Researchers are setting new speed records for soft robots: They have developed a new drive system that uses the stored energy of a spring. Triggered by the pressure of “pneumatic muscles”, the tensioned spring causes a drive element to snap from one position to another in a flash. This means that it can gallop soft robots or give aquatic versions a powerful flap.
Soft and flexible instead of hard and stiff – soft robots enable applications that conventional systems with their rigid structures do not offer: for example, they can handle very sensitive objects, move flexibly in complex environments or squeeze through narrow openings. This gives you the potential to develop rescue robots or industrial applications. Various research groups are therefore concerned with the development of increasingly powerful “softbot” concepts.
The previous systems of soft robotics are usually based on soft plastic materials that are moved by pneumatic or hydraulic effects: changes in pressure in the artificial muscles of the soft robots result in changes in shape that can also provide drive. So far, however, the techno beings have been quite slow and sluggish, because their soft bodies and the slow response times of the printing systems limit locomotion. The researchers led by Jie Yin from North Carolina State University in Raleigh are devoting themselves to the development of corresponding improvement opportunities.
Role model cheetah
“We were inspired by the cheetahs in our work,” says Yin. “These fastest of all land creatures develop their speed and power by flexing their backs when racing,” says Yin. In principle, similar movements can also be achieved using conventional soft robot concepts. But they are not fast and powerful enough to ensure speed. “Previous soft robots moved like caterpillars that always stay in contact with the ground,” says Yin.
He and his colleagues have now developed a component that can look like a powerful, flexible back in a soft robot. The system consists of a tensioned spring and a joint, which together form a bistable element. Bistable means that it can assume two possible stable states that can be changed via an external impulse. In other words, the element can be snapped. “We can quickly switch between these states by pumping air into channels that line the soft silicone robot,” explains Yin. Specifically, this means: The pressure of the “pneumatic muscles” pushes the movable element over its snap point, then the tensioned spring ensures the rapid movement, which leads to the second stable state. Switching between the two states quickly releases a lot of energy so that the robot can suddenly exert force.
New record speeds in soft robotics
The researchers call this system “Leveraging Elastic instabilities for Amplified Performance” (LEAP). For demonstration purposes, they integrated it into a soft robot with four feet. The mechanism allows the prototype to gallop across surfaces – that is, its feet leave the ground. The movement is not as elegant as in cheetahs, but the principle is similar. The robot hops forward at a speed of up to 2.7 body lengths per second – more than three times as fast as previous systems. Tests show that the seven-centimeter-long and 45-gram LEAP robots are also able to climb steep slopes.
Floating soft robots can obviously also be accelerated by the concept: The scientists have built LEAP robots in which the snap system drives a fin. You will achieve a swimming speed of 0.78 body lengths per second. They are now beating the fastest aquatic soft robots to date, say the scientists. They were also able to demonstrate that two LEAP elements can be combined like a pair of pliers to grasp objects. What is special: They can be flexibly adjusted to the requirements: “By adjusting the forces exerted, we were able to lift objects that are as fragile as an egg. However, the elements can also lift objects weighing ten kilograms or more, ”says Yin.
As he and his colleagues emphasize, their previous designs are prototypes that illustrate the potential of the concept. They are currently working on making the designs even faster and more powerful. “Potential areas of application include search and rescue technologies that require speed and robotics in industrial manufacturing,” says Yin.
Source: North Carolina State University, professional article: Science Advances, doi: 10.1126 / sciadv.aaz6912