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Since wear particles usually contain valuable information about lubricant and wear condition of lubricated components, wear debris analysis is widely used to monitor machine/component wear. Current literature reports about the importance and necessity of 3-D surface characterization of wear particles as opposed to 2-D characterization. It may be borne in mind that traditional 3-D analysis has been a synonym only for local surface morphologies for stationary particles. This results in large errors when irregular particles are under observation. A new 3-D imaging methodology is proposed to reconstruct multiview 3-D surfaces for a moving particle whereby the target particle is passed through a microchannel with rolling motion, and recorded via a digital microscope. The multiple moving particles are tracked based on Kalman filter to obtain different-view images. Sparse and dense reconstruction of the particle surfaces are enabled by these images using Structure from Motion (SfM) and Shape from Shading (SfS) methodologies, respectively. The method was verified using real particles and evaluated by the results of laser scanning confocal microscopy. The proposed method is able to reconstruct wear particles under various perspectives, and the errors from the characterization parameters of the areal are less than 20 $\%$. [ABSTRACT FROM AUTHOR]

In this article, a low-frequency hybrid modulation technique which is composed of a phase shift-pulsewidth modulation (PS-PWM) and an asymmetric selective harmonic current mitigation-PWM (ASHCM-PWM) are proposed for cascaded multilevel converters to meet the harmonic limit of IEEE 519 2014. In the proposed technique, the harmonics within the concerned frequency range due to PS-PWM are reduced by the ASHCM-PWM so that the cascaded H-bridge (CHB) converter can meet IEEE 519 harmonic limit. The equation set which helps a grid-tied CHB converter meet both harmonic limit and total demand distortion, is developed. The design technique for critical parameters, such as the inductance and the switching frequency of the proposed hybrid modulation technique, is developed. Simulation and experiments are conducted on a single-phase 3-cell 7-level grid-tied CHB converter to validate the proposed technique. [ABSTRACT FROM AUTHOR]

This paper deals with the high accurate current set-points solution for interior permanent-magnet synchronous motors (IPMSM) in wide-speed range applications. Considering voltage and current constraints, the operating regions can be divided into maximum torque per ampere, maximum current, field weakening, and maximum torque per voltage regions, which requires solving different nonlinear functions in real time to obtain optimal current set-points. Traditional methods including curve-fitting methods and polynomial approximation (PA) methods are not easy to obtain these solutions, especially involving magnetic saturation problems. In this paper, Newton–Raphson algorithm for improving the control accuracy of the current set-points is proposed. Meanwhile, parameters influence including magnetic saturation and resistive voltage drop is fully investigated. Compared with PA method, the proposed method is able to converge to accurate solutions in few numbers of iterations with reduced execution time, which can be easily implemented on an off-the-shelf digital signal processor. Both simulation results and experimental results on an 8-kW IPMSM rig are conducted showing good agreement with the expected results. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the method of autonomous hovering control for the biomimetic underwater robot named RobCutt-II. First, a modular configuration for mimicry of undulatory propulsion is presented, followed by a coordinated control of dual fins for enhancing the maneuverability and stability of the RobCutt-II. Then the vision-based hovering problem is formulated. A dual-loop hovering control framework integrating an image processing module, a tracking differentiator, a hovering controller, a velocity controller, and a fuzzy-based control allocation module is proposed to govern the locomotion of the RobCutt-II. Finally, simulations and experimental results demonstrate the effectiveness of the proposed mechanical design and control methods. [ABSTRACT FROM AUTHOR]

In this paper, the models of active differential mode electromagnetic interference input filters for ac–dc converters are first investigated. The models are developed for active filters with single feedback (FB) and single feedforward (FF) configurations, which include an active filter, passive filters, and the noise model for a converter. To increase the gain of the single active filter, the models for FB–FF, FF–FB, parallel FB, and series feedback (SFB) configurations are developed and investigated. Loop gains and insertion gains for all of these configurations are derived and compared. Stability has been analyzed based on the loop gains and a compensation technique is introduced to ensure stability. Based on the comparison among all these control configurations, it has been found that the SFB configuration can achieve the highest noise reduction. The loop gains and insertion gains of an active filter prototype with the SFB configuration are measured using a network analyzer to validate the developed model and compensation technique. Finally, spectrum measurements with a commercial boost power factor correction ac–dc converter have been conducted to verify the developed modeling and control techniques as well as the predicted performance for the SFB configuration. [ABSTRACT FROM AUTHOR]

