Study On Spacecraft Attitude Angular Velocity Measurement Method Based On Gyrowheel

As an angular momentum body,the gyrowheel can change its angular momentum amplitude and direction by exerting external control torque to realize the output of the attitude control torque along the three-axis direction of the spacecraft.If the control torque and other related quantities are measured at the same time,the measurement of the spacecraft attitude angular velocities along the gyrowheel radial axis can be realized by a certain algorithm.This kind of implementation approach will greatly improve the integration and efficiency of the spacecraft attitude control system and reduce the mass and volume of the system.This paper takes the integrated realization of the spacecraft actuator and the sensor as the research background.In view of the problem of realizing the two dimensional attitude angular velocity measurement of the spacecraft using the gyrowheel with the function of a multi-degree of freedom momentum exchange,the following several aspects are studied.Firstly,aiming at the problem of establishing and validating the ideal model of gyrowheel,on the basis of the definition of coordinate system the ideal dynamic model of gyrowheel body is established by Newton-Euler method and Lagrange method respectively from the perspective of vector mechanics and analytical mechanics.At the same time,the simulation platform of the gyrowheel is built by the multi-body dynamics simulation software SimMechanics.By comparing the simulation platform with the dynamic model,the correctness of the ideal dynamic model of the gyrowheel is verified.Secondly,in view of the fact that the non-ideal influence of gyrowheel and the complicated dynamic characteristics of heeling rotor in practical engineering,the mathematical description of gyrowheel with rotor centroid offset,the non-perpendicular and noncoplanar of the orthogonal supporter are established respectively by D'Alembert's principle,Newton-Euler Method and Lagrange energy method.On this basis,the influence of the main non-ideal factors on rotor dynamic characteristics is analyzed.Furthermore,the nonlinear coupling mechanism of gyrowheel during the large angle precession is studied by gyro precession theory.The sensitivity of gyrowheel to the two-axis attitude angular velocity of spacecraft is revealed by mechanical analysis.Thirdly,in view of the problem of measuring attitude angular velocity of spacecraft by gyrowheel,since the dynamic equations of gyrowheel are characterized by multivariable constraints and strong nonlinearity,the differential evolution algorithm is used to simplify the dynamic equation of gyrowheel.By the simplified dynamic equation and the direct differentiation method,the sensitivity equation is established.The sensitivity of spacecraft attitude angle velocity is numerically analyzed.According to the conclusion of sensitivity analysis,the static measurement equation of attitude angular velocity is established and the static attitude angular velocity measurement scheme based on time-sharing multiplexing strategy is proposed.In order to realize the measurement and torque output functions simultaneously,the dynamic measurement equation of attitude angular velocity is proposed based on momentum exchange principle and the nonlinear observability of the proposed dynamic measurement equation is demonstrated.Then,in view of the error compensation and application problem of attitude angular velocity static measurement of spacecraft by the gyrowheel,the influence of system error and sensor error on attitude measurement accuracy are analyzed and the pre-distribution requirement of sensor accuracy is given by the error propagation analysis.The system error compensation of the static measurement equation of attitude angular velocity is analyzed.The classification calibration of different system parameters in the static measurement equation are realized by the rate method and multi-position method respectively.In order to make full use of the three-axis torque output function of gyrowheel on the basis of static measurement of attitude angular velocity,the time division multiplexing strategy of gyrowheel actuator function and sensor function is proposed based on the impulse equivalence principle and torque command planning.The time-sharing constraints are given to ensure that the gyrowheel can achieve two-axis attitude angular velocity measurement and three-axis torque output in the unit sampling time interval.Finally,aiming at the measurement of spacecraft attitude angular velocity in the process of gyrowheel tilting motion,the system model error in the dynamic measurement equation is analyzed.The random error of the sensor measurement is numerically analyzed by Monte Carlo method.On the basis of error analysis,the traditional nonlinear predictive filtering method is improved based on the central difference theory.An improved nonlinear predictive filtering method is proposed.Combined with the characteristics of dynamic measurement equation,the proposed filtering method is applied to the attitude angular velocity dynamic measurement,which suppresses the influence of system model error and sensor measurement noise and realizes the real-time attitude angular velocity estimation of spacecraft in gyrowheel tilting motion.