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In recent years, microgrid technology has been widely studied and applied. However, with times developing, the installed capacity of distributed power generation devices has been improved, and work is being carried out in increasingly complex situations, resulting in a decline in the control performance of microgrids. In view of this, to effectively improve inverter’s control performance, research is conducted on the fusion of Narendra model and adaptive control strategies for real-time voltage correction and compensation in complex situations. Compared to traditional inverters, inverters under research methods have faster voltage recovery speed when encountering load switching, and can recover in about one cycle, with good control performance. In the comparison between the improved inverter adaptive control system and the inverter adaptive system, the improved inverter voltage recovery speed is faster, can be restored within one cycle, and the control effect of the inverter is better. The harmonic rate of the port voltage has decreased from 10.43 to 1.92%. The applicability of the research method was verified. It indicats that the research method can improve inverter’s control effect and solve problems such as voltage deviation, three-phase asymmetry, harmonic pollution, etc. that are easily generated by the output terminal voltage. Simultaneously, research has provided theoretical basis and data support for the research of microgrids. [ABSTRACT FROM AUTHOR]

Copyright of Integrated Intelligent Energy is the property of Editorial Department of Integrated Intelligent Energy 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.)

Abstract In recent years, microgrid technology has been widely studied and applied. However, with times developing, the installed capacity of distributed power generation devices has been improved, and work is being carried out in increasingly complex situations, resulting in a decline in the control performance of microgrids. In view of this, to effectively improve inverter’s control performance, research is conducted on the fusion of Narendra model and adaptive control strategies for real-time voltage correction and compensation in complex situations. Compared to traditional inverters, inverters under research methods have faster voltage recovery speed when encountering load switching, and can recover in about one cycle, with good control performance. In the comparison between the improved inverter adaptive control system and the inverter adaptive system, the improved inverter voltage recovery speed is faster, can be restored within one cycle, and the control effect of the inverter is better. The harmonic rate of the port voltage has decreased from 10.43 to 1.92%. The applicability of the research method was verified. It indicats that the research method can improve inverter’s control effect and solve problems such as voltage deviation, three-phase asymmetry, harmonic pollution, etc. that are easily generated by the output terminal voltage. Simultaneously, research has provided theoretical basis and data support for the research of microgrids.

The US Environmental Protection Agency (USEPA) considers sediment toxicity tests as conditional registration requirements for pesticides with soil Kd ≥50 L/kg‐solid, Koc ≥1000 L/kg‐organic carbon, or log Kow ≥3. The hydrophobicity of these compounds often necessitates use of solvents to ensure accurate and homogeneous dosing of spiked‐sediment studies. For sediment tests, a volatile solvent (e.g., acetone) is generally used as a transient carrier. Due to low water solubility, test material is dissolved in a volatile solvent to create stock solutions. A measured aliquot of stock solution is then mixed with sand substrate, after which the solvent is evaporated. This spiking process results in negligible solvent exposure to organisms. In 2016, USEPA released final ecotoxicity test guidelines for subchronic freshwater (850.1735) and marine (850.1740) sediment test. These methods provide an option for conducting experiments with only a solvent control and no negative control. To adopt this testing strategy, functional equivalency between the negative and solvent control must be demonstrated. These test guidelines describe specific factors that should be considered for evaluating functional equivalency, including (a) the concentration of solvent in the test sediment after evaporation, (b) the levels of solvent that are known to affect organism health, (c) the known impurities in the solvent and their potential impact on organism health, and (d) the historical organism performance of solvent versus negative controls. Our analysis considers these factors and overall supports the elimination of the negative control requirement because this change is unlikely to impact the robustness or interpretability of spiked‐sediment toxicity tests. Environ Toxicol Chem 2024;43:1740–1746. © 2023 CropLife America. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

A periodic adaptive mechanism is proposed for a class of discrete‐time linear periodic systems with parametric uncertainties in this paper. Based on the periodic system model, the adaptive mechanism uses the weight function to update the controller parameters in real time, which reduces the influence of system parameter uncertainty on the controller performance and makes the system parameters converge to the ideal values. Finally, numerical examples are used to demonstrate the effectiveness and superiority of the adaptive mechanism in improving control performance and reference tracking performance. [ABSTRACT FROM AUTHOR]

