M.S. Thesis Presentation by Debao Zhou
Wednesday, March 17, 2003

(Dr. Kok-Meng Lee, advisor)


The need for simultaneous measurement of more-than-one degrees-of-freedom (DOF) motions of an object can be found in numerous applications such as robotic assembly, precision machining, optical tracking, wrist actuators, and active joysticks. Conventional encoders, though capable of providing high-resolution linear or angular measurements, are limited to single-DOF sensing in motion control. The use of these single-DOF encoders for measuring 3-DOF orientations in real time requires additional mechanical linkages that often introduce frictions, backlashes, and singularities. This thesis has focused on the use of microscopic surface features as natural patterns to derive incremental motion of the 3-DOF orientation. To achieve this objective, this thesis begins with modeling a sensor system that generates appropriate signals needed to characterize the 3-DOF orientation based on the detection of microscopic changes on a moving surface. The model has provided a rational basis for the development of an optical sensor for computing the three-DOF orientation of a spherical motor, as well as for an in-depth analysis for identifying key operational parameters that could significantly influence the sensor performance. A prototype optical sensor has been developed and experimentally tested. It is expected that this research will extend the use of optical-based measurement systems to real-time control applications that require simultaneous multiple degree-of –freedom measurement.