One of the main proposed uses for legged robots is the exploration of disaster sites. In order to walk across all that rubble, though, they would definitely need to be sure-footed – which is where new coffee-filled robot feet are designed to come in.
Being developed by scientists at the University of California San Diego, the feet each consist of a flexible latex sphere packed with loose, dry coffee grounds. Along with that coffee, each foot also contains a plant-root-inspired internal support structure.
When moving through the air, the feet remain soft and squishy. Upon meeting with the ground and conforming to its irregular contours, however, they stiffen up. This happens thanks to a phenomenon known as "granular jamming," in which the coffee grounds temporarily get jammed together when placed under pressure.
As a result, each foot is able to form a stiff, custom grip against uneven terrain, each time it's placed on the ground. This can be done passively, as the weight of the robot jams the coffee grounds together, or actively, wherein a vacuum pump is used to jam them by actually sucking the air out of the sphere.
In lab tests, a commercially available hexapod robot was equipped with the new feet.
When that bot was walking on wood chips or pebbles, it was able to move up to 40 percent faster than when using its regular rigid feet. This was partly because the coffee feet reduced the depth to which its appendages sank into the chips/pebbles by an average of 62 percent, and reduced the force required to pull them back out by 98 percent.
They also gave the robot better grip against both uneven and flat surfaces. The active jamming system was found to work best on the former, while the passive system was better-suited to the latter. Plans now call for sensors to be added to the underside of the feet, to ascertain the characteristics of the ground before the feet make contact.
The hexapod robot can be seen using the feet, in the video below.
And this isn't the first time we've heard about jamming coffee grounds being incorporated into robotic devices. They're currently utilized in a gripping device known as the Versaball, plus MIT used them in an object-grasping robotic elephant's trunk.
Source: UC San Diego Jacobs School of Engineering