In this paper, a cost-effective and highly accurate resolver-to-digital conversion method is presented. The core of the idea is to apply a third-order rational fraction polynomial approximation for the conversion of sinusoidal signals into the pseudo linear signals, which are extended to the range 0°–360° in four quadrants. Then, the polynomial least squares method is used to achieve compensation to acquire the final angles. The presented method shows better performance in terms of accuracy and rapidity compared with the commercial available techniques in simulation results. This paper describes the implementation details of the proposed method and the way to incorporate it in digital signal processor-based permanent magnet synchronous motor drive system. Experimental tests under different conditions are carried out to verify the effectiveness for the proposed method. The obtained maximum error is about 0.0014° over 0°–360°, which can usually be ignored in most industrial applications. [ABSTRACT FROM AUTHOR]

This paper investigates the critical parameter design technique for a cascaded H-Bridge (CHB) with selective harmonic elimination (SHE)/compensation (SHC) for single-phase systems. The critical parameters include the filter inductance, the number of H-bridge cells, the dc-bus voltage and the switching frequency. This paper derives the relationship of electrical parameters, topologies, and modulation techniques to the voltage/current harmonic envelopes, and compares the filter inductor design for an H-Bridge with sinusoidal pulsewidth modulation (SPWM), an H-Bridge (HB) with SHE/SHC and a CHB with SHE/SHC. Furthermore, a harmonic-envelope-based approach is developed to determine the optimum design parameters. The developed approach designs the harmonic envelope with two proposed criteria: the first one is the capacity criterion, which guarantees that the fundamental and controllable components are within the applicable solution range to avoid overmodulation; the other one is the attenuation criterion, which ensures that the uncontrollable harmonic complies with the grid limit. Simulations and experiments verified that a CHB designed with the proposed technique can simultaneously fulfill the compensation objectives and meet the harmonic limits. [ABSTRACT FROM AUTHOR]

This paper is devoted to an autonomous approach to a moving ship for unmanned vehicles. The problem is introduced and formulated first. Cooperation between the vehicle and the ship is needed, such that the moving ship to be approached is set to move at a constant speed along a straight line or a circle. Hence, an approaching algorithm based on 3-D path generation is proposed. The 3-D vehicle trajectory produced by the path generation realizes smooth transition from the initial pose to the final pose with geometric constraints. The final poses the unmanned vehicle and the ship's reach simultaneously are analyzed and obtained based on 3-D path generation. The related parameters for autonomous navigation of an unmanned vehicle are discussed according to the straight line or the circle that the ship sails along. The approaching algorithm is sequentially summarized. The simulations are conducted, and the results show the effectiveness and real-time performance of the proposed method. [ABSTRACT FROM PUBLISHER]

The interwinding parasitic capacitance of transformers and the parasitic capacitance between semiconductor switches and the ground are two major contributors to the common-mode (CM) noise currents in switched mode power converters. In this paper, a generalized CM current cancelation approach is proposed for the reduction of CM noise in isolated power converters. The approach is demonstrated in a forward converter. In this approach, the total effect of the two parasitic capacitances on CM noise is represented with an equivalent parasitic capacitance (EPC) at low frequencies. With this EPC, different CM current cancelation techniques can be efficiently organized to simultaneously cancel the low-frequency CM noise caused by these two parasitic capacitances. Furthermore, the EPC can be used to evaluate and quantify the performance of CM noise reduction techniques. Both theoretical analysis and experimental results show that the proposed approach is easy to implement and can significantly attenuate low frequency CM noise and therefore greatly reduce CM filter size and cost. [ABSTRACT FROM PUBLISHER]

This paper proposes novel electromagnetic interference (EMI) suppression techniques for dc–dc converters. For low-voltage high-current applications, windings are paralleled and interleaved. Although low conduction loss and low leakage inductance can be achieved, the winding capacitances are considerably increased, thereby deteriorating the converter's EMI and soft-switching performances. To solve these problems, a novel balanced choke concept is proposed, as well as other techniques. The advantages of the proposed concepts and strategies are verified and demonstrated on a 1-kW 1-MHz 400-V/12-V LLC resonant converter prototype. More than 52-dB noise attenuation and 75% equivalent winding capacitance reduction are achieved. Hence, EMI and soft-switching performances are significantly improved. [ABSTRACT FROM PUBLISHER]

