Real-Time Hybrid Substructuring for Shock Applications Considering Effective Actuator Control

Shock describes a rapid change in loading conditions and occurs in many mechanical, aerospace, and civil engineering systems. The shock response of these systems is of critical importance in their design and must therefore be studied. While experimental investigation of shock response offers accurate results, this approach is costly and requires highly specialized and unique facilities. In contrast, numerical investigation of shock events can be an effective alternative; however, modeling the systems accurately can be challenging. In this paper, the application of Real-Time Hybrid Substructuring (RTHS) to study the system response to a shock event is proposed. RTHS is a cyber-physical testing method, combining both experimental and numerical testing. The RTHS approach is intended to fully incorporate the dynamic interaction between the structure and the excitation source and realistically capture all dynamic phenomena. In this preliminary study of an RTHS shock test, the impact of a swinging pendulum on a mass-spring-damper system is investigated. This highly dynamic event requires precise actuator control and dynamics compensation. This work makes use of a model-based feedforward compensator, namely a minimum phase inverse compensator. To reduce any remaining frequency-dependent time delay or magnitude tracking errors, this compensator is combined with a P-type Iterative Learning Controller. The interaction force profile is studied for varying eigenfrequencies and mass ratios of the impacted mass-spring-damper system. The tests are able to replicate the free vibration response of the system accurately. Despite a good learning performance of the Iterative Learning Control, there are still tracking errors in the initial impact phase. Future work will look to improve actuator control and performance.