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In low-speed sensorless control of surface-mounted permanent magnet synchronous machine (SPMSM), high-frequency (HF) signal injection methods are often used to estimate the rotor position by tracking the motor saliency characterized by the inductances. Cross-saturation effects caused by the load current will influence the inductances, and consequently the saliency, which will introduce position estimation error to the sensorless drive, degrading the drive performance. Such load-dependent position estimation error, which is inherent in HF signal injection sensorless methods, is difficult to be identified by the sensorless algorithm itself. This article proposes a new online method to detect and compensate the load-dependent position estimation error for SPMSM without additional devices or the knowledge of the load-dependent HF inductances. The proposed method can identify effectively the load-dependent position estimation error by simply varying the direction of the current vector. Experimental results are presented to validate the proposed solution. [ABSTRACT FROM AUTHOR]

Flux-linkage based sensorless control method is well-known and has been widely used in the control of electrical machines. The closed-loop flux observer (CLFO), which is the adaptive combination of the machine voltage and current models, is commonly adopted. It can cover a wide speed operation range and was considered to be able to solve the dc drift and initial value problem associated to the pure integrator used in the observer. However, it is reported in this paper that this popular CLFO cannot always work as expected. In some situations, dc-offsets cannot be removed by this flux observer, causing large system oscillation at fundamental frequency and is very harmful to the drive system. This important issue has not been reported and discussed in the existing literatures of the CLFO. In this paper, this phenomenon is experimentally illustrated and solution to damp this harmful oscillation is proposed and verified experimentally on a synchronous reluctance machine drive system. [ABSTRACT FROM AUTHOR]

Small dc-link drive systems, built with film capacitors in the dc-link, present a new trend in many industrial applications and are obtaining increasing interests. It has the advantages of longer lifetime and the possibility to achieve a more compact design of the capacitor bank, especially at medium and high power rates. However, it could exhibit instability problems, mainly in the form of oscillations. The unexpected oscillation may result in overvoltage and shorten the lifetime of the power devices and the dc-link capacitors; increase the total harmonic distortion and also the partially weighted harmonic distortion of the grid supply current. Therefore, active damping methods are usually needed in order to stabilize such drive systems. This paper first analyzes the system characteristics and the principles of existing active damping methods. Then, a new voltage modulation based method named as “virtual positive impedance” method is introduced to guarantee the dc-link stability. This new approach is simple to apply and its implementation does not require the knowledge of system parameters and machine operating conditions. The proposed method is analyzed in details and verified by experiments. [ABSTRACT FROM AUTHOR]

As a severe public health concern directly endangering life safety, adolescent suicide has been extensively investigated in variable-centered studies. However, gaps remain in the knowledge of heterogeneous suicide risk patterns and their developmental nature. Additionally, little is known about protective factors associated with suicide risk patterns and changes. This study applied person-centered approaches to explore suicide risk profiles and transitions over time in early Chinese adolescents, along with their protective factors. A total of 1518 junior high school students (49.6% girls, Mage = 13.57, SD = 0.75) participated in two surveys within a 12-month interval. Latent Profile Analysis and Latent Transition Analysis were used to model the profiles and transitions of suicide risk. Three risk profiles were identified at both time points: low risk profile (73.9, 78.3%), medium risk-high threat profile (16.2, 10.2%), and high risk profile (9.9, 10.2%). Low risk profile was stable, while medium risk-high threat and high risk profiles showed great transitions over 12 months. Sense of control, meaning in life, and regulatory emotional self-efficacy served as protective factors against suicide risk profiles and transitions. Findings underscore the importance of comprehensively illustrating suicide risk states from multiple aspects, as well as understanding the fluid nature of transitions between different risk states. Prevention and intervention strategies aimed at enhancing resilience, such as increasing sense of control, perceived meaningfulness, and belief in emotional regulation, may contribute to reducing the risk of suicide among adolescents. [ABSTRACT FROM AUTHOR]

In this paper, a simple signal injection method is proposed for sensorless control of permanent-magnet synchronous machine (PMSM) at a low speed, which ideally requires one voltage vector only for position estimation. The proposed method is easy to implement, resulting in low computation burden. No filters are needed for extracting the high-frequency current signals for position estimation. The use of low-pass filters (LPFs) in the current control loop to obtain the fundamental current component is not necessary. Therefore, the control bandwidth of the inner current control loop may not need to be sacrificed. The proposed method may also be further developed to inject two opposite voltage vectors to reduce the effects of inverter voltage error on the position estimation accuracy. The effectiveness of the proposed method is demonstrated by comparing with other sensorless control method. Theoretical analysis and experimental results are given for validating the proposed new sensorless control method. [ABSTRACT FROM PUBLISHER]

In this paper, a simple and accurate method is proposed for online estimation of the rotor permanent magnet (PM) flux linkage for surface mounted PM synchronous machines. By advantageously utilizing an injected zero-voltage vector, the effects of inductance in estimating the PM flux linkage is eliminated. The inverter voltage error and phase resistive voltage drop effects are minimized by repeating the test at different speeds. Therefore, as a result, only the voltage commands are needed for PM flux linkage estimation, resulting in great simplicity. Filtering the current ripple caused by the zero-voltage vector injection is not necessary. The proposed method can be used with sensored or sensorless field-oriented control strategies. The experimental results have shown a good accuracy of the proposed new method. [ABSTRACT FROM AUTHOR]

