The tracking performance of motor current is an important factor that affects the assistance torque of electric power steering （EPS） system. Bad tracking performance will cause assistant torque delay, and make road ...The tracking performance of motor current is an important factor that affects the assistance torque of electric power steering （EPS） system. Bad tracking performance will cause assistant torque delay, and make road feeling bad, and is influenced by the input steering torque and system measuring noise. However the existing methods have some shortages on system＇s robust dynamic performance and robust stability. The mixed H2/H∞ strategy for recirculating ball-type EPS system in a pure electric bus is proposed, and vehicle dynamic model of the system is established. Due to the existence of system model uncertainty, disturbance signals, sensor noises and the demand of system dynamic performance, the indexes of robust performance and road feeling for drivers are defined as the appraisal control objectives. The H∞ method is introduced to design the H∞ controller, and the H2 method is applied to optimize the H∞ controller, thus the mixed H2/H∞ controller is designed. The response of EPS system to the motor current command with amplitude of 20 A, the road disturbance with amplitude of 500 N and the sensor random noise with the amplitude of 1 A is simulated. The simulation results show that the recirculating ball-type EPS system with the mixed H2/H∞ controller can attenuate the random noises and disturbances and track the boost curve well, so the mixed H2/H∞ controller can improve the system＇s robust performance and dynamic performance. For the purpose of verifying the performance of the designed control strategy, the motor current tracking performance ground tests are conducted with step response input of the steering wheel, double-lane steering test and lemniscate steering test, respectively. The tests show that the mixed H2/H∞ controller for the recirculating ball-type EPS system of pure electric bus is feasible. The designed controller can solve the robust performance and robust stability of the system, thus improve the tracking performance of the EPS system and provide satisfied road feeling fo展开更多
The present study investigated the emissions of naphthalene and other compounds from several different moth repellents(MRs) and one toilet deodorant block(TDB)currently sold in Korea,using a headspace analysis.The emi...The present study investigated the emissions of naphthalene and other compounds from several different moth repellents(MRs) and one toilet deodorant block(TDB)currently sold in Korea,using a headspace analysis.The emission factors and emission rates of naphthalene were studied using a small-scale environmental chamber.Paper-type products emitted a higher concentration of the total volatile organic compounds(VOCs)(normalized to the weight of test piece)than ball-type products,which in turn emitted higher con...展开更多
Let(X,ρ,μ)be a space of homogeneous type in the sense of Coifman and Weiss,and Y(X)a ball quasi-Banach function space on X,which supports both a Fefferman–Stein vector-valued maximal inequality and the boundedness ...Let(X,ρ,μ)be a space of homogeneous type in the sense of Coifman and Weiss,and Y(X)a ball quasi-Banach function space on X,which supports both a Fefferman–Stein vector-valued maximal inequality and the boundedness of the powered Hardy–Littlewood maximal operator on its associate space.The authors first introduce the Hardy space H_(Y)(X)associated with Y(X),via the Lusin-area function,and then establish its various equivalent characterizations,respectively,in terms of atoms,molecules,and Littlewood–Paley g-functions and g_(λ)^(*)-functions.As an application,the authors obtain the boundedness of Calderón–Zygmund operators from H_(Y)(X)to Y(X),or to H_(Y)(X)via first establishing a boundedness criterion of linear operators on H_(Y)(X).All these results have a wide range of generality and,particularly,even when they are applied to variable Hardy spaces,the obtained results are also new.The major novelties of this article exist in that,to escape the reverse doubling condition ofμand the triangle inequality ofρ,the authors subtly use the wavelet reproducing formula,originally establish an admissible molecular characterization of H_(Y)(X),and fully apply the geometrical properties of X expressed by dyadic reference points or dyadic cubes.展开更多
Polishing is an important finishing process in die and mold manufacturing. Hand polishing takes long time and much labor. Efforts are made to automate the polishing process while keeping accuracy. Recently grinding ce...Polishing is an important finishing process in die and mold manufacturing. Hand polishing takes long time and much labor. Efforts are made to automate the polishing process while keeping accuracy. Recently grinding centers have been developed, which are used for free surface polishing in the present work. The new polishing technique applies the same cutting locus as used in the cutting process to remove only cusp height effectively, keeping the form accuracy generated in the cutting process.展开更多
To obtain accurate forms and surfaces in free surface grinding, it is important to provide grinding conditions suitable for a curved surface. A grinding support system for the free surface （GSX-F） is proposed to hel...To obtain accurate forms and surfaces in free surface grinding, it is important to provide grinding conditions suitable for a curved surface. A grinding support system for the free surface （GSX-F） is proposed to help the operator grind a free surface with the high accuracy and the high productivity. To succeed in free surface grinding, the property of a ball type wheel must be known. Therefore, a basic study of free surface grinding with a ball type wheel is carried out based on the grinding center （GC）. Some working points for achieving sufficient accuracy in free surface grinding are discussed. GSX-F is constructed using the patch division method and is used to test grinding. Reasonable results are obtained.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 51005115, No. 51005248)Science Fund of State Key Laboratory of Automotive Safety and Energy of China (Grant No. KF11201)
