Most animals can quickly transition from walking to jumping to crawling and swimming if necessary without reorganizing or making major adjustments.
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 from crawling to rolling.
“We were inspired by nature to create a robot that can perform various tasks and adapt to its environment without adding stimuli or complexity,” says Dinesh K. – Institute of Computer Interaction. “Our bistable motor is simple, stable and durable, and lays the foundation for future work on dynamic, reconfigurable soft robotics.”
The durable actuator is made of 3D-printed soft rubber that contains shape memory alloy springs that respond to electrical currents by contracting, causing the actuator to bend. The team used this bistable motion to change the shape of the motor or robot. When the robot changes its shape, it is stable until another electrical charge returns it to its previous configuration.
“Matching how animals go from walking to swimming to crawling to jumping is a major challenge for bio-inspired and soft robotics,” said Carmel Majidi, a professor in the Department of Mechanical Engineering in CMU’s College of Engineering.
For example, one of the robots the team created has four curved actuators attached to the corners of a cell phone-sized body, which are made up of two bistable motors. On land, curved motors act as legs, allowing the robot to walk. In water, bistable actuators change the shape of the robot, placing the curved impulses in the ideal position as propellers so it can float.
“To walk on land you need legs, and to swim in water you need a propeller. Building a robot with separate systems for each environment adds complexity and weight,” said Xiaonan Huang, assistant professor of robotics. University of Michigan and Majidi’s former Ph.D. student “We use the same system for both environments to create an efficient robot.”
The team created two other robots, one that can crawl and jump, and one inspired by caterpillars and pills that can crawl and roll.
The actuators require only a hundred milliseconds of electrical charge to change their shape, and they are durable. The team had a human ride a bicycle over one of the motors several times and change the robot’s shape hundreds of times to demonstrate endurance.
In the future, robots could be used in rescue situations or to interact with marine animals or corals. The use of thermally activated sources in motors could open up applications in environmental monitoring, haptics, and reconfigurable electronics and communications.
“There are many interesting and exciting scenarios where such energy-efficient and versatile robots could be useful,” said Lining Yao, Cooper-Siegel Assistant Professor at HCII and head of the Morphing Matter Lab.
The team’s research, “A Highly Dynamic Biproximal Soft Motor for Reconfigurable Multimodal Soft Robots,” is featured on the cover of the January 2023 issue. Advanced materials technologies. The research team included first authors Patel and Huang; Yao; Majidi; Yiichi Luo, a mechanical engineering graduate student at CMU; and Mrunmai Mungekar and M. Khalid Javed, both of the Department of Mechanical and Aerospace Engineering at the University of California, Los Angeles.