LEGATO Gripper Hardware Manual

Overview

LEGATO Gripper is a hand-held gripper developed in LEGATO: Cross-Embodiment Imitation Using a Grasping Tool to advance cross-embodiment robot learning research. Created by Mingyo Seo and Shenli Yuan, LEGATO aims to democratize and support robot manipulation within the robot learning community by open-sourcing its modular hardware design.

We currently provide the following materials from this open-source project as a preview. More detailed documentation will be updated soon.
- Bill of materials
- 3D-printing parts
- Assembly instructions
- Python-based hardware control interface
- Simulation models for MuJoCo

Bill of Materials

Here is the list of off-the-shelf parts required to assemble one set of shared gripper components. Although ISO bolts from McMaster-Carr are specified in this list, any compatible bolts may be used as alternatives.
Item Quantity Unit Cost Total Cost Link
Dynamixel XM430-W350R 2 289.9 579.8
RealSense T265
(currently discontinued, alternative)		 1 >300 >300
Flanged Ball Bearing
(package of 4) 		1 6.89 20.67
Alloy Steel Shoulder Screws
⌀ 5mm x 30mm Shoulder, M4 x 0.7mm Thread		 6 3.03 18.18
M4 x 0.7mm Locknut
(package of 100, 6 required) 		1 5.57 5.57
Heat Set Insert
M3 x 0.5mm Thread Size, 3.8 mm Installed Length
(Package of 100, 4 required) 		1 20.44 20.44
M3 x 30mm Long Socket Head Screws
(pack of 50, 4 required)		 1 13.68 13.68
M3 x 12mm Long Socket Head Screws
(pack of 100, 10 required) 		1 11.29 11.29
M3 x 0.5 mm Nut
(packge of 100, 10 required) 		1 2.81 2.81
M6 x 14mm Long Socket Head Screws
(pack of 100, 4-6 required) 		1 19.69 19.69
M6 x 1mm Nut
(packge of 100, 4-6 required) 		1 3.14 3.14
M2.5 x 8mm Long Socket Head Screws
(packge of 50, 2 required) 		1 11.42 11.42
M2.5 x 6mm Long Socket Head Screws
(packge of 50, 8 required) 		1 11.56 11.56
M2 x 6mm Long Socket Head Screws
(packge of 100, 16-32 required) 		1 15.68 15.68
Other than the above components, the follow materials, 3D-printing filaments, and friction tapes are requred to assembly one set of the Gripper. The below table is the example of the items, but any compatible alternative can be used.
Item Cost Link
PLA 3D-printing filment 19.99
TPU 95A 3D-printing filment 41.99
Friction tape 49.00

3D-printing Parts

Here is the list of 3D-printed parts required to assemble one set of shared gripper components, along with optional handles for robots and a human demonstrator. The upper section of the table specifies the 3D-printed parts needed for the shared gripper components.
Item Material Quantity File
Base PLA 1
Dynamixel Mount PLA 2
Finger Link PLA 2
Upper Link PLA 2
Lower Link Half PLA 4
Finger Tip TPU 95A 2 coming
soon
Human Handle PLA 1
Spot Handle PLA 1
Panda Handle 1 PLA 1
Panda Handle 2 PLA 1

Assembly Instruction

Follow the video instructions below to assemble the shareable gripper components. Before assembly, use an appropriate press machine, such as , to heat-set inserts into the Base part.
For use, you can assemble the sharabe gripper with the corresponding handles. Currently, we provide three types of handles: one for a human demonstrator, one for the Franka Emika Panda, and one for the Boston Dynamics Spot. The assembly instructions are shown in the following figures.

Citation

 

      @misc{seo2024legato,
        title={LEGATO: Cross-Embodiment Visual Imitation Using a Grasping Tool},
        author={Seo, Mingyo and Park, H. Andy and Yuan, Shenli and Zhu, Yuke and
          and Sentis, Luis},
        year={2024}
        eprint={2411.03682},
        archivePrefix={arXiv},
        primaryClass={cs.RO}
      }

Acknowledgement

This work was conducted during Mingyo Seo's internship at the AI Institute. We thank Rutav Shah and Minkyung Kim for providing feedback on this manuscript. We thank Dr. Osman Dogan Yirmibesoglu for designing the fin ray style compliant fingers and helping with hardware prototyping. We thank Mitchell Pryor and Fabian Parra for their support with the real Spot demonstration. We acknowledge the support of the AI Institute and the Office of Naval Research (N00014-22-1-2204).