Magnetic lead screw (MLS) is a new type of high performance linear actuator that is attractive for many potential applications. The main difficulty of the MLS technology lies in the manufacturing of its complicated helical-shape magnetic poles. Structure simplification is, therefore, quite essential in promoting the MLS technology. In this paper, a new approach is proposed for forming the required helical-shape magnetic poles in a much simpler way. It is demonstrated that the traditional ring-shape magnetic poles, by proper rotating or shaping, can well approximate the complicated helical-shape magnetic poles. The performance of the new structure is compared with a MLS with ideal helical-shape magnetic poles using 3-D finite-element analysis. Halbach and flux concentration designs using the new approach are introduced. [ABSTRACT FROM AUTHOR]

This paper presents a sensorless-controlled, low-cost, low-power, and variable-speed drive system suitable for fan and pump applications. The main advantages of this drive system are the low system cost, simple converter structure, and simple but robust sensorless control technique. The drive motor is a special hybrid switched reluctance motor. The proposed sensorless control method beneficially utilizes the stator side PM field and its performance is motor parameter independent. The unique low-cost drive system solution, simple and robust sensorless control features of this drive system, is demonstrated in detail in this paper. Important design details for practical implementation of the sensorless control algorithm are included. The complete drive system performance is validated using a prototype drive system. [ABSTRACT FROM AUTHOR]

This paper presents a new transverse flux permanent magnet machine. In a normal transverse flux machine, complicated 3-D flux paths often exist. Such 3-D flux paths would require the use of soft magnetic composites material instead of laminations for construction of the machine stator. In the new machine topology proposed in this paper, by advantageously utilizing the magnetic flux path provided by an additional rotor, use of laminations that allow 2-D flux paths only will be sufficient to accomplish the required 3-D flux paths. The machine also has a high torque density and is therefore an attractive solution for various direct drive applications. [ABSTRACT FROM PUBLISHER]

This paper presents a new type electromagnetic lead screw (EMLS) intended for wave energy application. Similar to the mechanical lead screw, this electromagnetic version can transfer slow linear motion to high-rotational motion, offering gearing effects. Compared with the existing pure magnetic lead screw (MLS) employing permanent magnets only, the new EMLS proposed uses dc current to provide the required helical-shape magnetic field, offering a much simpler, robust structure compared with the MLS. The working principle and the performances of this EMLS are analyzed in this paper. Comparison with PM-type lead screw is given. In addition to this, the theoretical analysis to support the use of a 2-D finite element model to analyze the 3-D magnetic-type lead screw is given, which has not been well covered in the existing literature. [ABSTRACT FROM AUTHOR]

The back EMF-based sensorless control method is very popular for permanent magnet synchronous machines (PMSMs) in the medium- to high-speed operation range due to its simple structure. In this speed range, the accuracy of the estimated position is mainly affected by the inductance, which varies at different loading conditions due to saturation effects. In this paper, a new concept of using a constant artificial inductance to replace the actual varying machine inductance for position estimation is introduced. This facilitates greatly the analysis of the influence of inductance variation on the estimated position error, and gives a deep insight into this problem. It also provides a simple approach to achieve a globally minimized position error. A proper choice of the artificial machine inductance may reduce the maximum position error by 50% without considering the actual inductance variation in the control algorithm. Analytical and experimental results are given for validating the proposed theory. [ABSTRACT FROM AUTHOR]

In this paper, a new motor integrated permanent magnet gear (MIPMG) is discussed. The focus is on eddy current loss analysis associated to permanent magnets (PMs). A convenient model of MIPMG is provided based on 2-D field-motion coupled time-stepping finite element method for transient eddy current analysis. The model takes the eddy current effect of PMs into account in determination of the magnetic field in the air-gap and in the magnet regions. The eddy current losses generated in the magnets are properly interpreted. Design improvements for reducing the eddy current losses are suggested. The proposed model and the results presented in this paper will give useful guidelines for a reliable design and design optimization of the MIPMG. [ABSTRACT FROM PUBLISHER]

To identify the parameters of variable flux reluctance machines (VFRMs), the input voltage value is usually obtained from the reference voltage indirectly. However, the reference and actual voltages may be different due to the nonlinearity of the open winding inverter when using zero-sequence current, leading to the inaccuracy of parameter identification. To solve this problem, this paper proposes an equivalent nonlinearity voltage error model of the open winding inverter to compensate for the input voltage of VFRM during the online parameter identification. Since in the proposed method the phase current direction is not required, the calculation time can be reduced. Moreover, in the developed parameter identification model of VFRM the derived equivalent nonlinear voltage error is used to correct the input of the identification model so as to improve the accuracy of parameters. Finally, the experimental results on the prototype VFRM are presented for verification. [ABSTRACT FROM AUTHOR]

