Reproduction of Long-Period Ground Motion by Cable Driven Earthquake Simulator Based on Computed Torque Method

Abstract

In order to reproduce seismic waves classified in long-period ground motion by disaster prevention education facility, an earthquake simulator based on a cable-driven parallel mechanism has been constructed. In this paper, a feedforward-based control scheme was implemented in the cable-driven earthquake simulator for achieving high acceleration with frequent reverse rotation required to reproduce actually-observed seismic waves. The derivation of the dynamic model was done in two steps, the first step is calculating cable tensions to achieve a moving platform’s target acceleration, and the second is for each spooler’s torque calculation to achieve that tension. For a feedforward torque calculation using the second inverse dynamic model of cable spooler, an experimental identification scheme of model parameters which takes a rapid change of torque-velocity relationship of spooler at the moment of reverse rotation into account were figured out. By using the implemented control scheme with identified model parameters, capability of the developed earthquake simulator for reproducing an actually-observed typical long period ground motion was demonstrated by motion control experiments.