Vibration suppression of a state-of-the-art wafer gripper

Abstract

Vibration suppression of flexible end-effectors has become one of the great challenges within the semiconductor industry to achieve the precision required to produce chips. These end-effectors tend to be prone to vibrations due to their lightweight design and low thickness, whilst they still should have high accuracy and precision. This motivates the search for damping methods that can be implemented in industry, where the emphasis is set at the upcoming trend in the use of smart materials and structures. In this thesis, the application of piezoelectric transducers to a wafer gripper with a high stiffness is investigated. The main aim is to show a 'proof-of-concept'. This to show the feasibility of piezoelectric transducers that are used to effectively dampen modes of thin and stiff end-effectors. The dynamics of the gripper have been analyzed to determine to optimal placement of the piezoelectric transducers using the coupling relation between the gripper and the transducers. This relation has been studied to be used as a guideline for the design process. After the placement of the piezo electrics, an experimental setup has been built to perform active vibration control. 3.3% damping was achieved with a simple PPF controller with a limited gain for which the piezoelectric transducers where placed according to a simplified line optimization. This shows that the concept of dampening very stiff and thin end-effectors, such as the wafer gripper, is feasible.