
Jumping Robot Salto-1P Now Goes Where You Tell It To - sohkamyung
https://spectrum.ieee.org/automaton/robotics/robotics-hardware/jumping-robot-salto1p
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Animats
Nice. I used to work on that problem, because I was into legged running for
robots and animation. Rather than putting fans on the "torso" to provide
torques, I was doing that by having a leg with three joints and coordinating
them to apply torques to the torso.[1] This is how far I got. (Video,
generated on a Mac IIci. Hours of run time for seconds of simulation.)[2] I
notice the Berkeley group is using three joints, too. They should't need those
fans to exert side forces.

The real objective was to be able to handle running on slanted surfaces.
That's all about slip control.

I looked at this as a two-point boundary value problem with an underactuated
controller. You want to get a specific orientation, angular rate, and target
position at landing. You have more target variables than you have actuators.
You don't care too much about the intermediate states as long as the state at
landing is what you wanted. That's rocket science. Which is good, because
rocket trajectory control is a well understood problem.

Once you start solving this as a boundary value problem, you can make much
more aggressive moves. Going way off balance to get a fast change of speed or
direction is fine as long as the next landing is within bounds. Most running
robots today start out running in place and slowly accelerate forward. They
don't start by leaning forward and launching. That's because they work by
trying to maintain a stability criterion. In slow robots, that's static
stabiilty - CG over base. Faster ones use "ZMP", which is a generalization of
static stability which adds a momentum term.

There are newer approaches, and the most recent Boston Dynamics robots are
going into unstable positions to do things like flips, then recovering to a
stable position. That's looking one move ahead. If you can look two moves, or
footfalls, ahead, you get much more agility. Some of martial arts and dance is
learning sequences of three moves ahead. That's an athletic feat. You need two
moves ahead to do broken-field running or the stop by turning that horses do,
which is within the normal range of ability.

Fun problem, but decades later, still no market.

[1]
[http://www.animats.com/papers/articulated/articulated.html](http://www.animats.com/papers/articulated/articulated.html)

[2] [https://www.youtube.com/watch?v=kc5n0iTw-
NU&feature=youtu.be...](https://www.youtube.com/watch?v=kc5n0iTw-
NU&feature=youtu.be&t=104)

~~~
Isamu
I want to encourage you to expand on what you describe as broken-field
running. By two moves ahead you mean that you are planning not only for a
particular path and rate but for a rate of change as well, possibly both in
direction and speed.

~~~
Animats
OK. Think of it this way. Suppose you have a basic controller for a biped
which can achieve a stable stand after a landing on one foot provided that the
velocities are within certain limits. With a controller like that you can walk
or jog a little. That's classic Asimo-level locomotion.

The limits within such a controller can recover define a target basket. If you
can land within the target basket, you don't fall down. Unstable moves should
end with a landing inside that target basket, leading to a stable state.

Next, you want to go from a standing start to a fast run in one stride. You
lower the torso (probably by bending the knees, but it could be a piston-type
motion), fall forward, and at some angle, launch. While in the air, you make
the appropriate maneuvers to land on one foot within the target basket of the
basic controller. Doing that is a two-point boundary value problem. That's
planning one move ahead. One wildly unstable step and a controlled landing
within the target basket of the basic controller. That's Boston Dynamics's
flip.

Now if you could do two unstable footfalls in succession, you'd have a much
more powerful system. You could do two unstable steps and then land in the
target basket and let the basic controller take over for a safe stop. But you
now have the option of taking one unstable step and then planning two more if
possible for fast changes in speed and direction. There's always the
possibility of sticking with the original plan that lands you in the target
basket for a safe stop. But, while in flight for the first unstable step, you
can try planning a new two-step plan. If that problem can be solved, you can
continue with agile motion. If not, you fall back to the original plan and end
up stopped but safe.

Two point boundary problems can be solved using known techniques. See
"shooting method" and "relaxation method", both of which are optimization
schemes. Solving two two-point boundary problems in sequence is harder and
requires looking through a big solution space, but everybody is doing gradient
descent in bumpy spaces now and it's less mysterious than it used to be.

Good PhD thesis problem for someone. Startup potential, not so much.

------
xyproto
Now please like a large one, with a seat for one person.

~~~
wst_
And paper bag. Just in case.

~~~
xyproto
Surely it should be possible to dampen the seat, so that it could become
comfortable enough for at least day-to-day grocery shopping?

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colordrops
I know it doesn't make sense but somehow using drone propellers for yaw and
roll seems like cheating.

------
metaphor
It's outright terrorizing to imagine what a weaponized TRL9 swarm successor of
this could do just from a psychological warfare perspective...gives me anxiety
just thinking about it.

~~~
compelledToken
The deployment of a swarm of these things in any context is a great reason to
retaliate with nukes. Or at least B-52 carpet bombing.

But, then again, anybody without nukes or B-52 squadrons is out of luck.

