Abstract
The recent decade has seen an astounding increase of interest and advancement in a new field of robotics, aimed at creating structures specifically for the safe interaction with humans. Softness, flexibility, and variable stiffness in robotics have been recognized as highly desirable characteristics for many applications. A number of solutions were proposed ranging from entirely soft robots (such as those composed mainly from soft materials such as silicone), via flexible continuum and snake-like robots, to rigid-link robots enhanced by joints that exhibit an elastic behavior either implemented in hardware or achieved purely by means of intelligent control. Although these are very good solutions paving the path to safe human-robot interaction, we propose here a new approach that focuses on creating stiffness controllability for the linkages between the robot joints. This article proposes a replacement for the traditionally rigid robot link-the new link is equipped with an additional capability of stiffness controllability. With this added feature, a robot can accurately carry out manipulation tasks (high stiffness), but can virtually instantaneously reduce its stiffness when a human is nearby or in contact with the robot. The key point of the invention described here is a robot link made of an airtight chamber formed by a soft and flexible, but high-strain resistant combination of a plastic mesh and silicone wall. Inflated with air to a high pressure, the mesh silicone chamber behaves like a rigid link; reducing the air pressure, softens the link and rendering the robot structure safe. This article investigates a number of link prototypes and shows the feasibility of the new concept. Stiffness tests have been performed, showing that a significant level of stiffness can be achieved-up to 40 N reaction force along the axial direction, for a 25-mm-diameter sample at 60 kPa, at an axial deformation of 5 mm. The results confirm that this novel concept to linkages for robot manipulators exhibits the beam-like behavior of traditional rigid links when fully pressurized and significantly reduced stiffness at low pressure. The proposed concept has the potential to easily create safe robots, augmenting traditional robot designs.
Highlights
In the past decades, the introduction of soft robotics has redefined the limits of what a robot can accomplish
A number of solutions were proposed ranging from entirely soft robots, via flexible continuum and snake-like robots, to rigid-link robots enhanced by joints that exhibit an elastic behavior either implemented in hardware or achieved purely by means of intelligent control. These are very good solutions paving the path to safe human–robot interaction, we propose here a new approach that focuses on creating stiffness controllability for the linkages between the robot joints
The results confirm that this novel concept to linkages for robot manipulators exhibits the beamlike behavior of traditional rigid links when fully pressurized and significantly reduced stiffness at low pressure
Summary
The introduction of soft robotics has redefined the limits of what a robot can accomplish. As a consequence of these mechanical limitations, the maximum force exertable by such robotic systems is typically limited.[1] A deformation of the same relative order of magnitude is produced in the legs of the walking soft robot proposed in an article[7] once its pneumatic network is pressurized to perform a movement. These volume variations are generally difficult to model and difficult to predict, creating a significant control problem. The Conclusions section summarizes the conclusions and achievements of this article and proposes future work and potential applications for the new concept
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