The current research of air suspension mainly focuses on the characteristics and design of the air spring. In fact, electronically controlled air suspension (ECAS) has excellent performance in flexible height adjust...The current research of air suspension mainly focuses on the characteristics and design of the air spring. In fact, electronically controlled air suspension (ECAS) has excellent performance in flexible height adjustment during different driving conditions. However, the nonlinearity of the ride height adjusting system and the uneven distribution of payload affect the control accuracy of ride height and the body attitude. Firstly, the three-point measurement system of three height sensors is used to establish the mathematical model of the ride height adjusting system. The decentralized control of ride height and the centralized control of body attitude are presented to design the ride height control system for ECAS. The exact feedback linearization method is adopted for the nonlinear mathematical model of the ride height system. Secondly, according to the hierarchical control theory, the variable structure control (VSC) technique is used to design a controller that is able to adjust the ride height for the quarter-vehicle anywhere, and each quarter-vehicle height control system is independent. Meanwhile, the three-point height signals obtained by three height sensors are tracked to calculate the body pitch and roll attitude over time, and then by calculating the deviation of pitch and roll and its rates, the height control correction is reassigned based on the fuzzy algorithm. Finally, to verify the effectiveness and performance of the proposed combined control strategy, a validating test of ride height control system with and without road disturbance is carried out. Testing results show that the height adjusting time of both lifting and lowering is over 5 s, and the pitch angle and the roll angle of body attitude are less than 0.15°. This research proposes a hierarchical control method that can guarantee the attitude stability, as well as satisfy the ride height tracking system.展开更多
The existing investigations of vehicle ride comfort mainly include motion characteristics analysis based on creating a multi-body dynamic simulation model,and the parameters analysis to improve the suspension control ...The existing investigations of vehicle ride comfort mainly include motion characteristics analysis based on creating a multi-body dynamic simulation model,and the parameters analysis to improve the suspension control for the target.In the study of creating multi-body dynamics simulation models,there is usually without considering calibration and test verification,which make it difficult to ensure the production of engineering.In the study of improving the suspension control parameters for the target,there is a lack of systematic match about comfortable and human characteristics,so it is difficult to implement in the field of driving and leading the vehicle design.In this paper,based on the different characteristic of suspension system that effects on the vehicle ride comfort, according to the suspension system dynamic mechanism,the research methods of vehicle road test,bench test and CAE simulation is used,at the same time,several sensitivity analysis of vehicle ride comfort related to suspension stiffness and damping and speed is made. As a result,the key suspension systematic parameters are given that have important impact on vehicle ride comfort.Through matching parameters,a calibration analysis of suspension system based on human comfort is obtained.The analysis results show that the analysis methods for the design target of making the vehicle with best comfort are effective.On the basis of the theory study,five suspension parameter matching principles are explored to promise the vehicle with perfect ride comfort,which also provide theoretical basis and design methods for the passenger car best match of suspension system stiffness and damping.The research results have the promotional value of practicability and a wide range of engineering application.展开更多
The existing researches of the evaluation method of ride comfort of vehicle mainly focus on the level of human feelings to vibration. The level of human feelings to vibration is influenced by many factors, however, th...The existing researches of the evaluation method of ride comfort of vehicle mainly focus on the level of human feelings to vibration. The level of human feelings to vibration is influenced by many factors, however, the ride comfort according to the common principle of probability and statistics and simple binary logic is tmable to reflect these uncertainties. The random fuzzy evaluation model from people subjective response to vibration is adopted in the paper, these uncertainties are analyzed from the angle of psychological physics. Discussing the traditional evaluation of ride comfort during vehicle vibration, a fuzzily random evaluation model on the basis of annoyance rate is proposed for the human body's subjective response to vibration, with relevant fuzzy membership function and probability distribution given. A half-car