Tufts Passive Gripper

One of the two manipulators developed for my dissertation project, the Tufts Passive Gripper (TPG) was inspired by the Fin Ray Effect, a geometry developed by Lief Kniese of Evologics and employed by Festo in their FinGripper, and the passive grip of the Manduca Sexta. The TPG combines an optimized version of the Fin Ray Effect with the principles of passive grip and was capable of holding up to 530 g (1.2 lbs).

Design

For my dissertation I have sought to build a soft robotic manipulator that is safe for human interaction as well as cheap and easy to fabricate. The overarching goal is for my robotic manipulator to be a viable solution for an in-home robotic assistant; however, it could also have applications in a factory setting, specifically for the handling of food and fragile objects.

Two separate grippers inspired by the Fin Ray Effect were developed. The first gripper, TAG, has two fingers with the crossbeams angled down towards the center of the base and is actuated by a DC motor pulling a tendon in the palm. The second gripper, TPG, additionally takes inspiration from the Manduca sexta’s passive grip. Its crossbeams are angled tendons attached to the fingers’ exterior sides.

Optimization

Concurrent with the design, iteration, and testing of the TAG and TPG was the optimization. Experimentation with paper models and early versions of TAG provided insight into how the angling of the crossbeams, addition of different geometries for support, and incorporation of different materials would affect the performance of the gripper. However, in terms of optimizing the grippers, performing FEAs on crossbeam angles was more cost effective in terms of times and material.

Results

With TPG designed and fabricated, its performance was then tested. First, the the load capacity of each gripper was tested. Next, the forces exerted on objects were determined. Finally, several grasping tests were performed, including picking up objects, navigating environments, and opening doors.