Five-phase Synchronous Reluctance Machines Equipped with a Novel Type of Fractional Slot Winding

Multi-phase machines are so attractive for electrical machine designers because of their valuable advantages such as high reliability and fault tolerant ability.Meanwhile,fractional slot concentrated windings(FSCW)are well known because of short end winding length,simple structure,field weakening sufficiency,fault tolerant capability and higher slot fill factor.The five-phase machines equipped with FSCW,are very good candidates for the purpose of designing motors for high reliable applications,like electric cars,major transporting buses,high speed trains and massive trucks.But,in comparison to the general distributed windings,the FSCWs contain high magnetomotive force(MMF)space harmonic contents,which cause unwanted effects on the machine ability,such as localized iron saturation and core losses.This manuscript introduces several new five-phase fractional slot winding layouts,by the means of slot shifting concept in order to design the new types of synchronous reluctance motors(SynRels).In order to examine the proposed winding’s performances,three sample machines are designed as case studies,and analytical study and finite element analysis(FEA)is used for validation.

Encoderless Five-phase PMa-SynRM Drive System Based on Robust Torque-speed Estimator with Super-twisting Sliding Mode Control

In this paper,a robust torque speed estimator(RTSE)for linear parameter changing(LPC)system is proposed and designed for an encoderless five-phase permanent magnet assisted synchronous reluctance motor(5-phase PMa-SynRM).This estimator is utilized for estimating the rotor speed and the load torque as well as can solve the speed sensor fault problem,as the feedback speed information is obtained directly from the virtual sensor.In addition,this technique is able to enhance the 5-phase PMa-SynRM performance by estimating the load torque for the real time compensation.The stability analysis of the proposed estimator is performed via Schur complement along with Lyapunov analysis.Furthermore,for improving the 5-phase PMa-SynRM performance,five super-twisting sliding mode controllers(ST-SMCs)are employed with providing a robust response without the impacts of high chattering problem.A super-twisting sliding mode speed controller(ST-SMSC)is employed for controlling the PMa-SynRM rotor speed,and four super-twisting sliding mode current controllers(ST-SMCCs)are employed for controlling the 5-phase PMa-SynRM currents.The stability analysis and the experimental results indicate the effectiveness along with feasibility of the proposed RTSE and the ST-SMSC with ST-SMCCs approach for a 750-W 5-phase PMa-SynRM under load disturbance,parameters variations,single open-phase fault,and adjacent two-phase open circuit fault conditions.

Algorithm for Smooth S-curve Feedrate Profiling Generation

The algorithms for feedrate profile generation,such as linear and S-curve profiles,have been widely used in machinery controllers,and these algorithms can greatly improve the smoothness of motion.However,most of the algorithms lead to the discontinuous acceleration/deceleration and jerk,or high jerk levels,which is very harmful to machine tool or robot in most occasions. This paper presents a smooth S-curve feedrate profiling generation algorithm that produces continuous feedrate,acceleration,and jerk profiles.Smooth jerk is obtained by imposing limits on the first and second time derivatives of acceleration,resulting in trapezoidal jerk profiles along the tool path.The discretization of smooth S-curve feedrate is realized with a novel approach that improves the efficiency without calculating the deceleration point in each sampled time.To ensure that the interpolation time is a multiple of the value of sampled time,the feedrate,acceleration,jerk,and jerk derivative are recalculated.Meantime,to improve the efficiency,the interpolation steps of all regions are computed before interpolation.According to the distance of trajectory,the smooth S-curve acceleration and decelerations are divided into three blocks：normal block,short block type-Ⅰ,and short block type-Ⅱ.Finally feedrate discretization of short block type-Ⅰand type-Ⅱis obtained with considering the efficiency.The proposed generation algorithm is tested in machining a part on a five axis milling machine,which is controlled with the CNC system for newly developed high-speed machine tools.The test result shows that the smooth S-curve approach has the smoother feedrate,acceleration,deceleration,and jerk profiles than S-curve.The proposed algorithm ensures the automated machinery motion smoothness,and improves the quality and efficiency of the automated machinery motion planning.

Performance Analysis and Comparison of Two Fault-Tolerant Model Predictive Control Methods for Five-Phase PMSM Drives

Model predictive current control(MPCC)and model predictive torque control(MPTC)are two derivatives of model predictive control.These two control methods have demonstrated their strengths in the fault-tolerant control of multiphase motor drives.To explore the inherent link,the pros and cons of two strategies,the performance analysis and comparative investigation of MPCC and MPTC are conducted through a five-phase permanent magnet synchronous motor with open-phase fault.In MPCC,the currents of fundamental and harmonic subspaces are simultaneously employed and constrained for a combined regulation of the open-circuit fault drive.In MPTC,apart from the torque and the stator flux related to fundamental subspace,the x-y currents are also considered and predicted to achieve the control of harmonic subspace.The principles of two methods are demonstrated in detail and the link is explored in terms of the cost function.Besides,the performance by two methods is experimentally assessed in terms of steady-state,transition,and dynamic tests.Finally,the advantages and disadvantages of each method are concluded.