文摘The tracking performance of motor current is an important factor that affects the assistance torque of electric power steering （EPS） system. Bad tracking performance will cause assistant torque delay, and make road feeling bad, and is influenced by the input steering torque and system measuring noise. However the existing methods have some shortages on system＇s robust dynamic performance and robust stability. The mixed H2/H∞ strategy for recirculating ball-type EPS system in a pure electric bus is proposed, and vehicle dynamic model of the system is established. Due to the existence of system model uncertainty, disturbance signals, sensor noises and the demand of system dynamic performance, the indexes of robust performance and road feeling for drivers are defined as the appraisal control objectives. The H∞ method is introduced to design the H∞ controller, and the H2 method is applied to optimize the H∞ controller, thus the mixed H2/H∞ controller is designed. The response of EPS system to the motor current command with amplitude of 20 A, the road disturbance with amplitude of 500 N and the sensor random noise with the amplitude of 1 A is simulated. The simulation results show that the recirculating ball-type EPS system with the mixed H2/H∞ controller can attenuate the random noises and disturbances and track the boost curve well, so the mixed H2/H∞ controller can improve the system＇s robust performance and dynamic performance. For the purpose of verifying the performance of the designed control strategy, the motor current tracking performance ground tests are conducted with step response input of the steering wheel, double-lane steering test and lemniscate steering test, respectively. The tests show that the mixed H2/H∞ controller for the recirculating ball-type EPS system of pure electric bus is feasible. The designed controller can solve the robust performance and robust stability of the system, thus improve the tracking performance of the EPS system and provide satisfied road feeling fo
文摘The present study investigated the emissions of naphthalene and other compounds from several different moth repellents(MRs) and one toilet deodorant block(TDB)currently sold in Korea,using a headspace analysis.The emission factors and emission rates of naphthalene were studied using a small-scale environmental chamber.Paper-type products emitted a higher concentration of the total volatile organic compounds(VOCs)(normalized to the weight of test piece)than ball-type products,which in turn emitted higher con...
基金Supported by the National Key Research and Development Program of China(Grant No.2020YFA0712900)the National Natural Science Foundation of China(Grant Nos.11971058,12071197 and 11871100)the Fundamental Research Funds for the Central Universities(Grant Nos.500421359 and 500421126)。
文摘Let(X,ρ,μ)be a space of homogeneous type in the sense of Coifman and Weiss,and Y(X)a ball quasi-Banach function space on X,which supports both a Fefferman–Stein vector-valued maximal inequality and the boundedness of the powered Hardy–Littlewood maximal operator on its associate space.The authors first introduce the Hardy space H_(Y)(X)associated with Y(X),via the Lusin-area function,and then establish its various equivalent characterizations,respectively,in terms of atoms,molecules,and Littlewood–Paley g-functions and g_(λ)^(*)-functions.As an application,the authors obtain the boundedness of Calderón–Zygmund operators from H_(Y)(X)to Y(X),or to H_(Y)(X)via first establishing a boundedness criterion of linear operators on H_(Y)(X).All these results have a wide range of generality and,particularly,even when they are applied to variable Hardy spaces,the obtained results are also new.The major novelties of this article exist in that,to escape the reverse doubling condition ofμand the triangle inequality ofρ,the authors subtly use the wavelet reproducing formula,originally establish an admissible molecular characterization of H_(Y)(X),and fully apply the geometrical properties of X expressed by dyadic reference points or dyadic cubes.
基金Project supported by the Natural Science Foundation of Shaanxi Province(Grant No.2006E112)
文摘Polishing is an important finishing process in die and mold manufacturing. Hand polishing takes long time and much labor. Efforts are made to automate the polishing process while keeping accuracy. Recently grinding centers have been developed, which are used for free surface polishing in the present work. The new polishing technique applies the same cutting locus as used in the cutting process to remove only cusp height effectively, keeping the form accuracy generated in the cutting process.
文摘To obtain accurate forms and surfaces in free surface grinding, it is important to provide grinding conditions suitable for a curved surface. A grinding support system for the free surface （GSX-F） is proposed to help the operator grind a free surface with the high accuracy and the high productivity. To succeed in free surface grinding, the property of a ball type wheel must be known. Therefore, a basic study of free surface grinding with a ball type wheel is carried out based on the grinding center （GC）. Some working points for achieving sufficient accuracy in free surface grinding are discussed. GSX-F is constructed using the patch division method and is used to test grinding. Reasonable results are obtained.
