Barmeshwar Vikramaditya

Micro and Nano Assembly Using Dielectrophoretic Forces (Keynote)

The contact phase of an assembly task involving micro and nano building blocks is complicated by the presence of surface and intermolecular forces such as electrostatic, surface-tension and Van der Waals forces. Assembly strategies must account for the presence of these forces in order to guarantee successful repeatable micro and nanoassemblies with high precision. A detailed model for this electrostatic interaction is developed and analyzed. Based on the results of this analysis, dielectrophoretic assembly principles of MEMS/NEMS devices are proposed and experimentally verified with microtweezers for micro Ni parts and with nanoelectrodes fabricated with electron-beam lithography for carbon nanotube assembly. The successful manipulation and assembly of single carbon nanotubes (CNTs) using dielectrophoretic forces produced by nanoelectrodes will lead to a higher integration of CNTs into both nanoelectronics and NEMS.Copyright

Servo control techniques for track following on hard disk drive spin stand testers

This paper developed a real-time servo control system for high precision track following (head position control) on hard disk drive spin stand testers. The proposed servo control system includes a feedback linearization, a high-bandwidth feedback controller, an adaptive feedforward controller, and the Zero acceleration path technique. Experiments with a Seagate disk with track width of 77 nm showed that the servo control system could reduce the three-sigma (standard deviation) of the repeatable head position error to ~2.7 nm and the three-sigma of the non-repeatable error to ~2.2 nm. At the end it is demonstrated that with the track following ability, the head can coherently write and read data to and from the disk even with the presence of internal and external disturbances to the head.

A comparison of loop-shaping based robust control synthesis techniques for hard disk drive track-following

This paper compares multiple loop-shaping combined robust control methodologies including Glover-McFarlane method, H ∞ and H2 in the controller synthesis of track-following application for hard disk drive (HDD). According to the specified loop-shaping goal, the synthesis routines are applied on the Spinstand micro-actuator in order to achieve robust performance in terms of system uncertainties accommodation, sufficiently high bandwidth and disturbance rejection. The performance of the synthesized controllers is compared by their capability handling multiple sampling rates on the Spinstand environment while driving an acceptable level of Non-repeatable Runout (NRRO).