为了提高纵向换能器发射响应和工作带宽,本文以压电单晶PMNT做为有源驱动材料,采用双晶堆不同尺寸反相激励的方式,同时激发出一阶、二阶纵振模态,从而提高纵向换能器发射响应,拓宽工作频带。通过四端网络法简化换能器的等效电路并计算...为了提高纵向换能器发射响应和工作带宽,本文以压电单晶PMNT做为有源驱动材料,采用双晶堆不同尺寸反相激励的方式,同时激发出一阶、二阶纵振模态,从而提高纵向换能器发射响应,拓宽工作频带。通过四端网络法简化换能器的等效电路并计算其发射性能,利用ANSYS软件对模型进行优化设计并制作了试验样机,最终测试数据显示在工作频带27~65 k Hz,最大发射电压响应值不低于150 d B,带内起伏小于12 d B。研究结果表明:理论计算、有限元仿真计算与实测结果基本吻合,利用双晶堆反相激励的方式可实现纵向换能器较宽频带工作。展开更多
High efficiency and fast dynamic response are two main control objectives for dual active bridge(DAB)DC-DC converters. Traditional extended phase shift(EPS)control can significantly enhance the conversion efficiency o...High efficiency and fast dynamic response are two main control objectives for dual active bridge(DAB)DC-DC converters. Traditional extended phase shift(EPS)control can significantly enhance the conversion efficiency of DAB DC-DC converters by reducing current stress;however, it cannot fulfill fast dynamic response requirements. In this paper, a novel hybrid control scheme consisting of EPS control and direct power control(DPC),named as EPS-DPC, is proposed. EPS-DPC control has salient features in both efficiency and dynamic performance. In order to verify the outstanding performance of the proposed EPS-DPC scheme, an experimental comparison was carried out on a scale-down DAB DC-DC converter among several control strategies, including single phase shift control with traditional voltage-loop(SPS-TVL), EPS control with traditional voltage-loop(EPSVTL), and EPS-DPC. Experimental results have been high consistent with theoretical analysis, and verified these advantages of the proposed EPS-DPC scheme.展开更多
A novel method for robust collaborative design of complex products based on dual-response surface （DRS-RCO） is proposed to solve multidisciplinary design optimization （MDO） problems under uncertainty. Collaborativ...A novel method for robust collaborative design of complex products based on dual-response surface （DRS-RCO） is proposed to solve multidisciplinary design optimization （MDO） problems under uncertainty. Collaborative optimization （CO） which decomposes the whole system into a double-level nonlinear optimization problem is widely accepted as an efficient method to solve MDO problems. In order to improve the quality of complex product in design process, robust collaborative optimization （RCO） is developed to solve those problems under uncertain conditions. RCO does optimization on the linear sum of mean and standard deviation of objective function and gets an optimal solution with high robustness. Response surfaces method is an important way to do approximation in robust design. DRS-RCO is an improved RCO method in which dual-response surface replaces system uncertainty analysis module of CO. The dual-response surface is the approximate model of mean and standard deviation of objective function respectively. In DRS-RCO, All the information of subsystems is included in dual-response surfaces. As an additional item, the standard deviation of objective function is added to the subsystem optimization. This item guarantee both the mean and standard deviation of this subsystem is reaching the minima at the same time. Finally, a test problem with two coupled subsystems is conducted to verify the feasibility and effectiveness of DRS-RCO.展开更多
Rolling bearing and Squeeze Film Damper(SFD)are used in rotor support structures,and most researches on the nonlinear rotor-bearing system are focused on the simple rotor-bearing systems.This work emphasizes the compa...Rolling bearing and Squeeze Film Damper(SFD)are used in rotor support structures,and most researches on the nonlinear rotor-bearing system are focused on the simple rotor-bearing systems.This work emphasizes the comparative analysis of the influence of SFD on the nonlinear dynamic behavior of the dual-rotor system supported by rolling bearings.Firstly,a reduced dynamic model is established by combining the Finite Element(FE)method and the freeinterface method of component mode synthesis.The proposed model is verified by comparing the natural characteristics obtained from an FE model with those from the experiment.Then,the steady-state vibration responses of the system with or without SFD are solved by the numerical integration method.The influences of the ball bearing