I-Corps: Elastomeric Passive Transmission for Dynamic Adjustment of Mechanical Advantage

Cornell University, Ithaca NY

Investigators

Abstract

The broader impact/commercial potential of this I-Corps project is based on a device which passively adjusts the mechanical advantage of a motor-driven actuator. This device, known as the Elastomeric Passive Transmission (EPT), improves the force and speed of tendon-driven actuation systems with minimal impact to their size, weight, and cost. Approximately 40,000 people per year suffer from major upper limb loss in the United States. The grip strength, grasping speed, and active degrees-of-freedom of even the most advanced prosthetic hands used by these patients pale in comparison to those of a human hand. User studies have shown that 90% of patients with myoelectric prostheses consider their prosthetic hand to be too slow and 79% consider it to be too heavy. By incorporating the EPT into their designs, prosthetic limb manufacturers can increase the force and speed of their devices with reduced cost and weight. In addition to improving the performance of prosthetics, the EPT has the potential to bring performance benefits to grippers and manipulators in the field of robotic automation. This I-Corps project is leverages advances in additive manufacturing to produce simple, low-cost components to improve the performance of electromechanical systems. Each EPT is a composite consisting of both hard and soft polyurethane sections. The hard polyurethane serves as the core of the EPT ensuring that it does not slip on the motor shaft. This core is surrounded by a ring of soft, stretchable struts which give the system its dynamic spooling radius. The EPTs are 3D-printed in two parts and bonded together during the final curing stage. This leads to a single component transmission system which can passively sense the environment and adjust the output of a motor to improve performance and control. The benefits of EPTs have been demonstrated through integration into a 3D-printed prosthetic hand which demonstrates high speed and high force in an inexpensive and lightweight package. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.