Two different methods of Fuzzy-control and Machine-learning are proposed to control the vehicle's semiactive suspensions. To control performance of semiactive suspensions using machine learning (SS-ML) and semiactive suspensions using fuzzy control (SS-FC), a half-vehicle model has been established to calculate and simulate vibration equations under random road surfaces from ISO A-class to F-class. Via map of control rule data in SS-FC established at roads ISO A-class, B-class, ..., and F-class, SS-ML's Neuro-Adaptive-Learning has been trained for learning these control rules. The results obtained indicate that under the same road surface excitation of ISO C-class, the control performance of SS-FC and SS-ML is equivalent., and the vehicle's comfort level using both SS-FC and SS-ML is very well improved in comparison with passive suspensions without control (PS-WC) of the vehicle. Under a mixed road surface from ISO A-class to F-class and a change range of the vehicle's moving velocity from 2.5 m s−1 to 35m s−1 used for simulation, the vehicle's comfort level using SS-ML is better than vehicle's comfort level using SS-FC. Especially, the root mean square values of displacements and accelerations in vertical and pitch directions of the vehicle body with SS-ML are smaller than that of SS-FC by 13.4%, 23.2%, 20.7%, and 14.3%, respectively. Therefore, the control performance of SS-ML is better than SS-FC, and it should be used to control the vehicle's semiactive suspensions for enhancing the comfort level. [ABSTRACT FROM AUTHOR]

. The goal of the work is to create a new method for automatic re-tuning of PI controllers. It is achieved by solving the following problems. The first problem is to develop a method to identify a FOPDT estimation model by analyzing the dynamics of a control loop with a PI controller. The second problem is to demonstrate that the use of the estimated model allows to obtain better processes in control systems with PI controllers by comparing the resulting FOPDT model with a number of reduced models. The third problem is to develop a five-stage algorithm for automatic re-tuning of PI controllers. The fourth problem is to verify the software implementation of the developed algorithm. The most significant result was that the basis for estimating the FOPDT model in a loop with a Ziegler-Nichols tuned PI controller was the estimation the ratio of the delay to the time constant of the FOPDT model based on an assessment of the process overshoot. When the real control plant dynamics did not match with the dynamics of the FOPDT model this way was found effective for finding the optimal tuning of the PI controller. The significance of the results obtained was a structural robustness in case of estimated FOPDT model usage. The effectiveness of the procedure has been demonstrated on both linear and nonlinear models. The developed procedure is proposed to be used to automate the procedure of re-tuning SISO control systems when the control loop performance degradation has been detected.

The drum water level plays a crucial role in the safety and economy of heat recovery boilers. However, the control of the drum water level faces many challenges, such as external disturbances and system uncertainties. To enhance the control performance of the drum water level, a modified active disturbance rejection control (MADRC) optimized with sensitivity constraint is proposed in this paper. Firstly, the control structure of the three-element control system for the drum water level is introduced and analyzed. Based on the regular active disturbance rejection control (ADRC) structure, the structure of the MADRC is introduced and the convergence of the proposed MADRC is proven. Then a modified whale optimization algorithm (MWOA) with sensitivity constraint is applied to optimize the parameters of the MADRC. With different sensitivity constraints, the parameters of the MADRC and comparative controllers are obtained, and their control performance for tracking and disturbance rejection abilities is compared. Moreover, the ability to handle system uncertainties is analyzed. Simulation results and performance indexes show that the proposed MADRC can obtain the best tracking and disturbance rejection abilities with satisfactory robustness. The satisfactory control performance shows that the proposed MADRC has wide application potential for heat recovery boilers and other industrial processes. [ABSTRACT FROM AUTHOR]

Worldwide, food scarcity is becoming a debatable concern among the scientific fraternity due to the increased populace, leading to decreased arable land. This has compelled us to explore various innovative and technological solutions, for example, large‐scale greenhouse farming, to meet the surging demand for field production. In this context, research efforts have been continually made by various scientists and researchers to explore more control strategies/algorithms for keeping the indoor climate comfortable and enhancing the greenhouse's energy effectiveness. Considering this, an initiative was made to summarize the documented research findings in the last decade focusing on energy‐efficient greenhouse‐based crop cultivation. The findings of some studies considering selective parametric conditions have been presented in graphs/tables for reader clarity and discussion. Initially, the studies on existing energy efficient strategies, parameters, monitoring systems, sensing networks, and control algorithms have been discussed. A state of the art review found that control strategies are essential in low‐energy greenhouses since they influence crop yield and cost. It was observed that advanced control algorithms and energy conservation in greenhouses received more attention due to wide spread application, high compatibility, low‐cost, and user‐friendly operations. In terms of future perspectives, it is anticipated that the development of machine learning, big data, and artificial intelligence, combining these technologies with traditional and advanced control strategies would lead to a revolution in the management of greenhouse energy. [ABSTRACT FROM AUTHOR]

