University of Twente Student Theses


Active Vibration Isolation with an Active Stage

Kelder, R. (2021) Active Vibration Isolation with an Active Stage.

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Embargo date:11 June 2023
Abstract:Vibrations in high-precision machines can cause a loss of accuracy in moving part(s) and sensitive equipment. One of the limiting factors is the internal deformation between the moving part(s) and sensitive equipment. This deformation is caused by indirect and direct disturbances, where indirect disturbances act on the base of the machine, and direct disturbances directly on the sensitive payload. Especially indirect disturbances due to seismic activity and direct disturbances generated by the moving part(s) induce a major part of vibrations. Active vibration isolation systems can be used to attenuate the effect of these disturbances by using controllers which utilize measurements of the isolated base with the interconnected sensitive payload and the source of the disturbances as control inputs. The first tries to dampen the suspension modes of the vibration isolation system and attenuate vibrations with feedback control. With the use of absolute sensors in combination with the controller so-called virtual mass, skyhook stiffness, and skyhook damping can be added. This would ideally create an artificial suspension with respect to an imaginary hook in the sky, unaffected by indirect disturbances and less susceptible to direct disturbances. The second tries to generate forces with feedforward control which cancels the forces induced by the sum of all disturbances on the isolated base. In the case of only a vibration isolation system it is common to quantify the performance with the transmissibility of indirect disturbances and compliance for the direct disturbances. However, with an active stage with moving part(s) and sensitive equipment, the performance also depends on the tracking characteristics of the moving part(s) and the amount of internal deformation. So far, none considers an active stage in combination with a vibration isolation system. Therefore, in this research, a multi-objective control strategy is proposed for an active stage with a vibration isolation system wherein the goal is to have accurate tracking properties and minimal internal deformation. To achieve this, a theoretical framework is set up in which all important characteristics for are incorporated. According to this framework, all performance objectives are easily linked to the control strategies.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:50 technical science in general, 52 mechanical engineering, 54 computer science
Programme:Mechanical Engineering MSc (60439)
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