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The flexible direct current (DC) grid based on modular multilevel converter (MMC) has a high current peak value and a very fast rising speed during a DC short-circuit fault. In order to limit the impact of fault current on the system in a short period of time, a fault current-limiting combined control strategy suitable for half-bridge MMC was proposed. By using the high controllability of MMC itself, the fault limit can be achieved without external current limiting device, and it can reduce the technical requirements for DC circuit breakers. Firstly, two different current-limiting links and their basic principles in the current-limiting control strategy are explained. Secondly, the influences of the two current-limiting links on the DC fault current, AC current and bridge arm current are analyzed respectively, and the calculation formula of DC fault current under current-limiting control is deduced. Finally, a half-bridge MMC four-terminal DC grid model is built on the PSCAD/EMTDC platform for simulation analysis. The results show that the current limiting combined control strategy can effectively limit the DC fault current and reduce the power and voltage fluctuations of the near-end converter at the fault point. It can also reduce the peak value of AC current and bridge arm current.

Copyright of Electric Power Engineering Technology is the property of Editorial Department of Electric Power Engineering Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the experiment, the main tillage methods used against weeds in the field with cotton as a predecessor crop and the combined use of herbicides had a significant effect on annual and perennial weeds in the winter wheat field, which is of great importance in the growth and development of cultivated plants in their own vegetation [ABSTRACT FROM AUTHOR]

This article deals with a human–machine cooperative system for the control of a smart wheelchair for people with motor disabilities. The choice of a traded control mode is first argued. The paper then pursues two objectives. The first is to describe the design of the cooperative system by focusing on the dialogue and the interaction between the pilot and the robot. The second objective is to introduce a new cooperative mode. In this one, three features are proposed: two semi-autonomous features, a wall following and a doorway crossing, during which the user can intervene punctually to rectify a trajectory or a path, and an assisted mode where, conversely, the machine intervenes in a manual control to avoid obstacles. This mode of intervention of an entity, human or machine, supervising a movement controlled by the other is referred as "combined control." Examples of scenarios exploiting the cooperative capabilities of the system are presented and discussed. [ABSTRACT FROM AUTHOR]

This paper aims to provide a review of the conceptual design and theoretical framework of the main control schemes proposed in the literature for unmanned underwater vehicles (UUVs). Additionally, the objective of the paper is not only to present an overview of the recent control architectures validated on UUVs but also to give detailed experimental-based comparative studies of the proposed control schemes. To this end, the main control schemes, including proportional–integral–derivative (PID) based, sliding mode control (SMC) based, adaptive based, observation-based, model predictive control (MPC) based, combined control techniques, are revisited in order to consolidate the principal efforts made in the last two decades by the automatic control community in the field. Besides implementing some key tracking control schemes from the classification mentioned above on Leonard UUV , several real-time experimental scenarios are tested, under different operating conditions, to evaluate and compare the efficiency of the selected tracking control schemes. Furthermore, we point out potential investigation gaps and future research trends at the end of this survey. [ABSTRACT FROM AUTHOR]

Purpose. The purpose of the work is to ensure the improvement of the regulation quality of pulsed energy converters with simultaneous exclusion of undesirable dynamic modes from its dynamics. Construction of a simulation model of a bridge converter with phase control and soft switching operating on an arc load, studying static and dynamic characteristics, analyzing static and dynamic modes of a closed current stabilization system, studying the nonlinear dynamic properties of the considered converter with PWM, comparative analysis of the frequency characteristics of a real closed pulse system with the characteristics of its linear model. Methodology. Fundamental principles of feedback theory, frequency analysis of electrical circuit stability and control, mathematical modeling and spectral analysis of processes in nonlinear discrete systems, digital signal processing and experimental determination of characteristics and parameters of automatic control systems. The use of engineering techniques and universal computer programs based on new solutions of the matrix equations of circuits, which allow to perform time-consuming calculations of frequency characteristics that take into account the nonlinear nature of processes in closed modern high-power pulse systems at a qualitatively different level. Findings. The proposed current control system based on a converter with soft switching transistors has sufficient reliability and service life, allows to obtain high efficiency as well as quality and accuracy indicators in conditions of uncertainty of object parameters and disturbances. A technique has been developed for designing the Bode-optimal frequency characteristics of the loop gain of the considered converter with PWM, in the possibility of controlling the static and choosing the dynamic instability of the output current, in ensuring stable operation and eliminating the self-oscillating mode of the stabilized converter operating on an arbitrary complex load. Originality. The theory of frequency control has been further developed by extending it to a new class of objects — power sources for electrical technologies with improved quality and accuracy indicators, which makes it possible to raise welding technologies and related technologies to a higher level, to solve many problems, including the problem of improving the final product quality. Practical value. The analysis of static and dynamic characteristics considered in the article and the use of new methods for calculating and measuring the equivalent frequency characteristics of converting devices with PWM should be considered as one of the stages of creating engineering methods for synthesizing power supply regulators, considering the latter as essentially nonlinear systems and taking into account the possibility of undesirable dynamic modes . The closed-loop method allows to determine the frequency characteristics of the loop gain function of a PWM converter that adequately reflects the stability conditions and possible lasing modes.

