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The micro/nano positioning system discussed in this paper includes a piezoelectric actuator (PEA) and flexure-hinge-based positioning mechanism. Due to the existence of the hysteretic nonlinearity in the PEA and the friction in the system, the accurate positioning of the piezo-actuated positioning system calls applicable control schemes for practical applications. To this end, an implementable adaptive controller is developed in the paper, where a minimized parameterization hysteresis model is employed to reduce the computational load. The formulated adaptive control law guarantees the global stability of the controlled positioning system, and the positioning error can approach to zero asymptotically. The advantages of the proposed method making on-line implementation feasible are that the traditional inversion of the hysteresis does not need to be constructed directly; the real values of the parameters of the positioning system neither need to be identified nor measured; only the parameters in the formulation of the controller are estimated online. Comparison with the feedforward plus proportional-integral feedback control scheme is conducted and experimental results show the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper investigates the adaptive tracking-control problem for a class of nonlinear systems with uncertain parameters, disturbance, and unmodeled dynamics. A novel model reference adaptive control (MRAC) with external filter is proposed to not only stabilize the error system but also guarantee its transient performance. The proposed control strategy can mathematically ensure designable L\infty norm bounds of the difference between the original model’s and the reference model’s state and their control inputs as well. On the other hand, the reference model, which is deemed as a linear time-invariant (LTI) system, can be designed to run in a desired performance level by selecting a suitable filter in the control structure. Another improvement emphasizes that the proposed approach can attain the above performance without using a high-static adaptation gain, which avoids the possible negative effects in the context of robustness. Finally, simulation on a high-accuracy motion-system model driven by a direct-current (dc) motor is given to verify the proposed approach, and the effectiveness is shown based on the simulation curves and analysis. [ABSTRACT FROM PUBLISHER]

In this paper, distributed formation control laws for the multi-agent systems are proposed when the leader is moving constantly with unknown velocity. The proposed control laws are based on the distance-based formation control; therefore, each distance between agents is controlled measuring the relative position. Because the control laws use only local information such as relative position with respect to their own local reference frame, the control laws are completely decentralized. The proposed control laws are designed to make a group of agents keep the desired formation and move with a constant reference velocity in two-dimensional space. The considered system consists of three types of agents: 1) leader; 2) first follower; and 3) follower. The leader knows the reference velocity value, whereas the other agents do not know the reference velocity. For this reason, the first follower and follower estimate the reference velocity by using the adaptive method. Using graph theory and nonlinear control theory, the control laws are verified mathematically. Additionally, the three-agent case is extended to $N$-agent case by an inductive way. The stability and convergence of the system are theoretically analyzed, and the validity of the proposed control laws is clarified by performing simulations and real experiments. [ABSTRACT FROM PUBLISHER]

The compound active-clamp zero-voltage switching three-phase power factor correction (PFC) converter is used as the first stage converter of the heating power supply in the monocrystalline silicon growth furnace to achieve high efficiency and high power factor. Parameter uncertainty and variation are the main problems for the controller design of the converter. The conventional methods, including proportional–integral (PI) control, exact feedback linearization (EFL) control, etc., cannot deal with such problems. In this paper, we propose a model reference adaptive control for voltage outer loop to achieve adaptation for the load and capacitor variations, as well as a variable structure control with shrinking boundary layer for current inner loop to improve robustness to the parameters uncertainty. The simulation and experiment results show that the proposed controller improves the power factor and efficiency of the system, and it has better transient and steady-state performance with respect to the load variation, as compared with the traditional PI control method and the EFL control method. [ABSTRACT FROM PUBLISHER]

This paper presents a robust adaptive iterative learning control (ILC) algorithm for 3-DOF permanent magnet (PM) spherical actuators to improve their trajectory tracking performance. The dynamic model of a PM spherical actuator is a multivariable nonlinear system with interaxis coupling terms. Uncertainties such as modeling errors, loads, and external disturbances exist in the model unavoidably, which will affect the performance, including the precision of the control system. Hence, to compensate for these uncertainties, a new hybrid control scheme that consists of a proportional–derivative (PD) feedback control with varying gains, a PD-type ILC with adjustable gains, and a robust term is developed. The new control law combines the advantages of simplicity and easy design of the PD control, the effectiveness of the ILC to handle model uncertainties and repetitive disturbances, and the robustness of the robust term to random disturbances. In addition, to expedite the convergence rate, the gains in the PD feedback control and the PD-type ILC are adaptively adjusted according to the iteration times. It is shown that the system tracking error approaches zero as the number of iterations increases. To demonstrate the proposed algorithm and verify the established theoretical results, both simulations and experiments are conducted. The results have shown that the proposed control algorithm can effectively compensate for various uncertainties and can thus improve the trajectory tracking performance of spherical actuators. [ABSTRACT FROM AUTHOR]

