High-frequency micro-vibration isolation device of spacecraft control moment gyroscope

[0115] Simulation test example

[0116] For the CMG, the main frequency of its micro-vibration disturbance is the same as the speed of the high-speed rotor in the CMG, and the speed of the CMG is generally at 6000 rpm, that is, 100 Hz. Therefore, the analysis and verification of the vibration isolation performance of the device also focuses on the vibration near 100 Hz. frequency domain.

[0117] (1) Simulation calculation

[0118] The finite element dynamic models of the micro-vibration isolation device and CMG were established. The folded arm beam structure is modeled using beam elements, and other components are modeled using solid elements to improve the calculation accuracy of the model. The bottom plate is considered to belong to the spacecraft body, and may not be reflected in the finite element model.

[0119] In the dynamic analysis, the frequency variation of the dynamic performance (storage modulus and loss factor) of the viscoelastic material is considered. Through the structural sensitivity analysis and parameter optimization design, the structural size of the vibration isolation device is further optimized to improve the vibration isolation performance. The natural frequency of the vibration isolation system is calculated by the modal strain energy iteration method, as shown in Table 1. Since the seventh-order natural frequency is greater than 400Hz, it is not within the frequency band of interest in this article, so it is not listed in the table.

[0120] Table 1 The first six natural frequencies of the vibration isolation system calculated by simulation

[0121]

[0122] In the finite element model, the rotor node of the CMG is taken as the input point of the disturbance, and the constraint node at the lower end of the vibration isolation device is taken as the output point of the disturbance. Input disturbance force F in and disturbance moment M in , through the frequency response analysis of the model, the support reaction force F of the output node can be obtained out and supporting reaction moment M out , after passing through the vibration isolation device, the force transmission rate T of the disturbance can be obtained F =F out /F in , the force transmission rate T of the moment M = M out /M in ,like Figure 20 Shown is a schematic diagram of force/torque transmission rate calculation. exist Figure 20 Among them, P1 represents the rotor node, that is, the input point; P2 represents the outer frame node; P3 represents the output node.

[0123] The structural parameter optimization design of the vibration isolation device is carried out, and then the directions of six degrees of freedom (F X , F Y , F Z ,M X ,M Y ,M Z ) unit force/moment; where, F X , F Y and F Z represent the forces in the x, y and z directions, respectively; M X , M Y and M Z Represent the moments in the x, y and z directions, respectively; the analysis frequency domain is selected as 0-150Hz. The force/torque transmission rate curve obtained after the frequency response analysis is as follows: Figure 21-Figure 26 As shown, among them, Figure 21 F obtained after frequency response analysis X Comparison curve of directional transmissibility; Figure 22 F obtained after frequency response analysis Y Comparison curve of directional transmissibility; Figure 23 F obtained after frequency response analysis Z Comparison curve of directional transmissibility; Figure 24 M obtained after frequency response analysis X Comparison curve of directional transmissibility; Figure 25 M obtained after frequency response analysis Y Comparison curve of directional transmissibility; Figure 26 M obtained after frequency response analysis Z Directional transmissibility comparison graph. The numerical unit is decibel (dB), and the effective vibration isolation frequency in each degree of freedom direction is shown in Table 2. Figure 21-Figure 26 The transmissibility with or without considering the damping effect of the viscoelastic material is also compared in , where the dotted line is the damping effect without considering the viscoelastic material.

[0124] Table 2 Effective vibration isolation frequencies in six directions after optimization

[0125]

[0126] It can be known from the transmissibility curve and the finite vibration isolation frequency table that the maximum effective vibration isolation frequency of the optimized vibration isolation device is 28.97 Hz, that is, disturbances with a frequency greater than 28.97 Hz can be effectively isolated by the vibration isolation device, and the vibration isolation device provided by the present invention The micro-vibration frequency of a single-frame CMG is generally 100-150 Hz. Therefore, the novel vibration isolation device proposed by the present invention can effectively isolate the high-frequency micro-vibration generated on the six degrees of freedom of the CMG.

