Due to actuator time delay existing in an adaptive control of the active balancing system for a fast speed-varying Jeffcott rotor, if an unsynchronized control force (correction imbalance) is applied to the system, it...Due to actuator time delay existing in an adaptive control of the active balancing system for a fast speed-varying Jeffcott rotor, if an unsynchronized control force (correction imbalance) is applied to the system, it may lead to degradation in control efficiency and instability of the control system. In order to avoid these shortcomings, a simple adaptive controller was designed for a strictly positive real rotor system with actuator time delay, then a Lyapunov-Krasovskii functional was constructed after an appropriate transform of this sys-tem model, the stability conditions of this adaptive control system with actuator time delay were derived. After adding a filter function, the active balancing system for the fast speed-varying Jeffcott rotor with actuator time delay can easily be converted to a strictly positive real system, and thus it can use the above adaptive controller satisfying the stability conditions. Finally, numerical simulations show that the adaptive controller proposed works very well to perform the active balancing for the fast speed-varying Jeffcott rotor with actuator time delay.展开更多
Here the authors critically review the IPCC＇s claim that global warming is ＂very likely＂ caused by human activity： such a description underestimates the likelihood of the warming being due to this mechanism. Next ...Here the authors critically review the IPCC＇s claim that global warming is ＂very likely＂ caused by human activity： such a description underestimates the likelihood of the warming being due to this mechanism. Next examined are known alternative ＂natural＂ mechanisms which could give rise to the warming if, despite many claims, the man-made explanation was false because of compensation effects （greenhouse gases versus aerosol effects）. Also, a number of difficulties, as yet unresolved, in the human-induced warming explanation are considered.展开更多
文摘Due to actuator time delay existing in an adaptive control of the active balancing system for a fast speed-varying Jeffcott rotor, if an unsynchronized control force (correction imbalance) is applied to the system, it may lead to degradation in control efficiency and instability of the control system. In order to avoid these shortcomings, a simple adaptive controller was designed for a strictly positive real rotor system with actuator time delay, then a Lyapunov-Krasovskii functional was constructed after an appropriate transform of this sys-tem model, the stability conditions of this adaptive control system with actuator time delay were derived. After adding a filter function, the active balancing system for the fast speed-varying Jeffcott rotor with actuator time delay can easily be converted to a strictly positive real system, and thus it can use the above adaptive controller satisfying the stability conditions. Finally, numerical simulations show that the adaptive controller proposed works very well to perform the active balancing for the fast speed-varying Jeffcott rotor with actuator time delay.
文摘Here the authors critically review the IPCC＇s claim that global warming is ＂very likely＂ caused by human activity： such a description underestimates the likelihood of the warming being due to this mechanism. Next examined are known alternative ＂natural＂ mechanisms which could give rise to the warming if, despite many claims, the man-made explanation was false because of compensation effects （greenhouse gases versus aerosol effects）. Also, a number of difficulties, as yet unresolved, in the human-induced warming explanation are considered.
