Undergrad Self balancing stick based on flywheels

[RubinLicht]

so I recently saw a video where a stick had two flywheels attached on the top, they would accelerate or decelerate based on the pitch of the stick.

my question= if you delivered enough impulse do the stick, would the stick stop being able to balance? since the restoring torque is based on acceleration, if you push in one direction, it'll have to keep accelerating to generate an opposite torque. what happens when you can't accelerate the motor any more?

 

[anorlunda]

Can you provide a link to the video?

 

[RubinLicht]

 

[rumborak]

Given how the motor has a limited amount of torque it can exert through acceleration, I would think it's rather obvious that there will be an amount of impact above which the motor can not counteract.

 

[RubinLicht]

that was not what I asked. my question is about how a restoring torque is limited by how long the motor can speed up for.

what I mean is, the flywheel can only general a restoring torque through ACCELERATION, what this implies, is if you need to generate a constant restoring force, you need to accelerate for the entire time. however, there's clearly a point where the flywheel cannot accelerate past. so, how relevant is this limit? if you impart a non zero vector sum of impulse to the rod, will it eventually not be able to balance anymore?

 

[rumborak]

Your question comes down to, can you indefinitely accelerate a motor? I think the answer is kinda obvious.

 

[A.T.]

if you delivered enough impulse do the stick, would the stick stop being able to balance?

Trivialy yes.

since the restoring torque is based on acceleration, if you push in one direction, it'll have to keep accelerating to generate an opposite torque.

You are ignoring gyroscopic effects here.

 

[RubinLicht]

Sorry, I was confusing it with the cubli, which minimizes the flywheel velocities so that gyroscopic effects are negligible.

I was wondering, if you stopped just short of the motor reaching max rotational speed, would there be a way to "reset" the default rotational speed back to zero, or are you just stuck with the new "default" speed, which is very close to the max rotational speed.

cubli :

 

[jbriggs444]

I was wondering, if you stopped just short of the motor reaching max rotational speed, would there be a way to "reset" the default rotational speed back to zero, or are you just stuck with the new "default" speed, which is very close to the max rotational speed.

Yes.

If a motor was near maxing out in one direction, one would want the control system designed to generate a little extra torque with the last bit of available angular momentum. Enough extra to tip the stick back the other way. Then the motor could slowly spin down.

The same basic scheme is used on a Segway, a unicycle or a man walking down the street. If one is close to the limiting speed in one direction, it is time to push extra hard in that direction, cancelling the original lean angle, generating a reverse lean and slowing back down.

 

[RubinLicht]

ah yes I understand now. thanks.