This paper presents a new single-phase, Hybrid Switched Reluctance (HSR) motor for low-cost, low-power, pump or fan drive systems. Its single-phase configuration allows use of a simple converter to reduce the system cost. Cheap ferrite magnets are used and arranged in a special flux concentration manner to increase effectively the torque density and efficiency of this machine. The efficiency of this machine is comparable to the efficiency of a traditional permanent magnet machine in the similar power range. The cogging torque, due to the existence of the permanent magnetic field, is beneficially used to reduce the torque ripple and enable self-starting of the machine. The starting torque of this machine is significantly improved by a slight extension of the stator pole-arc. A prototype machine and a complete drive system has been manufactured and tested. Results are given in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a new method for computation of the nonlinear flux linkage in 3-D finite-element models (FEMs) of electrical machines. Accurate computation of the nonlinear flux linkage in 3-D FEM is not an easy task. Compared to the existing energy-perturbation method, the new technique introduced in this paper is much easier to use and is computational faster. This method is derived based on the “apparent energy.” Calculation of the nonlinear flux linkage from this energy avoids numerical differentiation, which is sensitive to numerical errors but is required in the traditional energy-perturbation method. The new method proposed is validated using experimental results on two different permanent magnet machines. [ABSTRACT FROM AUTHOR]

Permanent magnet transverse flux machine (PMTFM) is well known for its high torque density and is interested in various direct-drive applications. Due to its complicated 3-D flux components, design and design optimization of a PMTFM is more difficult and time consuming than for radial flux electrical machines. This paper addresses two important design considerations for PMTFM—the influence of permanent magnet leakage flux, which plays an important role in the determination of machine output torque, and the leakage inductance. A new simple method to provide a quick estimation of the armature leakage inductance is proposed, avoiding use of complicated 3-D equivalent reluctance network model to estimate the circumferential armature leakage flux component, and the pole face fringing flux component. Analysis results are supported by 2-D, and 3-D finite element (FE) analysis results, and measurement results on a prototype surface-mounted PMTFM. [ABSTRACT FROM AUTHOR]

The effects of saturation on torque production for non-salient, single-phase, permanent-magnet machines are studied in this paper. An analytical torque equation is proposed to predict the instantaneous torque with saturation effects. Compared to the existing methods, it is computationally faster and easier to calculate the torque using the analytical equation proposed. It can also handle arbitrary armature current waveforms and arbitrary flux linkage waveforms produced by the rotor permanent magnets. The results obtained by using the proposed torque equation are validated using finite-element results, and experimental results obtained on a prototype single-phase permanent-magnet machine. [ABSTRACT FROM AUTHOR]

This paper presents a new low-cost hybrid switched reluctance (HSR) motor intended for use in adjustable-speed pump drive systems. The motor is a single-phase motor, driven by a unipolar converter, which uses both the reluctance torque and the permanent magnet interaction torque. Compared with conventional single-phase switched reluctance motors, it has an increased torque density. The cogging torque is beneficially used in this motor for reducing the torque ripple. It is demonstrated that such a motor drive system can be a suitable candidate to advantageously compete with the existing motor drive systems for low-cost applications. Finite-element models are used to analyze and predict the motor's performance. The proposed motor drive system has been fabricated, and its performance has been tested in the laboratory. These experimental results are also presented. [ABSTRACT FROM AUTHOR]

• A new non-resonant and free/impact motion based EMEH with steel frame for ultra-low frequency and large amplitude vibration application is proposed. • Mathematical model and simulation procedure are established and well validated. • Experimental results are analyzed and show the valuable features of the proposed EMEH. In this paper, a new non-resonant, free motion based electromagnetic energy harvester is proposed for harvesting energy from low-frequency vibration sources. In this design, steel frame is beneficially utilized to enhance the flux and consequently the power density of the harvester. The steel frame can also function as a magnetic shield to protect the harvester from external magnetic field interferences. Prototype of this harvester is constructed and characterized experimentally. A dedicated model and simulation method including non-linear contact characteristics is presented in this paper for predicting the dynamic response of this harvester at different vibration frequencies and amplitudes, and different operation modes are characterized. The measured results have well validated the behaviors predicted by the proposed model. In particular, the developed prototype of this harvester can generate a power density 748 μW/c m 3 at a low-frequency of 4.5 Hz and 40 mm vibration amplitude. Compared to recently reported low-frequency energy harvesters summarized in Table 3 , this new harvester has the superiority of high-power density. It is a non-resonant harvester so it can harvest energy for a wide frequency band. [ABSTRACT FROM AUTHOR]

Improving the positioning response is one of the key goals for permanent magnet synchronous motor position servo systems. The sliding mode variable structure controller (SMVSC) is an effective method due to the advantages of strong robustness, fast response, and easy practical implementation. However, the existing SMVSCs have difficulties in optimizing the position tracking response speed and chattering performance at the same time. This article proposes an improved position speed integrated SMVSC (ISMVSC) with a new variable exponential reaching law based on position error and a saturation function, and a speed-limiting method using speed error and trajectory planning. The general design principle is given and various tests are carried out to verify the effectiveness of the proposed method. The experimental results show that compared with traditional methods, the ISMVSC can improve the positioning response speed and reduce chattering problems at the same time; it also exhibits a stronger transient speed-limiting ability. All these advantages make the proposed controller a superior method to achieve high-response positioning control of the servo system that performs point-to-point motion. [ABSTRACT FROM AUTHOR]

