Acceleration trajectory tracking control for earthquake simulators

The purpose of earthquake simulators is to reproduce reference accelerations on a shake table. However, acceleration control is extremely difficult in earthquake simulators due to an inability to directly control acceleration with feedback, inherent nonlinearities in servo hydraulic systems, control-structure interactions, etc. This study presents a control method called acceleration trajectory tracking control (ATTC) that improves the acceleration control performance of earthquake simulators. The ATTC method consists of an acceleration feed-forward controller, a system dynamics command shaping, an intentional time-delay, a Kalman filter for displacement measurement, and an actuator displacement feedback controller. The ATTC method not only provides acceleration tracking capability, but also ensures stability of the system. Following the theoretical description of the ATTC method, an experimental investigation is presented. The ATTC method is successfully implemented in the control system for the uniaxial earthquake simulator at Johns Hopkins University, and the experimental results show the superior performance of the ATTC method over the conventional displacement feedback with command shaping. Furthermore, repeatability of the ATTC method is experimentally verified.