Search

The reliable operation of battery management systems depends critically on the accurate estimation of the state of charge (SOC) and characterizing parameters of a battery system. SOC estimation employs models that must be robust against variations in battery cell electrochemical features, aging, and operating conditions. This paper reveals that commonly used SOC estimation schemes are fundamentally flawed in providing the robustness of SOC estimation against model uncertainties. Parameter estimation methodologies and adaptive SOC estimation design are introduced in this paper to enhance SOC estimation accuracy and robustness. By a scrutiny of the impact of parameter variations on SOC estimation accuracy, the SOC–open-circuit-voltage mapping is identified to be the most critical function that must be accurately established. Identification algorithms are introduced, and their convergence properties are established. The integration of the identification algorithms and SOC estimation schemes lead to an adaptive SOC estimation framework that is superior over the existing methods in providing much improved accuracy and robustness. Experimental studies are conducted to validate the algorithms. [ABSTRACT FROM PUBLISHER]

This paper suggests a cascade output voltage regulation strategy for dc/dc boost converters that embeds a robust inner-loop current controller against parameter variations. The contributions of this paper are divided into two parts. The first contribution is to present a simple and robust inner-loop current controller despite parameter uncertainties, guaranteeing the stability of the whole closed-loop system including the first-order internal dynamics. The second contribution is to show that an outer-loop proportional–integral regulator can stabilize the output voltage error without relying on any parameter information. Simulations and experiments using a 3-kW dc/dc boost converter showed that the proposed method offers satisfactory closed-loop performance in the presence of parameter uncertainties. [ABSTRACT FROM PUBLISHER]

Disturbance observer (DOB) has been one of the most widely used robust control tools since it was proposed by Ohnishi in 1983. This paper introduces the origins of DOB and presents a survey of the major results on DOB-based robust control in the last 35 years. Furthermore, it explains DOB's analysis and synthesis techniques for linear and nonlinear systems by using a unified framework. In final section, this paper presents concluding remarks on DOB-based robust control and its engineering applications. [ABSTRACT FROM AUTHOR]

The predictive control method deals with the prediction of the motor behavior based on a mathematical model of the motor. This model is dependent on the motor parameters. However, these parameters may not match with their actual values due to the measurement error or they may change during the operation of the motor. All these uncertainties and model inexactitude lead to inaccurate prediction of the motor behavior and deteriorate the performance of the predictive algorithm. This paper presents an extension of the predictive current control (PCC) method to improve the prediction accuracy for a permanent-magnet synchronous motor (PMSM). The proposed strategy not only reduces the current ripple but also improves the robustness of the system against parameter uncertainties. Simulation and experimental results that confirm the good performance of the proposed method are presented. [ABSTRACT FROM PUBLISHER]

This paper presents robustness evaluation of deadbeat-direct torque and flux control (DB-DTFC) of interior permanent-magnet synchronous machine (IPMSM) drives with respect to machine parameter variation. For performance comparison, current vector control (CVC), one of the most widely used control methods, is also implemented under identical operating conditions as DB-DTFC. As the metrics to evaluate dynamic performance of DB-DTFC and CVC IPMSM drives, command tracking is used to investigate torque command tracking performance and dynamics stiffness is used to evaluate disturbance rejection performance. In addition, the torque estimation accuracy of DB-DTFC and CVC is investigated with respect to parameter variation. Simulation and experimental results of robustness evaluation of DB-DTFC and CVC are presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper presents a practical robust controller that solves the problem of accurate motion control of ultrasonic motors (USMs) over prolonged durations, where temperature increases pose a significant challenge. This paper focuses on USMs with driver circuits that have a single user-controllable input. Prior to developing the robust controller, a nonlinear model of the system was identified by experimentally measuring the temporal relationship between motor speed and temperature to the applied input control signal. A linear approximation of this model was used to design two robust inverse dynamic controllers: one used temperature feedback and the other did not. Both control methods were implemented on a custom designed embedded control system and achieved highly consistent and accurate performance while under load over a range of working frequencies. Step-response experiments (1 rad) demonstrated a rise time of 0.1 s without any overshoot or steady-state error. A normalized RMSE below 3% with a delay of 25 ms was achieved for reference inputs with frequencies up to 1 Hz. This performance was maintained during prolonged continuous dynamic operation of several minutes, despite the great variation in the motor’s dynamics due to the temperature effects (over a range of 25 °C–45 °C) and modeling uncertainties. [ABSTRACT FROM AUTHOR]

Robust fault estimation plays an important role in real-time monitoring, diagnosis, and fault-tolerance control. Accordingly, this paper aims to develop an effective fault estimation technique to simultaneously estimate the system states and the concerned faults, while minimizing the influences from process/sensor disturbances. Specifically, an augmented system is constructed by forming an augmented state vector composed of the system states and the concerned faults. Next, an unknown input observer (UIO) is designed for the augmented system by decoupling the partial disturbances and attenuating the disturbances that cannot be decoupled, leading to a simultaneous estimate of the system states and the concerned faults. In order to be close to the practical engineering situations, the process disturbances in this study are assumed not to be completely decoupled. In the first part of this paper, the existence condition of such an UIO is proposed to facilitate the fault estimation for linear systems subjected to process disturbances. In the second part, robust fault estimation techniques are addressed for Lipschitz nonlinear systems subjected to both process and sensor disturbances. The proposed technique is finally illustrated by the simulation studies of a three-shaft gas turbine engine and a single-link flexible joint robot. [ABSTRACT FROM AUTHOR]

