Implementation of dynamics inversion algorithms in active vibration control systems: Practical guidelines

Abstract

It is common that excessive vibrations problems arise in modern slender, low-damping, lightweight structures such as footbridges or long-span floors subjected to human actions. The integration of inertial vibration controllers has been extensively used to mitigate the problems associated with vibration serviceability of such structures. Among them, the active vibration absorber constitutes the most sophisticated and effective alternative. Nonetheless, the inherent dynamics of the actuators used in the practical implementations of these systems may negatively affect their performance, compromising the overall system stability and performance. In this work, the practical application of dynamics inversion techniques to the force control of electrodynamic proof-mass actuators employed as active vibration absorption systems in lightweight structures subjected to human-induced vibrations is presented. The main idea behind the dynamics inversion approach is to find an approximate inverse of the actuator system which, upon implementation on a real-time controller, approximately cancels out actuator dynamics leading to an improved force tracking, with the subsequent enhancement in the performance of any force-based vibration control algorithm. The dynamics inversion has been applied to the classical direct velocity feedback approach, leading to a novel vibration control algorithm denominated velocity feedback with dynamics inversion. Additionally, the stability of the suggested method has been studied and practical guidelines, including a step-by-step design procedure, have been provided for researchers willing to apply the proposed algorithm. The goodness of the suggested method has been assessed by means of a tests campaign carried over an existing glass fiber reinforced polymer footbridge, which fulfills the static requirements at Serviceability and Ultimate Limit States, but exhibits excessive vibrations when its first resonance frequency is excited. Two types of tests have been performed: a walking load and a vandal bouncing excitation exerted at the midspan of the footbridge. In both cases, the experimental results show that the new procedure outperforms the classical velocity feedback approach thanks to the enhanced force tracking, leading to a remarkable reduction in the vibrations experimented by the structure under study.