Active control of human-induced vibrations on lightweight structures via electrodynamic actuator dynamics inversion

Abstract

The active vibration absorber represents an effective means to mitigate excessive vibrations in low-damping structures. Nevertheless, the dynamics of the actuators employed in such systems may negatively affect their performance and stability restricting their operational frequency range. This article presents an application of dynamics inversion techniques to the force control of electrodynamic proof-mass actuators employed as active vibration absorbers in lightweight pedestrian structures. The dynamics inversion approach is applied to enhance the classical direct velocity feedback scheme. Additionally, a novel method relying on dynamics inversion is presented: the Broadband Force Cancellation Algorithm. This procedure consists in estimating, in real-time, the equivalent force acting on the system to later apply it back to the structure with the opposed sign. The effectiveness of the proposed methods is assessed via numerical simulations carried over a realistic model of an existing lightweight footbridge and an electrodynamic proof-mass actuator. Two load cases are analyzed: a fixed swept-sine force and a walking load. Both cases account for the actuator-structure interaction. The human-structure interaction is considered in the latter scenario due to its importance when dealing with lightweight pedestrian structures. Simulation results demonstrate that the dynamics inversion techniques effectively cancel out actuator dynamics leading to an excellent tracking of the reference force output by the suggested or other vibration control algorithm. The proposed schemes are proved promising since they substantially outperform the widespread direct velocity feedback approach. In particular, the Broadband Force Cancellation Algorithm minimizes the action of the external forces within their estimation frequency range, thus being especially suited to tackle broadband excitations, important in lively pedestrian structures, whereas the velocity feedback methodology performs best at the structural resonant frequencies.

Application of dynamics inversion techniques to the force control of electrodynamic actuators used for active vibration absorption

“…In order to calculate the voltage which achieves theoretical PMA dynamics cancellation (𝑢 𝑐,𝐷𝐼 in figure 3), a particularization of the Structure Algorithm to linear systems in which some of the system inputs are known, as described in [12] has been followed. The first step in this process is to work out a statespace representation of the PMA system.…”

“…The first step in this process is to work out a statespace representation of the PMA system. This model takes the following form [12]:…”

“…The PMA is driven by an APS 125 amplifier [15]. The values of the parameters of the state-space model represented by equations (1a) and (1b) have been estimated through an identification process in which the PMA was installed on a rigid floor [12] yielding the following values: 𝑚 ̂𝑎=30.52 kg, 𝑘 ̂𝑎=303.56 N/m, 𝑐 𝑎 = 150.44 Ns/m, 𝑅 ̂𝑐= 2.45 Ω, 𝐿 ̂𝑐= 17.34 mH, 𝐾 ̂𝑒= 19.11 Vs/m and 𝐾 ̂𝑎𝑣 = 18.00 V/V, where hats denote estimates.…”

“…In this paper, the utilization of dynamic inversion (DI) techniques to improve the force control of electrodynamic proof-mass actuators (PMAs) usually employed in AVAs, for structures subjected to human-induced vibrations, is presented. The main idea behind this approach is to find an approximate inverse model of the actuator dynamics which, upon implementation on the real-time controller, leads to an approximate cancellation of the actuator dynamics, making it behave closer to an ideal one [12]. The proposed way of proceeding also accounts for the actuator-structure interaction (ASI) phenomenon [5]; thus, making the behavior of the actuator independent from the flexibility of the structure onto which it is mounted.…”

Structural Optimization of Lightweight Composite Floors with Integrated Constrained Layer Damping for Vibration Control

“…Two main types of damping strategies may be used to solve floor vibration problems. First, the use of inertial dampers, in their passive versions (most known as Tuned Mass Dampers or TMDs) [13], semi-active [14] and active versions [15] that apply counteract forces in real time to reduce the structural motion. Second, the use of dissipative strategies that enable increasing the inherent damping of the floor by wisely including specific elements that dissipate additional energy, such as viscous or Viscoelastic (VE) dampers.…”