In this study, we propose a novel method for enhancing the control performance of a degraded robot manipulator by leveraging digital twins and proximal policy optimization, a specific deep reinforcement learning algorithm. Recently, various robotic technologies with high levels of controllability, safety, and reliability that incorporate the fourth industrial technology have been developed. Nevertheless, repairs or replacements owing to the performance degradation of sophisticated robot hardware or control systems are still time-, cost-, and manpower-consuming. To address these challenges, we propose a new strategy:1) approximate the unstable dynamic characteristics of six-degree-of-freedom low-performance robot manipulators to a digital twin with parameter tuning of a physics engine; 2) improve the accuracy and stability of reaching target points under diverse conditions through deep reinforcement learning using the domain randomization method; and 3) deploy a trained policy on an actual robot manipulator with degraded capabilities to validate the control performance improvement. Our method reduced the position error of a real robot manipulator by 63.0% and 39.0% compared to the built-in control method and the proportional-integral-derivative control method, respectively. Randomizing parameters in the physics engine of the digital twin during training allowed the method to simulate the imprecise motions of an actual degraded robot manipulator, facilitating the development of a more robust policy. Notably, our method has the potential to be applicable to all types of articulated robots, and presents a promising solution for maintaining performance while reducing long-term costs.

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & 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.)

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office 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.)

The drum water level plays a crucial role in the safety and economy of heat recovery boilers. However, the control of the drum water level faces many challenges, such as external disturbances and system uncertainties. To enhance the control performance of the drum water level, a modified active disturbance rejection control (MADRC) optimized with sensitivity constraint is proposed in this paper. Firstly, the control structure of the three-element control system for the drum water level is introduced and analyzed. Based on the regular active disturbance rejection control (ADRC) structure, the structure of the MADRC is introduced and the convergence of the proposed MADRC is proven. Then a modified whale optimization algorithm (MWOA) with sensitivity constraint is applied to optimize the parameters of the MADRC. With different sensitivity constraints, the parameters of the MADRC and comparative controllers are obtained, and their control performance for tracking and disturbance rejection abilities is compared. Moreover, the ability to handle system uncertainties is analyzed. Simulation results and performance indexes show that the proposed MADRC can obtain the best tracking and disturbance rejection abilities with satisfactory robustness. The satisfactory control performance shows that the proposed MADRC has wide application potential for heat recovery boilers and other industrial processes.

This paper presents a comprehensive performance assessment of a two-stage power electronic (PE) converter for interfacing the grid of a lithium-ion battery energy storage system (Li-BESS) for building-integrated PV (BIPV) applications. A performance assessment of the control system was conducted for the two-stage PE interface with a common DC-link, which consisted of a bi-directional boost converter with a cascaded PI controller and an AC/DC converter with proportional-integral (PI) and proportional-resonant (PR) controllers. The assessment covered loss analysis and useful lifetime estimation for the 10 kW PE interface with a wide-bandgap SiC power MOSFET at different loads for both the charging and discharging modes of a 50 kWh lithium-ion battery system. Additionally, a performance comparison of various switching frequencies was performed. It was observed that the system was stable up to a switching frequency of 30 kHz, and that increasing the switching frequency improved the responsiveness of the converter by decreasing the settling time; however, there were diminishing returns at higher switching frequencies. To obtain a proper balance between responsiveness and lower loss, a switching frequency of 10 kHz was selected. [ABSTRACT FROM AUTHOR]

For a stochastic PID feedback control system, the uncertainty of the working environment often leads to the unsatisfied performance of the system, which does not meet the profit requirements. The working environment generally includes external disturbance and measurement noise, etc. Gaussian distributed measurement noise and disturbances are widely considered while non-Gaussian distributed measurement noise and disturbances are rarely considered. In this paper, the performance degradation of Gaussian/non-Gaussian disturbances and measurement noise on a stochastic PID feedback system is considered and analyzed. An efficient method, dynamic data reconciliation (DDR) is developed to filter measurement noise and disturbances and improve the performance of the stochastic PID feedback control system. By utilizing model-based and measured information, DDR avoids time delays in output estimation. With the detailed theoretical analysis and simulation verification, the effectiveness of the proposed DDR technology on the stochastic PID feedback control system is verified. Compared with conventional exponential filters, DDR can achieve better control performance. The proposed DDR is also used for the control system of the DC–AC​ converter. The improved effect of DDR on the output quality is demonstrated by the results. • Effect of Gaussian/non-Gaussian disturbances on control performances is analyzed. • Dynamic data reconciliation (DDR) is developed to enhance control performances. • DDR corrects measurements with Gaussian/non-Gaussian disturbances and noises. • SISO, MIMO, and DC–AC converter control systems are used for verification. [ABSTRACT FROM AUTHOR]