Accurate rotor position is significant for the back electromotive force (EMF)-based sensorless interior permanent-magnet synchronous motor (IPMSM) control. However, the ±(6 h±1)th harmonics will appear obviously in the estimated back-EMF due to the effect of the inverter nonlinearity and flux spatial harmonics. These harmonics will subsequently result in the ±(6 h)th harmonic pulsation in the estimated rotor position. In order to deal with this issue, a new complex-coefficient synchronous frequency filter (CCSFF)-based sliding mode observer combined with a quadrature phase-locked loop (PLL) is proposed to mitigate the back-EMF voltage distortion. Therefore, the performance of the position estimation is remarkably improved. The proposed CCSFF possesses both bandpass-filtering and frequency-adaptability characteristics. It can pass the fundamental component without magnitude attenuation and phase delay in different frequency scenarios. Moreover, the linearized model of the proposed CCSFF-PLL-based position estimation system is established and a systematic parameter design is presented to obtain promising dynamic performance. The effectiveness and feasibility of the proposed method are confirmed by experiments on a 1.5-kW IPMSM test platform. [ABSTRACT FROM AUTHOR]

Current-controlled variable inductors adjust the inductance of an alternating current (ac) coil by applying a controlled dc current to saturate the iron cores of the ac coil. The controlled dc current has to be maintained during operation, which results in increased power losses. This paper presents a new stress-based variable inductor to control inductance using the inverse magnetostrictive effect of a magnetostrictive material. The stress can be applied by a piezoelectrical material, and thus a voltage-controlled variable inductor can be realized with zero-power consumption. The new stress-based variable inductor concept is validated using a 3-D finite-element analysis. A prototype was manufactured, and the experimental results are presented. A linear relationship between inductance and applied stress can be achieved. [ABSTRACT FROM AUTHOR]

A typical giant magnetostrictive actuator (GMA) expands a magnetostrictive rod to generate strain by varying the current in the coil that surrounds the magnetostrictive rod. The heat generated by the current deteriorates the GMA performance. In particular, a constant current in the coil is required to produce the desired magnetic field when an output strain should be maintained. The GMA does not produce any mechanical power in this condition, but constant power is being consumed by the excitation coil. This paper presents a new type of motor-driven GMA (MDGMA), which works in a coil-free driven manner. The magnetic field in the iron–gallium alloy (Galfenol), which is a type of magnetostrictive material, is periodically altered by rotating the permanent magnets instead of varying the coil current in the traditional GMA. The proposed MDGMA not only achieves continuous adjustment of the output strain, but can also maintain a constant output strain without consuming any power. In addition, the coil-free design releases the new MDGMA from the heat generated by the excitation coil, which allows the MDGMA to work more stably. [ABSTRACT FROM AUTHOR]

Atrazine is considered as a potential environmental endocrine disruptors and exhibits various toxic effects on animals. It has a great impact in the aquatic ecosystems, but there are few studies on its immunotoxicity in crustaceans. In the present study, the Procambarus clarkii were utilized to assess the immune toxicity after 0.5 mg/L and 5 mg/L atrazine exposure. A significant decrease in total hemocytes count (THC) was observed at 5 mg/L atrazine exposure throughout the experiment. The activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were significantly inhibited, but the content of reactive oxygen species (ROS) and malondialdehyde (MDA) were up-regulated, indicating the potential oxidative stress. The analysis of the integrated biomarker response (IBR) showed the induction of oxidative stress biomarkers and the inhibition of antioxidants. After 5 mg/L atrazine exposure for 144 h, the integrity of crayfish hepatopancreas was destroyed with disappeared connections between tubules and increased liver tubules vacuoles. The relative expression levels of different immune genes in hepatopancreas after atrazine exposure were measured. Most of these genes were suppressed and exhibited a certain dose-dependent effect. The results of crayfish white spot syndrome virus (WSSV) replication shown the amount of virus in muscle was significantly higher and exhibited a higher mortality rate at 5 mg/L group than other groups. The present study determined the impact of atrazine exposure on WSSV outbreaks, and also provide an important basis for further assessing the occurrence of pesticides on diseases of P. clarkii. • Atrazine exposure could decrease the amount of hemocyte of P. clarkii. • Atrazine exposure inhibit the activities of antioxidant and immune-related enzymes. • Atrazine exposure (5 mg/L, 144 h) could destroy the integrity of hepatopancreas. • The expression of immune effectors were mostly inhibited after atrazine exposure. • Atrazine exposure enhances the proliferation of WSSV in P. clarkii. [ABSTRACT FROM AUTHOR]

The large normal force of a single-sided linear actuator may cause vibration, noise and reduce the positioning accuracy. To overcome these disadvantages, a new H-module linear actuator (HMLA) is proposed to reduce effectively the normal force without using expensive air suspension system or assisted guide. Compared to the existing HMLA, the teeth on the two opposite sides of the stator of this new HMLA are shifted by a tooth-shift-distance tsd. With a proper choice of tsd, the electromagnetic design and the force characteristics of the HMLA may be greatly improved. The finite element method (FEM) is employed to analyze the magnetic performance and the force characterization of an optimized HMLA with varying tsd. The performances when the HMLA is excited by rectangular and sinusoidal waveform currents are investigated. The result presented in this paper has shown that the total average tangential force of this new HMLA could be improved by 51% in comparison to the existing HMLA. [ABSTRACT FROM AUTHOR]

