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Educational SoftHand-A: Building an Anthropomorphic Hand with Soft Synergies using LEGO MINDSTORMS

Jared K. Lepora, Haoran Li, Efi Psomopoulou, Nathan F. Lepora

TL;DR

The Educational SoftHand-A tackles the challenge of teaching modern dexterous robotics using an accessible, LEGO-based platform. It adapts the Pisa/IIT SoftHand paradigm into a four-finger, anthropomorphic hand with a thumb, actuated by two motors and coordinated via antagonistic tendons and clutch-based soft synergies. The work presents a complete LEGO implementation, detailing finger/phalanx design, palm/tendon routing, and a differential drive unit, and validates performance through finger/hand tests and grasping experiments on diverse objects, with a qualitative comparison to a 3D-printed SoftHand-A. The result is a reactive, adaptively grasping hand that serves as an educational tool to inspire and educate students about contemporary robotic hand design and control.

Abstract

This paper introduces an anthropomorphic robot hand built entirely using LEGO MINDSTORMS: the Educational SoftHand-A, a tendon-driven, highly-underactuated robot hand based on the Pisa/IIT SoftHand and related hands. To be suitable for an educational context, the design is constrained to use only standard LEGO pieces with tests using common equipment available at home. The hand features dual motors driving an agonist/antagonist opposing pair of tendons on each finger, which are shown to result in reactive fine control. The finger motions are synchonized through soft synergies, implemented with a differential mechanism using clutch gears. Altogether, this design results in an anthropomorphic hand that can adaptively grasp a broad range of objects using a simple actuation and control mechanism. Since the hand can be constructed from LEGO pieces and uses state-of-the-art design concepts for robotic hands, it has the potential to educate and inspire children to learn about the frontiers of modern robotics.

Educational SoftHand-A: Building an Anthropomorphic Hand with Soft Synergies using LEGO MINDSTORMS

TL;DR

The Educational SoftHand-A tackles the challenge of teaching modern dexterous robotics using an accessible, LEGO-based platform. It adapts the Pisa/IIT SoftHand paradigm into a four-finger, anthropomorphic hand with a thumb, actuated by two motors and coordinated via antagonistic tendons and clutch-based soft synergies. The work presents a complete LEGO implementation, detailing finger/phalanx design, palm/tendon routing, and a differential drive unit, and validates performance through finger/hand tests and grasping experiments on diverse objects, with a qualitative comparison to a 3D-printed SoftHand-A. The result is a reactive, adaptively grasping hand that serves as an educational tool to inspire and educate students about contemporary robotic hand design and control.

Abstract

This paper introduces an anthropomorphic robot hand built entirely using LEGO MINDSTORMS: the Educational SoftHand-A, a tendon-driven, highly-underactuated robot hand based on the Pisa/IIT SoftHand and related hands. To be suitable for an educational context, the design is constrained to use only standard LEGO pieces with tests using common equipment available at home. The hand features dual motors driving an agonist/antagonist opposing pair of tendons on each finger, which are shown to result in reactive fine control. The finger motions are synchonized through soft synergies, implemented with a differential mechanism using clutch gears. Altogether, this design results in an anthropomorphic hand that can adaptively grasp a broad range of objects using a simple actuation and control mechanism. Since the hand can be constructed from LEGO pieces and uses state-of-the-art design concepts for robotic hands, it has the potential to educate and inspire children to learn about the frontiers of modern robotics.
Paper Structure (21 sections, 5 figures, 1 table)

This paper contains 21 sections, 5 figures, 1 table.

Table of Contents

  1. INTRODUCTION
  2. BACKGROUND AND RELATED WORK
  3. Highly-underactuated Anthropomorphic Robot Hands
  4. LEGO MINDSTORMS in Education
  5. Development of the Educational SoftHand-A
  6. Educational SoftHand-A Design Concept
  7. Finger, Phalanx and Joint Design
  8. Modular Finger Design
  9. Medial Phalanx Design
  10. Distal Phalanx Design
  11. Base Phalanx Design
  12. Palm Design and Tendon Layout
  13. Differential Drive Unit
  14. Results
  15. Finger and Hand Performance Testing
  16. ...and 6 more sections

Figures (5)

  • Figure 1: The Educational SoftHand-A is built and controlled entirely from standard LEGO® pieces and features a highly underactuated antagonistic tendon mechanism with adaptivity from soft synergies.
  • Figure 2: Finger design for the Educational SoftHand-A. Top: exploded view showing the axle rods that support the bearings for the driving agonist (blue) and antagonist (red) tendons. These are held in place with the phalanx covers. Bottom: side views showing the agonist and antagonist tendon routings.
  • Figure 3: Design of the Educational SoftHand-A. Left: exploded view of the SoftHand-A main parts, including the four fingers (thumb, index, middle and pinkie). These are held by front palm and back structures, which connect to a tendon spool mechanism with two motors and programmable controller. Right: assembled front view (without the front palm and back) showing the tendon guide mechanism and feed into the tendon spool (yellow part) that uses clutch gears (colored white) for a soft synergistic action.
  • Figure 4: Single finger test apparatus. A single finger is mounted on a custom base containing a pair of motors that each connect to a tendon spool via a clutch gear. The apparatus enables single finger tests such as bearing capacity, pushing capacity, and closing force.
  • Figure 5: Adaptive grasping with the Educational SoftHand-A. Front and side views of each grasp are shown, using 9 distinct objects of which 3 are shown with two different grasps. The fingers have adapted to different postures depending on the shape of the grasped object.