SUBJECT: M.S. Thesis Presentation
BY: Timothy McPherson
TIME: Friday, June 22, 2012, 1:00 p.m.
PLACE: Love Building, 109
TITLE: A Force and Displacement Self-Sensing Method for a MRI Compatible Tweezer End Effector
COMMITTEE: Dr. Jun Ueda, Chair (ME)
Dr. Aldo Ferri (ME)
Dr. Alper Erturk (ME)


This work describes a self-sensing technique for a piezoelectrically driven MRI-compatible tweezer style end effector, suitable for robot assisted, MRI guided surgery. Nested strain amplification mechanisms are used to amplify the displacement of the piezo actuators to practical levels for robotics. By using a hysteretic piezoelectric model and a two port network model for the compliant nested strain amplifiers, it is shown that force and displacement at the tweezer tip can be estimated if the input voltage and charge are measured. One piezo unit is used simultaneously as a sensor and an actuator, preserving the full actuation capability of the device. Experimental validation shows an average of 12\% error between the self-sensed and true values.