In recent years, design and tuning of fractional-order controllers for use in motion control have attracted much attention. This paper deals with one of the interesting methods that have been recently proposed for tuning fractional-order proportional and derivative (FOPD) motion controllers. The FOPD controller tuned based on the considered method results in simultaneously meeting the desired phase margin, the desired gain crossover frequency, and the flatness of the phase Bode plot at such a frequency. Since, in this tuning method, the derivative parameter and order are determined in a graphical way, in the first view, it is not clear for which pairs of phase margin and gain crossover frequency an FOPD controller can be found to satisfy the mentioned specifications. In this paper, necessary and sufficient conditions are presented via an analytical approach to check the solution existence of the considered tuning method in both cases of absence and presence of time delay in feedback loop. Furthermore, the uniqueness of the controller parameters obtained from the method is investigated. Moreover, some numerical and experimental examples are presented to confirm the analytical results of this paper. [ABSTRACT FROM PUBLISHER]

CLLC-type dc transformer (CLLC-DCT) is very popular in the hybrid ac–dc microgrid thanks to its high-power density advantage and good bidirectional power transfer capacity. In the hybrid ac/dc microgrid, the open-loop control is always utilized by the CLLC-DCT to cooperate with the bidirectional interlinking converter to realize the power and voltage conversion between the ac and dc bus. This paper first studies the circuit parameters design of the open-loop controlled CLLC-DCT with consideration of such a realistic problem: The real inductors/capacitors values are actually different with their theoretically designed values due to the operation power and temperature variation. To solve this problem, a robust circuit parameters design scheme is proposed for the CLLC-DCT in this paper. With the proposed scheme, the designed CLLC-DCT exhibits good power transmission and voltage regulation ability in the hybrid ac/dc microgrid even when its actual inductors/capacitors values vary with the practical power and temperature. The robust design method is experimentally verified in a hybrid ac/dc microgrid prototype. [ABSTRACT FROM AUTHOR]

Due to the recent trend of the application of robots and other mechatronic devices to human life support, the force control draws more attention than ever. However, to use force sensors in all the required cases makes the system not only expensive but also bulky. Force-sensor-less power-assist control (FSPAC) which uses only encoders to obtain the external force information and provides force control performance can address this problem. Due to its simplicity and wide application, FSPAC is an essential technology to control a motor in a human-friendly way, but the design of FSPAC is different from the conventional feedback controllers so a new design methodology needs to be established. In order to attack this problem, this paper generalizes and analyzes the structure and characteristics of FSPAC. The generalized structure reveals how FSPAC can achieve the assistance, and the transfer function analysis based on the structure addresses the robustness and assistance performance evaluation problems. The robustness of FSPAC is analyzed in terms of the gain margin and robust stability, and the limitation of the power assistance to guarantee the robust stability is derived. Then, the evaluation way of feedback control design in FSPAC is provided. All the discussion in this paper provides the readers with understanding and appropriate design methodology of FSPAC. [ABSTRACT FROM PUBLISHER]

This paper describes a simple approach for model-based template matching, which is robust to undergo rotation and scaling variations. An efficient image warping scheme spiral aggregation image (SAI), which has been utilized in this paper, provides a method for generating projection profiles for matching. In addition, it determines the rotation angle and is invariant to scale changes. The proposed spiral projection algorithm (SPA) for template matching enables the simultaneous representation for each value of projection profile, obtained through SAI, and provides structural and statistical information on the template. The experimental evaluation shows that the proposed SPA achieves very attractive results for template matching in the industrial automation application. [ABSTRACT FROM PUBLISHER]

In the process industry, the key performance indicator (KPI)-related prediction and fault diagnosis are important steps to guarantee the product quality and improve economic benefits. A popular monitoring method as it has been, the partial least squares (PLS) algorithm is sensitive to outliers in training datasets, and cannot efficiently distinguish faults related to KPI from those unrelated to KPI due to its oblique projection to the input space. In this paper, a novel robust data-driven approach, named advanced partial least squares (APLS), is presented to handle process outliers under an improved framework of PLS. By means of a weighting strategy, APLS can remove the impact of outliers on process measurements and establish a more accurate model than PLS for fault diagnosis in the monitoring scheme, whose effectiveness has been verified through the Tennessee Eastman (TE) benchmark process. Simulation results demonstrate that the proposed approach is suitable not only for the KPI-related process prediction but also for the diagnosis of KPI-related faults. [ABSTRACT FROM AUTHOR]

This paper proposes a novel motion reproduction method based on environmental disturbance (EnvDs) compensation. The preservation of skillful techniques is an important issue. Although the motion-copying system (MCS) was proposed to deal with this problem, a clear strategy still does not exist for adapting to the environmental variances between the motion saving and reproduction phases. Conventional methods cannot adapt to the difference properly because their control systems are just one-degree-of-freedom (DOF) control systems. In this paper, variances were defined as EnvDs, and the effect on the MCS was demonstrated. A 2-DOF control system structure was developed to compensate for EnvDs. The effectiveness of the proposed system was demonstrated through analysis and experimental results. [ABSTRACT FROM PUBLISHER]