clearance,unbalance,centralizing spring stiffness and oil film clearance of SFD on the nonlinear steady-state vibration responses of the dual-rotor system are analyzed.Results show that SFD can effectively suppress the amplitude jump of the dual rotor system sustaining two rotors unbalance excitations.As the ball bearing clearance or unbalance increases,the amplitude jump phenomenon becomes more obvious,the resonance hysteresis phenomenon strengthens or weakens,the resonant peaks shift to the left or the right,respectively.SFD with unreasonable parameters will aggravate the system vibration,the smaller the oil film clearance,the better the damping performance of the SFD,the larger the centralizing spring stiffness is,the larger resonance amplitudes are.展开更多
This paper aims to gain insight into the nonlinear modal characteristics and the possible influence of the modes on the responses for the practical dual-rotor system with rub-impact in aero-engine.The finite solid ele...This paper aims to gain insight into the nonlinear modal characteristics and the possible influence of the modes on the responses for the practical dual-rotor system with rub-impact in aero-engine.The finite solid element method combined with a constraint stiffness model produced by rub-impact is introduced to build the governing equation of the complicated nonlinear dual-rotor system.In order to deal with the efficiency and numerical divergence in the process of solving the nonlinear modes of this large-scale nonlinear system,an analysis strategy is proposed by integrating a two-layer reduction technique into the harmonic balance method.The effectiveness of the analysis strategy is validated by applying to a simple rotor system,which can easily obtain the theoretical result.Based on the modeling method and analysis strategy,the modal characteristics of an aero-engine dual-rotor system with rub-impact are revealed.The results show that the modal frequency of the dual-rotor system increases when rub-impact occurs and has the feature of interval,which allows us to obtain the critical speeds of the rubbing system by traditional Campbell diagram.The rotation direction is an important factor since it can not only affect the gyroscopic effect but also change the friction effect of the rub-impact.It is found that the modal frequencies of the counter-rotation dual-rotor are less than those of co-rotation condition.More importantly,the forward modes of the counter-rotation dual-rotor may be instable when rub-impact occurs at a certain rotor,while the corresponding modes under the co-rotation condition are always stable.Furthermore,by analyzing the rubbing response of the dual-rotor,it is found that the modal characteristics have an important influence on rotor’s response.The instable forward modes existing in the counter-rotation dual-rotor may lead to the divergence of the response when passing the corresponding critical speed.展开更多
文摘为了提高纵向换能器发射响应和工作带宽,本文以压电单晶PMNT做为有源驱动材料,采用双晶堆不同尺寸反相激励的方式,同时激发出一阶、二阶纵振模态,从而提高纵向换能器发射响应,拓宽工作频带。通过四端网络法简化换能器的等效电路并计算其发射性能,利用ANSYS软件对模型进行优化设计并制作了试验样机,最终测试数据显示在工作频带27~65 k Hz,最大发射电压响应值不低于150 d B,带内起伏小于12 d B。研究结果表明:理论计算、有限元仿真计算与实测结果基本吻合,利用双晶堆反相激励的方式可实现纵向换能器较宽频带工作。
基金supported by the National Natural Science Foundation of China(No.51577160)
文摘High efficiency and fast dynamic response are two main control objectives for dual active bridge(DAB)DC-DC converters. Traditional extended phase shift(EPS)control can significantly enhance the conversion efficiency of DAB DC-DC converters by reducing current stress;however, it cannot fulfill fast dynamic response requirements. In this paper, a novel hybrid control scheme consisting of EPS control and direct power control(DPC),named as EPS-DPC, is proposed. EPS-DPC control has salient features in both efficiency and dynamic performance. In order to verify the outstanding performance of the proposed EPS-DPC scheme, an experimental comparison was carried out on a scale-down DAB DC-DC converter among several control strategies, including single phase shift control with traditional voltage-loop(SPS-TVL), EPS control with traditional voltage-loop(EPSVTL), and EPS-DPC. Experimental results have been high consistent with theoretical analysis, and verified these advantages of the proposed EPS-DPC scheme.