Hydraulic crawler excavators have been widely used for construction in industry, mining, and agriculture because of their special ability to work on weak soil support. However, the elastic properties of the ground increase the undesired vibrations of the entire operating machine. These oscillations significantly influence the working productivity, the level of fuel expenditure, and the comfort of the driver. There have been many works addressing this problem, although they mainly focus on mechanical dampers. Considering the system from robotic and control aspects, this study presents a new approach to deal with the abovementioned problem. A controller design, which uses a combination of feedback linearization and sliding mode control, is proposed based on a dynamic model. This control law reduces the vibrations of the system working on an elastic foundation, while also allowing for accurate tracking performance of the links. This control law is applied to a small-scale platform to investigate its feasibility for practical applications. [ABSTRACT FROM AUTHOR]

Series and parallel resonance tend to occur and cause harmonic distortion when the distribution system contains a shunt power capacitor to compensate inductive load and dynamic capacitor (D-CAP) to suppress harmonics. This study focuses on the series and parallel resonance active damping of three-phase buck-type D-CAP, so as to achieve better power quality control. Two virtual resistor damping methods for series resonance, D-CAP power capacitor voltage or D-CAP front-end buffer inductor current feedback, are introduced and compared. Then, parallel resonance is damped by generating certain harmonic currents in the phase with the selective harmonic voltage at the point of common coupling (PCC), equivalent to controlling the D-CAP as a virtual harmonic resistor. In addition, the power balance of D-CAP is interpreted to ensure no additional energy control loop is needed for the active damping. To further improve the parallel resonance damping, the self-adjusted damping gain is proposed by the closed-loop regulation of harmonics in PCC voltage. Finally, coordinated control between reactive and multiple harmonic currents is introduced for the whole combined control to avoid over-modulation. A wide variety of experimental results from a 33 kVar/220 V laboratory prototype are provided to demonstrate the validity of the combined control. [ABSTRACT FROM AUTHOR]

• The synthesized diode LBM process can effectively remove the material. • The combined SOD and PWM control methodology is effective one. • The combined control can control peak pulse energy, spot size and power density. • The combined control of produces larger MRR and lower kerf width. Due to a variety of benefits over traditional cutting techniques, the usage of laser technology has risen substantially in recent times. In the present study, an effort was made to investigate the effects of different control approaches in laser power diode based cutting process on leather specimens. Since kerf Width (KW) and material removal Rate (MRR) can impact the process efficiency, these outcomes were used in this study. The leather specimens were cut using 20 W laser diode with various approaches such as open loop standoff distance (SOD) control, closed loop SOD control, open loop pulse width modulation (PWM) control, closed loop PWM control and combined closed loop SOD and PWM control. The synthesized diode LBM process can effectively remove the material from leather specimen under various control approaches such SOD control, PWM control and combined control methodology. The high power with less spot size under pulsed mode can produce higher power density. Due to the ability of controlling beam shape and size under 20 W laser diode module, the combined control could produce lower kerfwidth and higher MRR. Since the combined control of SOD and PWM can also control peak pulse energy and power density at the same time, it can produce better performance measures as compared with other mode of control. Owing to the ability of controlling peak pulse energy and pulse width, the combined control of SOD and PWM produces larger MRR. [ABSTRACT FROM AUTHOR]

To improve automobile travel safety and relieve the intension of driving fatigue, a synergetic strategy on the throttle and brake combined control of automobile cruise system is proposed based on fuzzy control theory. A hierarchical control structure, including the upper fuzzy controller and the lower model match controller, is designed for integrated control function. The upper controller consists of the two input variables, that is, the deviation of the theoretical safe distance and the relative distance and the relative velocity between the host car and the preceding vehicle, and the single output variable, that is, the excepted acceleration of host car. The lower controller has achieved the fast compensation of excepted acceleration by adopting parallel feedforward and feedback compensator to input into the inverse dynamics model of automobile cruise system. Using MATLAB/Simulink, the control function on the proposed synergetic strategy is validated for different working cases. The results show that the synergetic strategy possesses an integrated capability involved automated stop & go control, and following the preceding car to prevent rear-end collision, and the constant velocity cruise whether the driving conditions of the city road or expressway. [ABSTRACT FROM AUTHOR]