The purpose of this paper is to comment on the reference voltage tracking ability of a recently proposed state observer based adaptive sliding mode control for boost converters. It is shown that the control in the cited paper cannot track the reference voltage. A modified control law that enables reference voltage tracking while preserving the other advantages of the commented paper is proposed and validated by simulation and experimentation on laboratory hardware. [ABSTRACT FROM PUBLISHER]

This paper analyzes a disturbance observer with a focus on parameter variations. The parameter variations are the inertia variation and the variation of torque coefficient. Conventionally, their nominal values are designed not as control parameters but the same values as the actual ones. However, disturbance observer is able to include the effect of phase compensation by properly selecting the nominal model parameters. In this paper, these nominal model parameters are actively designed to achieve the phase compensation. This paper proposes the design method of observer to achieve phase compensation based on disturbance observer. Compared with implementing phase compensator, the control system is simple and easy to design. The selection of these parameters has some restriction. When the nominal model parameters are much separated from the actual ones, the stability of the control system deteriorates. This paper focuses on the inertia variation and neglects the variation of torque coefficient. Furthermore, the stability of position and force control systems is analyzed. The validity of the proposed design method and the effect of phase compensation are verified by some experimental results. [ABSTRACT FROM AUTHOR]

Controlling robots in contact with the environment is an important problem in industry applications. In the conventional force control, much research has paid attention to develop novel force control systems and implemented force sensors to detect external force. This paper shows that narrow bandwidth of force sensor has a big influence on the force control system. Generally, to solve the instability in force control, the velocity feedback gain is enlarged. The system becomes unstable with small velocity feedback gain, and robot's response becomes slow with large one. Inasmuch as there is a tradeoff between the stability and the response, it is considered that force control by robots is difficult. This paper proposes a force control system with disturbance observer. It is possible to obtain the force information with wide bandwidth by using the disturbance observer. This paper shows that bandwidth of force sensing is very important for contact motion control. By using the wide bandwidth of force sensing, both stability and response are improved. Furthermore, force control is attainable by the construction of the easiest force control architecture. Therefore, the ideal zero-stiffness-force control is attained. The numerical and experimental results show viability of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a practical discrete-time fractional order terminal sliding mode (DFOTSM) control strategy for high-precision tracking tasks based on a linear motor. In particular, the practical parametric uncertainties involving sliding friction, uncertain payload, and disturbance in tracking tasks are considered in this paper. Combining Grünwald–Letnikov fractional order definition and terminal sliding mode technique, the proposed method synthesizes a novel DFOTSM control law to drive the sliding mode dynamics into the stable region in finite steps theoretically, even though the system is suffering from uncertainties and disturbances, and the motion on the surface can guarantee higher tracking precision than the conventional discrete-time terminal sliding surface by selecting suitable controller parameters. The theoretical analyses give out the guideline of parameter selection, and experiments are carried out on the linear-motor-based test platform to demonstrate that the proposed controller is easily implemented and can achieve high-precision tracking, fast response, and considerable robustness to uncertainties. [ABSTRACT FROM AUTHOR]

This paper presents a robust observer–controller scheme for sensor fault-resilient control in dc servomotor drive-based applications (such as antennae control for satellite tracking, radio telescopes, and conveyor belt systems). In contrast to the earlier works on abrupt faults, this paper considers incipient sensor faults and detects using the higher order sliding mode (HOSM) observer, followed by a tracking controller, which maintains the acceptable drive performance. A robust output tracking controller based on fractional integral terminal sliding mode surface with HOSM terms is developed to ensure faster and finite-time convergence of the error trajectory. Moreover, various slopes of incipient faults are considered to analyze the detection delay, and switching strategy reconfigures the system with the estimated speed whenever the residual crosses the threshold. The closed-loop performance in the presence of most common faults (abrupt, incipient, and intermittent) is experimentally validated on a dc motor-based industrial mechatronic drives unit with belt-drive inertial load (which exhibits nonlinear friction, torque variations, and other disturbances). [ABSTRACT FROM PUBLISHER]

In this paper, we design a linear time-invariant two-input-two-output controller for the permanent magnet synchronous motor (PMSM). First, the nonlinear system of a PMSM is approximated using a linear system with structured uncertainties according to the geometric structures of PMSM. We then design a linear controller for the approximated linear system using a standard $\mu$-synthesis robust control method. The main contribution of this paper is that we recognize that the nonlinear PMSM can be reduced to a linear system to apply the mature modern control theory, without referring to classical PID control, thus largely reducing the design effort. The newly designed robust controller is not only easy to calculate, it is also easy to implement and requires less sensors. By virtue of modern robust control theory, it responds fast to exogenous inputs, and robust against parameter uncertainties as well. The applicability of the designed robust controller is both numerically simulated and experimentally verified on a TMS320 F28335 based control board, with performance further compared with the widely used field-oriented controller. [ABSTRACT FROM PUBLISHER]