This paper concerns high-accuracy tracking control for hydraulic actuators with nonlinear friction compensation. Typically, LuGre model-based friction compensation has been widely employed in sundry industrial servomechanisms. However, due to the piecewise continuous property, it is difficult to be integrated with backstepping design, which needs the time derivation of the employed friction model. Hence, nonlinear model-based hydraulic control rarely sets foot in friction compensation with nondifferentiable friction models, such as LuGre model, Stribeck effects, although they can give excellent friction description and prediction. In this paper, a novel continuously differentiable nonlinear friction model is first derived by modifying the traditional piecewise continuous LuGre model, then an adaptive backstepping controller is proposed for precise tracking control of hydraulic systems to handle parametric uncertainties along with nonlinear friction compensation. In the formulated nonlinear hydraulic system model, friction parameters, servovalve null shift, and orifice-type internal leakage are all uniformly considered in the proposed controller. The controller theoretically guarantees asymptotic tracking performance in the presence of parametric uncertainties, and the robustness against unconsidered dynamics, as well as external disturbances, is also ensured via Lyapunov analysis. The effectiveness of the proposed controller is demonstrated via comparative experimental results. [ABSTRACT FROM PUBLISHER]

This paper deals with consensus disturbance rejection of network-connected dynamic systems using disturbance observers. The control objective of consensus disturbance rejection is to achieve a common state trajectory for the network-connected subsystems that are under deterministic disturbances. The difference from the existing disturbance rejection methods is that only the relative state information is used for disturbance rejection, and as a consequence of using the relative state information, only the part of the disturbances that affect the common trajectories will be rejected. The conditions for designing disturbance observers for consensus control are identified for networked-connected multiagent systems. Certain features of the individual subsystems are analyzed for possible implementation of disturbance-observer-based rejection, and the disturbance observers are designed based on the relative state information obtained from the neighboring subsystems under different network connections. When the network connectivity is available for the disturbance observer design, consensus disturbance rejection is achieved for a directed network with a spanning tree. A fully distributed consensus disturbance rejection design is presented for an undirected network with the use of adaptive parameters for the estimation of the unknown network connectivity. Disturbance observers are also proposed for disturbance rejection in the leader–follower consensus control. [ABSTRACT FROM PUBLISHER]

This study mainly focuses on the development of two newly designed control strategies including an adaptive control scheme and a fuzzy neural network (FNN) control system for a single-stage boost inverter. First, the dynamic model of a single-stage boost inverter is analyzed and built for the later control manipulation. Then, a model-based adaptive control scheme and a model-free FNN control system with varied learning rates are designed sequentially. The effectiveness of the proposed adaptive control scheme and the proposed FNN control system is verified by experimental results of a 1-kW single-stage boost inverter prototype, and their merits are indicated in comparison with a traditional double-loop proportional-integral (PI) control framework. Experimental results show that the superior FNN control system has significant improvements of 45.2% total harmonic distortion and 37.1% normalized mean square error compared to the conventional double-loop PI control framework under nonlinear loads. [ABSTRACT FROM PUBLISHER]

In this paper, we present the vibration control design for a Euler–Bernoulli beam with the boundary output constraint. To prevent the constraint violation, a novel barrier Lyapunov function is employed for the control design and stability analysis. This paper represents an important step in extending the barrier Lyapunov function theory to distributed parameter systems. Model-based barrier control is proposed to suppress the vibration of a flexible Euler–Bernoulli beam under the boundary output constraint. Then, adaptive control is designed to handle the system parametric uncertainties. The vibration suppression is well achieved without violation of the constraint. Numerical simulations are provided to illustrate the performance of the control system. [ABSTRACT FROM PUBLISHER]

A reconfiguration control scheme is proposed for a quadrotor helicopter with loss of control effectiveness via simple adaptive control and quantum logic. Some good control performances of the helicopter can be achieved by applying quadratic optimal control with scheduled stability degree when the system is in normal operation. A parallel feedforward compensator is introduced to fulfill the condition of positive realness, and thus, the simple adaptive controller can be utilized for the helicopter. Quantum logic is also applied to the quadrotor control system, which achieves the quantization of the disturbances patterns. A mathematical model of the quadrotor helicopter for application is obtained from its dynamic equations with pitch, roll, and yaw axes, which includes the parameter perturbation and outer disturbances. Several simulation and experimental results for the faulty helicopter validate the robustness and reconfiguration control capability of the proposed scheme. [ABSTRACT FROM PUBLISHER]

This paper studies the distributed consensus problem of multiagent systems (MASs) in the presence of nonidentical unknown nonlinear dynamics and undetectable actuation failures. Of particular interest is the development of a robust adaptive fault-tolerant consensus protocol capable of compensating uncertain dynamics/disturbances and time-varying yet unpredictable actuation failures simultaneously. By introducing the virtual parameter estimation error into the artfully chosen Lyapunov function, the consensus problem is solved with a robust adaptive fault-tolerant control scheme based upon local (neighboring) agent state information. It is shown that the proposed method is user friendly in that there is no need for detail dynamic information of the agent or costly detection/diagnosis of the actuation faults in control design and implementation, resulting in a structurally simple and computationally inexpensive solution for the leaderless consensus problem of MAS. Simulation results illustrate and verify the benefits and effectiveness of the proposed scheme. [ABSTRACT FROM PUBLISHER]

