LM-8 inherited mature modules from other launch vehicles,adapting the overall design through the combination of engine throttling,wind compensation and load relief control,so as to reduce the aerodynamic load during f...LM-8 inherited mature modules from other launch vehicles,adapting the overall design through the combination of engine throttling,wind compensation and load relief control,so as to reduce the aerodynamic load during flight.This paper proposes a rapid evaluation method for load relief performance,which takes launch vehicle’s characteristics,wind field,control parameters,aerodynamic deviation and structure deviation into consideration,and provides a quick estimation method for load relief performance.The load relief performance of the LM-8 launch vehicle estimated by this method achieved 10%-20%in pitch and 20%-40%in yaw.The specific results are related to parameter deviation,the altitude of wind shear and the relationship between wind direction and trajectory angle.Simulation results for a typical case with six degrees of dynamic freedom of flight proves that the comprehensive load relief performance would be between 14%to 34%,which is in line with the aforementioned method.In addition,simulation results indicate that the more severe the wind shear is,the better performance of load relief can be achieved.展开更多
In order to satisfy the increasing demand on high performance planetary transmissions, an important line of research is focused on the understanding of some of the underlying phenomena involved in this mechanical syst...In order to satisfy the increasing demand on high performance planetary transmissions, an important line of research is focused on the understanding of some of the underlying phenomena involved in this mechanical system. Through the development of models capable of reproduce the system behavior, research in this area contributes to improve gear transmission insight, helping developing better maintenance practices and more efficient design processes. A planetary gear model used for the design of profile modifications ratio based on the levelling of the load sharing ratio is presented. The gear profile geometry definition, following a vectorial approach that mimics the real cutting process of gears, is thoroughly described. Teeth undercutting and hypotrochoid definition are implicitly considered, and a procedure for the incorporation of a rounding arc at the tooth tip in order to deal with corner contacts is described. A procedure for the modeling of profile deviations is presented, which can be used for the introduction of both manufacturing errors and designed profile modifications. An easy and flexible implementation of the profile deviation within the planetary model is accomplished based on the geometric overlapping. The contact force calculation and dynamic implementation used in the model are also introduced, and parameters from a real transmission for agricultural applications are presented for the application example. A set of reliefs is designed based on the levelling of the load sharing ratio for the example transmission, and finally some other important dynamic factors of the transmission are analyzed to assess the changes in the dynamic behavior with respect to the non-modified case. Thus, the main innovative aspect of the proposed planetary transmission model is the capacity of providing a simulated load sharing ratio which serves as design variable for the calculation of the tooth profile modifications.展开更多
An Electro-hydraulic loading system is designed based on a test-bed of tractor's hydraulic steering by-wire. To simulate the steering resistance driving tractor in many kinds of soils and roads,the loading force i...An Electro-hydraulic loading system is designed based on a test-bed of tractor's hydraulic steering by-wire. To simulate the steering resistance driving tractor in many kinds of soils and roads,the loading force is controlled to make proportional and continuous variable by an electro-hydraulic proportional relief valve. A steering resistance loading test-bed is built to test three kinds of steering resistance including constant,step and sine style. Tire lateral resistance is also tested under different steering conditions. The result shows that the electro-hydraulic loading system has high stability and following performance. Besides,the system's steady state error is lower than 3. 1%,and it meets the test requirement of tractor's hydraulic steering by-wire.展开更多
文摘LM-8 inherited mature modules from other launch vehicles,adapting the overall design through the combination of engine throttling,wind compensation and load relief control,so as to reduce the aerodynamic load during flight.This paper proposes a rapid evaluation method for load relief performance,which takes launch vehicle’s characteristics,wind field,control parameters,aerodynamic deviation and structure deviation into consideration,and provides a quick estimation method for load relief performance.The load relief performance of the LM-8 launch vehicle estimated by this method achieved 10%-20%in pitch and 20%-40%in yaw.The specific results are related to parameter deviation,the altitude of wind shear and the relationship between wind direction and trajectory angle.Simulation results for a typical case with six degrees of dynamic freedom of flight proves that the comprehensive load relief performance would be between 14%to 34%,which is in line with the aforementioned method.In addition,simulation results indicate that the more severe the wind shear is,the better performance of load relief can be achieved.
基金Supported by the Project DPI2013-44860 funded by the Spanish Ministry of Science and Technology
文摘In order to satisfy the increasing demand on high performance planetary transmissions, an important line of research is focused on the understanding of some of the underlying phenomena involved in this mechanical system. Through the development of models capable of reproduce the system behavior, research in this area contributes to improve gear transmission insight, helping developing better maintenance practices and more efficient design processes. A planetary gear model used for the design of profile modifications ratio based on the levelling of the load sharing ratio is presented. The gear profile geometry definition, following a vectorial approach that mimics the real cutting process of gears, is thoroughly described. Teeth undercutting and hypotrochoid definition are implicitly considered, and a procedure for the incorporation of a rounding arc at the tooth tip in order to deal with corner contacts is described. A procedure for the modeling of profile deviations is presented, which can be used for the introduction of both manufacturing errors and designed profile modifications. An easy and flexible implementation of the profile deviation within the planetary model is accomplished based on the geometric overlapping. The contact force calculation and dynamic implementation used in the model are also introduced, and parameters from a real transmission for agricultural applications are presented for the application example. A set of reliefs is designed based on the levelling of the load sharing ratio for the example transmission, and finally some other important dynamic factors of the transmission are analyzed to assess the changes in the dynamic behavior with respect to the non-modified case. Thus, the main innovative aspect of the proposed planetary transmission model is the capacity of providing a simulated load sharing ratio which serves as design variable for the calculation of the tooth profile modifications.
基金Supported by National Natural Science Foundation of China(51175269)Jiangsu Provincial Science and Technology Support Program(Agriculture)(BE2012384)
文摘An Electro-hydraulic loading system is designed based on a test-bed of tractor's hydraulic steering by-wire. To simulate the steering resistance driving tractor in many kinds of soils and roads,the loading force is controlled to make proportional and continuous variable by an electro-hydraulic proportional relief valve. A steering resistance loading test-bed is built to test three kinds of steering resistance including constant,step and sine style. Tire lateral resistance is also tested under different steering conditions. The result shows that the electro-hydraulic loading system has high stability and following performance. Besides,the system's steady state error is lower than 3. 1%,and it meets the test requirement of tractor's hydraulic steering by-wire.
