Abstract
This work studies the influence of a vibration isolator on the response of a flexible base structure. Two strategies are compared: passive and active vibration isolation (PVI, AVI). Although the multiple advantages of AVI over PVI techniques are well known, their effect in the base structure has not to date been compared. This interaction has an important role in the performance of the general control system, especially when the vibration isolation system is not the only system on the base structure or when there are multiple isolators working simultaneously on it. In addition, the structural serviceability of the base structure can also be affected. The analysis of the vibration isolation problem is made from a wide perspective, including the effect that isolator has on the base structure. Hence assuming the base structure is a non-rigid system. The effect of the isolation system on the base response is studied for an extensive range of base structures, thus showing different possible scenarios. The influence is quantified by comparing the peak magnitude response of the base when both passive and active vibration isolation techniques are used. The theoretical results have been corroborated by undertaking experimental tests on a full-scale laboratory structure.
Highlights
Base support vibrations can lead to dangerous relative displacements in structures, as occurs in buildings [5], or to misalignment and focusing problems in vibration sensitive devices, such as exist in research centres with scientific equipment, precision manufacturing industries or space applications, in which more than one device can be involved in the same task [6, 17, 19, 23]
To show the effect that passive vibration isolation (PVI) and active vibration isolation (AVI) have on the base response, three different cases of rm and rx are studied for damping values fp 1⁄4 f0:1; 0:5; 0:9g
3.3.1 Case rm 1⁄4 0:0889 and rx 1⁄4 0:8. This case shows an example for which the collocation of the isolator implies a reduction of the base response, but the use of AVI control in the isolator increases the response in the base structure compared with the passive mode
Summary
Base support vibrations can lead to dangerous relative displacements in structures, as occurs in buildings [5], or to misalignment and focusing problems in vibration sensitive devices, such as exist in research centres with scientific equipment, precision manufacturing industries or space applications, in which more than one device can be involved in the same task [6, 17, 19, 23]. In PVI systems, the control force is generated by the isolator as a reaction to the relative displacement between the platform and the support structure [26] due to platform inertia This technique presents some disadvantages, such as the fact that attenuation of platfoprmffiffi response occurs only for frequencies greater than 2 times the natural frequency of the isolator, the inability to achieve zero static deflection or the impossibility to adapt the control force to changes in the conditions of the vibration isolation task. The control force in AVI systems is generated as a reaction of the relative movement between base and platform but an actuator is located between them, allowing application of an additional control force by the use of feedback or feedforward control techniques.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call