The changes in tire pressure will cause braking force to significantly vary due to the change in the tire-to-road contact during hard braking. The most important reason of this issue is the changes in road contact because of the changes in the vertical stiffness and slip stiffness of tire, as tire pressure varies. Therefore, in this study, it was aimed to investigate the effects of the tire pressure on anti-lock brake system (ABS) control performance through vertical and slip stiffness of tire. For this, first, the friction coefficient extended to tire pressure was integrated into the braking dynamics equations using the magic tire model. In this way, the effects of tire pressure were analytically revealed on braking performance. Then, taking into account the theoretical results, ABS braking tests were carried out with three different tire pressures: higher (38 psi) and lower (25 psi) tire pressure than the nominal (33 psi) tire pressure. In experimental studies, tests were carried out for braking initial speeds 30 and 60 km/h with the same tire pressures in µ-jump road conditions. In this way, the effects of the tire pressure were experimentally investigated on control performance of ABS under critical road conditions. At 33 psi tire pressure, the highest brake pressure was observed when switching to wet roads. At 25 psi tire pressure, the brake pressure did not build up in time. This showed that low tire pressure causes brake pressure to increase with a delay. On the slippery part, the lock-up limit is closer at 38 psi tire pressure. Therefore, it was seen that the decrease and increase in tire pressure have great effect on control performance of ABS under µ-jump road conditions. [ABSTRACT FROM AUTHOR]

Counterbalance valves (CBVs) are broadly applied in hydraulic manipulators, which is essential to ensure safe operation while moving a heavy load. They inevitably introduce additional energy consumption and poor dynamic performance. For the manipulator joint in tunnel boring machines, smooth and precise motion control has to be realized. However, for the forward design considerations, in this case, no systematic work has been done to determine the component parameters based on an energy-saving approach and to derive the natural frequency of the joint at the hydraulic level. To fill this gap, this paper proposes a forward design approach for the proportional valve-controlled hydraulic cylinder system containing CBVs, which is a basic hydraulic configuration adopted for the manipulator joint. Specifically, the optimization model aiming at the minimum energy consumption is defined and improved to solve the key parameters, including the pilot ratio of the CBV and the area ratio of the cylinder. By considering constraints, the other component parameters could be further calculated. After that, the theoretical derivation of natural frequency is given to evaluate the response capability of the system. The overall design procedure is presented to determine the cylinder, CBV, control valve, and constant pressure supply. Based on the validated numerical model, the energy-based design principle is proven effective and could ensure that energy saving is not less than 5% and not more than 36% on average. Furthermore, the natural frequency obtained by the sweep test is verified to be consistent with the theoretical value, and the impact of this parameter on control performance is analyzed. The results indicate that the proposed approach has an excellent guide for the forward design of such systems. [ABSTRACT FROM AUTHOR]

Summary: This paper studies attack detection and security analysis for cyber‐physical systems from the viewpoint of control performance. The performance residual generated by Bellman equation has been presented to construct the attack detector. Then, the control‐performance‐based attack detection schemes are designed for state measurable system and state unmeasurable system, respectively. Furthermore, the data‐driven realizations of control‐performance‐based attack detection are presented via kernel identification. Moreover, the security analysis of the proposed control‐performance‐based attack detection schemes is studied, in which the undetectable state and output attacks are designed. Finally, simulations on the model of a flight vehicle demonstrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Fractional order PID (FOPID) has received much attention in recent years and has been applied in different fields. However, the parameter tuning of FOPID is a tough problem. In order to design an optimal FOPID controller, a parameter tuning method based on minimum variance control (MVC) rule is proposed in both SISO and MIMO control systems Considering the influence of measurement noise with Gaussian and non-Gaussian distribution, which is generally ignored in the controller design based on MVC rule, this paper applies dynamic data reconciliation (DDR) technology to suppress its influence and improve the control performance of the designed FOPID. In the case of considering Gaussian and non-Gaussian distributed measurement noise, SISO and MIMO control systems are employed to verify the effectiveness of the proposed FOPID parameter tuning and DDR method. The results show that the designed FOPID improves the performance of the control system, and the DDR technology suppresses the negative effect of measurement noise and improves the control performance of the designed FOPID. • A minimum variance control (MVC) rule is used to design the parameters of FOPID. • An efficient DDR formulation is derived and used in the MVC based FOPID. • The DDR is feasible for measurement noise with a Gaussian or non-Gaussian distribution. • The effectiveness of FOPID design and DDR is demonstrated through the simulations. [ABSTRACT FROM AUTHOR]