This paper presents a novel asymptotic tracking controller for an underactuated quadrotor unmanned aerial vehicle using the robust integral of the signum of the error (RISE) method and an immersion and invariance (I&I)-based adaptive control methodology. The control system is decoupled into two parts: the inner loop for attitude control and the outer loop for position control. The RISE approach is applied in the inner loop for disturbance rejection, whereas the I&I approach is chosen for the outer loop to compensate for the parametric uncertainties. The asymptotic tracking of the time-varying 3-D position and the yaw motion reference trajectories is proven via the Lyapunov-based stability analysis and LaSalle's invariance theorem. Real-time experiment results, which are performed on a hardware-in-the-loop simulation testbed, are presented to illustrate the performance of the proposed control scheme. [ABSTRACT FROM PUBLISHER]

Kalman filtering has been largely used in adaptive control for motor drive applications. However, few works relate to applications in the field of monitoring. In this paper, a fault indicator for interturn short circuits detection in permanent-magnet synchronous generators (PMSGs) is introduced. Based on the extended form of the Kalman filter and associated to an appropriate model of PMSG expressed in the $dq$ frame, this indicator has been developed through the identification of parameters specifically introduced to point out stator faults. Special attention has been paid to the indicator sensitivity and its robustness to the generator operation mode, which implies a large range of operating points. The indicator performances have been first evaluated using an appropriate simulation model. A complete experimental campaign has been performed to validate previous simulation results. A faulty PMSG, specifically built for stator fault experiments, has been associated to a digital signal processor for an online implementation of the proposed indicator. Finally, the issue of parameter uncertainties is solved by introducing a variable threshold for detection improvement. [ABSTRACT FROM PUBLISHER]

An adaptive robust position control for real-time high-performance applications of induction motors is developed in this work. The proposed sliding-mode controller provides a global asymptotic position tracking in the presence of model uncertainties and load torque variations. The proposed control scheme incorporates an adaptation law for the switching gain, so that the controller can calculate the switching gain value that is necessary to overcome the existing system uncertainties. The design also incorporates a sliding-mode-based load torque and rotor flux observers in order to improve the control performance without using sensors that increase cost and reduce reliability. The proposed design does not present a high computational cost and, therefore, can be easily implemented in real-time applications. Simulated and experimental results show that this scheme provide high-performance dynamic characteristics, and that it is robust with respect to plant parameter variations and external load disturbances. [ABSTRACT FROM PUBLISHER]

In this paper, a novel energy-saving control strategy is proposed for the accurate motion tracking of a hydraulic manipulator. To achieve independent pressure regulation for each chamber of the cylinder, as well as energy recovery during the back-and-forth movement of the cylinder, a hardware configuration with five low-cost programmable cartridge valves and an accumulator is developed to control the motion of the cylinder. Based on the hardware configuration, a novel multilevel control algorithm is proposed, which consists of the desired motion and pressure tracking control level (level I), the flow distribution level (level II), and the offside pressure profile planning level (level III). The proposed approach is theoretically shown to be able to minimize the energy consumption of the system while maintaining good motion tracking performance. Experimental studies confirm that the proposed strategy can indeed achieve both accurate motion tracking and minimum energy consumption simultaneously. Compared with the previous four-valve scheme and five-valve flow regeneration scheme without the use of accumulator by Liu and Yao, the proposed strategy has much less total energy consumption and equally good tracking performance. [ABSTRACT FROM PUBLISHER]

In this paper, a multiple adaptive observer-based strategy is proposed for the control of multi-input multi-output nonlinear processes using input/output (I/O) data. In the strategy, the pseudopartial-derivative parameter matrix of compact form dynamic linearization is estimated by a multiple adaptive observer, which is used to dynamically linearize a nonlinear system. Then, the proposed data-driven model-free-adaptive-control algorithm is only based on the online identified multiobserver models derived from the I/O data of the controlled plants, and Lyapunov-based stability analysis is used to ensure that all signals of the close-loop control system are bounded. A numerical example and a Wood/Berry distillation column example are provided to show that the proposed control algorithm has a very reliable tracking ability and a satisfactory robustness to disturbances and process dynamics variations. [ABSTRACT FROM PUBLISHER]

In this paper, a flexible cable with a payload attached at the bottom is considered to be the model of a crane system used for positioning the payload. The dynamics of the flexible cable coupled with the tip payload contribute to a hybrid system represented by partial-ordinary differential equations. An integral-barrier Lyapunov function (IBLF)-based control is proposed to suppress the undesirable vibrations of the flexible crane system with the boundary output constraint. Adaption laws are developed for handling parametric uncertainties. A novel IBLF is adopted to guarantee the uniform stability of the closed-loop systems without the violation of the boundary constraint. All closed-loop signals are ensured to be bounded. Extensive simulations are demonstrated to illustrate the performance of the control system. [ABSTRACT FROM PUBLISHER]