This paper deals with the problem of pose estimation (or motion estimation) for multirotor unmanned aerial vehicles (UAVs) by using only an off-board camera. An extended Kalman filter (EKF) is often adopted to solve this problem. However, the accuracy and robustness of an EKF are limited partly by the usage of an existing linear constant-velocity process model applicable to many rigid objects. For such a reason, a nonlinear constant-velocity process model featured with the characteristics of multirotor UAVs is proposed in this paper, the superiority of which is explained from the perspective of observability. With the new process model and a generic camera model, a practical EKF method suitable for conventional cameras and fish-eye cameras is then proposed. By taking EKF implementation into account, a general correspondence method that could handle any number of feature points is further designed. Simulation and real experiments show that the proposed EKF method is more robust against noise and occlusion than currently employed filtering methods. [ABSTRACT FROM PUBLISHER]

This paper addresses the problem of preserving the nominal performance of a conventional cascade controller for electric motor drives in the presence of parameter uncertainties and external disturbances. Practical reduced-order proportional-integral (PI) observers are incorporated with predesigned PI controllers in order to enhance the robust performance of current and speed controllers. A unified analysis based on the singular perturbation theory is presented to confirm the desired approximation of the augmented system with the PI observers to the nominal closed-loop system. The validity of the proposed dual observer-based control scheme is tested via computer simulations and experiments using a dc motor system. Both results verify that the proposed controller can be used effectively to recover the nominal performance of the conventional cascade scheme for electric motor drives. [ABSTRACT FROM PUBLISHER]

This paper presents a robust input–output linearization controller as maximum power point tracking (MPPT) technique in a photovoltaic (PV) buck dc–dc converter with applications to dc microgrids, solar vehicles, or stand-alone systems. Due to the control structure proposed in this paper, the MPPT control system is able to track very fast irradiance changes. Meanwhile, the internal stability of the overall closed-loop system is guaranteed for different load scenarios. A sector condition is only required for the load current, which is satisfied for most of the current PV applications. In turn, this condition implies the robustness against oscillations in the dc bus voltage. Finally, the MPPT control system is validated through experimental results, where the closed-loop performance is evaluated under abrupt irradiance and set-point changes, parametric uncertainty, and dc bus load variations. [ABSTRACT FROM PUBLISHER]

This paper analyzes the robustness and stability of disturbance observer (DOb)-based explicit force control systems. Conventional analysis methods, which only consider ideal robustness, are impractical due to the design constraints of a DOb, e.g., bandwidth limitations. This paper shows that not only the stability but also the robustness of a DOb-based explicit force control system changes by environmental impedance variations. The robustness of a DOb-based explicit force control system is clarified by deriving new sensitivity functions. Implicit and explicit environmental impedance estimation methods are considered by analyzing the dynamics of a force sensor and a reaction force observer (RFOb), respectively. It is shown that the stability and performance of an explicit force control system can be improved by using an explicit environmental impedance estimation method, i.e., an RFOb, intrinsically. However, an RFOb is more sensitive than a force sensor to external disturbances, and the stability of the explicit force control system drastically changes by the design parameters of a DOb and an RFOb. Force-sensor- and RFOb-based explicit robust force control systems are compared in terms of stability, robustness, and performance in detail. The validity of the proposals is verified by simulation and experimental results. [ABSTRACT FROM PUBLISHER]

This paper presents a control design method for motion control in a global coordinate system of an oscillatory-base manipulator, which can be regarded as a model system of mechanical systems installed on vessels or oceanic structures. This paper proposes a control design method for such systems exploiting \calH\infty control and proportional and derivative (PD) control. In order to evaluate the proposed method, tracking control simulations and experiments were conducted for both attitude control and position control with practical constraints such as sensor error and actuator saturation. Furthermore, the proposed controller was compared with a conventional proportional, integral, and derivative (PID) controller. The results demonstrate that the proposed controller is successfully effective and is superior to the PID controller. Moreover, robust control experiments and robust stability analyses using our proposed machinery show that the proposed controller has strong robustness against physical parametric perturbations. Our developed robust stability analysis machinery is based on the state-dependent coefficient form and applicable to a wider class of systems than the previous one. [ABSTRACT FROM PUBLISHER]

The proportional-integral-derivative (PID) controller is a widely used controller in automation industries. Several advanced PID tuning/design methods, such as response-based design, internal model control, and controller optimization by stochastic algorithms, have been proposed in the literature. However, regardless of the advantages and accuracy of developed tuning methods, due to the process modeling error and parametric uncertainties, the experimental response always differs from the theoretical response, which required online fine-tuning of the PID parameter. Manual adjustment of three PID parameters disturbs the robustness of the controller from its desired value; also, it does not guarantee the stability of the process. Therefore, this paper focuses on online PID controller tuning with the guaranteed robustness of the controller. A new single variable tuning method is developed for the online robustness and performance adjustment. Moreover, the proposed rules only depend upon the previously optimized PID parameters. The proposed method is an additional feature to all existing PID tuning methods, including optimal PID controller with stochastic optimization algorithms. The proposed method is validated with the help of optimal PID controller design by existing optimal tuning rules, optimized PID with particle swarm optimization and experimental validation on the canonical tank system. [ABSTRACT FROM AUTHOR]

