Active vibration control is needed for future space telescopes, space laser communication and other precision sensitive payloads which require ultra-quiet environments. A Stewart platform based hybrid isolator with 6 ...Active vibration control is needed for future space telescopes, space laser communication and other precision sensitive payloads which require ultra-quiet environments. A Stewart platform based hybrid isolator with 6 hybrid struts is the effective system for active/passive vibration isolation over 5-250 Hz band. Using an identification transfer matrix of the Stewart platform, the coupling analysis of six channels is provided. A dynamics model is derived, and the rigid mode is removed to keep the signal of pointing control. Multi objective robust H∞ and μ synthesis strategies, based on singular values and structured singular values respectively, are presented, which simultaneously satisfy the low frequency pointing and high frequency disturbance rejection requirements and take account of the model uncertainty, parametric uncertainty and sensor noise. Then, by performing robust stability test, it is shown that the two controllers are robust to the uncertainties, the robust stability margin of H, controller is less than that of μ controller, but the order of μ controller is higher than that of H, controller, so the balanced controller reduction is provided. Additionally, the μ controller is compared with a PI controller. The time domain simulation of the μ controller indicates that the two robust control strategies are effective for keeping the pointing command and isolating the harmonic and stochastic disturbances.展开更多
In the earliest Abrahamic scriptures,the writers made clear that God did not want to divulge a personal name he could be called.Despite all the differences among the Abrahamic traditions,one critical point all agree o...In the earliest Abrahamic scriptures,the writers made clear that God did not want to divulge a personal name he could be called.Despite all the differences among the Abrahamic traditions,one critical point all agree on is the decision that God’s creatures may refer to him and pray to him but not to speak to the God who declares“I am that I am”.It turns out that in the 20th century a Hassidic rebbe figured why that prohibition may be so critical to all cultural traditions of the Abrahamic collection of faiths.In addition,philosophy of language supports the rebbe’s reasoning as does an analogical argument about knowledge inaccessible to simultaneous objectifying.All this sums to the grounds for building a platform for international cooperation with religious understanding as more worthy and less risky than the scheming and greed surrounding economic competition.展开更多
文摘Active vibration control is needed for future space telescopes, space laser communication and other precision sensitive payloads which require ultra-quiet environments. A Stewart platform based hybrid isolator with 6 hybrid struts is the effective system for active/passive vibration isolation over 5-250 Hz band. Using an identification transfer matrix of the Stewart platform, the coupling analysis of six channels is provided. A dynamics model is derived, and the rigid mode is removed to keep the signal of pointing control. Multi objective robust H∞ and μ synthesis strategies, based on singular values and structured singular values respectively, are presented, which simultaneously satisfy the low frequency pointing and high frequency disturbance rejection requirements and take account of the model uncertainty, parametric uncertainty and sensor noise. Then, by performing robust stability test, it is shown that the two controllers are robust to the uncertainties, the robust stability margin of H, controller is less than that of μ controller, but the order of μ controller is higher than that of H, controller, so the balanced controller reduction is provided. Additionally, the μ controller is compared with a PI controller. The time domain simulation of the μ controller indicates that the two robust control strategies are effective for keeping the pointing command and isolating the harmonic and stochastic disturbances.
文摘In the earliest Abrahamic scriptures,the writers made clear that God did not want to divulge a personal name he could be called.Despite all the differences among the Abrahamic traditions,one critical point all agree on is the decision that God’s creatures may refer to him and pray to him but not to speak to the God who declares“I am that I am”.It turns out that in the 20th century a Hassidic rebbe figured why that prohibition may be so critical to all cultural traditions of the Abrahamic collection of faiths.In addition,philosophy of language supports the rebbe’s reasoning as does an analogical argument about knowledge inaccessible to simultaneous objectifying.All this sums to the grounds for building a platform for international cooperation with religious understanding as more worthy and less risky than the scheming and greed surrounding economic competition.
