Force Limited Vibration Test Interface Force Calculation Model And Simplify The Research

In conventional vibration test of space hardware, the acceleration input at the interface between the test article and the mounting structure is controlled to a specification which is the envelope of the acceleration peaks in the flight environment. This traditional approach of testing is known to produce great overtesting to the test article at its own resonance frequencies. An improved approach called force-limited vibration (FLV) testing was developed and implemented at NASA Jet Propulsion Laboratory (JPL), in the 1990s.In addition to controlling the input acceleration, the FLV testing measures and limits the reaction forces between the test article and the shaker. This approach can reduce the over-testing. However, it is very difficult to derive the force data of the interface during the flight, which is supposed to be used to define the force specifications of the FLV test. So it becomes very critical to find a way to get the force specifications with the acceleration data and the dynamic model of the spacecraft. This paper derived the expression of the relationship between the interface force and acceleration using component modal synthesis method with a dynamic model of the spacecraft system.Then according to the contribution of every mode of the system to the interface responses in a certain range of frequency, we reduce the dynamic model into a complex two-degree-of-freedom system which has already been introduced in many literatures. Through this reduction process we theoretically find how the Complex TDFS method works with its simplification model.And then we analyzed the error of the method with a numerical example.