This paper considers the problem of designing adaptive output feedback sliding mode controllers for a class of linear systems with matched external disturbances, where the norm bound of the external disturbance is unknown. First, we derive a new design approach of linear sliding surface in the singular system framework, and propose an adaptive output feedback sliding mode controller such that the motion of the closed-loop system is uniformly ultimately bounded stable. Second, to improve the transient performance, a memory-based adaptive output feedback sliding mode controller is also proposed. Finally, an illustrative example is utilized to demonstrate the design procedures proposed in this paper. It is shown that the memory-based adaptive output feedback sliding mode control approach provides a better transient performance. [ABSTRACT FROM PUBLISHER]

In this paper, we have developed a novel large measurement-range atomic force microscopy (AFM) system performing the tapping mode operation. This system consists of a compact/low-cost scanning probe-type sensing system (z-scanner) and a hybrid xy-scanner. To achieve precision measurement through image scan of given samples, a thorough mathematical modeling is established first, and an advanced robust adaptive controller is then proposed, which can deal with unknown parameters, cross-talk effects, external disturbances, and unknown hysteresis phenomena. The salient properties of the resulting closed-loop AFM system includes long traveling range, high precision, and fast response after integrating two kinds of actuations. To demonstrate and qualify the scanning capability of the proposed system, systematic experiments have been conducted. [ABSTRACT FROM PUBLISHER]

This paper describes a novel development of a lower limber exoskeleton for physical assistance and rehabilitation. The developed exoskeleton is a motorized leg device having a total of 4 DOF with hip, knee, and ankle actuated in the sagittal plane. The exoskeleton applies forces and learns the impedance parameters of both robot and human. An adaptive control scheme by incorporating learning control approaches into the exoskeleton system is developed to help the leg movement on a desired periodic trajectory and handle periodic uncertainties with known periods. The proposed control approach does not require a muscle model and can be proven to yield asymptotic stability for a nonlinear muscle model and an exoskeleton model in the presence of bounded nonlinear disturbances (e.g., spasticity and fatigue). The performance of the controller is demonstrated through closed-loop experiments on human subjects. The experiments illustrate the ability of the exoskeleton to enable the leg shank to track single and multiple period trajectories with different periods and ranges of motion. [ABSTRACT FROM PUBLISHER]

In a plasma display panel, optimal address driving mode for reducing address power varies depending on the input image and thus the optimal addressing modes of adjacent scan lines are different. To reduce address power for various input image, address driver needs to operate adaptively according to input image, in which fast mode change is required. This paper proposes a fast mode change method in which the efficiency of LC resonance is improved. In the proposed method, the conventional RC mode and the modified picture-based adaptive (M-PBA) mode are used. In the proposed scheme, the efficiency of LC resonance is almost the same as that in picture-based adaptive scheme while the speed of addressing mode change is improved. Experimental results show that address power of the proposed method is reduced by 17% compared with previous work. [ABSTRACT FROM AUTHOR]

To accomplish superior harmonic compensation performance using distributed generation (DG) unit power electronics interfaces, an adaptive hybrid voltage and current controlled method (HCM) is proposed in this paper. It shows that the proposed adaptive HCM can reduce the numbers of low-pass/bandpass filters in the DG unit digital controller. Moreover, phase-locked loops are not necessary as the microgrid frequency deviation can be automatically identified by the power control loop. Consequently, the proposed control method provides opportunities to reduce DG control complexity, without affecting the harmonic compensation performance. Comprehensive simulated and experimental results from a single-phase microgrid are provided to verify the feasibility of the proposed adaptive HCM approach. [ABSTRACT FROM AUTHOR]

This paper presents the coordinated control of distributed energy storage systems in dc microgrids. In order to balance the state-of-charge (SoC) of each energy storage unit (ESU), an SoC-based adaptive droop control method is proposed. In this decentralized control method, the droop coefficient is inversely proportional to the nth order of SoC. By using a SoC-based droop method, the ESUs with higher SoC deliver more power, whereas the ones with lower SoC deliver less power. Therefore, the energy stored in the ESU with higher SoC decreases faster than that with lower SoC. The SoC difference between each ESU gradually becomes smaller, and finally, the load power is equally shared between the distributed ESUs. Meanwhile, the load sharing speed can be adjusted by changing the exponent of SoC in the adaptive droop control. The model of the SoC-based adaptive droop control system is established, and the system stability is thereby analyzed by using this model. Simulation and experimental results from a 2 \times 2.2 kW parallel converter system are presented in order to validate the proposed approach. [ABSTRACT FROM AUTHOR]