Most industrial processes are regulated using PID control. However, many such processes often operate far from optimally because PID may not be the most suitable control method. Moreover, second-order models represent a large class of all controlled systems. This work studies the performance of some commonly used industrial PID controllers relative to MPC to understand when it is more suitable to use Model predictive control. MPC is used for this comparison because it has been the most successful industrial controller after PID. It can be concluded from the studies that improved performance can be achieved with MPC, even for modest dead time and when the damping ratio is relatively low. These improvements are prominent for dead-time dominant systems, whose dead-time to time-constant ratio is at least three. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive performance assessment of a two-stage power electronic (PE) converter for interfacing the grid of a lithium-ion battery energy storage system (Li-BESS) for building-integrated PV (BIPV) applications. A performance assessment of the control system was conducted for the two-stage PE interface with a common DC-link, which consisted of a bi-directional boost converter with a cascaded PI controller and an AC/DC converter with proportional-integral (PI) and proportional-resonant (PR) controllers. The assessment covered loss analysis and useful lifetime estimation for the 10 kW PE interface with a wide-bandgap SiC power MOSFET at different loads for both the charging and discharging modes of a 50 kWh lithium-ion battery system. Additionally, a performance comparison of various switching frequencies was performed. It was observed that the system was stable up to a switching frequency of 30 kHz, and that increasing the switching frequency improved the responsiveness of the converter by decreasing the settling time; however, there were diminishing returns at higher switching frequencies. To obtain a proper balance between responsiveness and lower loss, a switching frequency of 10 kHz was selected.

A tuned mass damper is a kind of vibration damping device which has been widely used in tall buildings, machinery, bridges, aerospace engineering and other fields. In practical engineering applications, due to large deformation caused by large displacement, errors in engineering constructions and the existence of limit devices, the structure and tuned mass dampers inevitably produce some nonlinear characteristics, but these nonlinearities are often ignored. The results of this study confirm that the nonlinearity of the structure and the mass damper should be considered in the process of optimal frequency design, otherwise there will be a large deviation between the design optimal frequency of the mass damper and the actual optimal frequency. In this paper, nonlinear characteristics of the tuned mass damper and the main structure are considered. The first-order differential equations are obtained by using the complex average method, and the nonlinear equations of the tuned mass damper system are derived by using the multi-scale method. On this basis, the parameters are determined. The numerical results show that the error of the approximate solution method is small in the given example. The nonlinear tuned mass damper with nonlinear design exhibits a better control performance [ABSTRACT FROM AUTHOR]

The article presents the virtual experimentation of a closed circuit hydrotronic transmission that aims at the precise control of an angular displacement with the help of a semi-rotary hydraulic actuator, experimentation performed by using Simcenter Amesim numerical simulation software. Such position control systems are often used in industry; such a system is suitable and can be used to control the pitch angle of the blades of a wind turbine. The article deals extensively with the control capabilities of a hydrotronic transmission. Combining highperformance hydraulic components with sensors and a PID controller - components of a hydrotronic transmission - the result is an energy-efficient transmission, with outstanding control capabilities. [ABSTRACT FROM AUTHOR]

The tunable approximated explicit model predictive control (MPC) comes with the benefits of real-time tunability without the necessity of solving the optimization problem online. This paper provides a novel self-tunable control policy that does not require any interventions of the control engineer during operation in order to retune the controller subject to the changed working conditions. Based on the current operating conditions, the autonomous tuning parameter scales the control input using linear interpolation between the boundary optimal control actions. The adjustment of the tuning parameter depends on the current reference value, which makes this strategy suitable for reference tracking problems. Furthermore, a novel technique for scaling the tuning parameter is proposed. This extension provides to exploit different ranges of the tuning parameter assigned to specified operating conditions. The self-tunable explicit MPC was implemented on a laboratory heat exchanger with nonlinear and asymmetric behavior. The asymmetric behavior of the plant was compensated by tuning the controller's aggressiveness, as the negative or positive sign of reference change was considered in the tuning procedure. The designed self-tunable controller improved control performance by decreasing sum-of-squared control error, maximal overshoots/undershoots, and settling time compared to the conventional control strategy based on a single (non-tunable) controller. • Self-tunable control technique does not need any intervention during control. • Tuning based on operating conditions compensates for the nonlinear plant behavior. • Implementation of the proposed tuning method on a laboratory heat exchanger. • Control performance improved compared to utilizing explicit MPC with constant setup. [ABSTRACT FROM AUTHOR]