In order to enhance the tracking performance and improve the stability of intelligent electric vehicles, combined Lane keeping and direct yaw moment control is a good choice. In this paper, an uncertain model of intelligent electric vehicles for combing the lane keeping and direct yaw moment control is deduced, in which time delay and data dropouts are involved. Since the intelligent electric vehicles have the features of time delay and strong uncertainties, a novel robust guaranteed cost combined lane keeping and direct yaw moment control system is constructed to manage the lateral motion of intelligent electric vehicles. The asymptotic stability of combined lane keeping and direct moment control system is verified based on the Lyapunov stability theory. Simulation tests are carried out to demonstrate the feasibility of the proposed control approach, and the results indicate that the presented robust combined control approach can accurately achieve the lane tracking capability, stability and maneuverability of intelligent electric vehicles. [ABSTRACT FROM AUTHOR]

In order to mitigate the excessive longitudinal displacement responses of suspension bridge girders induced by vehicle braking force, as one of the possible dynamic loadings, a combined control strategy consisting of viscous dampers and friction pendulum bearings is developed in this paper. Firstly, the vehicle composition and the braking force models of the Pingsheng Bridge are obtained by traffic survey and testing results, respectively. Then, the vibration response analysis for the bridge under the braking force is implemented using the MIDAS finite element model. Furthermore, viscous dampers and friction pendulum bearings are separately employed to reduce the vibration responses. The influence matrix method is first used to determine the optimal parameters of viscous dampers. Finally, the effect of the combined control strategy for the vibration control is investigated. The numerical analysis results indicate that utilizing the influence matrix method for the parameter optimization of viscous dampers is feasible and effective. It is also shown that the longitudinal displacement response of the Pingsheng Bridge subjected to the vehicle braking force can be effectively mitigated by viscous dampers, friction pendulum bearings or the combined control with the optimized parameters, and the combined control outperforms the viscous dampers or the friction pendulum bearings alone.

The possibility of applying the neighborhood model to control the station of maintaining polyol optimum temperature is investigated. State and control act as parameters. The identification of the model, the thermotechnical calculation and the combined control of the neighborhood model for determining the heat transfer coefficient are performed. The obtained values of the heat transfer coefficient are compared. [ABSTRACT FROM AUTHOR]

This paper proposes a combined wind farm controller based on Model Predictive Control (MPC). Compared with the conventional decoupled active and reactive power controls, the proposed control scheme considers the significant impact of active power on voltage variations due to the low $X/R$ ratio of wind farm collector systems. The voltage control is improved. Besides, by coordination of active and reactive powers, the Var capacity is optimized to prevent potential failures due to Var shortage, especially when the wind farm operates close to its full load. An analytical method is used to calculate the sensitivity coefficients to improve the computation efficiency and overcome the convergence problem. Two control modes are designed for both normal and emergency conditions. A wind farm with 20 wind turbines was used to verify the proposed combined control scheme. [ABSTRACT FROM PUBLISHER]

To optimize the structure of multicell-type transistor converter with combined control it is proposed to use an additive criterion, wich would take into account such particular criteria as efficiency, cost and construction volume of the converter.

In this paper we consider the problem of locating an object moving on a horizontal plane, whose initial position is known to be from a given subset of points of the plane. The search is carried out by the means of accelerating an object through space, which adheres to certain geometrical constraints on the vertical plane such as that the object cannot move past a certain maximum elevation. A combined control algorithm has been developed, that is guaranteed to locate the object by means of a varying linear and curvilinear trajectories, modeled as circles with varying radii. Geometrical and physical parameters have been calculated which allow to solve the problem of guaranteed positioning. [ABSTRACT FROM AUTHOR]