A novel observer-based parameter estimation scheme with sliding mode term has been developed to estimate the road gradient and the vehicle weight using only the vehicle's velocity and the driving torque. The estimation algorithm exploits all known terms in the system dynamics and a low-pass filtered representation of the dynamics to derive an explicit expression of the parameter estimation error without measuring the acceleration. The proposed parameter estimation scheme which features a sliding-mode term to ensure the fast and robust convergence of the estimation in the presence of persistent excitation is augmented to an adaptive observer and analyzed using Lyapunov Theory. The analytical results show that the algorithm is stable and ensures finite-time error convergence to a bounded error even in the presence of disturbances. In the absence of disturbances, convergence to the true values in finite time is guaranteed. A simple practical method for validating persistent excitation is provided using the new theoretical approach to estimation. This is validated by the practical implementation of the algorithm on a small-scaled vehicle, emulating a car system. The slope gradient as well as the vehicle's mass/weight are estimated online. The algorithm shows a significant improvement over previous results. [ABSTRACT FROM AUTHOR]

Prognostics and health management (PHM) play a key role in increasing the reliability and safety of systems especially in key sectors (military, aeronautical, aerospace, nuclear, etc.). This paper presents a new methodology which combines data-driven and experience-based approaches for the PHM of roller bearings. The proposed methodology uses time domain features extracted from vibration signals as health indicators. The degradation states in bearings are detected by an unsupervised classification technique called artificial ant clustering. The imminence of the next degradation state in bearings is given by hidden Markov models, and the estimation of the remaining time before the next degradation state is given by the multistep time series prediction and the adaptive neuro-fuzzy inference system. A set of experimental data collected from bearing failures is used to validate the proposed methodology. Experimental results show that the use of data-driven and experience-based approaches is a suitable strategy to improve the PHM of roller bearings. [ABSTRACT FROM AUTHOR]

This paper presents an add-on self-tuning (ST) control scheme for a Unified Power Flow Controller (UPFC) to assist its conventional PI control system in damping power oscillations. The ST control algorithm is based on a Pole Shift (PS) technique that has previously been successfully applied in Adaptive Power System Stabilizers (APSSs). For a wide range of operating conditions, the conventional PI-UPFC unless retuned suffers from insufficient/nonoptimal damping performance. To overcome this problem, the authors propose supplementing the PI controllers with an ST feedback loop comprised of an identifier and a PS control algorithm. With a CRLS identifier tracking the system conditions online, this scheme eliminates the need for PI parameter retuning. Further, to correctly identify system parameters during large disturbances, a constrained recursive least squares (CRLS) identification procedure is adopted here. An improved damping performance with the proposed add-on scheme assisting the nonoptimal PI-UPFC is demonstrated for a two-area power system. [ABSTRACT FROM PUBLISHER]

This paper proposes an adaptive control for a class of nonlinear mechanisms with guaranteed transient and steady-state performance. A performance function characterizing the convergence rate, maximum overshoot, and steady-state error is used for the output error transformation, such that stabilizing the transformed system is sufficient to achieve the tracking control of the original system with a priori prescribed performance. A continuously differentiable friction model is adopted to account for the friction nonlinearities, for which primary model parameters are online updated. A novel high-order neural network with only a scalar weight is developed to approximate unknown nonlinearities and to dramatically diminish the computational costs. Comparative experiments on a turntable servo system are included to verify the reliability and effectiveness. [ABSTRACT FROM PUBLISHER]

This paper investigates the control problem of a marine riser installation system. The riser installation system consisting of a vessel, a flexible riser, and a subsea payload is modeled as a distributed parameter system with one partial differential equation and four ordinary differential equations. Based on Lyapunov's direct method, adaptive boundary control is proposed at the top and bottom boundaries of the riser to position the subsea payload to the desired set point and suppress the riser's vibration. With the proposed control, uniform boundedness of the steady-state error between the boundary payload and the desired position is achieved by suitably choosing the design parameters. Numerical simulations are presented for demonstrating the effectiveness of the proposed control. [ABSTRACT FROM PUBLISHER]

This paper proposes an adaptive control method of three-phase inverters for stand-alone distributed generation systems (DGSs). The proposed voltage controller includes two control terms: an adaptive compensating term and a stabilizing term. The adaptive compensating control term is constructed to avoid directly calculating the time derivatives of state variables. Meanwhile, the stabilizing control term is designed to asymptotically stabilize the error dynamics of the system. Also, a fourth-order optimal load current observer is proposed to reduce the number of current sensors and enhance the system reliability and cost effectiveness. The stability of the proposed voltage controller and the proposed load current observer is fully proven by using Lyapunov theory. The proposed control system can establish good voltage regulation such as fast dynamic response, small steady-state error, and low total harmonic distortion under sudden load change, unbalanced load, and nonlinear load. Finally, the validity of the proposed control strategy is verified through simulations and experiments on a prototype DGS test bed with a TMS320F28335 DSP. For a comparative study, the control scheme of feedback linearization for multi-input and multioutput is implemented, and its results are presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper proposes a recurrent fuzzy cerebellar model articulation controller (RFCMAC) for a dual-axis micromotion stage powered by piezoelectric actuators. The proposed RFCMAC employs an adjustable input space quantization method with a learning rate capable of self-tuning. The proposed RFCMAC is aimed at dealing with the adverse effects due to unknown hysteresis nonlinearity, modeling uncertainty, and external disturbance that are commonly found in the piezoelectric actuator systems. The proposed RFCMAC mainly focuses on overcoming the drawbacks of the conventional CMAC control scheme when used to control a piezoelectric actuator system. In particular, the adjustable input space quantization method uses a simple repartitioning decision function to determine an appropriate input space quantization. In addition, the self-tuning law for the learning rate of the proposed RFCMAC is derived based on the discrete-time Lyapunov function so that convergence and faster learning can be guaranteed. Finally, in order to validate the effectiveness of the proposed control methodology, several contour-following experiments were conducted on a dual-axis piezoelectric actuated micromotion stage. Experimental results show that the proposed control scheme is feasible, and its performance is superior to that of the conventional CMAC control scheme. [ABSTRACT FROM PUBLISHER]

