showed that the piperazine ring was the main group involved in the chlorination reaction, and the main point involved in the chlorination reaction was the N4 atom on the piperazine ring. We also found that, as the reaction time increases, the concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs) increase and THMs mainly exist in the form of trichloromethane (TCM) while HAAs mainly exist in the form of monochloroacetic acid (MCAA).

A Sliding Mode Force and Position Controller Synthesis for Series Elastic Actuators

SummaryThis paper deals with the robust force and position control problems of series elastic actuators (SEAs). It is shown that an SEA’s force control problem can be described by a second-order dynamic model which suffers from only matched disturbances. However, the position control dynamics of an SEA is of fourth order and includes matched and mismatched disturbances. In other words, an SEA’s position control is more complicated than its force control, particularly when disturbances are considered. A novel robust motion controller is proposed for SEAs by using disturbance observer (DOb) and sliding mode control. When the proposed robust motion controller is implemented, an SEA can precisely track desired trajectories and safely contact with an unknown and dynamic environment. The proposed motion controller does not require precise dynamic models of environments and SEAs. Therefore, it can be applied to many different advanced robotic systems such as compliant humanoids, industrial robots and exoskeletons. The validity of the proposed motion controller is experimentally verified.

Preparation and performance of aminated polyacrylonitrile nanofibers for highly efficient copper ion removal

As promising sorbent, nanofibers with high specific surface area and adsorption site loading show excellent adsorption capacity. Polyacrylonitrile (PAN) is an industrial by-product with abundant nitrile groups (CN). However, raw polyacrylonitrile shows almost no binding ability toward metal ions. Herein, aminated polyacrylonitrile (APAN) nanofibers are synthesized by electrospinning followed by grafting branched polyethyleneimine (bPEI). The microstructures of these nanofibers show a uniform fiber diameter of 595 nm and a high surface area of 2.81 m2 g−1. In addition, the > N/NH group loading is as high as 5.7 wt.%. Fourier transform infrared spectroscopy and elemental analysis results confirm the formation of covalent bonds (C(O)NH) between PAN and bPEI, resulting in a stable structure and hence excellent reproducibility. And the original adsorption capacity can be maintained by 61.6% after 5 cycles. The influence of solution pH, adsorption isotherm, initial concentration, and contact time on Cu2+ adsorption is systematically investigated. The maximum adsorption capacity of APAN nanofibers is 149.8 mg g-1, which is difficult to achieve by most low density adsorbents. Furthermore, sorption-isotherm experiments reveal that the adsorption behavior obeys Langmuir model, and the adsorption kinetic agrees second-order dynamics model. Cu2+ ions are chelated with > N/NH groups in five-membered rings. Therefore, these APAN nanofibers open up delighted opportunities for the efficient removal of Cu2+ from industrial wastewater.