Identification and control of overactuated mechatronic systems
Paul Tacx defended his PhD thesis at the Department of Mechanical Engineering on September 18th.
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Technological advancements in scientific instruments and manufacturing equipment have revolutionized the modern society. These developments enabled a major increase in welfare, economic growth, and scientific breakthroughs. Examples include smartphones and the exploration of the universe through large telescopes which were unimaginable only several decades ago. The latter require advanced mechatronic system design. For his PhD thesis, Paul Tacx explored the control of overactuated mechatronic systems.
The quality, productivity, and performance of advanced instruments, machines, and products are largely determined by advanced mechatronic system design.
One example is that of wafer scanners where the productivity and product quality are dependent on the positioning performance of mechatronic systems, which are required to operate at extreme speeds while maintaining sub-nanometer precision.
Another is the case of ground-based telescopes where adaptive secondary mirrors correct for turbulence-induced wavefront aberrations through a deformable mirror with many actuators. Next-generation mechatronic systems are subject to increasingly stringent requirements regarding performance and throughput.
A shift is needed
Therefore, a shift in the design and control of mechatronic systems is needed.
Traditional mechatronic system design addresses the structural and thermal dynamics based on passive design optimization. Next-generation mechatronic systems are envisioned to adopt an active control approach to deal with structural and thermal dynamics, as an integral part of the control approach.
By employing active control solutions, passive design requirements can be relieved, enabling, for example, higher throughput in wafer scanners through lightweight wafer stage design and enhanced image quality in astronomy by increasing the dimensions of adaptive secondary mirrors.
Advanced control methods
Advanced control methodologies for next-generation mechatronic systems need to deal with several key challenges. First, next-generation mechatronic systems incorporate many actuators and sensors (overactuation and oversensing) to actively control the structural dynamics.
Second, structural dynamics lead to interactions between different parts of the system.
Finally, structural dynamics lead to inherently spatio-temporal system behavior, hence, extrapolating the dynamics measured at the sensor locations to the critical performance locations is no longer trivial. To achieve high-performance operation, active control relies on advanced modeling and control strategies. However, the necessary control and modeling algorithms are not yet available.
This research
The modeling and control methods that are developed in the PhD research of facilitate the envisioned shift from passive solutions to active control in next-generation overactuated mechatronic systems.
In the first part of his thesis, two contributions are outlined which focus on improving the system identification step and uncertainty modeling step for robust control.
The second part of his thesis presents three contributions that improve several applied and experimental aspects within the process from data to control through the development of methodologies for, experimental design validation, spatio-temporal modeling for control, and centralized robust control.
The methods developed in Tacx鈥檚 research have been successfully demonstrated in various applications, including astronomy and semiconductor manufacturing, through experiments involving an experimental deformable mirror and an overactuated reticle stage.
These results confirm the applicability and performance potential of the developed methods for overactuated mechatronic systems.
Title of PhD thesis: . Supervisors: Tom Oomen, Marcel Heertjes, and Gert Witvoet.