Design and Assessment of an Upper Extremity Prosthetic System
Bennett, Daniel Alvin
This dissertation presents the design, development, characterization, and assessment of a transhumeral prosthesis which includes a 9 degree of freedom (DOF) multigrasp hand, a single DOF wrist rotator, and a single DOF elbow joint. Through characterization of the achievable joint torques and speeds, the prosthesis was proven capable of performing the majority of activities of daily living (ADLs) that a typical amputee would find necessary. The purpose of the prosthesis was to serve as a testbed for novel control methodologies, and so for the practical assessments and simulated ADLs it was used to test several different controllers. The controllers implemented on the prosthesis were the Multigrasp Myoelectric Controller (MMC) for the control of the multigrasp hand, and an inertial measurement unit (IMU) based coordinated controller for the control of a wrist. The MMC was developed prior to the work presented in this dissertation, and allowed full access to multigrasp hand functionality with a standard 2-site myoelectric interface. The development of the IMU based coordinated controller was a major piece of this dissertation, and used an IMU to take advantage of motion synergies between wrist pronation/supination and shoulder abduction. In this controller, shoulder abduction directly controlled the rotational velocity of the wrist, which can be coupled with a myoelectric hand control interface to enable simultaneous control and coordination of multiple sound and prosthetic joints. In a study where 5 able-bodied subjects using the hand and wrist prostheses with an adapter to perform simulated ADLs, the coordinated controller was shown to complete the tasks approximately 35% faster without any significant increase in compensatory motion when compared with a traditional sequential myoelectric controller.