four degrees of freedom suspension vibration model is described, subject to irregular excitations from the road surface, with the aid of software Matlab/Simulink. A new kind of evaluation method for ride comfort of vehicles is proposed in the paper, i.e., the annoyance rate evaluation method. The genetic algorithm and neural network control theory are used to control the system. Simulation results are obtained, such as the comparison of comfort reaction to vibration environments between before and after control, relationship of annoyance rate to vibration frequency and weighted acceleration, based on ISO 2631 / 1 (1982), ISO 2631-1 (1997) and annoyance rate evaluation method, respectively. Simulated assessment results indicate that the proposed active suspension systems prove to be effective in the vibration isolation of the suspension system, and the subjective response of human being can be promoted from very uncomfortable to a little uncomfortable. Furthermore, the novel evaluation method based on annoyance rate can further estimate quantitatively the number of passengers who feel discomfort due to vibration. A new analysis method of vehicle comfort is presented.展开更多
In the present research two different whole vehicle multibody models are established respectively, including rigid and rigid-flexible coupling multibody vehicle models. The former is all composed by rigid bodies while...In the present research two different whole vehicle multibody models are established respectively, including rigid and rigid-flexible coupling multibody vehicle models. The former is all composed by rigid bodies while in the later model, the flexible rear suspension is built based on the finite element method (FEM) and mode superposition method, in which the deformations of the components are considered. The ride simulations with different speeds are carried out on a 3D digitalized road, and the weighted root mean square (RMS) of accelerations on the seat surface,backrest and at the feet are calculated. The comparison between the responses of the rigid and rigid-flexible coupling multibody models shows that the flexibility of the vehicle parts significantly affects the accelerations at each position, and it is necessary to take the flexibility effects into account for the assessment of ride comfort. C 2013 The Chinese Society of Theoretical and Applied Mechanics. [doi: 10.1063/2.1301304]展开更多
Few study gives guidance to design weighting filters according to the frequency weighting factors,and the additional evaluation method of automotive ride comfort is not made good use of in some countries.Based on the ...Few study gives guidance to design weighting filters according to the frequency weighting factors,and the additional evaluation method of automotive ride comfort is not made good use of in some countries.Based on the regularities of the weighting factors,a method is proposed and the vertical and horizontal weighting filters are developed.The whole frequency range is divided several times into two parts with respective regularity.For each division,a parallel filter constituted by a low-and a high-pass filter with the same cutoff frequency and the quality factor is utilized to achieve section factors.The cascading of these parallel filters obtains entire factors.These filters own a high order.But,low order filters are preferred in some applications.The bilinear transformation method and the least P-norm optimal infinite impulse response(IIR) filter design method are employed to develop low order filters to approximate the weightings in the standard.In addition,with the window method,the linear phase finite impulse response(FIR) filter is designed to keep the signal from distorting and to obtain the staircase weighting.For the same case,the traditional method produces 0.330 7 m · s^–2 weighted root mean square(r.m.s.) acceleration and the filtering method gives 0.311 9 m · s^–2 r.m.s.The fourth order filter for approximation of vertical weighting obtains 0.313 9 m · s^–2 r.m.s.Crest factors of the acceleration signal weighted by the weighting filter and the fourth order filter are 3.002 7 and 3.011 1,respectively.This paper proposes several methods to design frequency weighting filters for automotive ride comfort evaluation,and these developed weighting filters are effective.展开更多
RFID (Radio Frequency Identification) is a new technology making use of radio frequency to do non-touch- ing, two-way data transit between the reader and the electronic tag to identify target and exchange data. Becaus...RFID (Radio Frequency Identification) is a new technology making use of radio frequency to do non-touch- ing, two-way data transit between the reader and the electronic tag to identify target and exchange data. Because it is non-touching;it can work from long distance;it is fit to work in an unfavorable environment;it can identify moving target, it is widely used in industry, commerce, storage, transportation. This paper introduces the application of the RFID technology and its state of development and discusses the general situation of its application in different fields. Moreover, this paper takes the tourist mini-train as an example, designs a security monitoring system based on RFID and discusses its application in tourist industry.展开更多