The effective identification of the load torque is one of the key methods to improve the positioning accuracy of the position servo system, and the sliding mode observer (SMO) is a common identification method in the speed control system because of its advantages of insensitive parameters and easy physical realisation. However, the existing SMO cannot achieve high precision and high response identification of load torque in the full speed range when the motor is running at variable-speed or variable-load, which limits its application in the position servo system. Based on the analysis of the stability and the adaptive law of feedback gain coefficient, an improved SMO for adaptive identification based on adaptive control and improvement of cut-off frequency is proposed. To verify the proposed method, the dedicated simulation model and test platform are built. The results show that the proposed observer can realize the adaptive identification of the load torque under the condition of variable-speed or variable-load, and the estimation accuracy is high. The position servo system designed by the proposed observer can improve the response against load change, which is an effective method for high-precision positioning control of the position servo system with a variable-speed or variable-load. [ABSTRACT FROM AUTHOR]

• A smith predictor-based delay compensation scheme is proposed for the suppression of the undesired speed overshoot/variation phenomena caused by the speed filter. • The effectiveness and stability of the proposed solution are verified analytically and experimentally. • The robustness of the proposed solution against system parameter mismatch is verified analytically and experimentally. • The proposed structure is simple to implement with a low calculation burden and no parameters need to be tuned. The load disturbance rejection ability of the electrical machine systems is an important consideration factor in many applications, including both power generation (e.g., wind power generator) and consumption (e.g., servo systems such as high-precision machining and continuous motion in manufacturing automation). Existing studies on load disturbance rejection mainly focus on developing disturbance observers with improved steady state and dynamic performance. However, the performance of the disturbance rejection control is not only determined by the performance of the disturbance observers but also influenced by the speed response control during the transient. The latter problem might require more attention, especially due to the fact that speed filter is widely used in many actual systems to suppress the speed ripples or noise. The speed control performance would suffer from the delay caused by the filter and result in an undesired oscillatory speed response. In this paper, load disturbance rejection control based on a sliding mode disturbance observer is considered as an investigation platform, where an adaptive filter is proposed to further improve the performance of the observer. More importantly, a Smith predictor-based speed filter delay compensator is proposed to mitigate the undesired variation in the speed response caused by speed filter, achieving enhanced transient speed response under load disturbance. This structure is simple to implement, and no control parameters need to be tuned. The effectiveness of the proposed solution has been verified on a permanent magnet synchronous machine drive system. [ABSTRACT FROM AUTHOR]

This study introduces a new structure of the magnetic lead screw (MLS) intended for wave energy conversion (WEC) applications. One of the key challenges in the application of MLS technology for wave energy lies in the manufacturing of its complicated ideal helix. Structural simplification and processing technology are quite essential in promoting the development of the magnet screw. This study proposes a new method for shaping the desired ideal helix in a simple way with parallelly magnetised magnets. This simple structure reduces manufacturing complexity while maintaining good force density. The magnets with parallel magnetisation are also easier and cheaper to manufacture than the magnets with radial magnetisation. A prototype is manufactured and tested in the laboratory. In addition, the electromagnetic performance of the new structure is evaluated as compared with the magnet screw with ideal helix using the three‐dimensional finite element analysis, verifying the advantages of the proposed structure. [ABSTRACT FROM AUTHOR]

An improved anisotropic vector Preisach model is proposed in this paper to describe the hysteresis properties of nonoriented (NO) electrical steel sheet (ESS) under 50 Hz rotating magnetic fields. The proposed model consists of three components, static hysteresis component, eddy current component, and excess component, which is based on the iron loss separation theory. The static hysteresis component is constructed by the static vector Preisach model. The proposed model is identified by the measured hysteresis properties under 1 Hz and 50 Hz magnetic fields. Finally, the experimental results prove the effectiveness of the proposed anisotropic vector hysteresis model. [ABSTRACT FROM AUTHOR]

Fast and reliable initial rotor position detection is essential for restarting sensorless permanent magnet synchronous motors (PMSMs) in free-running condition. In this article, a fast initial rotor position estimation method for low-speed free-running motor is proposed, which utilizes a combined sinusoidal current and square-wave voltage injection method. The sinusoidal current is imposed into the estimated d-axis to magnify the magnetic saturation effect. The amplitudes of the d-axis current caused by injected square-wave voltage are then accumulated. The large difference of the two integrated signals for positive and negative d-axis currents can be reliably used to identify the rotor polarity. Meanwhile, in low-speed free-running stage, the change of saturation degrees introduced by the injected sinusoidal signal does not affect the position estimation accuracy. Moreover, even if the sinusoidal current signal is injected in the incorrect d-axis, the resultant torque is small and unexpected rotation of the rotor is prevented. Its influence on the free-running motor is negligible, due to the combined injection with continuously online updated estimated rotor position by high-frequency square-wave voltage injection during the polarity identification process. Finally, the effectiveness of the proposed method is investigated on a 1.5 kW interior PMSM test platform. [ABSTRACT FROM AUTHOR]

