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 Reaction wheels are widely used for spacecraft attitude control in missions that require fine pointing accuracy and stabilization nowadays. But the friction produced by the reaction wheel assembly (RWA) itself when crossing zero is one of the most significant sources of disturbance. And it is necessary to eliminate these disturbances, especially for those cases that the wheels are running at lowspeed throughout the space mission. The mathematical model of the reaction wheel assembly driven by a DC motor is... Reaction wheels are widely used for spacecraft attitude control in missions that require fine pointing accuracy and stabilization nowadays. But the friction produced by the reaction wheel assembly (RWA) itself when crossing zero is one of the most significant sources of disturbance. And it is necessary to eliminate these disturbances, especially for those cases that the wheels are running at lowspeed throughout the space mission. The mathematical model of the reaction wheel assembly driven by a DC motor is presented on the base of Dahl friction equations. And a state observer is constructed to estimate the friction torque in order to compensate for it. A numerical simulation model, which assumes the satellite attitude is controlled by three reaction wheels arranged in an orthogonal geometry, is established. The simulation results prove that this method can improve the satellite attitude pointing accuracy and stability efficiently. Finally, the integration of the observer method and a slidingmode control law is discussed.  反作用轮在现代高精度卫星姿态控制中占据着重要的地位。但由于反作用轮工作于低速状态,其转速过零时摩擦力矩的非线性特征将会对姿态控制精度产生较大的影响,并影响卫星运行寿命。基于Dahl摩擦模型建立了直流电机驱动的反作用轮系统数学模型,在此基础上设计了用于改善反作用轮低速性能的补偿观测器,并将其应用于三正交结构姿态控制系统。数字仿真说明此方法可以有效地抑制反作用轮低速摩擦产生的扰动,从而大幅度改善卫星姿态控制精度及其姿态稳定性。最后探讨了该观测器方法同变结构控制方法的综合应用前景。  Nowadays, reaction wheels are widely used as attitude control actuators in space missions that require fine pointing accuracy and stabilization. But the inner disturbances introduced by the reaction wheel assembly (RWA) itself are among the most significant ones. These include bearing frictions, flywheel imbalance, structural vibrations, etc. The mathematical models of the reaction wheel with such characteristics were presented. And the associated computer models were implemented in the MATLAB/Simulink environment.... Nowadays, reaction wheels are widely used as attitude control actuators in space missions that require fine pointing accuracy and stabilization. But the inner disturbances introduced by the reaction wheel assembly (RWA) itself are among the most significant ones. These include bearing frictions, flywheel imbalance, structural vibrations, etc. The mathematical models of the reaction wheel with such characteristics were presented. And the associated computer models were implemented in the MATLAB/Simulink environment. Then the models were applied to a satellite attitude dynamics simulation, with the assumption that the satellite was working in a threeaxis stability mode. The numerical results show that the RWA disturbances are significant.  反作用轮在卫星姿态控制中得到广泛应用;但对于指向精度要求高的任务,必须充分考虑反作用轮本身引入的干扰,即反作用轮系统的内干扰。首先建立了反作用轮系统的内干扰数学模型,包括摩擦干扰、弹性振动干扰及飞轮质量分布不均引入的干扰,以此为基础,在MATLAB/Simulink环境下建立了相关的仿真模型,并将其应用到卫星三轴稳定姿态控制动力学仿真中。  Reaction wheel is one of the main disturbance sources that affect the precision of attitude control system of spacecraft. The purpose of setting up a disturbance model of reaction wheel is to predict the effects of the disturbance on the spacecraft, and then adopt corresponding control methods and isolation systems to restrain them. This paper presents the experimental disturbance model of reaction wheel. By analyzing the experimental data of reaction wheel, the parameters of the disturbance model, harmonic... Reaction wheel is one of the main disturbance sources that affect the precision of attitude control system of spacecraft. The purpose of setting up a disturbance model of reaction wheel is to predict the effects of the disturbance on the spacecraft, and then adopt corresponding control methods and isolation systems to restrain them. This paper presents the experimental disturbance model of reaction wheel. By analyzing the experimental data of reaction wheel, the parameters of the disturbance model, harmonic numbers and amplitude coefficients are determined. The energy compensation method is then given. The simulation results show that the identification accuracy of harmonic numbers does not exceed 0.04%. When adopting the amplitude spectrum method to compute the amplitude coefficients, the error is high up to 15.5%, however the error not over 1.1% when adopting energy compensation method. It indicates that the energy compensation method improves the identification accuracy of amplitude coefficients. This paper aims at providing a certain basis for improving the attitude control precision and stabilization of the spacecraft.  反作用轮系统是影响航天器姿控系统精度的主要扰动源之一．建立反作用轮扰动模型的目的是预测扰动对航天器产生的影响,并采取相应的控制方法和隔离系统．基于反作用轮的扰动实验模型,通过对反作用轮扰动实验数据的分析,确定出反作用轮扰动实验模型中的参数:谐波数和幅值系数,并在此基础上提出了能量补偿法,最后进行了数值仿真．结果表明,谐波数的辨识精度不超过0．04％,当采用振幅谱法计算幅值系数时,误差高达15．5％;而用能量补偿法,其幅值系数的精度不超过1．1％．可见能量补偿法提高了幅值系数的辨识精度．本文研究为改善航天器姿态控制精度和稳定度奠定了一定的基础．   << 更多相关文摘 
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