This paper presents a novel voltage regulator design methodology for a three-phase voltage source inverter with uncertain load dynamics. Different from existing literature, the load is treated as a dynamic uncertainty and a robust optimal state-feedback controller is proposed through the integration of optimal output regulation theory and backstepping method. To avoid sensing the inductor current, an output-feedback control scheme is developed as well. Stability of the inverter–load system is rigorously analyzed via the small-gain techniques. It is ensured that the tracking error asymptotically converges to zero through both the proposed state-feedback and output-feedback controllers. A standard proportional resonant controller is also designed for the purpose of comparison. It is shown that the proposed controller has inherent robustness and does not require retuning with different applications. The controller design method is generalized for grid-tie applications, since the grid can be regarded as a stable load system. Simulations and experimental results show the effectiveness of the control approaches. [ABSTRACT FROM AUTHOR]

Dimension reduction is a fundamental task of machine learning and computer vision, which is widely used in a variety of industrial applications. Over past decades, a lot of unsupervised and supervised algorithms have been proposed. However, few of them can automatically determine the feature dimension that could be adaptive to different data distributions. To obtain a good performance, it is popular to seek the optimal dimension by exhaustively enumerating some possible values. Clearly, such a scheme is ad hoc and computationally extensive. Therefore, a method which can automatically estimate the feature dimension in an efficient and principled manner is of significant practical and theoretical value. In this paper, we propose a novel supervised subspace learning method called multiple marginal Fisher analysis (MMFA), which can automatically estimate the feature dimension. By maxing the interclass separability among marginal points while minimizing within-class scatter, MMFA obtains low-dimensional representations with outstanding discriminative properties. Extensive experiments show that MMFA not only outperforms other algorithms on clean data, but also show robustness on corrupted and disguised data. [ABSTRACT FROM AUTHOR]

The magnetic suspension system of a low-speed maglev train is presented in this paper. The design and realization of the magnetic suspension controller are discussed, and a nonlinear mathematical model of the magnetic suspension system is built. Then, the proportion integration differentiation controller is investigated, which indicates that it is sensitive to disturbances. To reject the disturbance and parameter perturbations, an adaptive neural-fuzzy sliding mode controller is presented, which employs a sliding mode control, adaptive-fuzzy approximator, and the neural-fuzzy switching law. The sufficient simulation and experimental results are included to demonstrate that the presented robust controller significantly reduces the impact of the disturbance and parameter perturbations with a smooth control current. [ABSTRACT FROM AUTHOR]

Model-predictive control (MPC) is an optimization-based control technique. It has the benefits of being flexible and achieving a quick time response. However, this controller suffers from computational burden and sensitivity toward measurement noises, parametric variations, and model inaccuracies. Nowadays, the computation of MPC is no longer a problem, thanks to the new digital devices that exist on the market. However, robustness is still a major problem that complicates the usage of MPCs in applications, where the system model and parameters are not accurately known. A good example is the control of outer loops in cascaded control schemes. This paper presents multiple attempts to robustify the speed outer loop of a synchronous motor driven by a two-level power converter. An intuitive MPC speed outer-loop algorithm is first introduced. This first algorithm is weak against parametric variation, model inaccuracies, and measurement noises. Thus, a second more robust algorithm based on a torque balance expression is presented. This algorithm is robust toward parametric variations and model inaccuracies yet weak against measurement noises. Therefore, a subsequent improvement is added in a third algorithm in order to achieve a robust MPC controller. Furthermore, a least mean square identification algorithm is added to all control laws in order to identify the dynamical model parameters. These MPC controllers were experimentally tested and compared with a classic proportional–integral controller. Finally conclusions are drawn. [ABSTRACT FROM AUTHOR]

A grid-forming inverter (GFI) is an important component for the operation of an islanded microgrid. Its purpose, similar to a conventional slack bus generator, is to build up a reference voltage for other distributed generating units in the microgrid. Usually, a nested-loop proportional plus integral (PI) control structure is employed to control a GFI in a dq reference frame. However, conventional PI-based nested-loop control method has a deteriorative performance under parameter variations. In this paper, a novel nested-loop control strategy is proposed for control of a GFI system containing an {LC} output filter and loads. The proposed method does not require a precise model for the inverter system and can better deal with uncertainties and {LC}$ filter resonance without using any passive or active damping mechanisms. It utilizes a sliding-mode control in the inner current loop and a mixed {H_2}/{H_\infty } optimal control in the outer voltage loop, which provides the advantages of constant switching frequency, low total harmonic distortion, robustness against parameters variations, and fast transient response. The simulation and hardware experiments presented in this paper demonstrate the proposed controller's improved transient and steady-state performance in various key criteria, over conventional PI-based nested-loop control strategy. [ABSTRACT FROM AUTHOR]

