Engineers at the University of California San Diego have actually produced a four-legged soft robotic that does not need any electronics to work. The robotic only requires a continuous source of pressurized air for all its functions, including its controls and locomotion systems.

The team, led by Michael T. Tolley, a professor of mechanical engineering at the Jacobs School of Engineering at UC San Diego, details its findings in the Feb. 17, 2021 issue of the journal Science Robotics.

“This work represents a fundamental yet substantial step towards fully-autonomous, electronics-free strolling robots,” said Dylan Drotman, a Ph.D. student in Tolley’s research group and the paper’s very first author.

Applications include inexpensive robotics for home entertainment, such as toys, and robotics that can run in environments where electronics can not operate, such as MRI makers or mine shafts. Soft robots are of particular interest due to the fact that they quickly adapt to their environment and operate safely near humans.

The majority of soft robots are powered by pressurized air and are managed by electronic circuits. However this approach requires complicated components like circuit boards, valves and pumps– frequently outside the robotic’s body. These parts, which constitute the robot’s brains and nerve system, are normally large and pricey. By contrast, the UC San Diego robot is controlled by a light-weight, low-cost system of pneumatic circuits, made up of tubes and soft valves, onboard the robot itself. The robotic can stroll on command or in reaction to signals it senses from the environment.

“With our approach, you might make an extremely intricate robotic brain,” stated Tolley, the research study’s senior author. “Our focus here was to make the simplest air-powered nerve system needed to manage strolling.”

The robot’s computational power roughly imitates mammalian reflexes that are driven by a neural reaction from the spinal column rather than the brain. The group was motivated by neural circuits found in animals, called main pattern generators, made from really basic aspects that can create rhythmic patterns to manage motions like walking and running.


To simulate the generator’s functions, engineers built a system of valves that serve as oscillators, controlling the order in which pressurized air goes into air-powered muscles in the robot’s 4 limbs. Researchers built an innovative component that coordinates the robot’s gait by delaying the injection of air into the robot’s legs. The robotic’s gait was motivated by sideneck turtles.

The robotic is also geared up with easy mechanical sensing units– little soft bubbles filled with fluid put at the end of booms protruding from the robotic’s body. When the bubbles are depressed, the fluid flips a valve in the robotic that causes it to reverse direction.

The Science Robotics paper builds on previous work by other research study groups that established oscillators and sensors based on pneumatic valves, and includes the components required to achieve top-level functions like walking.

How it works

The robot is equipped with three valves serving as inverters that cause a high pressure state to spread out around the air-powered circuit, with a delay at each inverter.


Each of the robot’s four legs has three degrees of liberty powered by 3 muscles. The legs are angled downward at 45 degrees and made up of three parallel, connected pneumatic round chambers with bellows. When a chamber is pressurized, the limb bends in the opposite direction. As a result, the three chambers of each limb offer multi-axis bending needed for walking. Scientist paired chambers from each leg diagonally throughout from one another, simplifying the control issue.

A soft valve switches the direction of rotation of the limbs in between counterclockwise and clockwise. That valve functions as what’s known as a latching double pole, double toss switch– a switch with two inputs and 4 outputs, so each input has two matching outputs it’s connected to. That mechanism is a little like taking two nerves and switching their connections in the brain.

Next actions

In the future, scientists wish to improve the robotic’s gait so it can walk on natural surfaces and uneven surfaces. This would permit the robot to navigate over a range of challenges. This would need a more sophisticated network of sensing units and as an outcome a more intricate pneumatic system.

The group will likewise take a look at how the technology could be utilized to produce robots, which are in part controlled by pneumatic circuits for some functions, such as walking, while standard electronic circuits deal with greater functions.

This work is supported by the Office of Naval Research study, grant numbers N00014-17-1-2062 and N00014-18-1-2277.