Multipoint Control for Single Axis Vibration Testing

Abstract

In mechanical testing for system qualification, test engineers often face the challenge of representing a multi-axis vibration environment using a single-axis shaker table with only one degree of freedom for control. On large, complicated systems, the target environments are often defined as power spectral densities (PSDs) of a random vibration signal at multiple locations. These PSDs are almost invariably defined such that they are not physically realizable in any boundary condition. If one location responds with exactly its target PSD, another location will respond with a PSD that is different from its respective target. This paper presents a control strategy that minimizes an error between the responses and their respective targets, given a single actuation input. By estimating a model in real-time, an optimal input can be solved for each iteration of the control loop to adjust the excitation input and properly track responses. Implementing this control algorithm on a linear time invariant system by filtering the feedback sent to standard shaker controller hardware, there was a 4.3 dB and 3.5 dB variance in filter magnitude when using a 2.5 s model history and 5 s model history respectively. When applying this scheme to the LTV model, we noticed a stable change in filter magnitude. This paper has been approved for release as LA-UR-17-29695.

Appendix (Tables 19.2 and 19.3)

Table 19.2 Control parameters

Table 19.3 Structure parameters