University of Twente Student Theses
Non-Smooth Controller Optimization for Active Vibration Isolation Suspension of an Einstein Telescope Mirror
Sijtsma, S.K. (2024) Non-Smooth Controller Optimization for Active Vibration Isolation Suspension of an Einstein Telescope Mirror.
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| Abstract: | Gravitational waves are ripples in space-time that carry valuable information about interactions between large interstellar objects, such as neutron stars, black holes or supernovae. The information that gravitational waves carry can reveal new insights about physics and our understanding of the universe. These signals are measured by gravitational wave observatories. These observatories employ laser interferometry to detect gravitational waves, which relies on measuring a phase difference between two perpendicularly reflected laser beams that originate from a single laser source. This phase difference is induced by a disruption of space-time between the lasers, that can be the cause of a gravitational wave passing through the earth. These observatories are extremely sensitive to seismic activities from the earth’s surface. Therefore, an elaborate vibration isolation suspension guards the mirrors, that alter the path of the lasers, from the seismic noise. Without these suspensions, a gravitational wave measurement would vanish in noise. Usually, the control systems for gravitational wave applications are designed via classical frequency domain design methods, such as loop-shaping. This design approach can be time consuming, labour intensive and often requires much expertise and knowledge about the suspension design in order to successfully design suitable controllers. A more modern approach for the design of controllers is via optimal controller synthesis methods. The great benefit of these optimal controller design techniques is that they largely automate the controller design. This allows to quickly evaluate the achievable performance for many suspension configurations within the available design space. This makes optimal controller synthesis especially usefull for future gravitational wave observatories that are still in the design phase. This research investigates the usefulness of a non-smooth optimal controller design strategy, specifically for the controller design for the mirror suspensions that are present in gravitational wave observatories. Additionally, optimization of the actuation distribution and suspension mechanics is integrated with the controller design for a more holistic design approach. Moreover, the suitability of the optimal controller design method is investigated in terms of its ability to encapsulate typical requirements that are found for gravitational wave applications into a suitable optimization problem. Part of the research is therefore dedicated to shaping the requirements into a relevant optimization problem. Besides the optimization of the controller and actuation distribution, some relevant extensions are investigated to showcase the versatility and flexibility of the non-smooth optimization algorithm. These extensions involve simultaneous optimization of both the controller and the dynamics of the plant. The results show how the proposed methodology is able to successfully shape controllers and the distribution of the actuation over the stages of the suspension according to requirements. The controllers generally achieve good suppression of seismic disturbances, while conforming to frequency dependent bounds and stability margins. |
| Item Type: | Essay (Master) |
| Clients: | Nikhef/VU, Amsterdam, Netherlands |
| Faculty: | ET: Engineering Technology |
| Subject: | 52 mechanical engineering |
| Programme: | Mechanical Engineering MSc (60439) |
| Link to this item: | https://purl.utwente.nl/essays/104100 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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