This article investigates and proposes an efficient control design to address the degradation in the mechanical speed of a traction machine drive (TMD) in an electric vehicle (EV) caused by thermal effects during its operation. Variations in the operating as well as ambient temperature cause unexpected uncertainties in TMD parameters such as stator and rotor resistances, which results in significant degradation in EV's speed performance capability. To mitigate this problem, an output feedback robust linear parameter varying (LPV) controller-observer set is designed using H $_{\infty }$ control theory that enhances the EV's speed performance in field-oriented control (FOC) frame. The internal stability of the closed-loop control and the $L_{2}$ gain bound are ensured by linear matrix inequalities. The performance of the proposed control technique is compared with that of conventional FOC, sliding mode control (SMC) and higher order sliding mode control (HOSMC) to validate its efficacy and advantages. The robustness of the proposed control technique is tested for an EV operation against the Worldwide Harmonised Light Vehicles Test Procedure (WLTP) Class 3 driving cycle. The nonlinear MATLAB simulation results guarantee the effectiveness of the proposed controller-observer set. These results are verified experimentally on an induction machine drive setup. [ABSTRACT FROM AUTHOR]

This study proposes a magnetic lead screw (MLS) as a continuous propulsion device for the general transport system (GTS). By integrating the outer rotor machine with the MLS, it is possible to construct a high force design with the improved operating surface area. Initially, a brief statement of the novel GTS is given, leading to an introduction of the MLS. Besides, a scaled 2.6‐kN MLS demonstrator is presented to verify the propulsion principle and thrust force. Furthermore, the MLS design focuses on several types, which use different materials and magnetic structures. The three‐dimensional finite element analysis is used to optimise design, with the goal of force performance. Moreover, the shear stress, cost‐effectiveness, magnetic losses, and mechanical stress of the different topologies are compared, revealing that the MLS made by ferrite magnet is more suitable for employed in GTS applications. Finally, a dynamic model of the GTS is developed to verify the acceleration and speed responded. [ABSTRACT FROM AUTHOR]

In the back electromotive force (EMF)-based sensorless control of interior permanent magnet synchronous motor (IPMSM), the inverter nonlinearity and flux linkage spatial harmonics will possibly give rise to (6k ± 1)th harmonics in the estimated back EMF, especially the fifth and seventh harmonics. Those harmonics will consequently introduce (6k)th harmonic ripples to the estimated rotor position, especially the sixth harmonic component. In order to solve this problem, a bilinear recursive least squares (BRLS) adaptive filter is proposed and integrated into a sliding-mode position observer to suppress the dominant harmonic components in the estimated back EMF and as a result, the accuracy of the estimated rotor position can be greatly improved. A unique feature of the BRLS adaptive filter is its ability to track and suppress the specified harmonic components in different steady state and dynamic operational conditions. The proposed method can compensate for harmonic ripples caused by the inverter nonlinearity and machine spatial harmonics at the same time; this method is also robust to machine parameter variation, and the BRLS algorithm itself is machine parameter independent. The implementation of the proposed BRLS filter in the sensorless control of IPMSM is explained in details in this paper. The enhanced drive performances using the BRLS filter have been thoroughly validated in different steady state and dynamic operational conditions on a 1.5-kW IPMSM sensorless drive. [ABSTRACT FROM AUTHOR]

Effective identification of the load torque is one of the key aspects in improving the performance of servo drive systems against load disturbances. Sliding mode variable structure control has become a popular method in the development of a load torque identification (LTID) algorithm due to its parameter insensitivity and easy realization features. However, existing LTID sliding mode observers (SMO) with conventional structure have the disadvantages of high-frequency chattering and poor estimation accuracy, which limit its application in high-performance servo systems. In this paper, the mathematical model of the conventional LTID-SMO is deduced and analyzed. A new LTID-SMO is proposed by replacing the sign function with a saturation function and an additional feedback loop in the load torque observer. The effectiveness of the proposed observer is verified by various experiments. The results show that compared to conventional load torque observer, the proposed observer can identify the load torque with higher accuracy and faster response in different operational conditions. [ABSTRACT FROM AUTHOR]

This paper presents an identification algorithm of the scalar Preisach model by using a set of symmetric minor hysteresis loops and suggests an improved vector Preisach model to describe the vector and anisotropic hysteresis behavior of a non-oriented (NO) electrical steel sheet (ESS) under rotating magnetic fields. Symmetric minor hysteresis loop is quite easy measured, so an identification algorithm based on symmetric minor hysteresis loop instead of first-order reverse curve is presented in this paper. The vector Preisach model employs a nonlinear coefficient, which is a function of magnitude and a direction of magnetic flux density, to describe the anisotropic property of the NO ESS and increases the numerical accuracy. The validity of the suggested vector Preisach model is investigated through comparisons with the experimental results under various magnetic field conditions. [ABSTRACT FROM AUTHOR]