Fault-Tolerant Operation of Five-Phase Permanent Magnet Synchronous Motor with Independent Phase Driving Control

The multi-phase motor drive system with multiple H-bridge power supply has high fault tolerance,which is widely used in aerospace,electric vehicle,ship integrated power system and other fields.In this paper,a fault-tolerant control strategy based on decoupling control and stator current compensation is proposed for the propulsion system of five-phase PMSM with independent neutrals.Firstly,the mathematical model of PMSM is established by using vector space decoupling method;Secondly,a stator current compensation method is adopted to carry out fault-tolerant control after the motor has single-phase and two-phase open-circuit faults and the fault-tolerant control system based on decoupling control is established;Finally,the decoupling control model and the fault-tolerant control of stator current compensation are verified by the simulation and experiment.The simulation and experiment results show that the method can reduce the torque ripple caused by the stator winding open-circuit fault,and the operation performance of the motor under fault condition is significantly improved.

Comparative Study on Torque Performance of Five-phase Single-Stator and Double-Stator Permanent Magnet Synchronous Motors

This paper compares the torque characteristics of single stator permanent magnet synchronous motor(PMSM)and double-stator PMSM under different split-ratios,air-gap lengths and shaft diameters by finite element method.Firstly,the effects of split-ratio towards the torque characteristics of the two motor structures under different air-gap lengths are researched,the results show that the optimal split-ratios of the two motor structures do not change under different air-gap lengths,and the optimal split-ratio of the double-stator motor is greater than that of single-stator,and the torque of the double-stator motor is greater than that of single-stator motor with arbitrary split-ratio under the same air-gap length;Finally,the effects of the shaft diameter to the torque of the two motor structures are investigated,obtaining that with the increasing of shaft diameter,the electromagnetic torque of the single-stator motor is almost unchanged,however,the torque of the double-stator is gradually reduced,when the shaft diameter reached a certain extent,the electromagnetic torque of the double-stator motor is smaller than that of single-stator motor with the split ratio within a certain range,and the torque/quality ratio of the double-stator motor is smaller than that of single-stator motor with their optimal split ratio separately.

Analysis of Direct Torque Control for Marine Five-Phase Induction Motor

Based on the principle of direct torque control,a DTC(Direct Torque Control)system with five-phase induction motor has been studied.Providing direct control of stator flux and electromagnetic torque by optimized voltage vector,five-phase induction motor enhances flexibility of the invert states selection by increasing the number of voltage vectors,resulting in more precise control of stator flux and electromagnetic torque.The model of DTC for five-phase induction motor is constructed on equations and the method of approximate circle of torque track is used to conduct the simulation analysis of the system.The simulation results demonstrate that the DTC for five-phase induction motor control has merits of little calculation compared with vector control,simple structure,fast response and greater dynamic performance.

Speed sensorless FCS-MPTC based on FOSM-MRAS five-phase permanent magnet synchronous motor

For the two-level five-phase permanent magnet synchronous motor(FP-PMSM)drive system,an improved finite-control-set model predictive torque control(MPTC)strategy is adopted to reduce torque ripple and improve the control performance of the system.The mathematical model of model reference adaptive system(MRAS)of FP-PMSM is derived and a method based on fractional order sliding mode(FOSM)is proposed to construct the model reference adaptive system(FOSMMRAS)to improve the motor speed estimation accuracy and eliminate the sliding mode integral saturation effect.The simulation results show that the FP-PMSM speed sensorless FCS-MPTC system based on FOSM-MRAS has strong robustness,good dynamic performance and static performance,and high reliability.

基于网站营销的声誉系统的分析

本文分析网站销售的热点问题"声誉系统建设"。针对VC疯狂投资B2C现象,借鉴S-Curve成长曲线原理,提出电子商务建设"声誉维护"问题,并列举实证方案,探讨了销售网站如何通过建立信誉维护系统,渡过产品营销最危险推广期的关键问题,即通过诚信建设,逐渐建立起自己的信誉平台,以最大程度地获得客户的认可和支持,为企业持续发展营造健壮的源动力。

Exponential response electrical pole-changing method for a five-phase induction machine with a current sliding mode control strategy

Electrical pole-changing technology leads to torque ripple and speed fluctuation despite broadening the constant power speed range of the multiphase induction machine （IM） system. To reduce the torque ripple and speed fluctuation of the machine, we investigate an exponential response electrical pole-changing method for five-phase IM with a current sliding-mode control strategy. This control strategy employs the dual-plane （dr-q1 and d2-q2） vector control method, which allows the IM to operate under different pole modes. Current sliding-mode controllers are applied instead of conventional proportional integral （PI） controllers to adjust the current vectors, and exponential current response achieves a smooth transition between the d1-q1 and d2-q2 planes. Compared with the step response pole-changing with PI control method, the proposed pole-changing method greatly reduces the torque ripple and speed fluctuation of the IM during the pole-changing process. Experimental results verify the ex- ceptional performance of the proposed electrical pole-changing strategy.

