Abstract This article describes the development and evaluation of our passively actuated closed-loop articulated wearable (CLAW) that uses a common slider to passively drive its exo-fingers for use in physical training of people with limited hand mobility. Our design approach utilizes physiological tasks for dimensional synthesis and yields a variety of design candidates that fulfill the desired fingertip precision grasping trajectory. Once it is ensured that the synthesized fingertip motion is close to the physiological fingertip grasping trajectories, performance assessment criteria related to user–device interference and natural joint angle movement are taken into account. After the most preferred design for each finger is chosen, minor modifications are made related to substituting the backbone chain with the wearer’s limb to provide the skeletal structure for the customized passive device. Subsequently, we evaluate it for natural joint motion based on a novel design candidate assessment method. A hand prototype is printed, and its preliminary performance regarding natural joint motion, wearability, and scalability are assessed. The pilot experimental test on a range of healthy subjects with different hand/finger sizes shows that the CLAW hand is easy to operate and guides the user’s fingers without causing any discomfort. It also ensures both precision and power grasping in a natural manner. This study establishes the importance of incorporating novel design candidate assessment techniques, based on human finger kinematic models, on a conceptual design level that can assist in finding design candidates for natural joint motion coordination.
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Multi-segment soft robotic fingers enable robust precision grasping
In this work, we discuss the design of soft robotic fingers for robust precision grasping. Through a conceptual analysis of the finger shape and compliance during grasping, we confirm that antipodal grasps are more stable when contact with the object occurs on the side of the fingers (i.e., pinch grasps) instead of the fingertips. In addition, we show that achieving such pinch grasps with soft fingers for a wide variety of objects requires at least two independent bending segments each, but only requires actuation in the proximal segment. Using a physical prototype hand, we evaluate the improvement in pinch-grasping performance of this two-segment proximally actuated finger design compared to more typical, uniformly actuated fingers. Through an exploration of the relative lengths of the two finger segments, we show the tradeoff between power grasping strength and precision grasping capabilities for fingers with passive distal segments. We characterize grasping on the basis of the acquisition region, object sizes, rotational stability, and robustness to external forces. Based on these metrics, we confirm that higher-quality precision grasping is achieved through pinch grasping via fingers with the proximally actuated finger design compared to uniformly actuated fingers. However, power grasping is still best performed with uniformly actuated fingers. Accordingly, soft continuum fingers should be designed to have at least two independently actuated serial segments, since such fingers can maximize grasping performance during both power and precision grasps through controlled adaptation between uniform and proximally actuated finger structures.
more » « less- NSF-PAR ID:
- 10139393
- Publisher / Repository:
- SAGE Publications
- Date Published:
- Journal Name:
- The International Journal of Robotics Research
- ISSN:
- 0278-3649
- Page Range / eLocation ID:
- Article No. 027836492091046
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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