SUBJECT: Ph.D. Dissertation Defense
BY: Mark Elton
TIME: Monday, October 29, 2012, 2:00 p.m.
PLACE: MARC Building, 114
COMMITTEE: Dr. Wayne Book, Chair (ME)
Dr. Jun Ueda (ME)
Dr. William Singhose (ME)
Dr. Ayanna Howard (ECE)
Dr. Frank Durso (PSY)


Various roles for operators in human-machine systems have been proposed. This thesis shows that all of these views have in common the fact that operators perform best when given feedback that matches their intent. Past studies have shown that position control is superior to rate control except when operating large-workspace and/or low-bandwidth manipulators and for tracking tasks. Operators of large-workspace and/or low-bandwidth manipulators do not receive immediate position feedback. To remedy this, a ghost arm overlay was displayed to operators of a dynamically slow manipulator, giving feedback that matches their intent. Operators performed several simple one- and two-dimensional tasks (point-to-point motion, tracking, path tracking) with the different controllers (position control with and without a ghost, rate control) to measure how task conditions influence operator intent. Giving the operator position feedback via the ghost significantly increased the performance with the position controller and brought it to the level of rate control. These results were further validated by testing coordinated position control with and without a ghost arm and coordinated rate control on an excavator simulator. The results show that position control is not superior to rate control, as previously thought. Unlike previous work, this research compared the fuel efficiencies of different HMIs, as well as time efficiencies. This work not only provides the design law of matching the feedback to the operator intent, but also gives a guideline for when to choose position or rate control based on the speed of the system.