Design of a Variable Mechanical Advantage Mechanism for the Delft Cylinder Hand

Design of a Variable Mechanical Advantage Mechanism for the Delft Cylinder Hand

Schipperen, R.D.

Plettenburg, D.H. (mentor)

Mechanical, Maritime and Materials Engineering

Biomechanical Engineering

2015-08-27

The Delft Cylinder Hand and similar body powered hand prostheses require an input force that is too high for daily tasks. The force is perceived as uncomfortable and leads to a high rate of users abandoning their prosthesis. Reducing the input force by increasing the mechanical advantage of the system is not feasible, as this would unfavourably increase the required input displacement to close the prosthetic hand. The goal of the research is to significantly reduce the input force, without exceeding the input displacement limit by designing a variable mechanical advantage (VMA). The VMA is specifically designed for the Delft Cylinder Hand. The input force, when applying a 30 N pinch force, should always be lower than 50±4 N, without compromising the 53 mm maximum input displacement. Two load cases are used to determine the VMA properties, the worst-geometry load case and the realistic-pinch load case. Calculations show that a VMA design is feasible for the Delft Cylinder Hand. In the case of the worst-geometry load case, a design is only feasible when friction losses are excluded, while for the realistic-pinch load case the friction losses can be included. Simulations confirm that the designed VMA mechanism is able to pinch an object with 30 N, with an input force lower than 50±4 N for the feasible loading conditions. Practical testing was too inconclusive to validate the simulation.

variable mechanical advantage
Delft Cylinder Hand
body-powered prosthesis
hydraulic

http://resolver.tudelft.nl/uuid:33108b7b-57f6-46f4-b96a-17f4bc3d2c3d

Student theses

master thesis

(c) 2015 Schipperen, R.D.