Spring 2000

ME/IE 8773-8774

 

DESIGN AND CONTROL OF A NEW ROTARY FAST TOOL SERVO FOR DIAMOND TURNING OF ASYMMETRIC OPTICS

by

David L. Trumper, Ph.D.
Associate Professor of Mechanical Engineering
Massachusetts Institute of Technology
Cambridge, MA 02139

Wednesday, March 1, 2000
3:35 - 4:25 p.m.
Room 108 ME
Broadcast on UNITE Channel A
Coffee will be available in 152 ME following the seminar

My research group at MIT has developed a new type of fast tool servo for cutting asymmetric optics, with an emphasis on plastic eyeglass lenses. Eyeglass lenses with astigmatic correction require a toric surface to be cut on the back side of the lens. In extreme cases, this toric surface has amplitude variations of up to 20 mm peak-to-peak at the periphery of a 100 mm diameter lens blank. To address this manufacturing problem, our fast tool servo mounts the diamond tool at the end of an 80 mm arm which is rotated to move the tool into and out of the part. This novel design allows us to move the tool with accelerations of 500 m/sec^2 (50 g's) over a travel of 40 mm, and with micrometer-level accuracy. To achieve this accuracy at spindle speeds in excess of 1000 rpm requires the use of adaptive feedforward control laws which we have developed. The presentation will describe the mechanical details of our machine, explain the key dynamics and controls issues, and show experimental results.

David L. Trumper joined the MIT Department of Mechanical Engineering in August 1993, and currently is an Associate Professor. He received the B.S., M.S., and Ph.D. degrees from MIT in Electrical Engineering and Computer Science, in 1980, 1984, and 1990, respectively. Following the Bachelor's degree, Professor Trumper worked two years for the Hewlett-Packard Co. After finishing the Master's degree, he worked for two years for the Waters Chromatography Division of Millipore. Upon completing the Ph.D. degree, for three years he was an Assistant Professor in the Electrical Engineering Department at the University of North Carolina at Charlotte, working within the precision engineering group. Professor Trumper's research interests are in the area of the control of electromechanical systems with a specialization in, precision motion control, high-performance manufacturing equipment, and magnetic suspensions and bearings. He is a member of the IEEE, ASME, SME, ASPE, and JSPE, is an Associate Editor of Precision Engineering and is a corresponding member of CIRP

Faculty Hosts: Profs. William K. Durfee, Perry Li, and Kim A. Stelson