The ride comfort experimental assessment of crawler off-road vehicle is relatively overlooked, and is expensive and difficult to execute with higher and higher ride comfort performance requirements. To trade off betwe...The ride comfort experimental assessment of crawler off-road vehicle is relatively overlooked, and is expensive and difficult to execute with higher and higher ride comfort performance requirements. To trade off between precise and cost, an experimental method based on the similitude theory is proposed. Under the guidance of the similitude theory, a 1:5 crawler power chassis scale model equipped with a kind of variable stiffness suspension system is used. The power spectrum density(PSD), the root mean square(RMS) of weighed acceleration, peak factor, average absorbed power(AAP) and vibration dose value(VDV) are selected as ride comfort evaluation indexes, and tests results are transformed via similarity indexes to predict the performance of full-scale power chassis. PSD shows that the low-order natural frequency of the vertical natural frequency(z axis) is 1.1 Hz, and the RMS, AAP and VDV values indicate the ride comfort performance of this kind of power chassis is between the "A little uncomfortable" and "Rather uncomfortable". From the results, low-order vertical natural frequency, obtained by PSD, validates that the similarity relationship between two models is satisfied, and 1:5 scale model used in experiment meets the similarity relationship with the full-scale model; consequently, the ride comfort prophase evaluation with the 1:5 scale model is feasible. The attempt of applying the similitude theory to crawler vehicle ride comfort test study decreases the cost and improves the test feasibility with sufficient test precise.展开更多
This paper presents the development and performance capability of a comprehensive Low voltage ride through (LVRT) control scheme that makes use of both the DC chopper and the current limiting based on the required rea...This paper presents the development and performance capability of a comprehensive Low voltage ride through (LVRT) control scheme that makes use of both the DC chopper and the current limiting based on the required reactive power during fault time. The study is conducted on an 8.5 MW single stage PV power plant (PVPP) connected to the Rwandan grid. In the event of fault disturbance, this control scheme helps to overcome the problems of excessive DC-link voltage by fast activation of the DC chopper operation. At the same instance, AC current is limited to the maximum rating of the inverter as a function of the injected reactive current. This helps overcome AC-over- current that may possibly lead to damage or disconnection of the inverter. The control scheme also ensures voltage support and power balance through the injection of reactive current as per grid code requirements. Selected simulations using MATLAB are carried out in the events of different kinds of fault caused voltage dips. Results demonstrate the effectiveness of the proposed LVRT control scheme.展开更多
In this study, commercial biaxially oriented polypropylene (BOPP), polyvinyl chlo- ride (PVC) and poly (methyl methacrylate) (PMMA) films were treated with nitrogen plasma over different exposure times in a Py...In this study, commercial biaxially oriented polypropylene (BOPP), polyvinyl chlo- ride (PVC) and poly (methyl methacrylate) (PMMA) films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemi- cal changes that appeared on the surface of the samples were investigated using Fourier transform infrared (FT4R) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR- FTIR) spectroscopy after treatment for 2 min, 4 min and 6 rain in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy (AFM) and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.展开更多
With continuously increasing of photovoltaic (PV) plant’s penetration, it has become a critical issue to improve the fault ride-through capability of PV plant. This paper refers to the German grid code, and the PV sy...With continuously increasing of photovoltaic (PV) plant’s penetration, it has become a critical issue to improve the fault ride-through capability of PV plant. This paper refers to the German grid code, and the PV system is controlled to keep grid connected, as well as inject reactive current to grid when fault occurs. The mathematical model of PV system is established and the fault characteristic is studied with respect to the control strategy. By analyzing the effect of reactive power supplied by the PV system to the point of common coupling (PCC) voltage, this paper proposes an adaptive voltage support control strategy to enhance the fault ride-through capability of PV system. The control strategy fully utilizes the PV system’s capability of voltage support and takes the safety of equipment into account as well. At last, the proposed control strategy is verified by simulation.展开更多
