Self balancing stick based on flywheels

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Discussion Overview

The discussion revolves around the mechanics of a self-balancing stick that utilizes flywheels for stabilization. Participants explore the implications of imparting impulse to the stick and how it affects the ability to maintain balance, particularly focusing on the limitations of motor torque and acceleration in generating restoring forces.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a stick with flywheels can maintain balance if enough impulse is delivered, suggesting that the restoring torque relies on continuous acceleration.
  • Another participant asserts that there is a limit to the torque a motor can exert, implying that beyond a certain impact, the motor may not be able to counteract the forces effectively.
  • A participant clarifies that the restoring torque is contingent on acceleration, raising concerns about the implications of reaching the motor's maximum rotational speed.
  • There is a discussion about the possibility of "resetting" the default rotational speed of the flywheels if they approach maximum speed, with one participant suggesting that a control system could manage this effectively.
  • Gyroscopic effects are mentioned as a factor that may influence the dynamics of the system, with a participant acknowledging confusion with another system (the cubli) that minimizes flywheel velocities.

Areas of Agreement / Disagreement

Participants express differing views on the limits of motor acceleration and the implications for balance. While some agree on the existence of a maximum torque limit, there is no consensus on the exact mechanics of how impulse affects balance or the feasibility of resetting rotational speeds.

Contextual Notes

The discussion includes assumptions about motor capabilities and the nature of restoring torque, which may not be fully explored or defined. The relationship between impulse delivery and balance remains unresolved.

RubinLicht
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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?
 
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Can you provide a link to the video?
 
 
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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.
 
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?
 
Your question comes down to, can you indefinitely accelerate a motor? I think the answer is kinda obvious.
 
RubinLicht said:
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.
 
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 :
 
RubinLicht said:
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.
 
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ah yes I understand now. thanks.
 

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