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dc.contributor.author
Maamari, Nadim
dc.contributor.supervisor
Wegener, Konrad
dc.contributor.supervisor
Dual, J.
dc.date.accessioned
2020-08-17T06:37:01Z
dc.date.available
2020-08-14T14:57:57Z
dc.date.available
2020-08-17T06:37:01Z
dc.date.issued
2019
dc.identifier.uri
http://hdl.handle.net/20.500.11850/431500
dc.identifier.doi
10.3929/ethz-b-000431500
dc.description.abstract
Bearings and guideways are critical components in precision positioning machines. Among diverse types of bearing technologies, passive aerostatic bearings offer excellent precision to cost ratio, yet have limited performance due to the inherent compromise between stiffness and damping, hindering the performance of the machine. Active bearing solutions based on either magnetic or aerostatic levitation rely heavily on the positioning feedback measurements needed for disturbance rejection, and are sensitive to electronic noises, which requires a compromise between system bandwidth and positioning stability. This thesis deals with the development of a disruptive technology involving a smart active aerostatic bearing. The concept is based on a centrally fed orifice compensation air bearing that features a compliance in the bearing back plate rendering it deformable to the air pressure distribution. The novel design based on integrated leaf springs ensures a linear gap deformation along the radial direction, represented by a conicity angle. The featured variation in the conicity angle is optimized to mechanically amplify the response of the pad to external loading, resulting in ultra-high passive stiffness. To ensure positioning capabilities, a Lorentz based actuator having the magnets mounted on the outer radius of the pad’s back plate and a coil attached to the center, induces a torque altering the conicity angle, resulting in servo actuation and positioning functionality. The linear gap deformation overcomes the dilemma’s between high passive stiffness and servo compliance. A novel nonlinear numerical model encapsulating the interaction between, the inlet orifice, the thin-film and the structural domains is used to illustrate the static performances of the proposed bearing. Based on the modeling method, the first generation of active bearing is realized using integrated leaf spring and a voice coil actuation. Finite element analysis validated the mechanical design, and experimental results showed a quasi-infinite passive static stiffness in open loop operation. In addition, the actuation ensured servo compliance of 3.4 μm/A. To investigate the dynamic performance namely stiffness, damping and actuation reactivity, this work presents a novel dynamic model encapsulating the fluid-structure interaction based on linear perturbation around a static operating point. A comprehensive sensitivity analysis illustrated the impact of the design variables on the dynamic response. Based on the numerical model and the requirement for proper actuation bandwidth, the 2nd generation pads are designed and tested. Experimental results validated the dynamic model, and the pad’s performance in terms of stiffness and damping. The active pads exhibit ultra-high stiffnesses, however, due to the compressibility of the air, negative damping is encountered. To overcome the negative damping leading to unstable system poles, a novel control architecture based on active inertial damping is illustrated using commercially available geophones. The compensation strategy is based on emulating a damper mounted in parallel to the air bearing. Mechatronic simulation encapsulating the aerostatic bearing, the controller, and the inertial mass, illustrated the capability of the compensation method to render the system poles stable and overdamped. To test and validate the control architecture, a system consisting of three 2nd generation pads suspending a 24 Kg payload having a triangular shape is designed and manufactured. The configuration allowed for positioning along three degrees of freedom. As predicted by simulation, the system in open loop had unstable poles due to the aerostatic bearing negative damping. In closed loop operation, using velocities measured by the geophones, the system attains stability and increasing the controller gain renders the system poles overdamped. Experimental results showed a system bandwidth of 250 Hz across the three degrees of freedom and positioning stability within 3 nm.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.rights.uri
http://rightsstatements.org/page/InC-NC/1.0/
dc.subject
Aerostatic bearing
en_US
dc.subject
precision mechatronics
en_US
dc.title
Smart Active Aerostatic Bearing
en_US
dc.type
Doctoral Thesis
dc.rights.license
In Copyright - Non-Commercial Use Permitted
dc.date.published
2020-08-17
ethz.size
179 p.
en_US
ethz.code.ddc
DDC - DDC::6 - Technology, medicine and applied sciences::620 - Engineering & allied operations
en_US
ethz.identifier.diss
26362
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02130 - Dep. Maschinenbau und Verfahrenstechnik / Dep. of Mechanical and Process Eng.::02623 - Inst. f. Werkzeugmaschinen und Fertigung / Inst. Machine Tools and Manufacturing::03641 - Wegener, Konrad / Wegener, Konrad
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02130 - Dep. Maschinenbau und Verfahrenstechnik / Dep. of Mechanical and Process Eng.::02623 - Inst. f. Werkzeugmaschinen und Fertigung / Inst. Machine Tools and Manufacturing::03641 - Wegener, Konrad / Wegener, Konrad
en_US
ethz.tag
system dynamic
en_US
ethz.date.deposited
2020-08-14T14:58:05Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2020-08-17T06:37:13Z
ethz.rosetta.lastUpdated
2021-02-15T16:10:58Z
ethz.rosetta.versionExported
true
ethz.COinS
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