Research on Torque Ripple Under Healthy and Open-Circuit Fault-Tolerant Conditions in a PM Multiphase Machine

In this paper,research into torque ripple production has been undertaken for both the healthy and open-circuit faulttolerant conditions of a five-phase permanent magnet(PM)machine by using the instantaneous power(I-Power)approach.When only the fundamental component of the phase currents is applied to the phase windings,it has been shown that the 9th and 11th harmonics of the back-electromotive force(back-EMF)causes torque ripples in a five-phase PM machine and its frequency is ten times the frequency of the fundamental phase currents.When the combined fundamental and third harmonic components of the phase currents are applied to the phase windings,it has been shown that the 7th and 13th harmonic of the back-electromotive force(back-EMF)causes additional torque ripples in a five-phase PM machine.These torque ripples under fault-tolerant conditions have been analyzed analytically,as well.It has been proven that there are interactions between the fundamental component of current and the third harmonic component of the back-EMF and vice versa.These interactions cause torque ripples.A finite element analysis(FEA)model of the five-phase PM machine has been done to validate the analytical results.

Fault-tolerant Deadbeat Model Predictive Current Control for a Five-phase PMSM with Improved SVPWM

The main drawbacks of traditional finite set model predictive control are high computational load,large torque ripple,and variable switching frequency.A less complex deadbeat(DB)model predictive current control(MPCC)with improved space vector pulse-width modulation(SVPWM)under a single-phase open-circuit fault is proposed.The proposed method predicts the reference voltage vector in the a-β subspace by employing the deadbeat control principle on the machine predictive model;thus,the exhaustive exploration procedure is avoided to relieve the computational load.To perform the constant switching frequency operation and achieve better steady-state performance,a modified SVPWM strategy is developed with the same conventional structure,which modulates the reference voltage vector.This new approach is based on a redesigned and adjusted post-fault virtual voltage vector space distribution that eliminates the y-axis harmonic components in the x-y subspace and ensures the generation of symmetrical PWM pulses.Meanwhile,the combined merits of the DB,MPCC,and SVPWM methods are realized.To verify the effectiveness of the proposed control scheme,comparative experiments are performed on a five-phase permanent magnet synchronous motor(PMSM)drive system.

Adaptation of feed rate for 3-axis CNC high-speed machining

To improve the efficiency of CNC machining, assumptive transit circular arc is used to contour two adjacent moves together on the comer to make smooth paths. The radios of transit circular arc can be adjusted with contour accuracy, and the feed rate on the corner can be controlled through limiting the maximum feed rate of transit circular arc segment. A look-ahead algorithm for a series of moves is proposed for speed adjustment in advance, which avoids the occurrence of overload of cutting tool on the comer and reduces the servo track error of parts on the corner or of circular arc move. Equivalent trapezoidal velocity profile is used to analyze the speed of S-curve velocity profile and work out its accurate interpolation, which overcomes the disadvantage of looking up table to calculate feed rate approximately, hence high accuracy and fine surface quality can be obtained while the machining speed is high. The proposed methods can meet the requirements of real-time analysis of high-speed machining. The presented algorithm is effective and has been adopted by CNC system of newly developed high-speed milling machine.

Field-Oriented Control and Direct Torque Control for a Five-Phase Fault-Tolerant Flux-Switching Permanent-Magnet Motor

This paper presents a comparative performance analysis of a new five-phase fault-tolerant flux-switching permanent-magnet(FT-FSPM)motor for high-reliability applications under the two most popular control schemes,namely,field-oriented control(FOC)and direct torque control(DTC)based on stator-flux orientation.Firstly,the new motor topology and structural characteristics are briefly presented.Secondly,the d-and q-axis for the FT-FSPM motor are defined,which is crucial to the mathematical model and control scheme,and the mathematical models are derived.Then,two control schemes,i.e.,FOC and DTC,and the main system are proposed.The operational principles of the two control schemes are presented,and space vector pulse width modulation(SVPWM)based on four neighboring vectors is adopted to reduce current harmonics and torque ripples.Finally,the simulated and experimental results are given,and performance analysis of the two control schemes are compared and discussed.The results reveal that FOC scheme has the sinusoidal phase current and low torque ripples,while the DTC scheme has fast dynamic response,verifying the effectiveness of the two proposed control schemes.This paper is a primary investigation for more possible improvements in the control schemes of the five-phase FS-FTPM motor.