Robots have the potential to assist and complement humans in the exploration of hostile environments. For example, underwater vehicle–manipulator systems (UVMSs) have been researched and applied in underwater operations. Motivated by the need for collecting marine organisms cultivated in shallow sea aquafarm, a lightweight and portable UVMS propelled by flexible flippers (named, F-UVMS), rather than typical propellers or jet-based propulsion systems, is investigated. To this end, integrative mechatronic design of F-UVMS is first presented, involving six flipper propulsors for generating thrust in a flapping way, a four-degree-of-freedom arm for grasping, and a certain amount of onboard sensors for environment perception. A thrust–power measurement platform is established to evaluate thrust–power relationship for different sizes and stiffness of flippers. Meanwhile, the locomotion modalities of F-UVMS are analyzed. A framework based on the nonlinear model-predictive control method is implemented to govern autonomous tracking marine organisms. The capabilities of F-UVMS are validated through a series of experiments in laboratory pool and field missions in real sea conditions. [ABSTRACT FROM AUTHOR]

This article presents the design of a biomimetic underwater vehicle-manipulator system (BUVMS) with bioinspired long-fin propulsion and its control methods. The kinematic analysis of bioinspired long-fin propulsion is conducted, and the maximum thrust of this propulsion derived from our thrust measurement platform can be up to 25 N. Bioinspired long-fin propulsion is introduced to construct the BUVMS for inspection and manipulation tasks, and the system architecture of the BUVMS is described. Moreover, real-time dynamic dubins-helix path planning and tracking of the biomimetic vehicle are proposed to realize the arrival of the desired pose. The tracking error is less than 0.23 body length. Finally, coordinated control between the biomimetic vehicle and the manipulator is developed to achieve autonomous manipulation. The reaction of the manipulator served as feedforward compensation is added into the closed-loop control of the biomimetic vehicle. The experimental results are provided to illustrate the validity of the proposed methods. [ABSTRACT FROM AUTHOR]

The rotor structure of synchronous reluctance machines (SynRel) is conventionally retained mechanically by iron ribs. In this paper, a novel structure for high-speed synchronous reluctance rotor is presented. The novelty of this paper is the proof of a concept of SynRel machine without iron ribs. Structurally, the rotor iron lamination segments are embedded in an adhesive resin material with high temperature resistance and mechanical strength. Three four-pole SynRel machines have been designed with the target of improving motor torque, and compared for different ribs configuration. It has been shown that the proposed motor performs enhanced torque, power factor, and efficiency with respect to conventional SynRel with iron ribs. An extensive sensitivity analysis of the ribless rotor geometry is carried out, followed by both mechanical analysis and experimental over speed test to guarantee its robustness above the operating speed range. The manufacturing procedure of this novel rotor is introduced. Finally, the experimental results on both SynRel prototypes are presented, showing the increase in torque, power factor, and efficiency of the proposed solution. This paper is a first step toward the definition of a viable and novel solution of SynRel machines with improved performance. [ABSTRACT FROM AUTHOR]

This paper addresses the achievement of floating autonomous manipulation of the underwater biomimetic vehicle-manipulator system (UBVMS). A practical vehicle-manipulator coordinated plan and control methodology of the UBVMS for autonomous interventions are designed. First, the system configuration is introduced, and the optimal work space is confirmed. Then, the control framework of the UBVMS mainly consisting of online motion planning, multitask kinematic control, dynamic feedforward compensation, and adaptive parameter undulatory control for autonomous manipulation is presented. The online motion planning method with resort to tracking differentiator is developed to produce desired task trajectory and reference rate. The singularity-robust multitask kinematic control algorithm with state observers is designed to obtain system reference velocity. The couple influence on the vehicle induced by the presence of the manipulator is described as the dynamic feedforward compensation signal to reduce undesired waggle of the UBVMS. Adaptive parameter modifier of the biomimetic propulsor is designed to satisfy multifarious performance requirements in different motion phases. Finally, pool experiments in multiple scenarios for autonomous grasping manipulation are conducted to verify the effectiveness and adaptability of the developed coordinated plan and control strategy. [ABSTRACT FROM PUBLISHER]

The selective harmonic current mitigation pulsewidth modulation (SHCM-PWM) technique can be used in cascaded multilevel converters to extend the harmonic reduction spectrum, reduce the coupling inductance and increase the efficiency. The offline SHCM-PWM technique has small number of switching transitions as its switching angles can only change once in a fundamental cycle and relatively long time delays because it uses FFT. As a result, its dynamic response has a lot to desire. As it will be proven in this paper, in four-quadrant power converters, to have a good transient dynamic response, both active and reactive power must be controlled at least two times in a fundamental cycle. In this paper, a hybrid modulation technique is introduced. The proposed technique uses SHCM-PWM under steady state and phase-shift PWM (PSPWM) under transient. In addition, in order to extend the modulation index range and ensure that SHCM-PWM can process four-quadrant active and reactive power, the constraints of the switching angles for the SHCM-PWM are modified. Simulations and experiments are conducted on a seven-level cascaded H-bridge converter to verify the proposed technique. [ABSTRACT FROM PUBLISHER]