In the paper, the Linear–Quadratic–Gaussian (LQG) control strategy in regulatory mode (disturbance attenuation, zero value of the reference signal) in single-loop control is used to stabilize the system equipped in a non-integer order plant. The influence of the optimal controller design sophistication on control quality in terms of output variance is examined. It has been shown that the optimal implementation length of fractional-order difference is relatively low (several dozen in considered examples). Therefore, further increasing the controller's complexity in terms of approximation length does not improve the control performance. Furthermore, it is presented that, under bounded control signal variance, the optimal fractional order of the controller may be significantly different from the actual fractional order of the plant (in the examples, the difference is up to 0.66). [ABSTRACT FROM AUTHOR]

In the forthcoming era of the Tactile Internet, haptic communication is foreseen as one of its major use cases with impact in manufacturing, healthcare, education, as well as the service industry. Recent efforts in networking attempt to meet the requirements of such use cases providing the latency and reliability for bilateral teleoperation, the main component of haptic communication. However, the impact of changes in latency on bilateral teleoperation system performance varies among different control schemes and is dependent on the application domain. Furthermore, while recent efforts to reduce latency in wireless communication with tailored configurations have been successful, an increasing number of haptic communication flows could potentially compete when sharing network resources. In this paper, we provide a tractable model for teleoperation system performance that captures the impact of latency on different performance criteria. We then use this performance model to shape queuing prioritisation of different traffic flows. The proposed framework considers the requirements of high and low priority flows to suggest the best possible control scheme option to be used by the high priority one and at the same time keep the impact of the network scheduling discipline on the low priority one at minimum.

Online parameter estimation of permanent magnet synchronous machines is critical for improving their control performance and operational reliability. This paper provides an overview of the recent achievements of online parameter estimation of PMSMs with examples. The critical issues in parameter estimation are firstly analysed, especially the rank-deficient issue and inverter nonlinearities. Then, the state-of-the-art online parameter estimation modelling techniques are reviewed and assessed. Finally, some typical applications and examples are outlined, e.g. estimation of mechanical parameters, improvement of sensored and sensorless control performance, thermal condition monitoring, and fault diagnosis, together with future research trends.

Most industrial processes are regulated using PID control. However, many such processes often operate far from optimally because PID may not be the most suitable control method. Moreover, second-order models represent a large class of all controlled systems. This work studies the performance of some commonly used industrial PID controllers relative to MPC to understand when it is more suitable to use Model predictive control. MPC is used for this comparison because it has been the most successful industrial controller after PID. It can be concluded from the studies that improved performance can be achieved with MPC, even for modest dead time and when the damping ratio is relatively low. These improvements are prominent for dead-time dominant systems, whose dead-time to time-constant ratio is at least three.

This article presents a model-based hybrid adaptive dynamic programming (ADP) framework consisting of continuous feedback-based policy evaluation and policy improvement steps as well as an intermittent policy implementation procedure. This results in an intermittent ADP with a quantifiable performance and guaranteed closed-loop stability of the equilibrium point. To investigate the effect of aperiodic sampling on the communication bandwidth and the control performance of the intermittent ADP algorithms, we use a Hamiltonian-driven unified framework. With such a framework, it is shown that there is a tradeoff between the communication burden and the control performance. We finally show that the developed policies exhibit Zeno-free behaviors. Simulation examples show the efficiency of the proposed framework along with quantifiable comparisons of the policies with different intermittent information. [ABSTRACT FROM AUTHOR]

This paper presents a generic robust controller that allows applications in various quadrotor unmanned aerial vehicle (UAV) systems effectively even when facing severe system uncertainties and unknown external disturbances. The fractional-order linear active disturbance rejection control (FOLADRC) scheme has combined the advantages of the fractional-order PID (FOPID) with the linear active disturbance rejection control (LADRC). Firstly, the structure of the FOLADRC-based quadrotor UAV is designed. Then, considering the difficulty of parameter tuning of FOLADRC and the demand for accuracy and rapidity of the controller, the improved sparrow search algorithm is applied. Finally, to illustrate the robustness and effectiveness of FOLADRC, the FOLADRC-based quadrotor UAV is firstly compared with PID and LADRC. The simulation and experiment results show that the FOLADRC method can suppress the influence of system uncertainties and external disturbance effectively, where the superiority compared to PID and LADRC has been demonstrated clearly.