A novel online discrete-time parameter identification algorithm suitable for surface-mounted permanent magnet synchronous machines (SPMs) is presented in this paper. It is developed by means of the model reference adaptive system technique and the Popov Hyperstability Criterion in order to identify SPM discrete-time model parameters. In particular, good accuracy of discrete-time parameters is required by digital control systems, particularly by predictive control algorithms, which present a low robustness against parameter mismatches. Hence, an extensive simulation study is first carried out in the Matlab Simulink environment with the aim of testing the effectiveness and robustness of the proposed identification algorithm against inverter unidealities. Then, the proposed identification procedure is experimentally validated on a predictive controlled radial-flux SPM, driven by a field programmable gate arrays control board. [ABSTRACT FROM PUBLISHER]

This paper presents the modeling and control processes of the single-phase cascade H-bridge multilevel converter used as a shunt active filter. Based on the obtained model, a controller is proposed to compensate for harmonic distortion and reactive power caused by a nonlinear load. These issues are solved by guaranteeing tracking of the line current toward an appropriately defined current reference. In the proposed approach, the current reference has been selected to be a signal proportional to either the line voltage or to its fundamental component; however, the proposed method can also be extended to other reference definitions. The proposed controller also includes voltage loops to guarantee regulation and balance of the involved capacitor voltages toward constant references. Experimental results on a 2-kVA prototype are presented to assess the performance of the proposed controller. [ABSTRACT FROM PUBLISHER]

This paper proposes an observer for the sensorless control of doubly fed induction machines which is based on the effect of a natural signal injection in the stator windings due to the fifth harmonic of the line voltage. A method to extract the rotor position and speed only from the rotor current and stator voltage measurements is developed: As a novelty, the stator current measurement and the anisotropies in the machine design are not required. A phase-locked loop is used in order to track the harmonic current component which is induced in the rotor by the fifth line voltage harmonic and whose speed and position are directly related to the rotor speed and position. The tuning of the observer parameters is discussed together with the effect of the other line voltage harmonics. This paper is completed by the experimental validation of the observer performances. [ABSTRACT FROM PUBLISHER]

Friction compensation is usually realized based on a friction model; however, the induced undercompensation or overcompensation, which can lead to steady-error or limit-cycle phenomenon, respectively, is inevitable. A novel straightforward reference compensation scheme for the brushless dc servo system independent of the friction model is presented to reject the aftereffect caused by the friction instead of its original mechanics. Neither the accurate friction model nor any estimation of some specific characteristic parameters is needed in this design. Moreover, the inexact velocity estimation information is not as crucial as it is in the traditional compensation methods. A linear control law is proposed based on a reduced-order observer, which could be readily implemented in low-cost embedded fixed-point chips. Two guidelines for the selection of control parameters are presented in terms of delay sensitivity and limit-cycle avoidance. The approach can be applied to the cases with multiple disturbance torque sources except the friction one, where the friction-model-based strategy is difficult to take effect. Finally, comparative mathematical simulation and practical experiment results are used to validate the effectiveness of the proposed method. Substantial low-velocity performance improvements are achieved in the hardware experiments. [ABSTRACT FROM PUBLISHER]

The paper proposes a new adaptive controller design for a synchronous reluctance motor drive system. In this paper, an online tuning adaptive controller, which is based on the least-mean-square algorithm, is proposed. The adaptive controller is constructed by using an adaptive model and an adaptive control. Both the adaptive-model parameters and the adaptive-control parameters are online tuned. A nonlinear programming optimization technique is used to improve the convergence rate of the online tuning method. By using the proposed method, the transient responses, load disturbance responses, and tracking responses of the drive system are improved. The experimental results show that the implemented drive system can perform a wide range in adjustable speed from 1 to 1800 r/min and a precise position control as well. A digital signal processor, TMS-320F-28335, is used to execute the adaptive current-loop, speed-loop, and position-loop controllers. Experimental results can validate the theoretical analysis and show the feasibility and correctness of the proposed method. [ABSTRACT FROM PUBLISHER]

