Researchers from Cornell University’s Organic Robotics Lab have developed a new type of minuscule combustion engine that gives a tiny frog robot the ability to leap explosively and have fine movement control. Unlike most robots that use electric actuators, this robot runs on combustion fuel, which offers higher performance due to energy-dense chemical fuels. The actuator, only 5 mm in diameter, accepts methane and oxygen into a combustion chamber, ignites it with a spark, and uses a highly elastic silicone Dragon Skin membrane to expand the chamber volume as the fuel burns, before pushing out the exhaust gases.
The actuator’s explosive capabilities are proven by its ability to expand the chamber volume by up to 140% and generate forces greater than 9.5 N. The actuators operate at frequencies over 100 cycles per second and can be controlled to vary spark frequency, fuel equivalence ratio, and fuel flow. The Cornell team embedded prototypes of these actuators in the frog robot’s foot pads, enabling it to crawl forward, hop at various heights, walk in a snake-like manner, and spin on the spot.
The frog robot demonstrated impressive jumping abilities, reaching heights of 56 cm (1.8 ft) and carrying cargo up to 32 grams. The researchers believe that these combustion actuators could offer a new option for roboticists when quick and powerful movements are required.
[Source: via IEEE Spectrum]