Conventional no-till seeders should cut or remove crop straw and residue,when in operation and thus present a number of problems,including high performance requirements for the cutting component,high power consumption...Conventional no-till seeders should cut or remove crop straw and residue,when in operation and thus present a number of problems,including high performance requirements for the cutting component,high power consumption,dust raising and interference from intertwined straw.In view of this,in this study,a driving roller dibbling-type no-till seeding and hole-forming(DGR-NT-SHF)system was designed to be capable of penetrating soil and creating holes without requiring any special preparation of the surface covering.The core mechanism of this system consisted of a land wheel-driven driving roller and a duckbill-type roller seeder,which were internally tangent to one another.The rotating roller rolled the straw into a thin layer,and the duckbills extended from the roller and penetrated this thin layer of straw and subsequently formed the holes and planted the seeds.Based on kinematic analysis,a mathematical model was established to depict the relations between the rear angle of the duckbill(α),the front angle of the duckbill(β),the angular velocity of the duckbill-type roller seeder(ω0),the angular velocity of the roller(ω1),and the aperture of the duckbill outlet on the roller(θ).In contrast to a driven roller-type no-till seeding and hole-forming DNR-NT-SHF system,several parameters of the DGR-NT-SHF system were established for planting seeds at a plant spacing that was an integral multiple of 100 mm:the radius of the duckbill-type roller seeder,200 mm;radius of the roller,400 mm;α,23°;andβ,5°.Based on the analysis of the models using the MATLAB Image Processing Module with a relation betweenω1 and the number of outlets on the roller as the constraint,the optimal number of outlets on the roller and theω1/ω0 ratio were determined to be 21 and 4/7,respectively.Kinematic simulation on a digital prototype was performed using computer aided three-dimensional interactive application(CATIA)to observe the motion of the DGR-NT-SHF system,when the duckbills on the duckbill-type roller seeder were open and to determine the locations of the duckbills relative to the outlets.To ensure the duckbills could be successfully opened,the chord length of the outlets was ultimately determined to be 71 mm.The prototype test results showed that the DGR-NT-SHF system met the design requirements and that the operation was straightforward and reliable.In addition,compared to the DNR-NT-SHF system,the DGR-NT-SHF system performed better in penetration and exerted no impact on the duckbills,thus providing an effective technical option for no-till seeding.展开更多
The existing plastic forming equipment are mostly driven by traditional AC motors with long trans- mission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In o...The existing plastic forming equipment are mostly driven by traditional AC motors with long trans- mission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In order to realize high performance forming processes, the driving device should be improved, especially for com- plicated processing motions. Based on electric servo direct drive technology, a novel AC servo rotating and linear composite driving device is proposed, which features implementing both spindle rotation and feed motion with- out transmission, so that compact structure and precise control can be achieved. Flux switching topology is employed in the rotating drive component for strong robustness, and fractional slot is employed in the linear direct drive component for large force capability. Then the mechanical structure for compositing rotation and linear motion is designed. A device prototype is manufactured, machining of each component and the whole assembly are presented respectively. Commercial servo amplifiers are utilized to construct the control system of the proposed device. To validate the effectiveness of the proposed composite driving device, experimental study on thedynamic test benches are conducted. The results indicate that the output torque can attain to 420 N-m and the dynamic tracking errors are less than about 0.3 rad in the rotating drive, the dynamic tracking errors are less than about 1.6 mm in the linear feed. The proposed research provides a method to construct high efficiency and accu- racy direct driving device in plastic forming equipment.展开更多
在“沙戈荒”地区风电经电网换相高压直流输电(line-commutated-converter based high voltage direct current,LCC-HVDC)外送系统中,采用基于匹配控制的构网型直驱风机(matching control permanent magnet synchronous generator,MC-PM...在“沙戈荒”地区风电经电网换相高压直流输电(line-commutated-converter based high voltage direct current,LCC-HVDC)外送系统中,采用基于匹配控制的构网型直驱风机(matching control permanent magnet synchronous generator,MC-PMSG)可以提升送端电网的稳定性。然而,当MC-PMSG位于LCC-HVDC整流站近区时,系统的次同步振荡(sub-synchronous oscillation,SSO)特性尚未明确。针对上述问题,该文采用模块化建模法建立MC-PMSG经LCC-HVDC送出系统的小信号模型,通过特征值法研究MC-PMSG与LCC-HVDC对系统各SSO模态的参与情况与系统运行方式变化对次同步振荡阻尼特性的影响,通过阻尼重构法分析LCC-HVDC并网对系统振荡风险的影响机理。研究结果表明,系统存在匹配控制型风机主导、LCC-HVDC参与的SSO模态,MC-PMSG与LCC-HVDC间的次同步交互作用为SSO提供负阻尼;当混合型风电场中的MC-PMSG占比增大、MC-PMSG风电场容量增大或短路比减小、LCC-HVDC定电流控制器的比例系数增大、风机网侧换流控制器外环积分系数减小、直流电容增大时,SSO阻尼增大。通过PSCAD/EMTDC电磁暂态仿真证明理论分析结果的有效性。展开更多
