A perspective on the vibration overtest problem

The traditional vibration test methodology of controlling the interface environment at the test article only to a motion-based specification is often too conservative, inducing potentially excessive vibration responses at hardware resonant frequencies. This problem has been recognized for quite some time, and a synopsis of the various remedial procedures proposed in the literature is presented. Of these, the dual-control or force-limited vibration test has recently emerged as a viable solution for ameliorating overtest conditions on a wide variety of hardware. The underlying theoretical basis of the dual-control technique is derived using Thevenin's and Norton's theorems for equivalent mechanical systems. Practical implementation considerations in selecting the appropriate control variables are also discussed. References are provided to cover this topic and to serve as a useful database for potential new users.