Date of Award

Summer 8-16-2024

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Babak Hejrati

Second Committee Member

Andrew Goupee

Third Committee Member

Vincent Caccese

Abstract

Difficulties walking can originate from a wide variety of conditions, from neurological or musculoskeletal disorders to the effects of increasing age. In most cases, physical therapy in the form of gait rehabilitation plays a critical role in effective patient recovery. Because of the repetitive nature of physical therapy and significant time commitment for both the patient and a physical therapist, the incorporation of technology (such as robot assistance, exoskeletons, and feedback devices) into the rehabilitation process has been investigate to both improve the effectiveness of therapy, as well as allow for self-training between sessions. Although lower limb exoskeletons dominate this area of research, upper limb solutions show some promise as incorporation of arm swing into gait training has been shown to have a positive effect on gait. Most exoskeletons designed for the arm are intended for arm movement therapy, for providing the user assistance while lifting, or as load assistance/support in industrial applications. Minimal research has been done into the use of arm exoskeletons for the purpose of gait rehabilitation. Gait rehabilitation devices generally employ one of three basic methods for interacting with the wearer: assistive force feedback, kinesthetic feedback, or tactile feedback. Although some research has been done into the use of both assistive force feedback and tactile feedback in gait training, very little has been conducted on the use of kinesthetic feedback for this purpose. This thesis discusses the construction of a prototype upper arm exoskeleton, called the Kinesthetic Testing Exoskeleton - 12 (KTE-12), built for the purpose of evaluating a human subject’s response to kinesthetic feedback during gait training. This thesis covers the construction of the KTE-12, and evaluates its workspace, static loading performance, and dynamic loading performance. The KTE-12 was designed to limit restriction to the natural movement of the wearer, specifically around the shoulder joint. To accomplish this, a double parallelogram linkage (DPL) was utilized. Workspace evaluation consisted of a simulation of the workspace, measurement of a subject’s movements while wearing the KTE-12, and tasking multiple subjects to attempt several positions while wearing the KTE-12. The results of the workspace analysis revealed a generally large workspace and showed that a high degree of shoulder flexion/extension and abduction/adduction were possible while wearing the KTE-12. Limited internal/external rotation of the shoulder were noted during experimentation, but the range of motion was thought to be adequate for the intended kinesthetic testing. The powertrain of the KTE-12 was designed to provide adequate torque at the end effector for a wide variety of subjects and testing conditions. A simulation was conducted, and a target output torque of 12 N · m was selected. Static load testing results exceeded the target by producing an output torque of 15.09 N · m before system failure. Dynamic load testing was unable to reach the target, producing an output torque of only 10.74 N · m. This was, however, deemed an acceptable amount of torque, as the original target was set intentionally high. Amplitude and frequency were also investigated during dynamic load testing to determine if the KTE-12 could mimic walking maximums with an amplitude of 40◦ and frequency of at least 0.9 Hz. Due to deficiencies found in several components of the KTE-12, the system was not able to consistently reach the target amplitude, either never reaching or exceeding the value. The KTE-12 was able to reach frequencies above 0.9 Hz for all tested loads. With some improvements, the KTE-12 would be capable of performing the desired kinesthetic feedback testing.

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