A 3D overhead crane is an underactuated system consisting of five outputs: trolley position, bridge translation, cable length, and two cargo swings. These outputs are controlled by three actuators for cargo hoisting, trolley motion, and bridge traveling. This study proposes the use of a nonlinear controller that performs five tasks concurrently: cargo hoisting, trolley tracking, bridge motion, payload vibration suppression during transport, and cargo swing elimination at the destination. The proposed algorithm is combined with two control components: (i) partial feedback linearization, which is a precursor to controller design, to suppress cargo vibration; and (ii) sliding mode method, which provides robust control in lifting the payload and driving trolley and bridge motions against model imprecision and uncertainty. These two control mechanisms are successfully merged into a combined controller because the kinematic relationships between the state variables are made apparent in the system dynamics. Simulation and experimental results show that the proposed controller asymptotically stabilizes all system responses. [ABSTRACT FROM AUTHOR]

Copyright of Çalışma ve Toplum is the property of Calisma ve Toplum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents different control strategies for controlling cable insulation thickness for a plastic-on-wire extrusion process. Different control strategies are compared like cascade control, feedforward control. Finally a combined control strategy [dynamic feedforward and cascade (hot and cold control)] is proposed and its effectiveness is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: The control system and the characteristics of the turbine governor are reviewed and the analysis is provided, based on which the combined control method is proposed. The simulation results show that this method enables the turbine to maintain stable work in a smooth state, so as to solve the severe turbine vibrations caused by turbine speed instability. These vibrations are apt to cause damage to the equipment and the recovery system does not work properly and so on. Thus the integrated control mode would keep safe and stable operation of the hydraulic turbine, and then energy recovery systems could run efficiently. [Copyright &y& Elsevier]

We study a nonlinear elliptic variational inequality associated with the combined stochastic control problem. By using the dynamic programming principle and the method of penalization, we establish the existence of a unique viscosity solution of the variational inequality and describe it as the value function of the corresponding combined stochastic game problem. [ABSTRACT FROM AUTHOR]

We study the variational inequality associated with the combined stochastic control problem and establish the existence of a unique viscosity solution without uniform ellipticity. An application to the quasi-variational inequality is given. [ABSTRACT FROM AUTHOR]

We study a non-linear elliptic variational inequality which corresponds to a zero-sum stopping game (Dynkin game) combined with a control. Our result is a generalization of the existing works by Bensoussan [ Stochastic Control by Functional Analysis Methods (North-Holland, Amsterdam), 1982], Bensoussan and Lions [ Applications des Inéquations Variationnelles en Contrôle Stochastique (Dunod, Paris), 1978] and Friedman [ Stochastic Differential Equations and Applications (Academic Press, New York), 1976] in the sense that a non-linear term appears in the variational inequality, or equivalently, that the underlying process for the corresponding stopping game is subject to a control. By using the dynamic programming principle and the method of penalization, we show the existence and uniqueness of a viscosity solution of the variational inequality and describe it as the value function of the corresponding combined-stochastic game problem. [ABSTRACT FROM AUTHOR]

The aim of this paper is not only to present various methods for combining lateral force and yaw moment control but also to find out how the mix between them should be applied to maximize the stability limit as well as vehicle responsiveness. Approximated two-degree-of-freedom (2DOF) vehicle model responses of side-slip angle and yaw rate are used to introduce the required total lateral force and yaw moment control. Three different cases of combining lateral force and direct yaw moment control have been investigated using computer simulations. A direct yaw moment control to follow the yaw rate response only is taken as a comparison case in order to show the effect of the combined control on vehicle stability and responsiveness. A computer simulation of a closedloop driver-vehicle system subjected to quick lane change with braking is used to prove the influence of the combined control. It is found that the influence of the combined control on vehicle stability and responsiveness is significant. [ABSTRACT FROM AUTHOR]

• Effects of Neospora caninum infection on economic performance are evaluated. • Cost of control together with annual loss is the assessment criterion. • Vaccination is the most economical option in regions with high prevalence. • Combined controls provide better financial outcomes against a single control. Neospora caninum infection is regarded as one of the most important infectious causes of abortion in dairy cattle. To intervene in its spread, four potential controls including test-and-cull, medication, vaccination, and selective breeding are considered and assessed in this study. The cost of each control, together with the inevitable annual loss due to population dynamics, is adopted as an assessment criterion from an economic point of view. By performing simulation and sensitivity analysis, our results demonstrate that compared with each single control, combined controls are worthwhile with better financial outcomes. For farm affected with significant prevalence (equal to or greater than 30%), vaccine treatment is the most effective and economical option among all control strategies. On the other hand, for farm where prevalence is relatively low (around 10%), combined control, by applying vaccination followed with test-and-cull, medication or selective breeding, could be alternative treatment to provide better financial outcome against single control in an observed period. [ABSTRACT FROM AUTHOR]