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Author Topic: Self balancing 2 wheel robot  (Read 7135 times)

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Offline newInRoboticsTopic starter

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Re: Self balancing 2 wheel robot
« Reply #30 on: December 10, 2010, 04:27:42 PM »
The stall current may be 9.6A BUT when changing direcion from full reverse to full forward this can double! but don't panic.

This is something unbelievable; I've always thought that cannot draw more than stall current. Stall current is drawn when motor is... well... stalled, so how can current consumption go beyond that?


when balancing the goal is to stand still ,, ie 0 amps, and at a few degrees off you will only be using very low PWM % to correct . I have used NiMH 2.5 AH AA which give me hours (weeks) of development time per charge, they wont give 9.6A but are you sure you need it for initial tuning ? the motors burn the Amps mostly when they try to run off the table and you have to catch it !, have fun.

This is very useful tip, I've never thought of it this way.
By any chance You could post Your robot configuration:
  • Number of batteries used
  • Weight of robot
  • Motor stall current
  • Motor voltage
  • Motor torque
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Offline Soeren

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Re: Self balancing 2 wheel robot
« Reply #31 on: December 11, 2010, 05:18:03 PM »
Hi,

The stall current may be 9.6A BUT when changing direcion from full reverse to full forward this can double! but don't panic.

This is something unbelievable; I've always thought that cannot draw more than stall current. Stall current is drawn when motor is... well... stalled, so how can current consumption go beyond that?
The motor is a large inductor and when shifting direction, it will try to maintain current flow in that direction, so you need to feed this amount plus what you need to go the other way.
However, I don't think it would be an issue in your case.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline newInRoboticsTopic starter

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Re: Self balancing 2 wheel robot
« Reply #32 on: December 12, 2010, 09:29:08 AM »
Quote
The motor is a large inductor and when shifting direction, it will try to maintain current flow in that direction, so you need to feed this amount plus what you need to go the other way.

If You put it this way, it does make sense.


Coming back to capacity of battery, is there a way to calculate how much I need (without actually measuring average usage)?

If there is no way to do it, then, what would be the best guess?
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

Offline waltr

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Re: Self balancing 2 wheel robot
« Reply #33 on: December 12, 2010, 02:53:25 PM »
Quote
Coming back to capacity of battery, is there a way to calculate how much I need (without actually measuring average usage)?
There is an SoR Energy calculator in the tutorial section that gives a fair guess.

Offline newInRoboticsTopic starter

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Re: Self balancing 2 wheel robot
« Reply #34 on: December 13, 2010, 03:23:26 PM »
Quote
Coming back to capacity of battery, is there a way to calculate how much I need (without actually measuring average usage)?
There is an SoR Energy calculator in the tutorial section that gives a fair guess.

I do want to use it, that's why I asked certain questions about values I have to enter. Look below.

Quote
When I use Energy Calculator how can I determine Travel Distance (per Trip) and number of Trips if robot is balancing only and is not actually doing a Trip?

If I finally get Required Battery mAh I would use it in Battery Calculator; however, there is another problem. As robot balances, motors should be switching on and off all the time and going from stall to idle constantly.

How can I determine Expected Current Draw and Time % Motors Used?
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

Offline waltr

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Re: Self balancing 2 wheel robot
« Reply #35 on: December 13, 2010, 07:21:23 PM »
Ahh...sorry I don't recently see that post, only the last question.

Until you build the bot and actually measure the current draw you do have to make a guess.
So you could use a worst case with high percent of time at Stall current.

Quote
No offence, but I don't like guessing. I prefer mathematical calculations
In this case you would need to model the complete electromechanical system which is not trivial. Or make measurements with parts of the system, like one leg joint, then extrapolate to the entire system.

Offline newInRoboticsTopic starter

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Re: Self balancing 2 wheel robot
« Reply #36 on: March 13, 2011, 03:04:05 PM »
Time to take up this project again :) Submission date is getting closer and closer...

What is a useful range for gyro for such self balancing robot? Would -/+300 deg/s is good enough, or should I look for something closer to -/+150 deg/s or even -/+50 deg/s?
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

 


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