This brief investigates the problem of denial-of-service (DoS) attacks against linear quadratic regulator (LQR) control channels. Owing to energy constraints, the attacker can only launch consecutive DoS attacks with a certain length $m$ to block communication channels between the controller and actuator. We consider two compensation strategies commonly found in the literature, namely, zero-input and hold-input when control packets are blocked. It is shown that jamming from the initial instant is not always optimal for attackers. Necessary and sufficient conditions are given to ensure the optimality of blocking from the initial instant despite the randomness of initial states. In the case where attackers know the initial state, a finite-interval search method is given to obtain the optimal starting instant of DoS attacks. Numerical examples illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

The H-infinity optimal parameters of a pre-tensioned tuned mass damper are derived to overcome the great amplitude of un-damped primary structure vibrations under harmonic excitation. In this case, damping, mass, and stiffness elements are connected directly to the ground. The two fixed points approach is used to optimize analytically frequency response function, damping ratio and pre-tensioned stiffness coefficient. The optimum pre-tensioned spring is used to keep more the stability of structure according to the principle of preload elastic device properties. Finally, the mitigation of resonance oscillation amplitude of the primary structure using the proposed dynamic absorber is compared with the traditional one. Under conditions of optimal control performance, it is proved analytically that the proposed vibration absorber with pre-tensioned stiffness provides well attenuation in the resonant vibration range. Adding, this device can be also broadening the efficient frequency range of vibration. [ABSTRACT FROM AUTHOR]

In the paper, the Linear–Quadratic–Gaussian (LQG) control strategy in regulatory mode (disturbance attenuation, zero value of the reference signal) in single-loop control is used to stabilize the system equipped in a non-integer order plant. The influence of the optimal controller design sophistication on control quality in terms of output variance is examined. It has been shown that the optimal implementation length of fractional-order difference is relatively low (several dozen in considered examples). Therefore, further increasing the controller’s complexity in terms of approximation length does not improve the control performance. Furthermore, it is presented that, under bounded control signal variance, the optimal fractional order of the controller may be significantly different from the actual fractional order of the plant (in the examples, the difference is up to 0.66).

This study investigates the adaptive fault‐tolerate control for strict‐feedback non‐linear system, in which actuator and sensor faults may happen simultaneously. Moreover, the additive and multiplicative faults are considered, which cover the bias, drift, loss of accuracy, and loss of effectiveness faults. Under the multiple sensor faults, a modified backstepping technique involving in the faulted states is proposed by utilising the fuzzy approximation to the unknown non‐linear functions. Later, the adaptive fuzzy fault‐tolerant control strategy is designed to ensure the practical fixed‐time stability of the closed‐loop system. Meanwhile, the convergence time is independent of the initial states of the system, and the control performance can be ensured for arbitrary bounded initial states in this study. Finally, the Buck converter circuit is employed to demonstrate the effectiveness of the proposed fault‐tolerant control scheme. [ABSTRACT FROM AUTHOR]

Studies show that finite control set model predictive control (FCS MPC) is robust for single‐phase inverters in sinusoidal current tracking. That is, even if there are parameter uncertainties in inverter system, MPC can achieve accepted control performance. However, it is still necessary to reconstruct the unknown parameters. On the one hand, an accurate model is helpful to get better performance. On the other hand, accurate parameters can be used to determine the boundary of current reference. Relying on the strong robustness, under unknown offset free MPC (UOF MPC) frame, this study characterises the deviation of the parameters as an unknown sinusoidal signal, and designs two observers to reconstruct it. One is a linear observer for instantaneous value observation. The other is a time‐varying observer for the amplitude and phase identification. Its convergence is guaranteed by the Lyapunov function and the Laselle invariant set principle. All the proposed methods are validated by a rapid control prototype based on Labview FPGA platform. Moreover, experiments show that even if the reference exceeds the real maximum tracking current boundary, the proposed observers work well with accurate parameters identified and the reference can be adjusted online to avoid distorted current tracking. [ABSTRACT FROM AUTHOR]

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In this study, a DC micro-grid consisting of multiple paralleled energy resources interfaced by both bidirectional AC/DC and DC/DC boost converters and loaded by a constant power load (CPL) is investigated. By considering the generic dq transformation of the AC/DC converters' dynamics and the accurate nonlinear model of the DC/DC converters, two novel control schemes are presented for each converter-interfaced unit to guarantee load voltage regulation, power sharing and closed-loop system stability. This novel framework incorporates the widely adopted droop control and using input-to-state stability theory, it is proven that each converter guarantees a desired current limitation without the need for cascaded control and saturation blocks. Sufficient conditions to ensure closed-loop system stability are analytically obtained and tested for different operation scenarios. The system stability is further analysed from a graphical perspective, providing valuable insights of the CPL's influence onto the system performance and stability. The proposed control performance and the theoretical analysis are first validated by simulating a three-phase AC/DC converter in parallel with a bidirectional DC/DC boost converter feeding a CPL in comparison with the cascaded PI control technique. Finally, experimental results are also provided to demonstrate the effectiveness of the proposed control approach on a real testbed.

