Robotic Hands

The MERO (MEchanically RObust) hand

Although substantial progresses have been made in building prosthetic hands, lack of mechanical robustness remains a challenge for wide adoption of robotic hand prosthesis. This video presents the design and evaluation of the MERO hand, which is a MEchanically RObust anthropomorphic prosthetic hand using novel COmpliant Rolling-contact Element (CORE) joints. The proposed CORE joint, which has a straightforward structure, exhibits compliance in multiple directions. The MERO hand, using the CORE joint, was endowed with notable robustness. Experiments showed that the MERO could withstand severe disarticulation and violent impact. Grasp experiments verified that the hand can perform various adaptive grasps, suggesting that the proposed design might be a viable solution for robust prosthetic hand.

Reference

  1. Huan Liu, Kai Xu, Bruno Siciliano, and Fanny Ficuciello, "The MERO Hand: A Mechanically Robust Anthropomorphic Prosthetic Hand Using Novel Compliant Rolling Contact Joint," IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM), Hong Kong, China, 2019. (Best paper finalist). [FULLTEXT]

A partial hand prosthesis (the JTP hand)

Among the amputations that involved the upper extremity, approximately 92% of the cases were partial hand amputations. Contrarily, among the advances in upper extremity prostheses in the past decades, only a small fraction of the results was obtained for partial hand prostheses. Reasons for this discrepancy might be anatomical diversity of partial hand amputation and limited space for component integration.

After weighing the factors such as low output power from a miniature motor, low energy density of present battery, and the implementation challenges of EMG-based control, this project proposes the JTP hand, a wrist-powered partial hand prosthesis developed at Shanghai Jiao Tong University. Aimed at improving the existing wrist-driven partial hand prostheses, the JTP hand possesses i) a continuum differential mechanism (CDM) to allow adaptive grasping, ii) a force-magnifying partial gear pair to enhance the power of the grip, and iii) lockable index and middle fingers to enhance hand function.

The JTP hand, was designed with a planned finger placement and intended stump fitting process. Therefore, the partial hand, once worn on the amputee’s stump, will resemble the other hand that is intact. Wearing the JTP hand, the amputee performed grasps and pinches easily with his wrist flexed. Depending on the objects to be grasped or pinched, the wrist should flex in a range from 10° to 40°. The outputs from the (CDM) in the forearm cuff varied to form adaptive grasps and natural-looking pinch poses.

The widely used Southampton Hand Assessment Procedure (SHAP) was followed to systematically examined the function of the JTP hand. With the JTP hand, the amputee was able to perform all the SHAP tasks after using the prosthesis for a few hours. The IoF (Index of Functionality), which indicates the hand function level, was 83/100.

Following video present the JTP hand worn by the amputee and some of the tasks performed in the experiments.

Reference

Kai Xu, Huan Liu, Zhaoyu Zhang, and Xiangyang Zhu, "Wrist-Powered Partial Hand Prosthesis Using a Continuum Whiffle Tree Mechanism: A Case Study." IEEE Transactions on Neural Systems and Rehabilitation Engineering, Vol. 26, No. 3, pp. 609-618, 2018. [FULLTEXT]

Single-actuator transradial prosthesis

Substantial progresses have been obtained towards versatile anthropomorphic prosthetic hands in the past years using emerging technologies. However the trade-offs between functionality, reliability, affordability, appearance, etc. have not been fully settled. Prosthetic hand designs have spanned a wide spectrum of varieties.

One-actuator prosthetic hands are still widely used in clinics due to the structural simplicity and low cost, such as the SensorHand from Otto Bock. This company seems to prefer fewer motors. Even its latest product, the Michelangelo Hand, only has two actuators. A simple, robust and cheap hand design could be beneficial for its business success. With a similar belief, many researchers developed single-actuator prosthetic hands, using stacked lever linkages, differential pulleys, or compliant structures.

This project proposes the design of a single-actuator prosthetic hand using a continuum differential mechanism as shown in Fig. 1. Structure of the continuum differential mechanism is simple enough to allow all the components, including the actuator and a battery pack, to be packed into the palm.

Continuum differential mechanisms (CDMs) generate differential outputs via redistributions and/or deformations of their own materials and structures. Their working principle is fundamentally different from the existing differential mechanisms which generate differential outputs from the motions of the kinematic pairs.

The single-actuator prosthetic hand has eleven joints, including ten active joints and one passive joint (the rotation joint of the thumb). The passive joint could be adjusted by the healthy hand, whereas the active joints are actuated by the outputs from a two-stage planar continuum differential mechanism.

Two prosthetic hand was designed, fabricated and assembled. Various grasps could be formed as shown in following videos.

Reference

  1. Huan Liu, Bin Zhao, Xiangyang Zhu, and Kai Xu, "Design of a Single-Actuator Multigrasp Prosthetic Hand with Force Magnification", Submitted to ASME Journal of Mechanisms and Robotics.
  2. Huan Liu, Zhaoyu Zhang, Tianlai Dong, Xiangyang Zhu, and Kai Xu, "A Single-Actuator Gripper with a Working Mode Switching Mechanism for Grasping and Rolling Manipulation", in IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM), Auckland, New Zealand, 2018. [FULLTEXT]
  3. Kai Xu and Huan Liu, "Continuum Differential Mechanisms and Their Applications in Gripper Designs," IEEE Transactions on Robotics, Vol. 32, No.3, pp. 754-762, June 2016. [FULLTEXT]
  4. Kai Xu, Huan Liu, Zenghui Liu, Yuheng Du, and Xiangyang Zhu, "A Single-Actuator Prosthetic Hand Using a Continuum Differential Mechanism," in IEEE International Conference on Robotics and Automation (ICRA), Seattle, Washington, USA, 2015, pp. 6457-6462. [FULLTEXT]

Postural synergy and its mechanical implementation

Reference

  1. Kai Xu, Huan Liu, Yuheng Du, and Xiangyang Zhu, "A Comparative Study for Postural Synergy Synthesis Using Linear and Nonlinear Methods," International Journal of Humanoid Robotics, Vol. 13, No.3, pp. 1650009, 2016. [FULLTEXT]
  2. Kai Xu, Huan Liu, Yuheng Du, and Xiangyang Zhu, "Design of an Underactuated Anthropomorphic Hand with Mechanically Implemented Postural Synergies," Advanced Robotics, Vol. 28, No. 21, pp. 1459-1474, Nov 2014. [FULLTEXT]
  3. Kai Xu, Huan Liu, Yuheng Du, Xinjun Sheng, and Xiangyang Zhu, "Mechanical Implementation of Postural Synergies Using a Simple Continuum Mechanism," in IEEE International Conference on Robotics and Automation (ICRA), Hong Kong, China, 2014, pp. 1348-1353. [FULLTEXT]
  4. Kai Xu, Yuheng Du, Huan Liu, Xinjun Sheng, and Xiangyang Zhu, "Mechanical Implementation of Postural Synergies of an Underactuated Prosthetic Hand," in International Conference on Intelligent Robotics and Applications (ICIRA), Busan, Korea, 2013, pp. 463-474. [FULLTEXT]