In order to evaluate a full trailer’s vibration performance,lumped mass model of seven degrees of freedom is set up to predict the ride comfort of whole vehicle.The acceleration history and the transfer function of e...In order to evaluate a full trailer’s vibration performance,lumped mass model of seven degrees of freedom is set up to predict the ride comfort of whole vehicle.The acceleration history and the transfer function of each measuring point can be got from simulation.The analysis results show that the maximum acceleration RMS value of the vehicle mass center is about 0.3g,which satisfies the requirements of attenuating vibration of precision equipment being transported on particular roads and speeds.So the research provides valuable reference for the optimum selection of the suspension system’s parameters.展开更多
Terracotta rider fi gurines are common artifacts in the past, generally combinations of person riding animals like horse or camel, through these organic fi gures we can see vivid pictures of ancient social life and cu...Terracotta rider fi gurines are common artifacts in the past, generally combinations of person riding animals like horse or camel, through these organic fi gures we can see vivid pictures of ancient social life and cultural evolution. A lot of researches on terracotta fi gurines have been reported, but terracotta rider fi gurines have been less studied as an independent object. This paper studied terracotta rider fi gurines, and found that this cultural form originated from the Warring States Period, thrived in the Tang Dynasty, and declined gradually after the Yuan Dynasty. The declination of ancient terracotta rider fi gurine culture owes to the changing social environment in different historical periods. Researches on terracotta rider fi gurines explored social customs and conventions behind them, and provided signifi cant theoretical support for protecting the cultural heritage.展开更多
The world’s energy consumption and power generation demand will continue to rise.Furthermore,the bulk of the energy resources needed to satisfy the rising demand is far from the load centers.The aforementioned requir...The world’s energy consumption and power generation demand will continue to rise.Furthermore,the bulk of the energy resources needed to satisfy the rising demand is far from the load centers.The aforementioned requires long-distance transmission systems and one way to accomplish this is to use high voltage direct current(HVDC)transmission systems.The main technical issues for HVDC transmission systems are loss of synchronism,variation of quadrature currents,amplitude,the inability of station 1(rectifier),and station 2(inverter)to either inject,or absorb active,or reactive power in the network in any circumstances(before a fault occurs,during having a fault in network and after a fault cleared),and the variations of power transfer capabilities.Additionally,faults impact power quality such as voltage dips and power line outage time.This paper presents a method of overcoming the aforementioned technical issues using voltage-source converter(VSC)based HVDC transmission systems with SCADA VIEWER software and dynamic grid simulator.The benefits include having a higher capacity transmission system and proposed best method for control of active and reactive power transfer capabilities.Simulation results obtained using MATLAB validated the experimental results from SCADA Viewer software.The results indicate that the station’s rectifier or inverter can either inject or absorb either active power or reactive power in any circumstance.Also,the reverse power flow under different modes of operation can ride through faults.At a 100.0%power transfer rate,the rectifier injected 775.0 W into the network.At a 0.0%power transfer rate,the rectifier injected 164.0 W into the network.At a-100.0%rated power,the rectifier injected 1264.0 W into the network and direction was also changed.展开更多
In this paper, the performance of automotive ride comfort using Bouc-Wen type magneto-rheological (MR) fluid damper is studied using a two degree of freedom quarter car model. The sliding mode control is used to force...In this paper, the performance of automotive ride comfort using Bouc-Wen type magneto-rheological (MR) fluid damper is studied using a two degree of freedom quarter car model. The sliding mode control is used to force the MR damper to follow the dynamics of ideal sky-hock model. The model is tested on two excitations, the first is a road hump with severe peak amplitude and the second is a statistical random road. The results are generated and presented in time and frequency domains using Matlab/Simulink software. Comparison with the fully active, ideal semi-active and conventional passive suspension systems are given as a root mean square values. Simulation results, for the designed controller, show that with the controllable MR damper has a significant improvement for the vehicle road holding then its lateral stability as well as road damage in comparison with passive, fully active and ideal semi-active suspension systems.展开更多
