One-legged robot taught accurate jumping

American engineers have created a new one-legged robot control algorithm Salto-1P, which allows it to more accurately plan a touchdown point, as well as steadily land on uneven or recently moved surfaces. The development was presented at the conference IROS 2018, briefly tells about it IEEE Spectrum.

Salto-1P is a one-legged jumping robot created by engineers from the University of California at Berkeley in 2017 as a more advanced version presented by Salto a year earlier. He uses several mechanisms for jumping: a motor that drives a leg of several segments, as well as a mechanical analogue of the tail and two screws that compensate for the rotation of the robot.

In terms of its design, Salto-1P is a spring-loaded reverse pendulum, the basis for which was laid in the 1980s by American engineer Mark Reibert, who later founded Boston Dynamics, a company that develops humanoid and  four-legged robots. The main idea of ​​the Reibert algorithm is that the direction and acceleration of the robot can be set by changing the angle of the foot relative to the body and the surface, as well as the level of spring-loaded legs.Salto-1P has used this control principle before, but in the new paper, the authors refined the algorithm for a more accurate landing. Experiments have shown that with the new algorithm, the standard deviation of the error is 10 centimeters, and 95 percent of the jumps end no more than 30 centimeters from the planned touchdown point. Thanks to this, the robot can now jump even on small and uneven obstacles, for example, on a chair with a curved seat.


In addition, the new control algorithm allows the robot to quickly adapt to the offset of the target. For this, he uses an external motion capture system. The developers showed how the robot copes with jumping into a target applied to the board, even if the board is moved shortly before the jump.

In 2016, engineers from Disney Research presented their implementation of the spring-loaded reverse pendulum . It uses a leg with one segment that rotates relative to the body. Because of this design, the robot can maintain equilibrium only for a short period of time – the record sequence of jumps lasted 6.5 seconds.

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