A Fractal Suction-Based Robotic Gripper for Versatile Grasping

Abstract

Suction-based robotic grippers are common in industrial applications due to their simplicity and robustness but struggle with geometric complexity. Grippers that can handle varied surfaces as easily as traditional suction grippers would be more effective. Here we show how a fractal structure allows suction-based grippers to increase conformability and expand approach angle range. We develop a model for how the design parameters affect the range of curvatures and payloads a gripper can hold, and show when joint braking can increase payload capacity. We build a prototype gripper and develop a compact vacuum brake system for it. We then perform a series of experiments that demonstrate how the fractal structure enables corner grasping and expands the approach angle range from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\text{5}}^{\circ }$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\text{45}}^{\circ }$</tex-math></inline-formula>. We also show that adding brakes improves performance by over 30% at moderate contact angles. This letter demonstrates how fractal structures increase the utility of suction grippers through underactuation and locking.