This paper presents a new initial rotor position estimation method for an interior permanent magnet synchronous motor. The proposed method includes two steps. First, the minimum voltage vectors are injected to estimate the rotor position. Second, in order to identify the magnet polarity accurately, two opposite voltage pulses are injected on the estimated d-axis. In the proposed method, no filter is needed to draw the high frequency current signal for position estimation and no low-pass filter is required in the current control loop for extracting the fundamental current component for field-oriented control. The fast and reliable feature of this proposed method allows starting the motor with 100% load torque. The effectiveness of the proposed method is verified experimentally and the maximum position estimation error is around 6 electrical degrees. [ABSTRACT FROM AUTHOR]

Rotor position estimated with high-frequency (HF) voltage injection methods can be distorted by voltage errors due to inverter nonlinearities, motor resistance, and rotational voltage drops, etc. This paper proposes an improved HF square-wave voltage injection algorithm, which is robust to voltage errors without any compensations meanwhile has less fluctuation in the position estimation error. The average position estimation error is investigated based on the analysis of phase harmonic inductances, and deduced in the form of the phase shift of the second-order harmonic inductances to derive its relationship with the magnetic field distortion. Position estimation errors caused by higher order harmonic inductances and voltage harmonics generated by the SVPWM are also discussed. Both simulations and experiments are carried out based on a commercial PMSM to verify the superiority of the proposed method and the investigations in this paper. [ABSTRACT FROM AUTHOR]

In order to analyze the magnetic field distribution and thrust performance of the U-channel air-core permanent magnet linear synchronous motor (UAPMLSM), an analytical model is proposed based on the equivalent magnetization intensity method. The detailed analytical solutions of the magnetic flux density and thrust considering space harmonic components are derived, and then validated by the finite-element method results. With the provided analytical approach, it gives an insight into the key design parameters that may affect the characteristics of the magnetic field and thrust. The optimal design of the pole arc coefficient and coil span coefficient is given with minimized total harmonic flux density components and the thrust ripple. The proposed analytical model could be used for a quick and optimal design of the UAPMLSM. [ABSTRACT FROM AUTHOR]

• It is analyzed that current measurement error can cause steady-state speed ripple with multiple harmonics. • A robust plug-in repetitive controller is designed in the outer loop of PMSM. • A third order Butterworth filter with phase correction is designed to restrain ripples and ensure high-frequency stability. • A hybrid phase correction method is designed to ensure the stability and the fast error convergence at low frequencies. • The designed repetitive controller is robust to PMSM parameters variation within a normal range. Non-ideal factors can cause steady-state speed ripples for Permanent Magnet Synchronous Motor (PMSM). In this paper current measurement error is mainly analyzed since it can cause multiple (not only 1st- or 2nd-order as analyzed in the existing literature) harmonics when considering its influence on electrical angle. In order to suppress the ripples, a robust plug-in repetitive controller with phase compensation is designed in the outer speed loop of PMSM cascade PI control system. Compared with the repetitive controller added in the current loop, there are two technical challenges: more stringent requirement of high-frequency disturbance suppression and more complex phase compensation design. Hence, a third-order Butterworth filter with phase correction is proposed which can ensure the system's ability to resist low-frequency periodic disturbances and the high-frequency stability of the system. A hybrid phase correction method combining lead, lag and linear correction is designed which can ensure the stability and the fast convergence of the system at low frequencies. The designed repetitive controller is robust to PMSM parameters variation within a normal range. The experimental results prove that the proposed control strategy can effectively suppress motor speed fluctuation with good steady-state and transient performance. [ABSTRACT FROM AUTHOR]

In this paper, an effective cogging torque reduction method based on shifting the slot-openings is presented. Stator teeth are divided into groups and proper slot-opening shift is applied for each group. The cogging torque can then be greatly reduced while the back-EMF waveforms remain symmetrical. No additional back-EMF harmonic components will be introduced by this method. Analytical analysis revealing the working principle of this method is given, which gives a clear guide about how this method may be applied to different permanent magnet machines. [ABSTRACT FROM AUTHOR]

The single-sided linear actuator has usually large normal force which may induce large frictional force when using roll-bearings to support the linear motion. Otherwise, an air suspension system or assisted guide is needed to balance the normal force. A new H-module linear actuator (HMLA) with much lower normal force is proposed in this paper. The proposed new H-module linear actuator makes use of additional air suspension system unnecessary. The topology and working principle of the HMLA is illustrated in details in this paper. The force characteristics are analyzed by finite element method (FEM). The impacts of several key design parameters on the force characteristics are studied, and the HMLA is optimized afterwards. It is proved that the optimized HMLA could use less permanent magnet (PM) volume and generate larger useful tangential force and its normal force vs. tangential force ratio is much lower than that of the conventional single-sided linear actuator. [ABSTRACT FROM PUBLISHER]

In order to reduce the thrust ripple of linear servo system, a double-sided air core permanent magnet linear servo motor with trapezoidal shape permanent magnets (TDAPMLSM) is proposed in this paper. An analytical model of the motor for predicting the magnetic field in the air-gap at no-load is introduced. This model is derived based on the equivalent magnetization intensity method, and its accuracy is validated by using the results obtained from the finite-element method. The key dimensions that affect the air-gap magnetic field are analyzed based on the analytical model, and the design is optimized by using genetic algorithm. A thrust ripple reduction of 70.6% is achieved by optimization. The proposed analytical model may be used for a quick and reliable design and design optimization of the TDAPMLSM. [ABSTRACT FROM AUTHOR]

