Rubber computer eliminates the last hard components of software robots


Rubber computer eliminates the last hard components of software robots

A soft robot, attached to a balloon and immersed in a transparent column of water, dives and surfaces, then dives and rises to the surface, like a fish chasing flies. Soft robots have already done this kind of trick. But unlike most software robots, this one is manufactured and operated without hardware or electronic parts. Inside, a soft rubber computer tells the ball when to go up or down. For the first time, this robot relies exclusively on digital software logic.

Over the last decade, software robots have burst into the world of robotics, predominantly metallic. Assembly lines already use rubber-like silicone grips: Padded claws handle delicate fruits and vegetables such as tomatoes, celery and sausages, or extract bottles and sweaters from crates. In the labs, forceps can pick up slippery fish, live mice and even insects, eliminating the need for greater human interaction.

Software robots already need simpler control systems than their hard counterparts. The clamps are so flexible that they simply can not exert enough pressure to damage an object and without the need to calibrate the pressure, a simple on-off switch is enough. But until now, most software robots still relied on hardware: metal valves opened and closed air channels that operated clamps and rubber arms, and a computer told them when to move.

Today, researchers have built a flexible computer using only rubber and air. "We imitate the thought process of an electronic computer, using only soft materials and pneumatic signals, replacing the electronics with air under pressure," said Daniel J. Preston, first author of an article published in PNAS and a postdoctoral researcher working with George Whitesides, professor at Woodford L. University and Ann A. Flowers.

To make decisions, computers use digital logic gates, electronic circuits that receive messages (inputs), and determine reactions (outputs) according to their programming. Our circuits are not so different: when a doctor hits a tendon under our kneecap (entrance), the nervous system is programmed to shake our leg (exit).

A completely flexible gripping device with human control reacts to the pressure of a soft button. This robot can detect a variety of irregularly shaped or fragile objects even after being struck by a mallet. Credit: D. J. Preston, P. Rothemund, H.J. Jiang, M.P. Nemitz, J. Rawson, Z. Suo, and G. M. White

Preston's flexible computer replicates this system with silicone tubes and pressurized air. To achieve the minimum types of logic gates required for complex operations (in this case, PAS, AND, and OR), he programmed the soft valves to respond to different air pressures. For the logical NOT gate, for example, if the input is high pressure, the output will be low pressure. With these three logic gates, says Preston, "you can reproduce any observed behavior on any electronic computer".

The fish-like robot in the water tank, for example, uses an environmental pressure sensor (NOT modified gate) to determine what action to take. The robot plunges when the circuit detects a low pressure at the top of the tank and at the surface when it detects a high pressure in depth. The robot can also surface on command if someone presses an external programmable button.

Robots built with only soft parts have several advantages. In industrial environments, such as automobile factories, huge metal machines operate at unseen speed and power. If a human gets in the way, a sturdy robot could cause irreparable damage. But if a robot is shocked against a human being, Preston says "you would not have to worry about a catastrophic injury or failure." They can only exercise a lot of strength.

But software robots are much safer: they are generally cheaper and easier to manufacture, lightweight, resistant to damage and corrosive materials, and durable. Add intelligence and soft robots could be used for much more than handling tomatoes. For example, a robot can detect a user's temperature and emit a slight pressure to indicate a fever, alert a diver when water pressure rises too much or push through debris after a natural disaster to help find the victims and offer help.

Software robots can also venture where the electronics are in trouble: high radiative fields, such as those produced after a nuclear malfunction or in space, and in-house machinery & equipment Magnetic resonance imaging (MRI). As a result of a hurricane or flood, a robust and gentle robot can handle dangerous terrain and harmful airs. "If a car hits a car, it keeps working, which we do not have with hard robots," Preston said.

A semi-autonomous submersible robot measures the pressure of water with the help of a programmable computer. The robot plunges when it detects a low pressure (near the surface) and rises when it detects a high pressure (in depth). The robot also surfaces on command to the touch of an external button. Credit: D. J. Preston, P. Rothemund, H.J. Jiang, M.P. Nemitz, J. Rawson, Z. Suo, and G. M. White

Preston and his colleagues are not the first to control robots without electronics. Other research teams have developed microfluidic circuits that can use liquid and air to create non-electronic logic gates. A microfluidic oscillator helped an octopus-shaped robot to beat the eight arms.

However, microfluidic logic circuits often rely on hard materials such as glass or hard plastics. They use channels as thin as small amounts of air at a time, which slows the movement of the robot. In comparison, Preston's channels are wider – about one millimeter in diameter – allowing for much faster airflow rates. Its air grippers can grab an object in seconds.

Microfluidic circuits also consume less energy. Even at rest, the devices use a pneumatic resistor that sends air from the atmosphere to a source of vacuum or pressure to maintain stability. Preston's circuits do not require any standby power input. Such an energy saving could be crucial in emergency or disaster situations when robots move away from a reliable source of energy.

Rubber robots also offer an attractive possibility: Invisibility. Depending on the material selected by Preston, he can design a robot adapted to a specific substance. Thus, if he chooses a material that camouflages in water, the robot will appear transparent once submerged. In the future, he and his colleagues hope to create autonomous robots, invisible to the naked eye or even detected by sonar. "It's just a matter of choosing the right materials," he says.

For Preston, the proper materials are elastomers (or rubbers). While other fields are pursuing increased power with machine learning and artificial intelligence, the Whitesides team is turning away from the growing complexity. "There are a lot of possibilities out there," says Preston, "but it's also good to step back and ask yourself whether or not there is a simpler way of doing things that give you the same result, especially if it's not only as cheaper. "

Researchers develop "soft" valves to make fully soft robots

More information:
Department of Chemistry and Chemical Biology et al., "Daniel J. Preston, Philipp Rothemund, Haihui Joy Jiang, Markus P. Nemitz, Jeff Rawson, Zhigang Suo, George M. Whitesides," PNAS (2019).

Provided by
Harvard University

Rubber computer eliminates last hard components of software robots (2019, March 25)
recovered on March 26, 2019

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