Electric load simulator (ELS) is a resonant system and has a large coefficient caused by the stiffness of shaft. Its dynamic performance is always limited and stability is hard to be guaranteed. Besides, its external disturbance is the active motion of an actuator, and output is the load torque, which are both different from conventional servo systems. Therefore, the speed controller of ELS needs to be specially designed. In this paper, a speed controller for ELS is proposed to improve the dynamic performance and stability of ELS. The proposed controller consists of three control terms: a proportional (P) control term, a speed reference feedforward term, and a load torque compensation term. The tracking performance and surplus torque suppression performance of ELS with the proposed controller are analyzed in this paper. Stability analysis in discrete domain is carried out to guarantee the stability for digital applications. Robustness is also analyzed and an extended state observer is designed to compensate uncertainties and estimate speed. Furthermore, the proposed speed controller is compared with other three control methods. Experimental results on ELS are provided and validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper focuses on the H\infty fault detection (FD) problem for spring-mass systems (SMSs) over networks with distributed state delays, random packet losses, sensor saturation as well as multiplicative noises via unreliable communication channels. The output measurements are affected by sensor saturation which is described by sector-nonlinearities. The multiplicative noises are described as a form of Gaussian white noises multiplied by the states. A series of stochastic variables are introduced to describe the randomly occurring distributed state delays. Random packet losses are also introduced in unreliable communications. The purpose of this paper is to design an FD filter such that: 1) The FD dynamic system is exponentially stable in the mean square. 2) The error between the fault signal and the residual signal is controlled to the minimum. 3) The optimal H\infty filtering performance index is achieved. A sufficient condition for the FD filter design is derived in terms of the solution to a linear matrix inequality (LMI). When the LMI has a feasible solution, the explicit parameters of the desired FD filter can be obtained. Finally, a simulation experiment is illustrated to show the effectiveness and application of the designed method. [ABSTRACT FROM PUBLISHER]

Time delay in bilateral control system seriously deteriorates performance and stability. Acceleration-based bilateral control(ABC) is hybrid of position and force control in the acceleration dimension based on a disturbance observer. It can be divided into two modal spaces: common and differential modal spaces. The sum of master force and slave force is controlled to be zero in common modal space to realize the law of action-reaction. The difference of master position and slave position is controlled to be zero in differential modal space for position tracking. This paper analyzes the stability of each modal space under time delay. Based on modal space analysis, this paper proposes a novel “frequency-domain damping design” using high-pass filter for ABC. The validity of the proposed control system is confirmed by some experimental results. [ABSTRACT FROM PUBLISHER]

This paper addresses robust design of the active-power and dc-link control loops of power-synchronization control. Robustness is obtained by analytic gain selections, which give large enough stability margins. The proposed design allows robust stability irrespective of the grid strength and of the operating point, the latter with one exception. The proposed design is compared to design based on the principle virtual synchronous machine. Experiments show that the time-domain results correlate well with the frequency-domain results. [ABSTRACT FROM AUTHOR]

This paper presents the design, analysis, and verification of a novel reaching law for discrete-time sliding-mode control. The control gains of the reaching law are automatically regulated by the power function and the exponential term that dynamically adapts to the variation of the switching function. The reaching law also employs the perturbation estimation and the difference function to redefine the change rate as the second-order difference of the uncertainty. Compared with previous methods, the proposed reaching law has the capability to amend the control gains in a wise manner, further mitigate chattering, and guarantee a smaller width of the quasi-sliding-mode domain (QSMD). In order to describe the system dynamics in the reaching phase and the sliding phase with respect to control gain values, both the decrement band and the QSMD (ultimate band) of the proposed reaching law are theoretically analyzed. The reaching steps for the switching function to converge toward the sliding surface are also obtained. The effectiveness of the proposed method is verified through numerical simulations and experimental investigations on a piezoelectric actuator. [ABSTRACT FROM AUTHOR]

This paper presents a game-theoretic decentralized electric vehicle charging schedule for minimizing the customers’ payments, maximizing the grid efficiency, and providing the maximum potential capacity for ancillary services. Most of the available methods for electric vehicle charging assume that the customers are rational, there is a low-latency perfect two-way communication infrastructure without communication/computation limitation between the distribution company and all the customers, and they have perfect knowledge about the system parameters. To avoid these strong assumptions and preserve the customers’ privacy, we take advantage of the regret matching and the Nash Folk theorems. In the considered game, the players (customers) interact and communicate locally with only their neighbors. We propose a mechanism for this game, which results in a full Nash Folk theorem. We demonstrate and prove that the on-off charging strategy provides the maximum regulation capacity. However, our mechanism is quite general, takes into account the battery characteristics and degradation costs of the vehicles, provides a real-time dynamic pricing model, and supports the vehicle-to-grid and modulated charging protocols. Moreover, the developed mechanism is robust to the data disruptions and takes into account the long/short-term uncertainties. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive backstepping control scheme is presented to solve the position control problem for a gear transmission servosystem with unknown asymmetric sandwiched dead-zone nonlinearity. All the parameters involved in both the system and dead-zone models are allowed to be totally unknown. In contrast to the previous results where the effects of symmetric dead zone can be treated as additive disturbances in a transformed system, most of the unknown parameters of the transformed system are now time varying and dependent on the real-time value of relative displacement between the driving and driven gears. To deal with the above issue, new compensating terms in the quadratic form are introduced in the design of the virtual control signal for each recursive step. With the adaptive laws modified correspondingly, we can still show that all the closed-loop signals are ensured to be bounded and the output regulation error will converge to a compact set. Simulation results are provided to show the effectiveness of the proposed adaptive control scheme. [ABSTRACT FROM AUTHOR]

