M.B. Kaczmarek
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3 records found
1
Ultra Hard Mount Active Vibration Control
Improving the performance of ultra hard mount systems using vibration control strategies
High-precision mechatronic equipment often benefits from or even needs vibration isolation to function within specification. Examples of such equipment include metrology devices, space instrumentation and lithography assemblies. Vibration isolation is often the function of the mounting between the equipment and the floor or rest of the machine. An important factor for vibration isolation is the stiffness of this mount. High stiffness mounts result in high force disturbance rejection, at the cost of sensitivity to indirect disturbances. So-called ultra hard mount systems take advantage of ultra high stiffness to offer superior position stability in the presence of force disturbances. However, this also leads to an emphasized sensitivity to indirect disturbances. Active vibration control can be used to overcome this. Feedback is used to dampen the resonance mode of the mounting system. Feedforward is used to lower the transmissibility, resulting in reduced sensitivity to indirect disturbances. This has been successfully implemented on less stiff hard mount systems in the past, but the techniques remained unexplored on ultra hard mount systems. This research focusses on the experimental implementation of existing active vibration control techniques on an ultra hard mount system. It was found that the closed loop behaviour of piezo-based ultra hard mount systems are well predictable. Furthermore, it was found that good damping performance can be achieved by various methods, reducing the output vibrations up to 60%. Using straightforward stiffness compensation feedforward, the influence of indirect disturbances was shown to be reduced significantly. A reduction of 94% in the effect of indirect disturbances was realized using disturbance feedforward when compared to the uncontrolled case. This work shows that ultra hard mounts can be used in applications where strong direct disturbance rejection is required, even in the presence of indirect disturbances using a combined feedback and feedforward approach.
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High-precision mechatronic equipment often benefits from or even needs vibration isolation to function within specification. Examples of such equipment include metrology devices, space instrumentation and lithography assemblies. Vibration isolation is often the function of the mounting between the equipment and the floor or rest of the machine. An important factor for vibration isolation is the stiffness of this mount. High stiffness mounts result in high force disturbance rejection, at the cost of sensitivity to indirect disturbances. So-called ultra hard mount systems take advantage of ultra high stiffness to offer superior position stability in the presence of force disturbances. However, this also leads to an emphasized sensitivity to indirect disturbances. Active vibration control can be used to overcome this. Feedback is used to dampen the resonance mode of the mounting system. Feedforward is used to lower the transmissibility, resulting in reduced sensitivity to indirect disturbances. This has been successfully implemented on less stiff hard mount systems in the past, but the techniques remained unexplored on ultra hard mount systems. This research focusses on the experimental implementation of existing active vibration control techniques on an ultra hard mount system. It was found that the closed loop behaviour of piezo-based ultra hard mount systems are well predictable. Furthermore, it was found that good damping performance can be achieved by various methods, reducing the output vibrations up to 60%. Using straightforward stiffness compensation feedforward, the influence of indirect disturbances was shown to be reduced significantly. A reduction of 94% in the effect of indirect disturbances was realized using disturbance feedforward when compared to the uncontrolled case. This work shows that ultra hard mounts can be used in applications where strong direct disturbance rejection is required, even in the presence of indirect disturbances using a combined feedback and feedforward approach.
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.
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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.
A novel nonlinear stiffness unit cell aided magnetic gravity compensator is proposed for the purpose of isolating low-frequency vibrations. A negative stiffness magnet setup is combined with a compliant unit cell with tailored nonlinear force-displacement characteristics. This combination offers a large range of motion featuring low stiffness, a high force density, and passive stability, creating a large vertical displacement passive magnetic gravity compensator (LVDPMGC). The passive stability of the system eliminates the need for active stabilization, reducing costs and complexity. An adjustable load-bearing capacity can be obtained by changing the number of unit cells, increasing scalability compared to conventional magnetic gravity compensators (MGC's) which have a fixed load-bearing capacity. The stiffness characteristics of the unit cell and magnet setup are analysed with FEM, showing which parameters influence system performance. Parameters are iteratively adjusted after which a prototype is manufactured and tested. The experimental results show that the unit cell can effectively stabilize the magnet setup while increasing the low stiffness range of motion, force density, and scalability compared to conventional MGC's.
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A novel nonlinear stiffness unit cell aided magnetic gravity compensator is proposed for the purpose of isolating low-frequency vibrations. A negative stiffness magnet setup is combined with a compliant unit cell with tailored nonlinear force-displacement characteristics. This combination offers a large range of motion featuring low stiffness, a high force density, and passive stability, creating a large vertical displacement passive magnetic gravity compensator (LVDPMGC). The passive stability of the system eliminates the need for active stabilization, reducing costs and complexity. An adjustable load-bearing capacity can be obtained by changing the number of unit cells, increasing scalability compared to conventional magnetic gravity compensators (MGC's) which have a fixed load-bearing capacity. The stiffness characteristics of the unit cell and magnet setup are analysed with FEM, showing which parameters influence system performance. Parameters are iteratively adjusted after which a prototype is manufactured and tested. The experimental results show that the unit cell can effectively stabilize the magnet setup while increasing the low stiffness range of motion, force density, and scalability compared to conventional MGC's.