This paper proposes the new speed control method of electric vehicles by generating the longitudinal speed pattern for improving the ride comfort against the longitudinal acceleration/deceleration. Since the longitudi...This paper proposes the new speed control method of electric vehicles by generating the longitudinal speed pattern for improving the ride comfort against the longitudinal acceleration/deceleration. Since the longitudinal acceleration/deceleration of EVs causes the discomfort of passengers, reducing such bad effect of acceleration/deceleration acting on passengers is very important for not only the ride comfort of passengers but also vehicle running safety. The proposed method is applying the general optimal control theory and it generates the speed pattern for improving the passenger ride quality based on evaluating the variations of acceleration and the jerk which is time derivative of the acceleration. The effectiveness of the present method is demonstrated through numerical experiments compared with some conventional methods.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51105177)Jiangsu Provincial Natural Science Foundation of China(Grant No.BK20131255)+2 种基金Research Fund for the Doctoral Program of Higher Education of China(Grant No.20113227120015)Qing Lan Project of Jiangsu Province of China,Scientific Research Foundation for Advanced Talents,Jiangsu University,China(Grant No.11JDG047)Hunan Provincial Natural Science Foundation of China(Grant No.12JJ6036)
文摘The current research of air suspension mainly focuses on the characteristics and design of the air spring. In fact, electronically controlled air suspension (ECAS) has excellent performance in flexible height adjustment during different driving conditions. However, the nonlinearity of the ride height adjusting system and the uneven distribution of payload affect the control accuracy of ride height and the body attitude. Firstly, the three-point measurement system of three height sensors is used to establish the mathematical model of the ride height adjusting system. The decentralized control of ride height and the centralized control of body attitude are presented to design the ride height control system for ECAS. The exact feedback linearization method is adopted for the nonlinear mathematical model of the ride height system. Secondly, according to the hierarchical control theory, the variable structure control (VSC) technique is used to design a controller that is able to adjust the ride height for the quarter-vehicle anywhere, and each quarter-vehicle height control system is independent. Meanwhile, the three-point height signals obtained by three height sensors are tracked to calculate the body pitch and roll attitude over time, and then by calculating the deviation of pitch and roll and its rates, the height control correction is reassigned based on the fuzzy algorithm. Finally, to verify the effectiveness and performance of the proposed combined control strategy, a validating test of ride height control system with and without road disturbance is carried out. Testing results show that the height adjusting time of both lifting and lowering is over 5 s, and the pitch angle and the roll angle of body attitude are less than 0.15°. This research proposes a hierarchical control method that can guarantee the attitude stability, as well as satisfy the ride height tracking system.
基金supported by National Hi-tech Research and Development Program of China(863 Program,Grant No. 2008AA11A123)Jilin Provincial Technology Department Development Plan of China(Grant No.20086006)
文摘The existing investigations of vehicle ride comfort mainly include motion characteristics analysis based on creating a multi-body dynamic simulation model,and the parameters analysis to improve the suspension control for the target.In the study of creating multi-body dynamics simulation models,there is usually without considering calibration and test verification,which make it difficult to ensure the production of engineering.In the study of improving the suspension control parameters for the target,there is a lack of systematic match about comfortable and human characteristics,so it is difficult to implement in the field of driving and leading the vehicle design.In this paper,based on the different characteristic of suspension system that effects on the vehicle ride comfort, according to the suspension system dynamic mechanism,the research methods of vehicle road test,bench test and CAE simulation is used,at the same time,several sensitivity analysis of vehicle ride comfort related to suspension stiffness and damping and speed is made. As a result,the key suspension systematic parameters are given that have important impact on vehicle ride comfort.Through matching parameters,a calibration analysis of suspension system based on human comfort is obtained.The analysis results show that the analysis methods for the design target of making the vehicle with best comfort are effective.On the basis of the theory study,five suspension parameter matching principles are explored to promise the vehicle with perfect ride comfort,which also provide theoretical basis and design methods for the passenger car best match of suspension system stiffness and damping.The research results have the promotional value of practicability and a wide range of engineering application.
