School of Mechanical Engineering Ran Gabai
School of Mechanical Engineering Seminar
Monday, April 30, 2018 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
Non-contacting multi-degrees of freedom stage based on acoustic levitation- modeling, dynamics, and control
Dr. Ran Gabai
Dynamics and Mechatronics Laboratory
Faculty of Mechanical Engineering, Technion IIT , Haifa, Israel
A stage capable of positioning a planar object in the X-Y plane and performing rotation on a thin layer of air without contact is presented. This device is able to manipulate an object without contact, virtually eliminates all friction forces during the motion. Moreover, it eliminates any contaminations caused by particles transferred via mechanical contact.
To achieve accurate positioning without contact, several disciplines need to be combined: mechanical design, structural vibration, ultrasonic vibration amplification, signal processing and mechatronics. As part of the control design, model identification and real-time embedded programming are also required, as well as a novel representation of the wave kinematics attributed to structures with cyclic symmetry.
By creating ultrasonic vibrations in an annulus shaped structure, a thin air layer develops a dynamic acoustic pressure field able to levitate an object and to control its position. Motion is created by traveling pressure waves within the acoustic field, giving rise to directional forces acting on the levitated object. The novel configuration is based on three independent acoustic levitation motors. Each capable of levitating and apply forces to the levitated object simultaneously.
Closed loop control of the position is made possible by incorporating several sensors. The necessary forces for manipulating the acoustic vibrations, and therefore the pressure fields, are generated by an Hinf controller. The controller is robust enough to handle the strong internal coupling of the system and modeling uncertainties. A laboratory prototype in which the concept was developed is described and validated by a series of experiments. This work demonstrates the ability of acoustic levitation systems to manipulate objects without contact.