In 2005,Gogu,a Frenchman,analyzed 35 different existing formulas for mobility calculation and pointed that the formulas for quick mobility calculation had some limitations and were not general.Therefore,looking for a ...In 2005,Gogu,a Frenchman,analyzed 35 different existing formulas for mobility calculation and pointed that the formulas for quick mobility calculation had some limitations and were not general.Therefore,looking for a general and simple mobility formula is still a hot topic in mechanisms.At the meantime,it is also an important topic to complete the mechanism theory.Gogu proposed a new method that can avoid determining virtual constraints in 2008,but the method is still not general.To solve the problem,this paper defines the new concepts of link-group rank,general-kinematic-pair rank,virtual pair,virtual loop,and virtual-loop rank,and gives a new simple and general formula.Our method converts multi-loop mechanisms into some independent virtual loops,simplifies the problem,avoids calculating virtual constraints,and reduces the calculation difficulty.It is proved that the new formula is simple,general and effective through the mobility analysis of several different kinds of mechanisms.The application of this formula will provide great convenience for general engineers in mobility calculation.展开更多
不间断电源(uninterrupted power supply,UPS)是电力系统电能质量问题的重要解决方案,环流抑制问题是目前多台UPS并联技术中的研究重点与难点.基于CAN总线的模块化UPS并联控制策略,应用虚拟多回路输出阻抗下垂控制,并采用CAN总线通信实...不间断电源(uninterrupted power supply,UPS)是电力系统电能质量问题的重要解决方案,环流抑制问题是目前多台UPS并联技术中的研究重点与难点.基于CAN总线的模块化UPS并联控制策略,应用虚拟多回路输出阻抗下垂控制,并采用CAN总线通信实现各并联UPS模块间的同步和均流控制.实验结果表明,提出的方法在抑制子模块环流的同时解决了分布式系统的信号稳定性问题,保证了模块化UPS并联系统数据传输的准确性和实时性.展开更多
Compared with the parallel mechanisms, the mobility analysis of the general multi-loop spatial mechanisms（GMSMs） is more difficult to obtain correct results. The reason is that its multi-loop is formed through sever...Compared with the parallel mechanisms, the mobility analysis of the general multi-loop spatial mechanisms（GMSMs） is more difficult to obtain correct results. The reason is that its multi-loop is formed through several times of closings and there also exists motion coupling even strong coupling, where the over-constraints are concealed. However, the mobility analysis for this kind of mechanisms has been paid few attentions. A new systemic methodology for analyzing mobility is proposed for GMSMs also based on the screw theory. The key issue for mobility analysis is to recognize the over-constraint. Firstly, three theorems are given and point out： the reason and site of over-constraint occurrence, calculating the number of over-constraints by the screw theory, and how to analyze the over-constraints for a single-loop mechanism as well. Then, three closing forms for GMSMs are proposed including rigid closure, movable closure and dynamic closure, and for the three different forms the different analysis methods are also given. Especially, for the most difficult issue of GMSMs with the multi-loop Closure in many times and the inevitable motion coupling, two important methods are proposed： ＂recognizing over-constraints by analyzing relative movement＂ and ＂recognizing over-constraints by virtual loop＂. The two methods are well used to solve the issue. Above-mentioned principles are not only systematic and effective but also unified. They provide a theoretical basis for the general multi-loop spatial mechanisms.展开更多
文摘In 2005,Gogu,a Frenchman,analyzed 35 different existing formulas for mobility calculation and pointed that the formulas for quick mobility calculation had some limitations and were not general.Therefore,looking for a general and simple mobility formula is still a hot topic in mechanisms.At the meantime,it is also an important topic to complete the mechanism theory.Gogu proposed a new method that can avoid determining virtual constraints in 2008,but the method is still not general.To solve the problem,this paper defines the new concepts of link-group rank,general-kinematic-pair rank,virtual pair,virtual loop,and virtual-loop rank,and gives a new simple and general formula.Our method converts multi-loop mechanisms into some independent virtual loops,simplifies the problem,avoids calculating virtual constraints,and reduces the calculation difficulty.It is proved that the new formula is simple,general and effective through the mobility analysis of several different kinds of mechanisms.The application of this formula will provide great convenience for general engineers in mobility calculation.
文摘不间断电源(uninterrupted power supply,UPS)是电力系统电能质量问题的重要解决方案,环流抑制问题是目前多台UPS并联技术中的研究重点与难点.基于CAN总线的模块化UPS并联控制策略,应用虚拟多回路输出阻抗下垂控制,并采用CAN总线通信实现各并联UPS模块间的同步和均流控制.实验结果表明,提出的方法在抑制子模块环流的同时解决了分布式系统的信号稳定性问题,保证了模块化UPS并联系统数据传输的准确性和实时性.
基金Supported by National Natural Science Foundation of China(Grant No.51005195)Natural Science Research Fund for Youth in Higher Education Institutions of Hebei Province,China(Grant No.QN2014175)
文摘Compared with the parallel mechanisms, the mobility analysis of the general multi-loop spatial mechanisms（GMSMs） is more difficult to obtain correct results. The reason is that its multi-loop is formed through several times of closings and there also exists motion coupling even strong coupling, where the over-constraints are concealed. However, the mobility analysis for this kind of mechanisms has been paid few attentions. A new systemic methodology for analyzing mobility is proposed for GMSMs also based on the screw theory. The key issue for mobility analysis is to recognize the over-constraint. Firstly, three theorems are given and point out： the reason and site of over-constraint occurrence, calculating the number of over-constraints by the screw theory, and how to analyze the over-constraints for a single-loop mechanism as well. Then, three closing forms for GMSMs are proposed including rigid closure, movable closure and dynamic closure, and for the three different forms the different analysis methods are also given. Especially, for the most difficult issue of GMSMs with the multi-loop Closure in many times and the inevitable motion coupling, two important methods are proposed： ＂recognizing over-constraints by analyzing relative movement＂ and ＂recognizing over-constraints by virtual loop＂. The two methods are well used to solve the issue. Above-mentioned principles are not only systematic and effective but also unified. They provide a theoretical basis for the general multi-loop spatial mechanisms.