In this paper, a flexible enveloping grasper is proposed for pick-and-place tasks with low manipulation and task planning complexity for practical applications. The proposed grasper has two main characteristics: self-adaptivity and flexibility. Self-adaptivity means that the proposed grasper can grip an object in a self-adaptive way such that various process complexities (e.g., sensing, force control, and sensor–motor coordination) are significantly reduced. By flexibility, we mean that, by using a flexible material, a stable grip can be implemented to cause increased friction between the grasper and the target object as a result of increased contact area. These two properties help the proposed grasper to minimize internal forces in a passive manner and to achieve successful force distribution with self-adaptivity when performing enveloping grasping. Three sets of experiments were performed with an average success rate of 93.2% in pick-and-place tasks. [ABSTRACT FROM PUBLISHER]

This work considers the use of wind turbines for aiding upregulation of an electrical grid, by employing temporary overproduction with respect to available power. We present a simple model describing a turbine and show how the possible period of overproduction can be maximized by solving a series of convex problems, where the load is distributed among several turbines in a farm. Thereafter, we present an optimization scheme that guarantees a lower limit for the overproduction period and subsequently propose an adaptive implementation that is robust against parameter uncertainties. [ABSTRACT FROM PUBLISHER]

This paper presents a discrete-time adaptive current controller for grid-connected pulse width modulation voltage source converters with LCL filter. The main attribute of the proposed current controller is that, in steady state, the damping of the LCL resonance does not depend on the grid characteristic since the adaptive feedback gains ensure a predefined behavior for the closed-loop current control. An overview of model reference adaptive state feedback theory is presented aiming to give the reader the required background for the adaptive current control design. The digital implementation delay is included in the model, and the stability concerning the variation of the grid parameters is analyzed in detail. Furthermore, current distortions due to the grid background voltage are rejected without using the conventional stationary resonant controllers or the synchronous proportional-plus-integral controllers. Simulation and experimental results are presented to validate the analysis and to demonstrate the good performance of the proposed controller for grid-connected converters subjected to large grid impedance variation and grid voltage disturbances. [ABSTRACT FROM PUBLISHER]

In wave energy converters (WECs), the maximum power extraction would be achievable at the expense of a very high rating of the electric and power electronics equipment. The goal of this paper is to show how a convenient tradeoff between high-power extraction and viable electrical device rating can be achieved by a proper choice of the WEC control strategy. Referring to a direct coupled point absorber in heave operating in regular waves, it will be analytically shown how most common control techniques impact on both the power performance and the power takeoff (PTO) rating. Thus, a tool that can assist in the preliminary PTO sizing by taking into account the main constraints imposed by the application is obtained. Following, an adaptive control strategy including a reactive component is proposed, whose goal is to improve the overall system performance when the WEC is already operative in the sea. Its effectiveness in increasing the average power extraction while respecting the PTO peak power constraint is proved by computer simulations in both regular and irregular waves, and specific analyses also including the PTO force/torque limitation are finally developed. [ABSTRACT FROM PUBLISHER]

This paper deals with an adaptive control method to be used in the dc-link voltage controller of diesel-electric power supply units being arranged with both permanent-magnet generator and three-phase boost rectifier. The proposed control method is based on the suitable manipulation of the overall system transfer function to achieve an adaptive “closed-form” expression for the parameters of the dc-link voltage controller. Such an approach allows overcoming the inherent nonlinear behavior of the system, so that the overall system dynamic performance is not affected by the system load conditions. Moreover, a current feedforward technique based on the estimation of the load current will be introduced to improve the control stiffness to load unbalances. [ABSTRACT FROM PUBLISHER]

This paper presents a novel model reference adaptive control of five-phase interior-permanent-magnet (IPM) motor drives. The primary controller is designed based on an artificial neural network (ANN) to simulate the nonlinear characteristics of the system without knowledge of accurate motor models or parameters. The proposed motor drive decouples the torque and flux components of five-phase IPM motors by applying multiple-reference-frame transformation. Therefore, the motor can be easily driven below the rated speed with the maximum-torque-per-ampere operation or above the rated speed with the flux weakening operation. The ANN-based primary controller consists of a radial basis function network which is trained online to adapt system uncertainties. The complete IPM motor drive is simulated in Matlab/Simulink environment and implemented experimentally utilizing a dSPACE DS1104 controller board on a five-phase prototype IPM motor. [ABSTRACT FROM PUBLISHER]

To adaptively reduce the influence of phase lag of traditional current mode switching power amplifiers on system stability and static and dynamic performances for magnetic bearing systems, this paper proposes a new, simple, and effective phase-lead compensation strategy based on unsymmetrical current sampling resistance network. The common problems associated with the existing phase-lead compensation methods for magnetic bearing power amplifiers are successfully handled via this method without additional hardware or software resources. The effectiveness and superiority of this proposed strategy have been demonstrated by both simulation and experimental results. [ABSTRACT FROM PUBLISHER]

