Dynamic Unbalance Identification And Active Vibration Control For Gyrowheel

Gyro Wheel is an integrated device with attitude control and measurement functions,which meets the needs of small spacecraft for high integration,lightness and miniaturization,and low power consumption.The three-degree-of-freedom attitude control torque output can be realized by adjusting the rotation speed and tilting angles,and the attitude angular velocity measurement of the spacecraft can be calculated by the torquer current.However,the dynamic unbalance of the Gyro Wheel rotor will cause periodic vibration and measurement drift errors.The corrected residual unbalance disturbance torque is transmitted to the base and affects the working performance of the spacecraft load.Therefore,aiming at key issues in engineering realization such as the dynamic unbalance of the Gyro Wheel rotor and multi-frequency vibrations,the research on dynamic balancing and active vibration control method is of great significance to the integrated realization of torque output and attitude measurement.Motivated by the above facts,this paper studies the identification of the dynamic unbalance of the Gyro Wheel rotor,the active vibration control and gyro signal denoising.The contents are as follows:Firstly,by establishing the reference coordinate frames and introducing generalized coordinates,a complete Gyro Wheel dynamic model considering the attitude angular velocity of the spacecraft is derived based on the second kind of Lagrange’ s equation.It is transformed into case coordinate frames suitable for characterization to verify the correctness of the model.The dynamic model of the zero-tilting is simplified by the linearization theory.According to the periodic disturbance torque model,the relationship between the unbalanced excitation and the tilting angle is analyzed.The dynamic model established by vector mechanics and D’Alembert principle helps to analyze the influence of disturbance torque formed by centroid offset under gravity acceleration excitation.The multi-frequency vibrations caused by the dynamic unbalance are revealed.Secondly,aiming at the problem that the accuracy of the traditional dynamic balancing decreases under the anisotropic stiness and the measurement drift error caused by the non-coincidence of the centroid and the support center,a three-dimensional dynamic unbalance identification method of the Gyro Wheel supported by the equivalent point is studied.Considering that the actual running trajectory is not a perfect circle under the anisotropic stiffness and the nonlinear relationship between the phase angle of the characteristic vector and the phase angle of the unbalanced excitation,the equivalent vibration vector is constructed by using the forward precession component of the ellipse and based on the energy equivalence principle.The couple unbalance identificatioin based on the equivalent vibration vector and phase-shifting circle is given.Inspired by the full measurement drift error model,the axial static unbalance identification based on multi-position calibration is given by using the relationship among axial static unbalance,gravity acceleration,torquer current and drift error coefficients.Thirdly,in view of the periodic vibration of the spacecraft and loads caused by the residual unbalance after dynamic balance correction,an active vibration control method based on the torque compensation principle is studied.Through the force analysis of each sub-component,the vibration torque transmission mechanism of the spacecraft base is analyzed.In order to ensure the stable pointing accuracy of the spacecraft,a torquer current minimum control method based on variable-step LMS and sliding mode observer is proposed.Considering the influence of model parameter perturbation,a terminal sliding mode observer is designed to estimate the rotor unbalance.The switching gain is integrated to reduce the chattering phenomenon of the control signal.The adopted variablestep LMS algorithm can adaptively adjust the gain of the compensator to meet the low vibration transmission requirements in space environment applications.Finally,an experimental platform is built based on the Gyro Wheel prototype and the comprehensive experiments are carried out to verify the above research.The multi frequency vibration characteristics of the prototype are verified by analyzing the test signals of tilting angles and torquer current.In order to extract effective information from noisy test signals,threshold denoising of torquer current is realized using the com-plete ensemble EMD with adaptive noise.The iterative algorithm reduces the position sensitivity error in the EMD decomposition caused by random vibration,and realizes the effective reconstruction of the signal.The effectiveness of rotor dynamic unbalance identification method and active vibration control method proposed in this paper are verified by using Gyro Wheel prototype and two axis turntable.By combining offline and online means,the vibration suppression of Gyro Wheel is realized.