基金supported by National University Basic Scientific Research Fund of China(Grant No.N100403009)National Natural Science Foundation of China(Grant No.50875041)
文摘The existing researches of the evaluation method of ride comfort of vehicle mainly focus on the level of human feelings to vibration. The level of human feelings to vibration is influenced by many factors, however, the ride comfort according to the common principle of probability and statistics and simple binary logic is tmable to reflect these uncertainties. The random fuzzy evaluation model from people subjective response to vibration is adopted in the paper, these uncertainties are analyzed from the angle of psychological physics. Discussing the traditional evaluation of ride comfort during vehicle vibration, a fuzzily random evaluation model on the basis of annoyance rate is proposed for the human body's subjective response to vibration, with relevant fuzzy membership function and probability distribution given. A half-car four degrees of freedom suspension vibration model is described, subject to irregular excitations from the road surface, with the aid of software Matlab/Simulink. A new kind of evaluation method for ride comfort of vehicles is proposed in the paper, i.e., the annoyance rate evaluation method. The genetic algorithm and neural network control theory are used to control the system. Simulation results are obtained, such as the comparison of comfort reaction to vibration environments between before and after control, relationship of annoyance rate to vibration frequency and weighted acceleration, based on ISO 2631 / 1 (1982), ISO 2631-1 (1997) and annoyance rate evaluation method, respectively. Simulated assessment results indicate that the proposed active suspension systems prove to be effective in the vibration isolation of the suspension system, and the subjective response of human being can be promoted from very uncomfortable to a little uncomfortable. Furthermore, the novel evaluation method based on annoyance rate can further estimate quantitatively the number of passengers who feel discomfort due to vibration. A new analysis method of vehicle comfort is presented.
基金supported by the National Natural Science Foundation of China(51175379)the National Basic Research Program of China(2011CB711200)
文摘In the present research two different whole vehicle multibody models are established respectively, including rigid and rigid-flexible coupling multibody vehicle models. The former is all composed by rigid bodies while in the later model, the flexible rear suspension is built based on the finite element method (FEM) and mode superposition method, in which the deformations of the components are considered. The ride simulations with different speeds are carried out on a 3D digitalized road, and the weighted root mean square (RMS) of accelerations on the seat surface,backrest and at the feet are calculated. The comparison between the responses of the rigid and rigid-flexible coupling multibody models shows that the flexibility of the vehicle parts significantly affects the accelerations at each position, and it is necessary to take the flexibility effects into account for the assessment of ride comfort. C 2013 The Chinese Society of Theoretical and Applied Mechanics. [doi: 10.1063/2.1301304]
文摘Few study gives guidance to design weighting filters according to the frequency weighting factors,and the additional evaluation method of automotive ride comfort is not made good use of in some countries.Based on the regularities of the weighting factors,a method is proposed and the vertical and horizontal weighting filters are developed.The whole frequency range is divided several times into two parts with respective regularity.For each division,a parallel filter constituted by a low-and a high-pass filter with the same cutoff frequency and the quality factor is utilized to achieve section factors.The cascading of these parallel filters obtains entire factors.These filters own a high order.But,low order filters are preferred in some applications.The bilinear transformation method and the least P-norm optimal infinite impulse response(IIR) filter design method are employed to develop low order filters to approximate the weightings in the standard.In addition,with the window method,the linear phase finite impulse response(FIR) filter is designed to keep the signal from distorting and to obtain the staircase weighting.For the same case,the traditional method produces 0.330 7 m · s^–2 weighted root mean square(r.m.s.) acceleration and the filtering method gives 0.311 9 m · s^–2 r.m.s.The fourth order filter for approximation of vertical weighting obtains 0.313 9 m · s^–2 r.m.s.Crest factors of the acceleration signal weighted by the weighting filter and the fourth order filter are 3.002 7 and 3.011 1,respectively.This paper proposes several methods to design frequency weighting filters for automotive ride comfort evaluation,and these developed weighting filters are effective.
文摘RFID (Radio Frequency Identification) is a new technology making use of radio frequency to do non-touch- ing, two-way data transit between the reader and the electronic tag to identify target and exchange data. Because it is non-touching;it can work from long distance;it is fit to work in an unfavorable environment;it can identify moving target, it is widely used in industry, commerce, storage, transportation. This paper introduces the application of the RFID technology and its state of development and discusses the general situation of its application in different fields. Moreover, this paper takes the tourist mini-train as an example, designs a security monitoring system based on RFID and discusses its application in tourist industry.
