This setup was used for experiments with vibration reduction by absorption in multiple dimensions. An experimental setup containing an absorber demonstrator with three degrees of freedom was assembled, and the primary mass was represented by a base suspended on 4 elastic rods.
The goal was to prepare an experimental planar absorber demonstrator that was dynamically isotropic with one common triple natural frequency.
The proposed and assembled experimental setup consists of an absorber demonstrator with three degrees of freedom attached to the primary mass structure. The novel active vibration absorber is composed of a semicircular mass-plate being actively actuated by three linear voicecoil motors nested in the connecting links with linear bearings and springs. A Delayed position feedback is used at each of the voicecoils with the aim to turn the physical absorber to an ideal resonator at the excitation frequency. The primary structure is constructed of aluminum profiles and is flexibly suspended to the aluminum profile frame. The vibrations at the primary are generated by a rotational excentre. The whole setup is controlled by a dSpace.
The excentre starts rotating at time t=4s. Around t=10s, the whole platform uniformly vibrates in the planar coordinates, being only partially damped by the so far passive absorber. At t=21s a nonlinear control feedback compensating friction forces is turned on, which is followed by turning on the delayed control feedback at t=35s. As can be seen, in the effect of the active resonator, the vibration of the primary structure is almost ideally suppressed – the platform does not move despite being excited by the excentre all the time. The excitation forces are fully absorbed by the 2D resonator, exerting a periodic planar motion.
The more detailed description of the set-up and whole 2D resonator design can be found in PhD thesis of Karel Kraus, supervised by prof. Zbyněk Šika, and successfully defended on February 14, 2025. Journal publication is in preparation jointly with prof. Wim Michiels, KU Leuven, who contributed to the structural optimization of the 2D resonator.
Related publications
Kraus, K., 2025. Active multidimensional vibration absorbers for complex mechanical structures. PhD Thesis, Defense date 2025-02-14, CTU in Prague, Faculty of Mechanical Engineering, Department of Mechanics, Biomechanics and Mechatronics. Supervised by Z. Šika. http://hdl.handle.net/10467/121344
