Most animals can quickly switch from walking to hopping to crawling to swimming if necessary without major reconfiguration or modifications.
Most robots can’t. But researchers at Carnegie Mellon University have created soft robots that can seamlessly transition from walking to swimming, for example, or crawling to rolling over.
“Nature has inspired us to develop a robot that can perform different tasks and adapt to its environment without adding actuators or complexity,” said Dinesh K. Patel, a postdoctoral fellow at the Morphing Matter Lab in the School of Human Computer Science. Institute for Computer Interaction. “Our bistable actuator is simple, stable and durable, and lays the foundation for future work on dynamic and reconfigurable soft robots.”
The bistable actuator is made of soft 3D-printed rubber that contains shape memory alloy springs that react to electric currents by contracting, flexing the actuator. The team used this bistatic motion to change the shape of the actuator or robot. Once the robot changes shape, it is stable until another electrical charge transforms it back to its previous configuration.
“Matching how animals transition from walking to swimming to crawling to jumping is a huge challenge for soft, life-inspired robots,” said Karmel Majidi, a professor in the Department of Mechanical Engineering in the Carmel Mellon University College of Engineering.
For example, one robot the team created has four curved actuators attached at the corners of a cellphone-sized body made of two bistable actuators. On Earth, the curved motors act as legs, allowing the robot to walk. In the water, the bi-stabilizer motors change the shape of the robot, ideally positioning the curved motors to act as propellers so it can swim.
said Xiaonan Huang, assistant professor of robotics at the University of Michigan and Majidi’s former Ph.D. student. “We use the same system for both environments to create an efficient bot.”
The team created two more robots: one that can crawl and jump, and one inspired by caterpillars and grain bugs that can crawl and roll.
The actuators only require one hundred milliseconds of electrical charge to change shape, and they are durable. The team had someone bike over an actuator several times and changed the shapes of the robots hundreds of times to demonstrate durability.
In the future, robots could be used in rescue situations or to interact with sea animals or coral reefs. The use of heat-activated springs in actuators could open up applications in environmental monitoring, haptic devices, reconfigurable electronics and communications.
“There are many interesting and exciting scenarios in which energy efficient and versatile robots like this could be useful,” said Lining Yao, Cooper-Siegel Associate Professor at HCII and head of the Morphing Matter Lab.
The team’s research, “High Stability Dynamic Soft Drive for Intermodal and Reconfigurable Soft Robotics” appeared on the cover of the January 2023 issue of advanced materials technologies. The research team included senior co-authors Patel and Huang. Yaw. Majidi. Yichi Luo, a master’s student in mechanical engineering at CMU; and Mrunmayi Mungekar and M. Khalid Jawed, both of the Department of Mechanical and Aerospace Engineering at the University of California, Los Angeles.
