为能够给星上有效载荷提供一种超静环境,提出一种星上控制力矩陀螺群(CMGs,Control Moment Gyroscopes)的隔振方案,并对所使用的隔振平台的动力学特性进行研究分析.首先介绍了不同参数模型的隔振元件工作原理和参数特性;其次利用牛顿-欧拉法对含有隔振平台和CMGs的卫星进行动力学建模;最后通过频域和时域的方法分析并对比了各个参数模型下的隔振平台力衰减特性以及对星体姿态稳定度的改善程度.结果表明:两参数加调谐质量阻尼器模型下的隔振平台对共振峰值有一定的衰减作用,三参数模型下的隔振平台在力衰减和对姿态稳定度的改善程度上要明显优于其他2种模型.
The attitude control problem of a spacecraft underactuated by two single-gimbal control moment gyros(SGCMGs) is investigated.Small-time local controllability(STLC) of the attitude dynamics of the spacecraft-SGCMGs system is analyzed via nonlinear controllability theory.The conditions that guarantee STLC of the spacecraft attitude by two non-coaxial SGCMGs are obtained with the momentum of the SGCMGs as inputs,implying that the spacecraft attitude is STLC when the total angular momentum of the whole system is zero.Moreover,our results indicate that under the zero-momentum restriction,full attitude stabilization is possible for a spacecraft using two non-coaxial SGCMGs.For the case of two coaxial SGCMGs,the STLC property of the spacecraft cannot be determined.In this case,an improvement to the previous full attitude stabilizing control law,which requires zero-momentum presumption,is proposed to account for the singularity of SGCMGs and enhance the steady state performance.Numerical simulation results demonstrate the effectiveness and advantages of the new control law.
Although the simple adaptive control (SAC) is widely studied both in theory and application in flexible space structure control and other control problems, it is restricted by the almost strictly positive real (ASPR) conditions. In most practical control problems, the ASPR conditions are not satisfied. Therefore, based on the SAC theory, this paper proposes a backstepping simple adaptive control algorithm which suits the system with arbitrary relative degree with no need of parallel feedforward compensator. The proposed control algorithm consists of decomposition of the arbitrary relative degree system into a known subsystem and an unknown ASPR subsystem which are connected in cascade, design of constant output feedback controller for the known subsystem, and implementation of backstepping method and SAC of the unknown ASPR subsystem. Inheriting the characteristics of the SAC, this method can be adaptive online for the parameter uncertainties. Then, the application of the proposed controller to large flexible space structure with collocated sensors and actuators is studied, and the simulation results validate the proposed controller. It is a new strategy to apply the classical SAC to high relative degree plants.