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2006AA04Z160)National Key Technology R&D Program (Grant No. 2006BAF01A01)+1 种基金National Natural Science Foundation of China (Grant No. 60474059)Pre-Research Foundation of Military Equipment of China
文摘A novel method for robust collaborative design of complex products based on dual-response surface （DRS-RCO） is proposed to solve multidisciplinary design optimization （MDO） problems under uncertainty. Collaborative optimization （CO） which decomposes the whole system into a double-level nonlinear optimization problem is widely accepted as an efficient method to solve MDO problems. In order to improve the quality of complex product in design process, robust collaborative optimization （RCO） is developed to solve those problems under uncertain conditions. RCO does optimization on the linear sum of mean and standard deviation of objective function and gets an optimal solution with high robustness. Response surfaces method is an important way to do approximation in robust design. DRS-RCO is an improved RCO method in which dual-response surface replaces system uncertainty analysis module of CO. The dual-response surface is the approximate model of mean and standard deviation of objective function respectively. In DRS-RCO, All the information of subsystems is included in dual-response surfaces. As an additional item, the standard deviation of objective function is added to the subsystem optimization. This item guarantee both the mean and standard deviation of this subsystem is reaching the minima at the same time. Finally, a test problem with two coupled subsystems is conducted to verify the feasibility and effectiveness of DRS-RCO.
基金supported by the National Natural Science Foundation of China(Nos.11772089,11972112)the Fundamental Research Funds for the Central Universities,China(Nos.N170308028,N2003014 and N180708009)LiaoNing Revitalization Talents Program,China(Nos.XLYC1807008)。
文摘Rolling bearing and Squeeze Film Damper(SFD)are used in rotor support structures,and most researches on the nonlinear rotor-bearing system are focused on the simple rotor-bearing systems.This work emphasizes the comparative analysis of the influence of SFD on the nonlinear dynamic behavior of the dual-rotor system supported by rolling bearings.Firstly,a reduced dynamic model is established by combining the Finite Element(FE)method and the freeinterface method of component mode synthesis.The proposed model is verified by comparing the natural characteristics obtained from an FE model with those from the experiment.Then,the steady-state vibration responses of the system with or without SFD are solved by the numerical integration method.The influences of the ball bearing clearance,unbalance,centralizing spring stiffness and oil film clearance of SFD on the nonlinear steady-state vibration responses of the dual-rotor system are analyzed.Results show that SFD can effectively suppress the amplitude jump of the dual rotor system sustaining two rotors unbalance excitations.As the ball bearing clearance or unbalance increases,the amplitude jump phenomenon becomes more obvious,the resonance hysteresis phenomenon strengthens or weakens,the resonant peaks shift to the left or the right,respectively.SFD with unreasonable parameters will aggravate the system vibration,the smaller the oil film clearance,the better the damping performance of the SFD,the larger the centralizing spring stiffness is,the larger resonance amplitudes are.
基金support from the National Natural Science Foundation of China(Grant No.52005252)the Fundamental Research Funds for the Central Universities,China(Grant No.NT2020018)the National Science and Technology Major Project(2017-IV-0008-0045).
文摘This paper aims to gain insight into the nonlinear modal characteristics and the possible influence of the modes on the responses for the practical dual-rotor system with rub-impact in aero-engine.The finite solid element method combined with a constraint stiffness model produced by rub-impact is introduced to build the governing equation of the complicated nonlinear dual-rotor system.In order to deal with the efficiency and numerical divergence in the process of solving the nonlinear modes of this large-scale nonlinear system,an analysis strategy is proposed by integrating a two-layer reduction technique into the harmonic balance method.The effectiveness of the analysis strategy is validated by applying to a simple rotor system,which can easily obtain the theoretical result.Based on the modeling method and analysis strategy,the modal characteristics of an aero-engine dual-rotor system with rub-impact are revealed.The results show that the modal frequency of the dual-rotor system increases when rub-impact occurs and has the feature of interval,which allows us to obtain the critical speeds of the rubbing system by traditional Campbell diagram.The rotation direction is an important factor since it can not only affect the gyroscopic effect but also change the friction effect of the rub-impact.It is found that the modal frequencies of the counter-rotation dual-rotor are less than those of co-rotation condition.More importantly,the forward modes of the counter-rotation dual-rotor may be instable when rub-impact occurs at a certain rotor,while the corresponding modes under the co-rotation condition are always stable.Furthermore,by analyzing the rubbing response of the dual-rotor,it is found that the modal characteristics have an important influence on rotor’s response.The instable forward modes existing in the counter-rotation dual-rotor may lead to the divergence of the response when passing the corresponding critical speed.
