🍿PopcornFT - Compact LED-Based F/T Sensing for Robot Fingers

Sharfin Islam1, Pedro Piacenza1, Amr El-Azizi1, Eugene Sohn1, Kai Jiang3, Zewen (Anthony) Chen1, Joaquin Palacios3, Ioannis Kymissis2, Matei Ciocarlie1
1Mechanical Engineering, 2Electrical Engineering, 3Computer Science -- Columbia University
A collaboration between Columbia University's ROAM and CLUE labs.
Paper (V1) arXiv (V1) Video (V1)

PopcornFT is designed to make F/T sensing accessible for a variety of different robot hands. It is compact, easy to make, and builds towards a future where F/T sensors are used by the bucket by any lab building a robotic hand.

Dexterous manipulation with a PopcornFT-V2 sensor on each fingertip.

PopcornFT-V1

Sensor diagram

PopcornFT-V1 was the first version of our sensor, using two boards connected by a clear elastomer.

Abstract

We introduce a sensor designed for integration in robot fingers, where it can provide information on the displacements induced by external contact. Our sensor uses LEDs to sense the displacement between two plates connected by a transparent elastomer; when a force is applied to the finger, the elastomer displaces and the LED signals change. We show that using LEDs as both light emitters an receivers in this context provides high sensitivity, allowing such an emitter and receiver pairs to detect very small displacements. We characterize the standalone performance of the sensor by testing the ability of a supervised learning model to predict complete force and torque data from its raw signals, and obtain a mean error between 0.05 and 0.07 N across the three directions of force applied to the finger. Our method allows for finger-size packaging with no amplification electronics, low cost manufacturing, easy integration into a complete hand, and high overload shear forces and bending torques, suggesting future applicability to complete manipulation tasks.

Supplementary Video

BibTeX

@misc{elazizi2025compactledbaseddisplacementsensing,
      title={Compact LED-Based Displacement Sensing for Robot Fingers}, 
      author={Amr El-Azizi and Sharfin Islam and Pedro Piacenza and Kai Jiang and Ioannis Kymissis and Matei Ciocarlie},
      year={2025},
      eprint={2410.03481},
      archivePrefix={arXiv},
      primaryClass={cs.RO},
      url={https://arxiv.org/abs/2410.03481}, 
}

PopcornFT-V2

Sensor diagram

PopcornFT-V2 uses the same concept as V1, but replaces the clear elastomer with flexures that allow for 6-DOF displacement between the plates. Using flexures greatly simplifies the manufacturing process, increases robustness and introduces less sensor-to-sensor variability.

PopcornFT-V2 manuscript coming soon.....