In order to improve the control performance of the valve-controlled asymmetric cylinder system with negative overlap, it is proposed that the complex nonlinear system is transformed into a linear system based on the neural network inverse system. The structure of the inverse system is been constructed by the state model of the system, and optimised by adding state parameter feedback. So the pseudo-linear system is reduced to second order. An improved back-propagation neural network based on a genetic algorithm is used to solve the inverse model. Aiming at the problem of negative overlap of servo valves and laminar and turbulent flow, the sectional inverse system switched by reference speed is established to improve the accuracy of the inverse system model. For pseudo-linear systems, an internal model controller is designed to improve the control performance of the composite system. The proportion–integration–differentiation and the internal model control (IMC) of the sectional inverse system are compared with that of AMESIM and Simulink joint platform. The results show that the system controlled by the IMC of the sectional inverse system has better response performance, eliminates the asymmetric characteristics in extending and retracting motion response and is less affected by load fluctuation.

The inability of the coal mill control structure to monitor and control pulverized coal flow causes operational and environmental problems. The research was done to design the new control structure for coal mill in coal firing system to achieve an improvement on control system performance compared to the existing control structure. Cascade control, blend station, and feedback control was used to control the flow of coal, the flow of primary air, and temperature of the pulverized coal. The result of the evaluation shows that the new control structure capable of fulfilling all the control objectives applied to it. Implementation of the new control structure capable to make the step response of the coal mill to have an average settling time at 161.75 seconds with 0% overshoot. The new control structure also capable to make the pulverized coal fineness at the range of 70% to 75% and moisture content at the range of 2.18% to 2.28%. The result of the evaluation makes the control performance of the new control structure is better than the previous coal mill control structure.

There are mechanical coupling interference and hydraulic coupling interference in the vehicle wheel bridge simulation loading system based on secondary regulation, which can cause the control accuracy of the system to decrease obviously and seriously affect the control performance of the system. In order to eliminate the coupling interference between systems, two decoupling methods are proposed, one way to do this is to join the decoupling element, and the other is to join the robust compensator. The simulation results show that the decoupling control of decoupling element has a good decoupling effect on mechanical coupling, but it has no effect on hydraulic coupling. Robust decoupling control has a good decoupling effect on mechanical coupling and hydraulic coupling.

The relief valve overflowing energy loss is considered impossible to solve. This paper proposes a new type of proportional relief valve (PRV) with a hydraulic energy regeneration unit (HERU) connected to its outlet. The mathematical model of the proposed PRV is set up, and its stability is analyzed. A control strategy is put forward for designing the working modes which are based on the pressure of the hydraulic accumulator. The simulation model and the test rig, where a hydraulic accumulator is used as a HERU, are established to verify the effectiveness of the control strategy and energy savings of the proposed PRV. The results show that the system can switch among energy regeneration, energy release, and traditional modes according to the hydraulic accumulator pressure, indicating that the proposed control strategy works well. During the energy regeneration mode, the hydraulic accumulator is charged and the PRV inlet pressure decreases only slightly, indicating the HERU has little influence on the PRV working performance. During the energy release mode, the hydraulic accumulator is discharged and the PRV inlet pressure increases to its preset value. Both during the regeneration and release modes, the driving electric motor consumed less energy. Higher hydraulic accumulator pre-charging pressure can achieve higher energy regeneration efficiency, whereas lower hydraulic accumulator pre-charging pressure can regenerate more overflowing energy.

Actuator rate limit phenomenon is ubiquitous in control systems, but it has always been neglected in practical engineering. Especially, few papers are published to investigate the system identification while considering the rate limit. Step function is commonly used in parameter estimation and its first‐order derivative at the step time goes to infinity, which is not affordable by real actuators. As a result, the rate limit slows down the system response speed, misleads the parameter identification, and subsequently affects the controller design and deteriorates the control performance. This study proposes both graphical method and curve fitting method to identify the first‐order plus time‐delay (FOPTD) systems with consideration of the actuator rate limit effect whose limit value is unknown. Quantitative analyses of the parameter mismatch in the traditional FOPTD model and parameter sensitivity analyses are also carried out. Both simulation results and experimental results have shown the necessity and feasibility of defining a new model structure which includes the rate limit value. [ABSTRACT FROM AUTHOR]