Engineers at Carnegie Mellon University have built the world’s smallest self-contained bipedal robot. The tiny creation, which is about four centimetres tall, can self-start from a standstill, walk faster than a 0.8 km/h, turn, skip and ascend small steps with just the power of its on-board battery, actuator and control system.
The robot, affectionately known as ‘Zippy’ by its creators, is the latest output of a multiyear National Science Foundation-supported project led by Aaron Johnson and Sarah Bergbreiter. The project is aimed at understanding locomotion at small scales in order to build more capable miniature walking robots.
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‘In a world designed for humans, two-legged robots are able to navigate uneven terrains and manoeuvre around objects more easily than robots with wheels,’ explained Johnson, a professor of mechanical engineering. ‘For this reason, we have been investigating how to eliminate complex walking mechanisms to make simple, two-legged robots possible.’
Steven Man, one of the lead authors of the research, emphasised the complexity, and importance, of miniature legged robots. ‘They can go into tight spaces that people and even other robots cannot manage. Zippy could be a resource for emergency search and rescue, industrial inspection and even deployment to geologically interesting areas for scientific research,’ he said.
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Undergraduate students Soma Narita and Josef Macera helped to design Zippy based on the team’s prior steerable bipedal robot, Mugatu, which featured rounded feet and a single actuator at the hip.
Zippy walks by lifting its front leg and shifting its centre of gravity forward. The momentum from this shift, in combination with its rounded front foot, creates enough space for its other leg to swing through and take a full step. Because of its small size, Zippy uses an additional mechanical hard stop to act as a joint limit for its hip instead of a servo.
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‘Both Zippy’s small size and our mechanical adjustments enable Zippy to walk at an incredible 10 leg lengths per second, which would be equivalent to an average adult moving at 19 miles per hour (30 km/h). This makes Zippy not just the smallest, but the fastest power-autonomous bipedal robot of any size by that metric,’ said Bergbreiter, a professor of mechanical engineering.
Moving forward, the team plans to add sensors such as cameras to Zippy so that it can localise and autonomously navigate environments. With localisation capabilities, multiple robots could be deployed together to coordinate as a swarm for inspection or search and rescue operations in hazardous environments.