Load balancing is vital for the efficient and long-term operation of cloud data centers.With virtualization,post(reactive)migration of virtual machines(VMs)after allocation is the traditional way for load balancing an...Load balancing is vital for the efficient and long-term operation of cloud data centers.With virtualization,post(reactive)migration of virtual machines(VMs)after allocation is the traditional way for load balancing and consolidation.However,it is not easy for reactive migration to obtain predefined load balance objectives and it may interrupt services and bring instability.Therefore,we provide a new approach,called Prepartition,for load balancing.It partitions a VM request into a few sub-requests sequentially with start time,end time and capacity demands,and treats each sub-request as a regular VM request.In this way,it can proactively set a bound for each VM request on each physical machine and makes the scheduler get ready before VM migration to obtain the predefined load balancing goal,which supports the resource allocation in a fine-grained manner.Simulations with real-world trace and synthetic data show that our proposed approach with offline version(PrepartitionOff)scheduling has 10%–20%better performance than the existing load balancing baselines under several metrics,including average utilization,imbalance degree,makespan and Capacity_makespan.We also extend Prepartition to online load balancing.Evaluation results show that our proposed approach also outperforms state-of-the-art online algorithms.展开更多
In this paper,an outer-rotor parallel-hybrid-excited vernier machine is proposed.In order to realize the parallel hybrid excitation,the homopolar configuration is adopted to artfully combine the permanent magnet(PM)fl...In this paper,an outer-rotor parallel-hybrid-excited vernier machine is proposed.In order to realize the parallel hybrid excitation,the homopolar configuration is adopted to artfully combine the permanent magnet(PM)flux path and the electromagnet flux path together.Firstly,the structure of the proposed machine is presented.Secondly,its operating principle is studied and discussed.Thirdly,its performance for flux regulation is analyzed based on the 3-D finite element analysis.Finally,the prototype of the proposed machine is manufactured and tested to verify the analytical results.展开更多
Control strategies play a key role for operation of electric machines,which would directly affect the whole system performance.In fact,different control strategies have been executed and explored for electric machines...Control strategies play a key role for operation of electric machines,which would directly affect the whole system performance.In fact,different control strategies have been executed and explored for electric machines,which bring great impacts to industrial development and human society.This paper investigates and discusses the advantages control strategies for electric machines,including the field oriented control(FOC),direct torque control(DTC),finite control set model predictive control(FCS-MPC),sensorless control,and fault tolerant control(FTC).The corresponding control principles,control targets,fundamental approaches,advanced approaches,methodologies,merits and shortcomings are revealed and analyzed in detail.展开更多
基金supported by Shenzhen Industrial Application Projects of undertaking the National Key Research and Development Program of China under Grant No.CJGJZD20210408091600002the National Natural Science Foundation of China under Grant No.62102408Shenzhen Science and Technology Program under Grant No.RCBS20210609104609044.
文摘Load balancing is vital for the efficient and long-term operation of cloud data centers.With virtualization,post(reactive)migration of virtual machines(VMs)after allocation is the traditional way for load balancing and consolidation.However,it is not easy for reactive migration to obtain predefined load balance objectives and it may interrupt services and bring instability.Therefore,we provide a new approach,called Prepartition,for load balancing.It partitions a VM request into a few sub-requests sequentially with start time,end time and capacity demands,and treats each sub-request as a regular VM request.In this way,it can proactively set a bound for each VM request on each physical machine and makes the scheduler get ready before VM migration to obtain the predefined load balancing goal,which supports the resource allocation in a fine-grained manner.Simulations with real-world trace and synthetic data show that our proposed approach with offline version(PrepartitionOff)scheduling has 10%–20%better performance than the existing load balancing baselines under several metrics,including average utilization,imbalance degree,makespan and Capacity_makespan.We also extend Prepartition to online load balancing.Evaluation results show that our proposed approach also outperforms state-of-the-art online algorithms.
基金Supported in part by the National Natural Science Foundation of China under Grant 51607114in part by China Postdoctoral Science Foundation under Grant 2016M600673in part by Research Council of the University of Macao under Grant MYRG2017-00158-FST.
文摘In this paper,an outer-rotor parallel-hybrid-excited vernier machine is proposed.In order to realize the parallel hybrid excitation,the homopolar configuration is adopted to artfully combine the permanent magnet(PM)flux path and the electromagnet flux path together.Firstly,the structure of the proposed machine is presented.Secondly,its operating principle is studied and discussed.Thirdly,its performance for flux regulation is analyzed based on the 3-D finite element analysis.Finally,the prototype of the proposed machine is manufactured and tested to verify the analytical results.
基金Supported by the general program of National Natural Science Foundation of China under Grant 51677159a grant(Project No.CityU 21201216)from the Research Grants Council of HKSAR,China.
文摘Control strategies play a key role for operation of electric machines,which would directly affect the whole system performance.In fact,different control strategies have been executed and explored for electric machines,which bring great impacts to industrial development and human society.This paper investigates and discusses the advantages control strategies for electric machines,including the field oriented control(FOC),direct torque control(DTC),finite control set model predictive control(FCS-MPC),sensorless control,and fault tolerant control(FTC).The corresponding control principles,control targets,fundamental approaches,advanced approaches,methodologies,merits and shortcomings are revealed and analyzed in detail.
