MIT Robohepard - Boston Dynamics Cheetah competitor

Boston Dynamics's four-legged robots are not the only ones whose development DARPA has financed under the Maximum Mobility and Manipulation (M3) program. And although the cheetah, built in the laboratory of bionics at the Massachusetts Institute of Technology, still lags behind its more famous Boston fellow in speed and autonomy, it is also very interesting. In addition, unlike Boston Dynamics, MIT publishes much more details about the design and development process of its robots.

The creators of the Massachusetts cheetah consider energy efficiency of the robot to be one of their main goals. The less energy a robot spends on moving at a given speed, the more compact its power plant can be and the longer it will be able to work autonomously. The movement efficiency of the MIT cheetah, which uses the electric drive (unlike the Boston Dynamics robots, whose legs are hydraulically driven) is very close to the efficiency of a live cheetah and other similar land animals and is several times higher than Big Dog or the two-legged Honda ASIMO robot.
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The efficiency of movement of animals strongly depends on the environment in which they move. Waterfowl spend their energy most economically. They are followed by flying animals, and it is harder for all to be moved by land animals. The comparative effectiveness of different types of animals, humans, some mechanisms and robots is clearly visible on this graph:



It was possible to achieve such results with the help of specially designed electric motors and carefully thought-out leg design. Engines have a very large radius, due to which they develop a much higher torque than that of any serial drive. Due to the low speed of such an engine, it became possible to use a simple single-stage gearbox. Low losses in the gearbox and low engine speeds allow energy to be efficiently recovered - when the ground touches the ground, the electric motor serves as a shock absorber, but does not dissipate the push energy as heat, but returns it to the battery.



The thigh and knee engines are located at the hip joint, thanks to which the cheetah's foot has a very low weight. Additionally, it was possible to lighten the construction using Kevlar “tendons”, which remove a significant part of the load from the “bones”. Another method of peeped in nature - to keep balance and faster and more accurate maneuvers, the tail is actively used.



Now the project team has focused on the improvement of electric motors. According to the director of the bionics laboratory, Professor Kim Sang Be, with the new engines, the 30-pound MIT cheetah can accelerate to 56 km / h, which is 10 km / h faster than the Boston cheetah's record . And in terms of energy efficiency, it should overtake its natural prototype, approaching the performance of flying animals.