At first, we thought this robot was like a rabbit until we realized rabbits have a 300% bonus in the leg department. SALTO — a robot from [Justin Yim], [Eric Wang], and [Ronald Fearing] only has one leg but gets around quite well hopping from place to place. If you can’t picture it, the video below will make it very obvious.
According to the paper about SALTO, existing hopping robots require external sensors and often are tethered. SALTO is self-contained. The robot weighs a tenth of a kilogram and takes its name from the word saltatorial (adapted for leaping ) which itself comes from the Latin saltare which means to jump or leap.
The robot considers itself in four distinct modes: stance is when it is standing on the ground, liftoff is when it is launching itself, flight is in the air, and touchdown is when it reconnects with the ground. Balancing the robot during stance is old hat, of course. But upon liftoff, the robot computes an error term for the velocity and uses that to compute a correction value. The robot has a tail and two small propellers to control its attitude.
At the start, the robot balances on three points: its toe, its rear ankle, and one end of its tail. Using gyros, it is able to set initial values. It then stands up in different poses and uses the thrusters to zero out any roll and pitch.
We were not far into the video before we wondered if the beastie could climb stairs. It can’t. According to the authors say that estimate errors mean the foot can move up to a half meter away from where you wanted it to land. However, they believe future versions will have improved estimation that would let it climb stairs, leap over furniture or other obstacles, and handle a variety of terrain. We only hope they print the poor thing a kangaroo body.
Jumping robot always brings back our nightmares of Atlas breaking down our bedroom door. He has no problem with stairs. We’ve also seen a prototype lunar rover that can jump over things, even though that’s not its primary mode of locomotion.