基金Supported by Special Fund for Argo-scientific Research in the Public Interest,China(Grant No.201203024)National Natural Science Foundation of China(Grant No.51175498)
文摘The ride comfort experimental assessment of crawler off-road vehicle is relatively overlooked, and is expensive and difficult to execute with higher and higher ride comfort performance requirements. To trade off between precise and cost, an experimental method based on the similitude theory is proposed. Under the guidance of the similitude theory, a 1:5 crawler power chassis scale model equipped with a kind of variable stiffness suspension system is used. The power spectrum density(PSD), the root mean square(RMS) of weighed acceleration, peak factor, average absorbed power(AAP) and vibration dose value(VDV) are selected as ride comfort evaluation indexes, and tests results are transformed via similarity indexes to predict the performance of full-scale power chassis. PSD shows that the low-order natural frequency of the vertical natural frequency(z axis) is 1.1 Hz, and the RMS, AAP and VDV values indicate the ride comfort performance of this kind of power chassis is between the "A little uncomfortable" and "Rather uncomfortable". From the results, low-order vertical natural frequency, obtained by PSD, validates that the similarity relationship between two models is satisfied, and 1:5 scale model used in experiment meets the similarity relationship with the full-scale model; consequently, the ride comfort prophase evaluation with the 1:5 scale model is feasible. The attempt of applying the similitude theory to crawler vehicle ride comfort test study decreases the cost and improves the test feasibility with sufficient test precise.
文摘This paper presents the development and performance capability of a comprehensive Low voltage ride through (LVRT) control scheme that makes use of both the DC chopper and the current limiting based on the required reactive power during fault time. The study is conducted on an 8.5 MW single stage PV power plant (PVPP) connected to the Rwandan grid. In the event of fault disturbance, this control scheme helps to overcome the problems of excessive DC-link voltage by fast activation of the DC chopper operation. At the same instance, AC current is limited to the maximum rating of the inverter as a function of the injected reactive current. This helps overcome AC-over- current that may possibly lead to damage or disconnection of the inverter. The control scheme also ensures voltage support and power balance through the injection of reactive current as per grid code requirements. Selected simulations using MATLAB are carried out in the events of different kinds of fault caused voltage dips. Results demonstrate the effectiveness of the proposed LVRT control scheme.
文摘In this study, commercial biaxially oriented polypropylene (BOPP), polyvinyl chlo- ride (PVC) and poly (methyl methacrylate) (PMMA) films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemi- cal changes that appeared on the surface of the samples were investigated using Fourier transform infrared (FT4R) spectroscopy and attenuated total reflectance Fourier transform infrared (ATR- FTIR) spectroscopy after treatment for 2 min, 4 min and 6 rain in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy (AFM) and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.
文摘With continuously increasing of photovoltaic (PV) plant’s penetration, it has become a critical issue to improve the fault ride-through capability of PV plant. This paper refers to the German grid code, and the PV system is controlled to keep grid connected, as well as inject reactive current to grid when fault occurs. The mathematical model of PV system is established and the fault characteristic is studied with respect to the control strategy. By analyzing the effect of reactive power supplied by the PV system to the point of common coupling (PCC) voltage, this paper proposes an adaptive voltage support control strategy to enhance the fault ride-through capability of PV system. The control strategy fully utilizes the PV system’s capability of voltage support and takes the safety of equipment into account as well. At last, the proposed control strategy is verified by simulation.
基金Supported by Program of Natural and Science Funds of Shandong Province(ZR2009FL014)the Program of Natural and Science Funds of Shandong Jiaotong University(Z201228)
文摘In order to evaluate a full trailer’s vibration performance,lumped mass model of seven degrees of freedom is set up to predict the ride comfort of whole vehicle.The acceleration history and the transfer function of each measuring point can be got from simulation.The analysis results show that the maximum acceleration RMS value of the vehicle mass center is about 0.3g,which satisfies the requirements of attenuating vibration of precision equipment being transported on particular roads and speeds.So the research provides valuable reference for the optimum selection of the suspension system’s parameters.
