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Pneumatic random-access memory for controlling soft robots

Technology News |
By Rich Pell

Existing systems for controlling such soft robots currently require dedicated electromechanical hardware to maintain the actuation state of each independent actuator, which when combined with power, computation, and sensing components adds considerable cost, size, and power demands, thereby limiting the feasibility of soft robots in many important application areas. In their work, the researchers developed a pneumatic memory that uses air – not electricity – to set and maintain the states of large numbers of soft robotic actuators without dedicated electromechanical hardware.

To advance soft robotics toward the future, say the researchers, they looked back to the past. “Pneumatic logic” predates electronic computers and once provided advanced levels of control in a variety of products, from thermostats and other components of climate control systems to player pianos in the early 1900s.

In pneumatic logic, air flows through circuits or channels and air pressure is used to represent on/off or true/false. In modern computers, these logical states are represented by 1s and 0s in code to trigger or end electrical charges.

Pneumatic soft robots need a way to remember and maintain the positions of their moving parts. The researchers realized that if they could create a pneumatic logic “memory” for a soft robot, they could eliminate the electronic memory currently used for that purpose.

The researchers made their pneumatic random-access memory (RAM) chip using microfluidic valves instead of electronic transistors. Originally designed to control the flow of liquids on microfluidic chips, the microfluidic valves can also control the flow of air.

The valves remain sealed against a pressure differential even when disconnected from an air supply line, creating trapped pressure differentials that function as memories and maintain the states of a robot’s actuators. Dense arrays of these valves can perform advanced operations and reduce the expensive, bulky, and power-consuming electronic hardware typically used to control pneumatic robots.

After modifying the microfluidic valves to handle larger air flow rates, the researchers produced an 8-bit pneumatic RAM chip able to control larger and faster-moving soft robots, and incorporated it into a pair of 3D-printed rubber hands. The pneumatic RAM uses atmospheric-pressure air to represent a “0” or FALSE value, and vacuum to represent a “1” or TRUE value. The soft robotic fingers are extended when connected to atmospheric pressure and contracted when connected to vacuum.

By varying the combinations of atmospheric pressure and vacuum within the channels on the RAM chip, the researchers say they were able to make the robot play notes, chords, and even a whole song on a piano (see video below).

In theory, say the researchers, this system could be used to operate other robots without any electronic hardware and only a battery-powered pump to create a vacuum. In addition, the researchers note that without positive pressure anywhere in the system – only normal atmospheric air pressure – there is no risk of accidental overpressurization and violent failure of the robot or its control system. Robots using this technology would be especially safe for delicate use on or around humans, such as wearable devices for infants with motor impairments.

For more, see “A pneumatic random-access memory for controlling soft robots.”

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