Over-Actuation and Over-Sensing for Active Damping of Higher-Order Modes in a Flexure-Based Motion Stage
K. Khalili (TU Delft - Mechanical Engineering)
S.H. Hossein Nia Kani – Mentor (TU Delft - Mechanical Engineering)
Aditya Natu – Mentor (TU Delft - Mechanical Engineering)
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Abstract
High-precision motion systems are often limited by lightly damped flexible modes. These modes can increase tracking error, residual vibrations, and settling time, especially when higher motion speed and bandwidth are required.
This thesis examines if the vibrations of a flexure-based motion stage may be enhanced through the use of over-actuation and over-sensing. In essence, additional channels of actuation and sensing will allow flexible modes to be selectively observed and damped.
First, the mechanism is designed and optimized with the later vibration-control problem in mind. After this, actuator and sensor placement are investigated. Since single-point sensing and actuation are not sufficient for all modes, modal filtering is used to combine multiple sensor signals into mode-dominant virtual outputs. These virtual channels are then controlled using Positive Position Feedback and band-pass PPF controllers.
The proposed approach is then evaluated in the frequency domain and in the time domain. The results show how much vibration reduction can be obtained, while also showing the practical limitations caused by mode isolation quality and sensor noise.