[0127] Depend on Figure 21-Figure 26 The comparison results in the above shows that the structural damping of viscoelastic materials does not affect the natural frequency of the system, but greatly reduces the peak response of the system to disturbance in the resonance region, effectively reducing the damage to the structure caused by disturbance, and the damping effect on vibration isolation. The effect is very obvious.

[0128] (2) Experimental verification

[0129] Draw the engineering drawing of the micro-vibration isolation device, complete the processing and assembly of the actual object, and build a ground micro-vibration measurement system. The ground experiment system consists of a Kistler 9253B12 measurement platform, an optical vibration isolation platform, and a data acquisition and analysis system. The measurement system The composition and working principle of Figure 27 shown. Among them, the Kistler Table is widely used to measure the disturbance force and torque of aerospace components such as flywheels and digital transmission antenna drive mechanisms. It has the advantages of large measurement range, wide measurement frequency domain, and high measurement accuracy.

[0130] The disturbance input to the CMG is simulated with a high-speed rotating reaction flywheel. The verification experiment includes two working conditions. Working condition 1: the flywheel is directly connected to the Kistler Table platform rigidly through bolts, and working condition 2: the flywheel is indirectly connected to the Kistler Table platform through a vibration isolation device.

[0131] Start the flywheel, gradually adjust its speed to the working speed (6000rpm), measure the force and moment under the two connection conditions, and obtain the time domain disturbance output curve on the six degrees of freedom, and obtain the disturbance in the frequency domain through Fourier transform Output curves, specifically, such as Figure 28 As shown, it is the disturbance force at F X directional time domain graph; such as Figure 29 As shown, it is the disturbance force at F X Directional frequency domain graph; such as Figure 30 As shown, it is the disturbance force at F Y directional time domain graph; such as Figure 31 As shown, it is the disturbance force at F Y Directional frequency domain graph; such as Figure 32 As shown, it is the disturbance force at F Z directional time domain graph; such as Figure 33 As shown, it is the disturbance force at F Z Directional frequency domain graph; such as Figure 34 As shown, it is the disturbance force in M ​​at the operating speed of 6000rpm X directional time domain graph; such as Figure 35 As shown, it is the disturbance force in M ​​at the operating speed of 6000rpm X Direction frequency domain graph;

[0132] like Figure 36 As shown, it is the disturbance force in M ​​at the operating speed of 6000rpm Y directional time domain graph; such as Figure 37 As shown, it is the disturbance force in M ​​at the operating speed of 6000rpm Y Directional frequency domain graph; such as Figure 38 As shown, it is the disturbance force in M ​​at the operating speed of 6000rpm Z directional time domain graph; such as Figure 39 As shown, it is the disturbance force in M ​​at the operating speed of 6000rpm Z Direction frequency domain graph; Table 3 lists the disturbance output values ​​of the two working conditions under the working frequency (100Hz).

[0133] Table 3 Comparison of disturbance output values ​​at operating frequency (100Hz)

[0134]

[0135] Comparative analysis of the disturbance measurement results under the two working conditions shows that:

[0136] (1) In the time domain, the disturbance output under the connection condition of the vibration isolation device is greatly reduced compared with the rigid connection condition, and it is very obvious in the six degrees of freedom.

[0137] (2) In the frequency domain of 0-350Hz, the disturbance output under the connection condition of the vibration isolation device is smaller than that under the rigid connection condition, and the broadband disturbance can be effectively isolated.

[0138] In summary, the simulation calculation and experimental verification all show that the new micro-vibration isolation device proposed by the present invention has good vibration isolation performance at the CMG operating speed, and can effectively reduce the transmission of six degrees of freedom micro-vibrations to stars. It helps to improve the attitude stability and pointing accuracy of stars.