Miniaturisable deformable grippers represent the fusion of two important research areas
of the robotics laboratory, namely underactuated hands and deformable mechanisms.
Based on the research we conducted recently, we were able to create a miniature gripper
capable of effecting an autonomous grasp.
The use of under-actuation allowed the actuaters to be reduced to a limited number and enabled the architecture control
to be simplified. Deformable joints represent a solution to the problems of
lubrification, cleaning and sterilization usually encountered with miniature joints. Thus, a combination of these
technologies has led to an impressive degree of miniaturization
(1 cm3 per gripper).
Fig. 1: Miniature planar gripper made of shape memory alloy.
Research has led to the determination of the geometry which optimizes the quality of the grasp
and the selection of the geometry of the flexible joints which provides an improvement of the rigidity in
directions other than those of the natural rotation axis, while maintaining the required angular range of motion.
Several prototypes have been made through rapid prototyping so as to verify the real behaviour
of the hands and the stability of the grasps.
|Fig. 2: Three-finger hand enabling a complete closing of the fingers.
||Fig. 3: Optimized under-actuation of the hand to improve the quality of grasping.
The two prototypes in Figure 4 illustrate under-actuated fingers using blades of
nitinol (51 %Ni et 49 %Ti), a superelastic alloy, as joints. This alloy allows an impressive angular
range of motion (8 % of elastic deformation) to be obtained with joints of reasonable length.
Moreover, in view of a future medical commercialisation, nitinol is biocompatible and
responds very well to sterilization procedures normally used in the industry.
Fig. 4: Flexible under-actuated fingers optimized by analysis of the critical parameters (A)
and by artificial intelligence (B).
A poster was prepared in 2005 on deformable grippers and can be
downloaded with the PDF file below.
Mechanically intelligent grippers for telemedecine (2.1 Mb)