• Design a frequency-adaptive and parameters-robustness PIR controller for PMSM system. • Making a tradeoff between stability margin and harmonic suppression capability. • Ensuring the stability of the original system not being affected by PIR controller. • Improving the steady-state precision without affecting the transient performance. An adaptive proportional-integral-resonant (PIR) controller with piecewise phase compensation is proposed to suppress the steady-state speed ripple of permanent magnet synchronous motor (PMSM) drive due to current measurement error. The frequency-varying characteristic of PMSM drive makes the parameters determination of the resonant controller more complicated when considering frequency adaptation. In this paper, after theoretical analysis on the current measurement error, the resonant controller is added in the speed PI loop of the PMSM vector control system, which makes the system more prone to instability. In order to ensure the stability of the system at different speeds, the resonant gain is firstly restricted by root locus method to get a stable system in the full speed range. Then, the resonant gain and the phase angel are further designed to obtain a robust vector margin by Nyquist diagram in different speed ranges. Such piecewise phase compensation method can achieve good stability margin and harmonic suppression ability by making a trade-off between them, avoiding the complicated calculation of the trigonometric functions for compensation in real time. Both steady and transient experiment results indicate that the proposed PIR controller can well restrain the frequency-varying speed ripples caused by current measurement error. [ABSTRACT FROM AUTHOR]

A reluctance lead screw (RLS) is proposed in this paper which consists of a rotor and a translator, forming a magnetic device that is able to transfer low-speed linear motion into high-speed rotational motion. Permanent magnets (PMs) are only installed in the rotor, making it more suitable for long-stroke applications. The design aspects are assessed by finite element analysis (FEA) and the performance is evaluated. In addition, the thrust force per magnet volume is presented for evaluating the utilization rate of the PMs. The simulation results show that RLS has an advantage in terms of the PM utilization rate. A new method for realizing spiral magnets has also been developed which can not only reduce the manufacturing difficulties, but also ease the installation work. Finally, based on the simulations and analyses, two RLS prototypes designed for wave energy converters (WECs) are presented to show the potential applications of this novel topology. [ABSTRACT FROM AUTHOR]

Most of the existing (BLDCM) brushless dc motor drive systems are designed with the traditional drive scheme for long-time operation. For short-time and heavy-duty applications, there are problems of energy consumption, large volume, heavyweight and high-cost. In this paper, a new short-time high-overload BLDCM drive system based on "electronic flywheel" and time-division switching control is proposed, which includes three core contents: a crushing chamber based on combined cutter head, an energy storage device based on an "electronic flywheel" and high overload factor BLDC using a new calculation method of capacitance and a speed control system based on time-division switching control of the speed loop and the current loop. To prove the effectiveness of the proposed scheme, a kitchen garbage processor is developed and tested. The results show that the "electronic flywheel" energy storage driving device designed in this paper is able to provide most of the energy required in the heavy-duty driving process. The designed time-division switching control scheme can well meet the control requirements for the short-time heavy load drive of the kitchen waste processor. Compared with the traditional long-time rated load drive scheme, the proposed system has the advantages of energy-saving, small volume, lightweight and low-cost. [ABSTRACT FROM AUTHOR]

Presents corrections to financial information in the above titled paper. [ABSTRACT FROM AUTHOR]

The high-response and self-adaptive yarn delivery system used in weft accumulator is a critical component for improving the efficiency and quality of textile machinery. However, the existing drive system in the weft accumulator has problems such as slow start-up and slow speed-tracking responses, giving difficulties in achieving a high-efficient yarn delivery of the textile machinery. In this paper, a high-response self-balancing sensorless integrated control system of the induction motor for weft accumulator is proposed. Firstly, to enable the motor to start and respond adaptively and quickly to the number of yarn control loops and the speed control of the external equipment, a high-response sensorless vector control system for induction motor based on improved model reference adaptive control(MRAC) is proposed. Secondly, to achieve a high-response adaptive tracking performance of yarn input and output numbers and spool shaft speed, a self-balancing control strategy based on optical electromechanically integrated closed-loop control is proposed. For proving the effectiveness of the proposed scheme, a corresponding test platform was constructed for testing and validation. It can be observed from the results that the system designed in this paper has fast starting speed and better speed tracking performance, satisfying yarn delivery requirements at different speeds with high-response and adaptability. [ABSTRACT FROM AUTHOR]

An H-module linear actuator (HMLA) is proposed in this paper for medical equipment applications. Compared to the existing linear actuators used in medical equipment, the proposed H-module linear actuator has much lower normal force, which makes use of an additional air-suspension system unnecessary. The working principle of the HMLA is illustrated in detail in this paper, and its tangential and normal force characteristics are demonstrated by using finite element analysis (FEA). It is proved that the normal force of the HMLA can be greatly reduced without sacrificing the useful tangential force component. [ABSTRACT FROM AUTHOR]