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. 2018 Apr;5(2):216-227.
doi: 10.1089/soro.2017.0052. Epub 2018 Jan 3.

The TacTip Family: Soft Optical Tactile Sensors with 3D-Printed Biomimetic Morphologies

Benjamin Ward-Cherrier  1   2 , Nicholas Pestell  1   2 , Luke Cramphorn  2 , Benjamin Winstone  2 , Maria Elena Giannaccini  1   2 , Jonathan Rossiter  1   2 , Nathan F Lepora  1   2
Affiliations

The TacTip Family: Soft Optical Tactile Sensors with 3D-Printed Biomimetic Morphologies

Benjamin Ward-Cherrier et al. Soft Robot. 2018 Apr.

Abstract

Tactile sensing is an essential component in human-robot interaction and object manipulation. Soft sensors allow for safe interaction and improved gripping performance. Here we present the TacTip family of sensors: a range of soft optical tactile sensors with various morphologies fabricated through dual-material 3D printing. All of these sensors are inspired by the same biomimetic design principle: transducing deformation of the sensing surface via movement of pins analogous to the function of intermediate ridges within the human fingertip. The performance of the TacTip, TacTip-GR2, TacTip-M2, and TacCylinder sensors is here evaluated and shown to attain submillimeter accuracy on a rolling cylinder task, representing greater than 10-fold super-resolved acuity. A version of the TacTip sensor has also been open-sourced, enabling other laboratories to adopt it as a platform for tactile sensing and manipulation research. These sensors are suitable for real-world applications in tactile perception, exploration, and manipulation, and will enable further research and innovation in the field of soft tactile sensing.

Keywords: dexterous manipulation; soft sensors; tactile sensors.

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Conflict of interest statement

No competing financial interests exist.

Figures

<b>FIG. 1.</b>
FIG. 1.
TacTip project sensors. From left to right: open-TacTip (original), TacTip (improved), TacTip-GR2, TacTip-M2 (flat), TacTip-M2 (round), and TacCylinder.
<b>FIG. 2.</b>
FIG. 2.
The TacTip-M2 integrated into the open-hand model M2 gripper (left), the TacTip-GR2 mounted on the GR2 gripper (middle), and the TacCylinder in a simulated tumor detection experiment (right).
<b>FIG. 3.</b>
FIG. 3.
Intermediate ridges in the human skin (left) and a corresponding pin in the TacTip (right).
<b>FIG. 4.</b>
FIG. 4.
Open-TacTip (left): the original version of the sensor comprises a 3D-printed camera mount and base and a cast silicone skin. Improved TacTip (center): the redesigned base houses a reassembled webcam, and modular tips with 3D-printed rubber skin. Modular tips (right): separate modular tips with a nodular fingerprint (above) and flat tip (below).
<b>FIG. 5.</b>
FIG. 5.
Raw images from the TacTip family of sensors. From left to right: improved TacTip, TacTip-GR2, TacTip-M2, and TacCylinder. The TacTip images pins with a Microsoft Cinema HD webcam, whereas the TacTip-GR2 uses a Raspberry Pi spycam (Adafruit) and a fisheye lens to reduce the sensor's form factor. The TacCylinder uses a catadioptric mirror to achieve 360° vision.
<b>FIG. 6.</b>
FIG. 6.
The original TacTip-M2 (left) is used when the form factor is nonessential and the improved TacTip-M2 (right), more compact, is designed for integration onto the OpenHand M2 gripper.
<b>FIG. 7.</b>
FIG. 7.
The TacCylinder is designed for capsule endoscopy. The cylindrical design comprises a 3D-printed cylindrical skin and catadioptric mirror system to achieve 360° tactile sensing.
<b>FIG. 8.</b>
FIG. 8.
The TacTip, TacTip-GR2, TacTip-M2, and TacCylinder mounted on the ABB robot arm, with the 25 mm diameter cylinder being rolled over a 72 mm range.
<b>FIG. 9.</b>
FIG. 9.
Tactile data from all four sensors. Data were sampled at 0.1 mm intervals along the 72 mm range of cylinder motion (720 samples). (A, C, E, G) pin displacements along the x-axis and (B, D, F, H) along the y-axis (direction of the cylinder roll). The four right-most panels identify pins for each sensor and display the x- and y-directions.
<b>FIG. 10.</b>
FIG. 10.
Localization accuracy of the four sensors: TacTip (A), TacTip-GR2 (B), TacTip-M2 (C), and TacCylinder (D). The results are shown for 72 location classes, each corresponding to a 1 mm range.
<b>FIG. 11.</b>
FIG. 11.
Range of movement for the M2 gripper (left) and the GR2 gripper (right) with integrated TacTips.
See this image and copyright information in PMC

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