Structural Testing of High Value Test Articles: Integrated Risk Mitigation in Vibration Test Systems

Abstract

Structural testing and model verification are necessities in the development of high-value spacecrafts and components. Testing of such items using electrodynamic shaker systems is meticulously planned to avoid any accidental damage. Similarly, the controller and amplifiers used to drive the shakers must be capable of mitigating risk by safely responding to unplanned vibration excursions during a test, as well as to issues with the test system itself, or with facility resources such as electrical power. For example, what happens if the amplifier power source fails, or the network connecting the controller to the command computer goes down? External factors such as these are unpredictable, but careful consideration during vibration test system design makes it is possible for the system to handle such events reliably and minimize risk of damage. Recent advancements in technology have resulted in the design of a complete test system that stresses risk mitigation. The status of building power, safety interlocks, and other critical subsystems are continuously monitored by the controller. A failure on any of the critical subsystems will immediately trigger the controller to ramp down the sine sweep over a prescribed duration. The rate at which the controller reacts to an abort signal is critical. For example, if amplifier power loss is experienced during a sine sweep, the controller must be able to ramp down the drive and stop the test smoothly. Similarly, the amplifier needs stored backup power for the ramp down. These features protect the test article from any transients by preventing the shaker from abruptly stopping. This paper will investigate such safety concerns in structural testing of high value test articles, and the test system considerations associated with these concerns.