In order to help robots walk over uneven terrain faster — an issue plaguing robots designed for search and rescue missions and space exploration — researchers from the University of California (UC), San Diego have developed flexible feet that improves robot speeds by 40%.
"Robots need to be able to walk fast and efficiently on natural, uneven terrain so they can go everywhere humans can go, but maybe shouldn't," said Emily Lathrop, a Ph.D. student at the Jacobs School of Engineering at UC San Diego.
Researchers said that robots are generally only able to control motion at specific joints. The flexible feet, made of latex membrane and filled with coffee grounds, allow robots to walk faster and grip better because of a mechanism called granular jamming that enables the feet to navigate back and forth, behaving like both a solid and a liquid.
According to developers, when the feet hit the ground, they provide solid footing and then unjam and loosen up when transitioning between steps. Meanwhile, the support structures help the flexible feet remain stiff while jammed.
Researchers installed the feet on a hexapod robot and built an on-board system that generates negative pressure to control the jamming of the feet as well as apply positive pressure to unjam the feet between each step.
A vacuum pump removes air between the coffee grounds and stiffens the foot but then can be passively jammed when the weight of the robot pushes the air out. As the robot legs grip the ground, the robot’s speed increased while walking on sloped, uneven terrain.
"The natural world is filled with challenging grounds for walking robots — slippery, rocky, and squishy substrates all make walking complicated," said Nick Gravish, a professor in the UC San Diego Department of Mechanical and Aerospace Engineering. "Feet that can adapt to these different types of ground can help robots improve mobility."
The flexible feet reduced the depth of penetration in the sand on impact by 62% and reduced the force required to pull the foot out when compared to a fully rigid foot by 98%.
The next steps include using a soft sensor on the bottom of the feet to allow an electronic control board to identify what ground the robot is stepping on and whether the feet need to be jammed actively or passively.