In this paper, an optimal fault detection scheme is presented for a closed-loop control system, where an event-triggering mechanism is utilized for the transmission of output measurements, addressing the design of residual generation and evaluation, while considering the effects associated with unknown disturbances and faults in the system and event-triggered transmission errors on the generated residual. The triggering parameter-dependent residual generation is designed to achieve a best tradeoff between robustness against unknown disturbances and sensitivity to faults, and the residual evaluation is designed to deliver a time-varying threshold that accounts for the effects of disturbances and event-triggered transmission errors on the generated residual. The results are general and simplify to those developed for optimal fault detection in time-triggered systems. In addition, a vehicle lateral dynamic system is adopted to demonstrate the applicability of the proposed optimal fault detection scheme as well as its advantages over an existing widely used event-triggered fault detection scheme. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel event-triggered tracking framework for fast and robust visual tracking in the presence of model drift and occlusion. The resulting tracker not only operates in real time, but also is resilient to tracking failures caused by factors such as fast motion and heavy occlusion. Specifically, the tracker consists of an event-triggered decision model as the core module that coordinates other functional modules, including a short-term tracker, occlusion and drift identification, target redetection, short-term tracker updating, and online discriminative learning for a detector. Each functional module is associated with a defined event that is triggered when the proposed conditions are met. The occlusion and drift identification module is intended to perform online evaluation of the short-term tracking. When a model drift event occurs, the target redetection module is activated by the event-triggered decision model to relocate the target and reinitialize the short-term tracker. The short-term tracker updating is carried out at each frame with a variable learning rate depending on the degree of occlusion. A sampling pool is constructed to store discriminative samples that are used to update the detector model. Extensive experiments on large benchmark datasets demonstrate that the proposed tracking algorithm can effectively detect model drift and restore tracking, and more importantly, it outperforms the state-of-the-art approaches in terms of accuracy, efficiency, and robustness. [ABSTRACT FROM AUTHOR]

To deal with the registration of infrared and visible image with significant difference in contrast and large geometric distortion in electro-optical pod, a robust and fast registration method by using common structural features is proposed in this paper. First, to adjust the scales of input images, a geometric transformation model is built based on parameters of the cameras. Then, a global structural feature extraction strategy is developed by using phase congruency and significance ranking space. Those features are not only invariant to the scale and contrast but also embody the structural of the input images maximally and uniformly. Finally, to enhance the robustness to contrast, blurring, and incompleteness of structures, an adaptive feature matching method with kernelized correlation filter is presented. Experimental results demonstrate that the proposed method has better performance than several state-of-the-art methods in robustness and precision, and also confirm its validity in the real environment. [ABSTRACT FROM AUTHOR]

In previous research, the variable conductance of a parallel active power filter has been used for antiparallel resonance with parameter variations in power systems. Its disadvantages are many sensors, complicated harmonic detection, and complexity of the algorithm for successful accomplishment in antiparallel resonance. In order to eliminate such drawbacks, this paper presents the parallel active power filter based on source current detection for antiparallel resonance with robustness to parameter variations for power factor correction using capacitor banks. The proposed method employs only single harmonic detector and an open-loop shaping design for robustness to variations of source impedance and a sudden change of capacitor bank values for power factor correction. The proposed antiparallel resonance controller can be readily applied to both large-scale and laboratory-scale power systems without any change. The large-scale simulation and the laboratory-scale experiment results confirm the validity, the accuracy, and good performance for antiparallel resonance, harmonic suppression, and robustness to parameter variations in power systems. [ABSTRACT FROM AUTHOR]

This paper presents a novel cascade proportional-integral (PI) continuous second-order sliding mode control (SMC) for induction motor in the presence of operational constraints. The inner-loop SMC is designed to control the current dynamics of the motor, while the outer-loop control is the PI control of speed. The main advantage of the proposed method is that the PI control provides reference to the inner-loop SMC with constraints according to the system requirements in terms of maximum current and speed limits. Moreover, because the inner-loop dynamics of the motor are nonlinear, SMC design has more importance in terms of robustness and disturbance rejection capability. The proposed control is a continuous-time design strategy with fixed-time convergence, while its discretization is performed at the implementation stage. The performance of the developed controller is validated by carrying out real-time experimental studies on an industrial size induction machine. Experimental results demonstrate remarkable robust tracking performance of the controller in terms of transient speed response and steady-state accuracy. [ABSTRACT FROM AUTHOR]

In this paper, a new control strategy for single-inductor multiple-output (SIMO) converters is proposed. The strategy is based on the hybrid control scheme. Switched linear equations of the converter are used in the design procedure. As a result, the cross regulation is suppressed inherently. A minimum dwell-time constraint is considered to suppress the switching loss and electromagnetic interference. The proposed scheme can control both minimum phase and nonminimum phase SIMO converters. It will be shown that the system is robust to input voltage and load variations. In order to compare the results, a recent pulsewidth-modulation-based control system is considered. Performance of the system is evaluated by a number of simulations and experiments. [ABSTRACT FROM AUTHOR]