This paper develops a common-mode (CM) electromagnetic interference noise model for a three-level neutral point clamped topology. Compared with existing modeling techniques with only one CM noise source, two extra important CM noise sources and their characteristics are identified and derived for an accurate CM noise model. The impedances of CM noise path are also extracted. Based on the developed CM noise model, the CM noise spectrum can be well predicted. The effect of CM noise paths on CM noise is discussed based on two different LCL filters. A CM noise reduction technique with a balance bridge at a large impedance ratio is proposed based on the developed model. The technique can be easily implemented at low cost. Both simulations and experiments validate the developed theory and technique. [ABSTRACT FROM PUBLISHER]

A dual-transformer-based enhanced dual active bridge (DAB) dc–dc converter for wide voltage range applications is introduced in this article. A power leg and transformer of the conventional DAB converter (CDABC) are split in two parts, leading to an expansion of the control freedom. Its wide voltage operating range does not rely on the small leakage inductor design and high transformer turns ratio. The root mean square value of the leakage inductor current is optimized with the ensuring of full domain zero voltage switching. The conduction losses and switching losses can be significantly reduced in buck mode compared to the CDABC. A simple segment control strategy with four control degrees of freedom is employed to avoid inrush from mode switching. The analysis and control processes are simplified, and the control loop is a simple closed voltage loop without the need for look-up table checking. The discussed converter and control strategy are verified by a 1.0 kW prototype. [ABSTRACT FROM AUTHOR]

In-hand object localization and manipulation has always been a challenging task in robotic community. In this article, we address this problem by vision-based tactile sensing with high-spatial resolution. Specifically, we design a novel tactile sensor based on stereo vision, named GelStereo, which can perceive tactile point cloud with high-spatial resolution ($<\!1$ mm). A tactile-based in-hand object localization pipeline composed of saliency detection and probabilistic point-set registration algorithms of the perceived contact point cloud is presented. Furthermore, extensive qualitative and quantitative analyses of perceived tactile point cloud and in-hand localization and insertion experiments of small parts are performed on our robot platform. The experimental results verify the accuracy and robustness of the tactile point cloud sensed by the novel GelStereo tactile sensor and the proposed in-hand object localization pipeline. This novel high-resolution visuotactile sensing technology has predictable application potential in the field of dexterous robotic manipulation. [ABSTRACT FROM AUTHOR]

The concept of the more electric aircraft is aimed at electrifying the mechanical, hydraulic, and pneumatic subsystems on aircraft. With increasing usage of power electronics, the architecture of onboard electrical power distribution systems becomes more complicated. Therefore, it is necessary to analyze the stability of the system. This article, first, presents and validates an impedance model of a permanent magnet synchronous generator as a source and dual active bridge converter as a load. These models are used for the stability analysis of a simple dc power system. In addition, two new control strategies are proposed to enhance the stability of the system. The stabilization effects of the new control strategies are verified with experimental results. [ABSTRACT FROM AUTHOR]

A novel high switching frequency isolated voltage-fed hybrid bridge combining semiactive rectifier dc–dc converter is introduced for unidirectional power flow and wide voltage gain. Three potentially appropriate working patterns are elaborated, including ideal output power derivation, current stress analysis, working voltage matching, output power distribution, soft switching characteristics, etc. In consideration of the optimization of the minimum of the root-mean-square value of the leakage inductor current, two truly applicable working patterns are selected. Meanwhile, based on the consideration of soft switching, a segmented control strategy is implemented on it. With the optimization of current stress and the realization of soft switching, the converter can theoretically realize higher efficiency operation. Eventually, the effectiveness of the proposed converter and the control strategy is verified by a 1 kW prototype. [ABSTRACT FROM AUTHOR]

The problem of attitude control for a spacecraft model that is nonlinear in dynamics with inertia uncertainty and external disturbance has been investigated. Adaptive law and extended state observer are applied to estimate the disturbance, by which sliding-mode controllers are designed to combine the two approaches in order to force the state variables of the closed-loop system to converge to the reference attitude states. Also, simulation results are presented to illustrate the effectiveness of the control strategies. [ABSTRACT FROM AUTHOR]