Design of a 4-DoF hydraulic prosthetic arm for people with a shoulder amputation

Design of a 4-DoF hydraulic prosthetic arm for people with a shoulder amputation

Verhaegen, Tim (TU Delft Mechanical, Maritime and Materials Engineering)

Smit, G. (mentor)

Delft University of Technology

Mechanical Engineering | BioMechanical Design

2019-09-18

People with a shoulder amputation are very much dependent on active total arm prostheses to provide in their self-care and to perform basic daily activities. Research on the development of active upper limb prosthetics has been growing over the past couple of years. The state-of-the-art total prosthetic arms that have been developed are very advanced and have human-like strength and dexterity but at the same time are relatively heavy. Other prosthetic arms that have been developed are limited in their functionality and in the activities that can be performed, since they can only address a few DoF, have a limited RoM and can only carry a small payload. This lack of functionality and excessive weight are both factors for amputee patients to reject their prosthetic device. Rejection is clearly unwanted and therefore an alternative prosthetic arm design is desired. From the three conventional actuator technologies: electric motors, pneumatic drives and hydraulic actuators, the latter has the highest force/torque density and therefore it is expected that for the same force/torque output a more lightweight hydraulic actuator can be used. Since actuators determine the mass of the prosthetic arm to a great extent, it is expected that the choice for a hydraulic actuator will result in the design of a lightweight prosthetic arm. The goal of this thesis is to design a hydraulically actuated 4-DoF conceptual prosthetic arm, which includes the degrees of freedom of the shoulder and elbow joint and to validate the performance of the shoulder and elbow flexion mechanisms with a 2-DoF working prototype. The conceptual prosthetic arm is to be as light as a human arm and have the same functional use: a similar degree of freedom, range of motion and the ability to deliver comparable strength. Design requirements and a kinematic analysis of the prosthetic arm form the basis and boundaries for the design process. Several actuation mechanisms have been developed for each degree of freedom and the most suitable mechanisms have been combined into the design of the 4-DoF Hydraulic Prosthetic Arm. The Hydraulic Prosthetic Arm has a total weight of 2.75-2.9 kg including battery and is thereby lighter than a human arm (excluding hand), which weighs 3.1 kg on average. Tests with the 2-DoF working prototype have validated the shoulder and elbow flexion mechanisms and have shown their performance in terms of load lifting capability and rotational speed. The upper arm and forearm were able to lift a 500 gram and 2,500 gram load respectively at 15 bar pressure, which was the limit within the hydraulic circuit. The rotational speed of the upper arm and forearm was 11 and 9 degrees per second respectively. The Hydraulic Prosthetic Arm outperforms the existing lightweight prosthetic arms, but is inferior to the most advanced and state-of-the-art LUKE arm and Modular Prosthetic Limb in terms of shoulder joint RoM, joint speed and strength. However the Hydraulic Prosthetic Arm weighs 500 gram less than both these arms and therefore is expected to have a solid competitive advantage.

Upper limb prosthetics
Hydraulic Actuation
Design study

http://resolver.tudelft.nl/uuid:06359860-5482-4099-ad7c-0e82514b2fee

2021-09-18

Student theses

master thesis

© 2019 Tim Verhaegen