Development of multi-degree-of-freedom microvibration emulator for efficient jitter test of spacecraft

Abstract

A number of components and payload systems installed in satellites are found to be exposed to various disturbance sources, such as the reaction wheel assembly, the control moment gyro, coolers, and others. Low damping in space causes continuous microvibration that degrades the performance of various payload systems; this is customarily called jitter problem in spacecraft community. Various isolation systems have been developed to improve the performance of the optical payloads under the microvibration environments. During the spacecraft development process, an experimental validation of jitter effects (either controlled or not) on the performance of optical payloads using all the flight model components is not often conducted due to the scheduling issue or the product assurance activities. The disturbance characteristics of a prototype or an engineering model of the disturbance source such as reaction wheel assembly are significantly different from their flight model counterparts. Therefore, in order to facilitate jitter test as well as the performance evaluations of an isolator during the satellite development process, this article proposes a microvibration emulator that generates the real disturbance spectrums of flight models. The development procedure for the reaction wheel assembly emulator is described. Prototype single-axis and three-axis microvibration emulators are demonstrated, and the performances are evaluated by means of disturbance characteristics similar to those of the reaction wheel assembly.

Experimental Validation of Fly-Wheel Passive Launch and On-Orbit Vibration Isolation System by Using a Superelastic SMA Mesh Washer Isolator

“…From these results, it can be seen that the fundamental harmonic at the 5000 rpm has the largest amplitude and gradually decreases as the wheel speed decreases. In here, the amplitude of the fundamental harmonic is proportional to the square of the wheel speed [26]. Aside from the fundamental harmonic, a number of superharmonics were also observed in all axes with relatively lower amplitudes compared to the fundamental harmonic.…”

“…In practice, this electrical noise cannot be avoidable during the test even if some efforts were implemented towards reducing this noise [26]. However, the electrical noise is much smaller when compared to the harmonic disturbances; therefore, it can be ignored.…”

Simulating and Testing Microvibrations on an Optical Satellite Using Acceleration Sensor-Based Jitter Measurements

“…So far, an effective means is to integrate the structure, control, and optical system as a whole calculation model; this reflects the relationship between microvibrations and the camera, from perturbation sources through the loading path to imaging quality [11,12]. The whole calculation model can be checked and verified by ground testing [13]. Validation tests on ground are key in microvibration research.…”

A multi-directional vibration isolator based on Quasi-Zero-Stiffness structure and time-delayed active control

“…Numerous active control devices have been applied for vibration control for one direction or multi direction [22][23][24][25]. Timedelay in active control is considered as an adjustable parameter because appropriate value of time delay can induce different vibration control mechanisms such as vibration energy transmission in different modes [26,27], absorbing vibration energy [28,29] or changing equivalent stiffness and damping properties [30,31].…”