基金Supported by the Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province(LBH-Q14024)
文摘Conventional no-till seeders should cut or remove crop straw and residue,when in operation and thus present a number of problems,including high performance requirements for the cutting component,high power consumption,dust raising and interference from intertwined straw.In view of this,in this study,a driving roller dibbling-type no-till seeding and hole-forming(DGR-NT-SHF)system was designed to be capable of penetrating soil and creating holes without requiring any special preparation of the surface covering.The core mechanism of this system consisted of a land wheel-driven driving roller and a duckbill-type roller seeder,which were internally tangent to one another.The rotating roller rolled the straw into a thin layer,and the duckbills extended from the roller and penetrated this thin layer of straw and subsequently formed the holes and planted the seeds.Based on kinematic analysis,a mathematical model was established to depict the relations between the rear angle of the duckbill(α),the front angle of the duckbill(β),the angular velocity of the duckbill-type roller seeder(ω0),the angular velocity of the roller(ω1),and the aperture of the duckbill outlet on the roller(θ).In contrast to a driven roller-type no-till seeding and hole-forming DNR-NT-SHF system,several parameters of the DGR-NT-SHF system were established for planting seeds at a plant spacing that was an integral multiple of 100 mm:the radius of the duckbill-type roller seeder,200 mm;radius of the roller,400 mm;α,23°;andβ,5°.Based on the analysis of the models using the MATLAB Image Processing Module with a relation betweenω1 and the number of outlets on the roller as the constraint,the optimal number of outlets on the roller and theω1/ω0 ratio were determined to be 21 and 4/7,respectively.Kinematic simulation on a digital prototype was performed using computer aided three-dimensional interactive application(CATIA)to observe the motion of the DGR-NT-SHF system,when the duckbills on the duckbill-type roller seeder were open and to determine the locations of the duckbills relative to the outlets.To ensure the duckbills could be successfully opened,the chord length of the outlets was ultimately determined to be 71 mm.The prototype test results showed that the DGR-NT-SHF system met the design requirements and that the operation was straightforward and reliable.In addition,compared to the DNR-NT-SHF system,the DGR-NT-SHF system performed better in penetration and exerted no impact on the duckbills,thus providing an effective technical option for no-till seeding.
基金Supported by National Natural Science Foundation of China(Grant No.51335009)Major National Science and Technology Project of China(Grant No.2011ZX04001-011)
文摘The existing plastic forming equipment are mostly driven by traditional AC motors with long trans- mission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In order to realize high performance forming processes, the driving device should be improved, especially for com- plicated processing motions. Based on electric servo direct drive technology, a novel AC servo rotating and linear composite driving device is proposed, which features implementing both spindle rotation and feed motion with- out transmission, so that compact structure and precise control can be achieved. Flux switching topology is employed in the rotating drive component for strong robustness, and fractional slot is employed in the linear direct drive component for large force capability. Then the mechanical structure for compositing rotation and linear motion is designed. A device prototype is manufactured, machining of each component and the whole assembly are presented respectively. Commercial servo amplifiers are utilized to construct the control system of the proposed device. To validate the effectiveness of the proposed composite driving device, experimental study on thedynamic test benches are conducted. The results indicate that the output torque can attain to 420 N-m and the dynamic tracking errors are less than about 0.3 rad in the rotating drive, the dynamic tracking errors are less than about 1.6 mm in the linear feed. The proposed research provides a method to construct high efficiency and accu- racy direct driving device in plastic forming equipment.
文摘在“沙戈荒”地区风电经电网换相高压直流输电(line-commutated-converter based high voltage direct current,LCC-HVDC)外送系统中,采用基于匹配控制的构网型直驱风机(matching control permanent magnet synchronous generator,MC-PMSG)可以提升送端电网的稳定性。然而,当MC-PMSG位于LCC-HVDC整流站近区时,系统的次同步振荡(sub-synchronous oscillation,SSO)特性尚未明确。针对上述问题,该文采用模块化建模法建立MC-PMSG经LCC-HVDC送出系统的小信号模型,通过特征值法研究MC-PMSG与LCC-HVDC对系统各SSO模态的参与情况与系统运行方式变化对次同步振荡阻尼特性的影响,通过阻尼重构法分析LCC-HVDC并网对系统振荡风险的影响机理。研究结果表明,系统存在匹配控制型风机主导、LCC-HVDC参与的SSO模态,MC-PMSG与LCC-HVDC间的次同步交互作用为SSO提供负阻尼;当混合型风电场中的MC-PMSG占比增大、MC-PMSG风电场容量增大或短路比减小、LCC-HVDC定电流控制器的比例系数增大、风机网侧换流控制器外环积分系数减小、直流电容增大时,SSO阻尼增大。通过PSCAD/EMTDC电磁暂态仿真证明理论分析结果的有效性。
