TIME-DELAY COMPENSATION IN ACTIVE DAMPING OF STRUCTURES

With the higher modes being considered in structural vibration control, practical problems such as the effect of the time delay between sensing the structural motion and applying the control force become more pronounced. Instability due to time delay is observed experimentally using a carefully calibrated model of a typical single-span bridge modeled as a continuous system. The control action is applied using an accelerometer, analog integrator, cable, post, and hydraulic actuator in conjunction with an on-line digital microcomputer. A practical scheme for time-delay compensation based on response sampling, curve fitting, and extrapolation is employed. The purposed scheme has the advantage of eliminating the observation spillover that may cause instability in the control system on one hand, and may serve as an almost perfect state estimator on the other hand. The correlation between the analytical and experimental results is presented.