UC Berkeley

Hybrid simulation is an experimental technique involving the integration of a physical system and a computational system with the use of actuators and sensors. This method has a long history in the experimental community and has been used for nearly 40 years. However, there is a distinct lack of theoretical research on the performance of this method. Hybrid simulation experiments are performed with the implicit assumption of an accurate result as long as sensor and actuator errors are minimized. However, no theoretical results confirm this intuition nor is it understood how minimal the error should be and what the essential controlling factors are. To address this deficit in knowledge, this study considers the problem as one of tracking the trajectory of a dynamical system in a suitably defined configuration space. To make progress, the study strictly considers a theoretical hybrid system. This allows for precise definitions of errors during hybrid simulation. As a model system, the study looks at an elastic beam as well as a viscoelastic beam. In both cases, systems with a continuous distribution of mass are considered as occur in real physical systems. Errors in the system are then tracked during harmonic excitation using space-time L2-norms defined over the system's configuration space. A parametric study is then presented of how magnitude and phase errors in the control system relate to the performance of hybrid simulation. It is seen that there are sharp sensitivities to control system errors. Further, the existence of unacceptably high errors whenever the excitations exceed the system's fundamental frequency is shown to be present in hybrid simulation.