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Design of a Lightweight Soft Electrical Apple Harvesting Gripper

Christopher Ninatanta¹, Ryan Cole¹, Ian Wells¹, Jacob Benedict¹, Ryan Taylor¹, Ryan Dorosh¹, Manoj Karkee², Ming Luo¹

¹Department of Mechanical and Materials Engineering, ²BSysE Agricultural Automation Engineering, Washington State University

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Background

Washington State leads the nation in apple production.
To address the issues of increasing costs and labor shortages, we have been developing a soft growing manipulator for harvesting operations.

As a safety measure the pressure of the soft growing manipulator is limited to 10 psi, restricting the payload limit.

With apples weighing up towards 0.3kg, the rest of the payload including end effector must weigh less than 1.1kg

Design

Pulley

Servo Motor

Limit Switches

Silicone Finger with TPU Skeleton

Cross Sectional Area

Gyroid

Cross

Cross3D

The embedded skeletons are made from a TPU, a flexible 3D printable material.
Our 3D printer is capable of printing different infill patterns.
To further increase rigidity three infill patterns were tested.
9 patterns were originally tested, the top 3 performing patterns were used in full prototypes.

Force Analysis

Experimental Results

Cross3D

No Skeleton

Cross

Gyroid

Experimental Results

Conclusion and Future Work

Overall, grippers with silicone fingers and an embedded skeleton performed better than the one without.
Adding a twisting motion, similar to a human wrist, to maneuver fingers through branches.
A prototype version which can adjust the size of the palm, for different sized apples.
Integration with the soft growing robot and conduct a system evaluation.

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Acknowledgments

Thank You

Pulley

Servo Motor

Limit Switches

Silicone Finger with TPU Skeleton

Overall Dimensions: