Robotics is applied in various fields and thus robot components with various shapes and stiffness values are required. We previously developed a variable-stiffness and deformable link using a shape-memory alloy and the jamming transition phenomenon. The link can be fixed in an arbitrary shape and then restored to its initial shape via the shape memory effect. We previously attached a prototype link to a robot arm and evaluated its pick-and-place motion for various objects with different shapes and weights. However, as we used a lubricant to facilitate deforming the link, objects sometimes slipped off the link. Therefore, in this study, we propose a method for deforming the link without a lubricant. Another robot arm is added to press a mold onto the link to increase operational efficiency. We compare three deformation methods in terms of the time required to change molds, weight capacity, structural change during repeated motion, force required to deform the link, and positioning accuracy. The experimental results show that the weight capacity increased when the link was deformed without a lubricant. Moreover, similar to our previous study, changing the link shape to suit the target object improved positioning accuracy. Using the two-robot-arm system, the time required to change molds decreased by 94% compared to that in our previous study. Furthermore, the pressing force of the link during the fixing of the shape affected the contact length between the link and the object and the positioning accuracy.
Takashima et al. (Sun,) studied this question.