October 8, 2018
Oscillator Amplitude Control: Fast Tool Servos, Atomic Force Microscopy, Reticle Pushers, and More
This presentation describes the modeling and control of oscillation amplitude in the contexts of electrical oscillators, fast tool servos for diamond turning of precision surfaces, atomic force microscopes, and a reticle pusher for offloading acceleration forces in semiconductor lithography. A unifying viewpoint for amplitude control of such oscillators is given, along with design details in each system, including:
Atomic force microscopes can create surface images of nanometer-scale features. A common approach is to oscillate a microcantilever beam with a sharp tip, and use changes in the oscillation to detect tip contact with a surface. We have used this approach to create a high-accuracy atomic force microscope for very precise dimensional measurements. We have also used similar principles to create a macro-scale atomic force microscope for teaching mechatronics. The designs and operation of these AFMs will be presented.
Another area in which oscillation amplitude control is important is fast tool servos for diamond turning machines. Diamond turning machines are very precise machine tools which use a single-crystal diamond tool to cut materials with accuracy on the order of 10s of nanometers. A fast tool servo oscillates the diamond tool rapidly to cut parts with nonrotationally-symmetric surfaces. We have designed and tested a number of such fast tool servos for making parts such as eyeglass lenses, optical molds, and inertial fusion targets.
We have also used these perspectives to design a new type of reticle pusher device to intermittently engage with the edge of the quartz reticle during acceleration events. This reticle pusher uses self-resonance of a piezoelectric actuator to detect contact and control force so as to support the intermittent acceleration forces on the reticle in scanning semiconductor lithography.
David L. Trumper joined the MIT Department of Mechanical Engineering in August 1993, and holds the rank of 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 HewlettPackard 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 centers on the design of precision mechatronic systems, with a focus on the design of novel mechanisms, actuators, sensors, and control systems. He has conducted research in topics including precision motion control, high-performance manufacturing equipment, novel measurement instruments, biomedical and bioinstrumentation devices, and high-precision magnetic suspensions and bearings. He is a member of the IEEE, ASME, and ASPE (past-President).