טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShaham Ran
SubjectAcoustic Levitation - Design Implementation and Control
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Izhak Bucher
Full Thesis textFull thesis text - English Version


Abstract

Acoustic levitation occurs when compressed air is trapped within a thin layer between two surfaces that are in close proximity. This layer, often called thin-film or squeeze-film, acts as a spring-damper between the two bodies. The layer also applies a force to the entrapping surfaces due to the increase in the average pressure. If one of the surfaces is fixed and the other is free, this free body is said to be acoustically levitated. In many industries there is a need for nano-precision manipulation of highly sensitive and or fragile objects. A main obstacle for achieving this is contact. Contact between the manipulator and the object causes friction, and may also damage the manipulated object. By using the acoustic levitation phenomena, one can create a non-contact bearing. In this work some of the basic steps for generating such a bearing are presented. By using digital control and electro-mechanical actuators, one such bearing is realized. Propulsion is created by means of directional travelling waves whose magnitude and direction alter the acting forces. This type of actuator is capable of controlling the levitation height as well as rotation by applying torque to the levitated body, in addition to applying levitation force. Using several of these acoustic actuators, a contactless planar manipulation device is designed and analyzed. A proof of concept control scheme, using H-infinity loop shaping, was implemented and demonstrated. Another method for manipulating the levitated body is explored analytically. In this method the planar forces are applied by modulating the amplitudes of two acoustic bearings that levitated one object. This method is briefly explored, as it is a simpler task to modulate amplitudes than it is generating and controlling travelling waves.