This paper presents a load adaptive control approach to optimally control the amount of reactive current required to guarantee zero-voltage switching (ZVS) of the converter switches. The proposed dc/dc converter is used as a battery charger for an electric vehicle (EV). Since this application demands a wide range of load variations, the converter should be able to sustain ZVS from full-load to no-load condition. The converter employs an asymmetric auxiliary circuit to provide the reactive current for the full-bridge semiconductor switches, which guarantees ZVS at turn-on times. The proposed control scheme is able to determine the optimum value of the reactive current injected by the auxiliary circuit in order to minimize extra conduction losses in the power MOSFETs, as well as the losses in the auxiliary circuit. In the proposed approach, the peak value of the reactive current is controlled by controlling the switching frequency to make sure that there is enough current to charge and discharge the snubber capacitors during the deadtime. In addition, some practical issues of this application (battery charger for an EV) are discussed in this paper. Experimental results for a 2-kW dc/dc converter are presented. The results show an improvement in efficiency and better performance of the converter. [ABSTRACT FROM PUBLISHER]

In this paper, an adaptive fuzzy control scheme is introduced for permanent magnet synchronous machines (PMSMs). The adaptive control strategy consists of a Lyapunov stability-based fuzzy speed controller that capitalizes on the machine's inverse model to achieve accurate tracking with unknown nonlinear system dynamics. As such, robustness to modeling and parametric uncertainties is achieved. Moreover, no explicit currents loop regulation is needed, which simplifies the control structure and unlike other control strategies, no a priori offline training, weights initialization, parameters knowledge, voltage, or current transducer is required. The system's convergence and stability are proved by Lyapunov stability theory, which yields an improved performance. Simulation results for different situations highlight the performance of the proposed controller in transient, steady-state, and standstill conditions. Furthermore, the adaptive fuzzy systems inherent parallelism makes them a good candidate for implementation in real-time PMSM drive systems. [ABSTRACT FROM PUBLISHER]

When matrix converter (MC) and high-frequency link (HFL) are combined together, they become more complex and gain a safe commutation for the use of high-frequency transformer. To realize energy conversion and transmission, and to achieve reliable and safe commutation at the same time are particularly important and desirable. HFL matrix converter (HFLMC) can be divided into two types: high-frequency link matrix inverter (HFLMI) and high-frequency link matrix rectifier (HFLMR). A three-phase output HFLMI is selected as the object of this study, and a novel integration sinusoidal pulse width modulation (SPWM) control strategy with one-step adaptive commutation based on De-Re-coupling idea is proposed for it. After expounding on the De-Re-coupling idea, a kind of HFLMC equivalent circuit model based on the high-frequency transformer equivalent circuit is built up. Then, a detailed analysis of the voltage stress on power devices of the HFLMC by using this model is performed. A safe operation evaluation criterion of HFLMC is also gained. A suggestion of how to select carrier wave for integration SPWM is ascertained through detail discussion, and two kinds of specific Re-coupling logic circuits are presented, and at last some experimental results are shown to make a certification for feasibility and effectiveness of the new proposed SPWM strategy. [ABSTRACT FROM AUTHOR]

Four longitudinal control techniques are compared: a classical Proportional-Integral (PI) control; an advanced technique—called the i-PI—that adds an intelligent component to the PI; a fuzzy controller based on human experience; and an adaptive-network-based fuzzy inference system. The controllers were designed to tackle one of the challenging topics as yet unsolved by the automotive sector: managing autonomously a gasoline-propelled vehicle at very low speeds. The dynamics involved are highly nonlinear and constitute an excellent test-bed for newly designed controllers. A Citroën C3 Pluriel car was modified to permit autonomous action on the accelerator and the brake pedals—i.e., longitudinal control. The controllers were tested in two stages. First, the vehicle was modeled to check the controllers' feasibility. Second, the controllers were then implemented in the Citroën, and their behavior under the same conditions on an identical real circuit was compared. [ABSTRACT FROM AUTHOR]

This paper presents a novel two-level scheme for adaptive active visual servoing of a mobile robot equipped with a pan camera. In the lower level, the pan platform carrying an onboard camera is controlled to keep the reference points lying around the center of the image plane. On the higher level, a switched controller is utilized to drive the mobile robot to reach the desired configuration through image feature feedback. The designed active visual servoing system presents such advantages as follows: 1) a satisfactory solution for the field-of-view problem; 2) global high servoing efficiency; and 3) free of any complex pose estimation algorithm usually required for visual servoing systems. The performance of the active visual servoing system is proven by rigorous mathematical analysis. Both simulation and experimental results are provided to validate the effectiveness of the proposed active visual servoing method. [ABSTRACT FROM AUTHOR]

A new address energy recovery (AER) circuit of ac plasma display panel (PDP) (AC-PDP) is proposed. The proposed circuit converter shows the load-adaptive characteristics, which can minimize the unnecessary power consumption of AER circuit according to the displayed image. Moreover, the proposed circuit, employing a p-channel MOSFET which does not require a complex floating gate driver, can be implemented with low cost. Based on the estimated equivalent capacitance of PDP, the proposed AER circuit is designed to implement the prototype for 50-in high-definition PDP. The load-adaptive AER operation and the address-power-saving characteristic are verified experimentally. Therefore, the proposed circuit is very suitable for the low-cost AER circuit of AC-PDP. [ABSTRACT FROM AUTHOR]