文摘Terracotta rider fi gurines are common artifacts in the past, generally combinations of person riding animals like horse or camel, through these organic fi gures we can see vivid pictures of ancient social life and cultural evolution. A lot of researches on terracotta fi gurines have been reported, but terracotta rider fi gurines have been less studied as an independent object. This paper studied terracotta rider fi gurines, and found that this cultural form originated from the Warring States Period, thrived in the Tang Dynasty, and declined gradually after the Yuan Dynasty. The declination of ancient terracotta rider fi gurine culture owes to the changing social environment in different historical periods. Researches on terracotta rider fi gurines explored social customs and conventions behind them, and provided signifi cant theoretical support for protecting the cultural heritage.
基金support through GrantNo.(600005-Z17X0234)Quanzhou Science and Technology Bureau for financial support through Grant No.(2018Z010)+2 种基金Huaqiao University through Grant No.(17BS201)the Fujian Provincial Department of Science and Technology for financial support through Grant(2018J05121)Authors are also grateful for financial support from the Fujian Provincial Department of Science and Technology through Grant Nos.(2021I0014)and(2018J05121).
文摘The world’s energy consumption and power generation demand will continue to rise.Furthermore,the bulk of the energy resources needed to satisfy the rising demand is far from the load centers.The aforementioned requires long-distance transmission systems and one way to accomplish this is to use high voltage direct current(HVDC)transmission systems.The main technical issues for HVDC transmission systems are loss of synchronism,variation of quadrature currents,amplitude,the inability of station 1(rectifier),and station 2(inverter)to either inject,or absorb active,or reactive power in the network in any circumstances(before a fault occurs,during having a fault in network and after a fault cleared),and the variations of power transfer capabilities.Additionally,faults impact power quality such as voltage dips and power line outage time.This paper presents a method of overcoming the aforementioned technical issues using voltage-source converter(VSC)based HVDC transmission systems with SCADA VIEWER software and dynamic grid simulator.The benefits include having a higher capacity transmission system and proposed best method for control of active and reactive power transfer capabilities.Simulation results obtained using MATLAB validated the experimental results from SCADA Viewer software.The results indicate that the station’s rectifier or inverter can either inject or absorb either active power or reactive power in any circumstance.Also,the reverse power flow under different modes of operation can ride through faults.At a 100.0%power transfer rate,the rectifier injected 775.0 W into the network.At a 0.0%power transfer rate,the rectifier injected 164.0 W into the network.At a-100.0%rated power,the rectifier injected 1264.0 W into the network and direction was also changed.
文摘In this paper, the performance of automotive ride comfort using Bouc-Wen type magneto-rheological (MR) fluid damper is studied using a two degree of freedom quarter car model. The sliding mode control is used to force the MR damper to follow the dynamics of ideal sky-hock model. The model is tested on two excitations, the first is a road hump with severe peak amplitude and the second is a statistical random road. The results are generated and presented in time and frequency domains using Matlab/Simulink software. Comparison with the fully active, ideal semi-active and conventional passive suspension systems are given as a root mean square values. Simulation results, for the designed controller, show that with the controllable MR damper has a significant improvement for the vehicle road holding then its lateral stability as well as road damage in comparison with passive, fully active and ideal semi-active suspension systems.
文摘This paper proposes the new speed control method of electric vehicles by generating the longitudinal speed pattern for improving the ride comfort against the longitudinal acceleration/deceleration. Since the longitudinal acceleration/deceleration of EVs causes the discomfort of passengers, reducing such bad effect of acceleration/deceleration acting on passengers is very important for not only the ride comfort of passengers but also vehicle running safety. The proposed method is applying the general optimal control theory and it generates the speed pattern for improving the passenger ride quality based on evaluating the variations of acceleration and the jerk which is time derivative of the acceleration. The effectiveness of the present method is demonstrated through numerical experiments compared with some conventional methods.