Graduation Year

2022

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Mechanical Engineering

Major Professor

Kyle B. Reed, Ph.D.

Committee Member

Autar Kaw, Ph.D.

Committee Member

Seok Hun Kim, Ph.D.

Committee Member

William E. Lee, Ph.D.

Committee Member

Alfredo Weitzenfeld, Ph.D.

Committee Member

Tansel Yucelen, Ph.D.

Keywords

Human Robot Interaction, Sensorimotor Control, Dynamic Force Perception, Rehabilitation Engineering

Abstract

This dissertation furthers our understanding of how we (humans) sense and interact withforces, humans, and robots in three distinct cases, which affect robotics and rehabilitation. Chapter 2 examines physical therapists’ (PTs’) consistency when applying assistance forces during rehabilitation. Chapter 3 explores how control performance of an unstable system is affected by the system’s degrees of freedom (DoFs). Chapter 4 investigates the effects of the task speed and direction of perturbing forces on a dynamic task where position is controlled through self-generated forces.

Chapter 2 quantifies the consistency of forces that PTs apply during therapy by using a robotic device. The consistency within and between PTs is quantified across five levels of assistance (Contact Guard, Minimal, Moderate, Maximal, and Total assistance). As a corollary study, a survey was conducted to assess the first-hand perspective of PTs about their LOA consistency. In Chapter 3, a series of four cart inverted pendulums (CIPs) are used in a stabilizing task to ascertain their effects on stabilizing performance. Subjects perform a tracking task in Chapter 4 where a haptic robot provides perturbing forces and records their position. A tracked target dictates the required speed for a subject’s motion, and a force field is applied for an unmarked portion of the subject’s path. The results in this dissertation advance our understanding of how we sense and interact with forces on questions related to robotics and rehabilitation. Chapter 2 provides the first measurement of the force ranges PTs use for a reaching task in rehabilitation.

The results suggest that there is variation between therapists assistance and that PTs recognize this variance. The second study in this chapter assessed the perceptions of PTs about their LOA rating performance and found that the qualitative perceptions generally aligned with quantitative results. Chapter 3 contributes to the fundamentals of this field by studying three factors that affect control behavior while balancing an unstable system. The results challenge common assumptions in the literature and inform the design of future experiments in the field. The major findings of Chapter 4 show that force compensation accuracy depends on direction and that there is an inverse relationship with speed in a tracking task.

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