This paper investigates the finite-time attitude tracking problem for rigid spacecraft. Two backstepping finite-time slid- ing mode control laws are proposed to solve this problem in the presence of inertia uncertaint...This paper investigates the finite-time attitude tracking problem for rigid spacecraft. Two backstepping finite-time slid- ing mode control laws are proposed to solve this problem in the presence of inertia uncertainties and external disturbances. The first control scheme is developed by combining sliding mode con- trol with a backstepping technique to achieve fast and accurate tracking responses. To obtain higher tracking precision and relax the requirement of the upper bounds on the uncertainties, a se- cond control law is also designed by combining the second or- der sliding mode control and an adaptive backstepping technique. This control law provides complete compensation of uncertainty and disturbances. Although it assumes that the uncertainty and disturbances are bounded, the proposed control law does not require information about the bounds on the uncertainties and disturbances. Finite-time convergence of attitude tracking errors and the stability of the closed-loop system are ensured by the Lya- punov approach. Numerical simulations on attitude tracking control of spacecraft are provided to demonstrate the performance of the proposed controllers.展开更多
A full planar tunable band pass resonator is introduced, which is constructed by using novel symmetric step impedance resonator （SIR） and hyperabrupt varactors for wide bandwidth tuning and size reduction. The equiv...A full planar tunable band pass resonator is introduced, which is constructed by using novel symmetric step impedance resonator （SIR） and hyperabrupt varactors for wide bandwidth tuning and size reduction. The equivalent circuit model of the proposed resonator is set up. Theoretical analysis based on transmission line as well as odd and even-mode method is completed. The attractiveness of the approach presented lies in its simplicity. Based on the detailed analysis, a 6 GHz to 10 GHz varactor tuned resonator is designed, fabricated, and measured. It shows wideband tuning ability of 37%. The experimental results of the resonator have a good agreement with the analysis results.展开更多
文摘This paper investigates the finite-time attitude tracking problem for rigid spacecraft. Two backstepping finite-time slid- ing mode control laws are proposed to solve this problem in the presence of inertia uncertainties and external disturbances. The first control scheme is developed by combining sliding mode con- trol with a backstepping technique to achieve fast and accurate tracking responses. To obtain higher tracking precision and relax the requirement of the upper bounds on the uncertainties, a se- cond control law is also designed by combining the second or- der sliding mode control and an adaptive backstepping technique. This control law provides complete compensation of uncertainty and disturbances. Although it assumes that the uncertainty and disturbances are bounded, the proposed control law does not require information about the bounds on the uncertainties and disturbances. Finite-time convergence of attitude tracking errors and the stability of the closed-loop system are ensured by the Lya- punov approach. Numerical simulations on attitude tracking control of spacecraft are provided to demonstrate the performance of the proposed controllers.
文摘A full planar tunable band pass resonator is introduced, which is constructed by using novel symmetric step impedance resonator （SIR） and hyperabrupt varactors for wide bandwidth tuning and size reduction. The equivalent circuit model of the proposed resonator is set up. Theoretical analysis based on transmission line as well as odd and even-mode method is completed. The attractiveness of the approach presented lies in its simplicity. Based on the detailed analysis, a 6 GHz to 10 GHz varactor tuned resonator is designed, fabricated, and measured. It shows wideband tuning ability of 37%. The experimental results of the resonator have a good agreement with the analysis results.
