NRI: Liquid-Solid Metal for Embodied Intelligence in Semi-Soft, Human-Collaborative Robots

This National Robotics Initiative (NRI) grant supports research that will contribute new knowledge to the design and control of a novel semi-soft robot, promoting both the progress of science and enhancing national industrial and healthcare objectives. Flexible robots are able to navigate through restrictive environments. As such, they have the potential to revolutionize a variety of robotic tasks including industrial inspections, search-and-rescue operations, and minimally invasive surgery.

Existing flexible robots are either soft (made of rubbery elastic elements), which makes them safe, or hard (made of rigid support structures), which makes them able to lift heavy loads. The team supported by this award seeks to create a new kind of semi-soft robot that leverage the benefits of both paradigms. The researchers will pursue fundamental research to provide needed knowledge in the design and control of robots with internal skeletons that can transition from liquid to solid metal.

A semi-soft robot will be able to compress itself to pass through small openings, and then stiffen beyond, to manipulate its environment. Such a robot has the potential to benefit the U.S. economy and society with broad applications in infrastructure, manufacturing, disaster response, and medicine. This research involves several disciplines including mechanical engineering, mathematical modeling, control theory, computer science, and robot motion planning.

The research approach and associated outreach activities will help to broaden participation of underrepresented groups in robotics and positively impact engineering and computer science education.

Semi-soft robots will possess capabilities beyond existing robot designs via the phase transition of low melting point metal alloys, enabling the robot to control its stiffness from very soft (to deform through narrow openings), to very stiff (so that the robot can lift heavy loads and interact forcefully with its environment). These semi-soft robots will also have curved control tendons, endowing them with the potential to take on more complex shapes than current robots, which use straight control tendons.

However, scientific barriers remain before the potential of effective, controllable semi-soft robots is realized. This research will investigate the integration of the design, modeling, control, and motion planning of semi-soft robots. More specifically, the research team will (1) perform finite element modeling to understand the mechanical properties of a variety of low melting point alloy structure designs and their interaction with curved tendon actuation; (2) develop Cosserat Rod- and machine learning-based mechanical models of the robot; (3) investigate the use of resolved rates and model predictive control; (4) develop fast motion planning algorithms and a user interface that enables safe and accurate supervisory human control of the robot; and (5) validate these systems and concepts in simulated lung surgery.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.