Microstructures and dynamic processes within the five-phase system:Regarding COVID-19 as a complex system

The research uses the development of 2019 novel coronavirus disease(COVID-19)in the human body as an example to explore the microstructures and dynamic processes of a concise complex system from the lens of the five-phase system.Based on the structural balance theory and system dynamics,the research finds that Iransitive triads and cyclic triads in the fivephase system are both imbalanced.The integration of these differentiated triads comprises of a balaneed intermediate form in the shape of quadrangular cycles.These cycles serve as microstructures of the five-phase system,due to the inherent balancing feedback mechanism,and support the generation of resultants.The alter nation of quadra ngular cycles drives the spirali ng development of the whole system.By orderly and regular in terweaving of sig ned directed links,the research provides a holistic,process-oriented demonstrati on for the developme nt processes of COVID-19.It clarifies that the esse nee of the five-phase system is phase-tra nsition processes with the quadrangular cycle as carrier and supporter,rather than the static aggregati on of five elements.The research deep ens the understanding of system non linearity by visualizi ng the circular causality and promotes the academic dialogue between the Western process theory and the Chinese inherited notion of the fivephase system.

AltBOC navigation signal quality assessment and measurement

In order to ensure that Chinese BeiDou satellite navigation system runs smoothly,the assessment of signal quality has become a significant task.Alternative binary offset carrier(AltBOC)is BeiDou B2 frequency signal.The acquisition of BeiDou signal is processed in off-line mode and the evaluation is performed by taking signal power spectrum,eye diagram,constellation,correlation,loss and s-curve deviation on AltBOC as signal quality evaluation parameters.The results illustrate that the new system signal,namely AltBOC signal,has the best performance in code tracking precision,anti-jamming and anti-multipath.

Planning and Organizing the Projects in Team Co Cakovec, Croatia

The paper systemizes standard methods of planning, monitoring and controlling the realization of construction works in civil engineering projects and overviews the implementation of the methods in Team Co Cakovec from Croatia. The specificities of the methods are shown through the different construction works projects. Also, paper reviews the implementation, modification and improvement of existing methods for planning, monitoring and controlling the realization of projects in Team Co.

The S-Curve： China versus Its Major Trading Partners

China has been accused of manipulating its currency to gain international competitiveness and enjoy a trade surplus. The S-Curve is a hypothesis that could be used to test the depreciation. It claims that while future effectiveness of currency devaluation or values of the trade balance and current exchange rate are positively correlated, the past values of the trade balance and current exchange rate are negatively correlated. While China＇s aggregate trade flows with the rest of the world conforms to the S-Curve hypothesis, disaggregating trade flows by trading partner reveals that not all partners are affected equally by devaluation. Indeed, trade with 8 out of the 24 partners does not support the S-Curve hypothesis.

Dual-frequency Discontinuous Space Vector Pulse Width Modulation for Five-phase Voltage Source Inverters with Harmonic Injection

This paper proposes a dual-frequency discontinuous space vector pulse width modulation(DFDSVPWM)for a five-phase voltage source inverter with harmonic injection.In this modulation,for dual-frequency voltage output and reduction of switching losses,two different zero-vector-inserted modes are flexibly employed by alternatively using two types of zero vectors.Based on the comparison with continuous SVPWM,the idea and principle of the proposed DFDSVPWM are analyzed and an example of PWM signals for one bridge is also presented.For switching losses analysis,the impact factors and the calculation method are investigated and the corresponding implementation is given as well.The simulation and experimental results from a prototype verify the correctness and effectiveness of the proposed modulation and it has the advantages of outputting dual-frequency voltage and reducing switching losses.

Short-circuit fault-tolerant control for five-phase fault-tolerant permanent magnet motors with trapezoidal back-EMF

When a short-circuit fault occurs in a phase,the faulty phase needs to be removed artificially from the system because of the loss of the capability to generate torque.In this case,both the short-circuit current and phase-loss fault would generate additional torque ripples.In this study,a novel fault-tolerant control strategy is introduced to achieve low torque ripple operation of five-phase fault-tolerant permanent magnet synchronous motors with trapezoidal back electromotive force(FTPMSM-TEMF)in the event of a short-circuit fault.The key concept of this method is to compensate for the torque ripples caused by the short-circuit current and the adverse effect of the phase-loss.Based on the torque expression under fault conditions,the torque ripple caused by the short-circuit current can be offset by injecting a certain pulsating component into the torque expression in the phase-loss condition.This would result in smooth operation under fault conditions.Moreover,to track the fault-tolerant alternating currents,the model of the deadbeat current predictive control is extended and restructured for the fault condition.The effectiveness and feasibility of the proposed fault-tolerant strategy are verified by experimental results.