Safe and reliable operation of systems relies on the use of online condition monitoring and diagnostic systems that aim to take immediate actions upon the occurrence of a fault. Model-based solutions are often not practical in nonstationary environments. Thus, the evolving data stream requires the data-driven model to be adaptive. In this paper, we propose a framework for the fault detection and classification that is accomplished on the data stream with both the gradual and abrupt drifts. The framework is only provided with prior information about the possible faults at the initial step; however, despite this, the framework can still detect the novel faults without receiving any update. Furthermore, an efficient fault classification algorithm is presented to maximize the efficiency of the proposed framework. Finally, the proposed framework is applied for diagnosing bearing defects in the induction motors to demonstrate its feasibility for industrial applications. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to solve the position tracking control problem for the permanent magnet linear motor by using the discrete-time fast terminal sliding mode control (SMC) method. Specifically, based on Euler's discretization technique, the approximate discrete-time model is first obtained and analyzed. Then, by introducing a new type of discrete-time fast terminal sliding surface, an improved discrete-time fast SMC method is developed and an equivalent-control-based fast terminal SMC law is subsequently designed. Rigorous analysis is provided to demonstrate that the fast terminal SMC law can offer a higher accuracy than the traditional linear SMC law. Numerical simulations and experimental results are finally performed to demonstrate the effectiveness of the proposed approach and show the advantages of the present discrete-time fast terminal SMC approach over some existing approaches, such as discrete-time linear sliding mode control approach and the PID control method. [ABSTRACT FROM AUTHOR]

The control of automobile electronic throttle (AET) systems is a challenging task owing to multiple nonlinearities, i.e., transmission friction, gear backlash, limp-home spring set, and external load disturbance. In this paper, a practical tracking control scheme of an AET system is developed using a continuous fast nonsingular terminal sliding mode (CFNTSM) technique based on uncertainty observer. By using the prescribed CFNTSM surface and fast terminal sliding mode-based reaching element, the proposed control implementation guarantees the fast error convergence characteristic and high tracking accuracy under parameter uncertainties and perturbations. Furthermore, due to the adoption of the finite-time exact observer (FEO) for the lumped uncertainty estimation in the controller, the ease of the selection of the control gains is well-achieved since they only depend on the uncertainty estimation error. The closed-loop stability and finite-time convergence are presented based on the Lyapunov stability theory. Experimental verifications are conducted to validate the remarkable performance of the proposed control, in terms of the step and sinusoidal tracking as well as anti-disturbance ability. [ABSTRACT FROM PUBLISHER]

This paper discusses a tolerance design approach for the feedback compensation networks of dc-dc switching regulators, identifying the most reliable solutions among different feasible alternatives that fulfil closed-loop design constraints. A voltage-mode-regulated dc-dc buck converter is considered as a case study. Given the performance and stability constraints, as tolerance ranges for crossover frequency and phase margin, feasible design solutions are sought by means of Monte Carlo and Interval Arithmetic computations. The search space is a set of available commercial values of H-C parameters and related tolerances. Best design is identified by a weighted fitness function, exploring the set of solutions provided by different design approaches. The results presented in the paper highlight that the tolerance design approach allows one to find compensation networks that fit the given performance/robustness priorities better than those ones found by means of the classical nominal design approach. [ABSTRACT FROM AUTHOR]

This paper presents two continuous finite-time convergent control algorithms driving an output (the highest relative degree state) of an $n$-dimensional integrator to zero for a finite time using a scalar input in the presence of both matched and unmatched unbounded disturbances. No knowledge of all system states is required: only the output should be available for the control design. No knowledge or reconstruction of individual disturbances is assumed as well. This paper concludes with a case study of controlling an industrial benchmark DC motor, whose third-order mathematical model is perturbed by matched and unmatched disturbances. [ABSTRACT FROM PUBLISHER]

This paper aims to realize compact actuation systems by sensorless approach. This study adopts solenoid actuators which have advantageous characteristics from the view point in inexpensive cost, simple structure, and high-output force in spite of difficulty in low cost position and force sensing. Some sensorless position estimation techniques for solenoid actuators were reported. However, position and force simultaneous estimation has not sufficiently been achieved. In addition, any real-time feedback control has not been reported. This paper proposes sensorless feedback position control for compact solenoid actuators. The force generation and position/force estimation are conducted by using a dc supply power superposed by an ac component. This control technique has three main features: 1) separation of the power supply into ac and dc components for the position estimation, 2) simultaneous real-time estimation of position and force, and 3) robust feedback position control. Simulations and experiments were conducted for verification of the proposed control with the above three features, and the results indicated that error between the estimation and actual positions was within 0.2 mm. This proposed system offers a new avenue for compact and inexpensive application field. [ABSTRACT FROM PUBLISHER]

This paper presents the design, analysis, and verification of a new output-based digital integral terminal sliding mode predictive control (DITSMPC) scheme, which is dedicated to precision motion control of a piezoelectric-driven positioning system. Unlike existing similar work, the controller is easy to implement because it does not require a hysteresis model and a state observer. Moreover, it is chattering free and is capable of delivering an $O(T^2)$ output error. The stability of the control system is demonstrated in theory. It is found that the model predictive control (MPC) enables a further improvement on the tracking accuracy in comparison with the digital integral terminal sliding mode control (DITSMC) schemes. The effectiveness of the proposed control strategy is confirmed through experimental investigations. Experimental results show that the DITSMPC control is superior to DITSMC and robust DITSMC (RDITSMC) schemes in motion tracking application, which is enabled by a well robustness property in the presence of model disturbances. [ABSTRACT FROM PUBLISHER]