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Unread 14-01-2017, 10:57
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Re: Shooting Motors and wheels

Quote:
Originally Posted by jojoguy10 View Post
As a follow-up to the question, does anyone know of any papers/guides on building high shooters?
The best guide for making new systems is to prototype a lot, and to take inspiration from past robots from previous years.

No paper will ever have the one answer for you, your team, and your needs.
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Unread 14-01-2017, 11:03
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Re: Shooting Motors and wheels

Quote:
Originally Posted by Kyle Heaton View Post
The best guide for making new systems is to prototype a lot, and to take inspiration from past robots from previous years.

No paper will ever have the one answer for you, your team, and your needs.
I agree, and don't forget kids, CHECK YOUR WIRING! )
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Unread 14-01-2017, 19:31
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Smile Re: Shooting Motors and wheels

Thanks for all the help, our prototype is shooting 6 out of 12 balls and the rest of overshooting. We r now just adjusting the compression and hood. As most of the comments said it's just trial and error
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Unread 14-01-2017, 20:43
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Re: Shooting Motors and wheels

How are you controlling your motor at the moment? If you're not doing closed loop speed control, you're going to have some difficulty getting good accuracy at a high rate of fire. If you ARE doing closed loop speed control, you want to set your gearing so the motor is spinning at about 50% max speed when you're at your target speed for firing. That'll give you the best control and recovery time.
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Unread 15-01-2017, 02:14
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Re: Shooting Motors and wheels

We r just have it hooked from wires to battery
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Unread 15-01-2017, 02:18
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Re: Shooting Motors and wheels

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Originally Posted by YashBrowns View Post
We r just have it hooked from wires to battery
We do have vision tracking though if u that's what you mean by a closed loop
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Unread 15-01-2017, 02:32
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Re: Shooting Motors and wheels

You want to hook up a sensor (encoders, etc) to measure the RPM of your flywheel. Differing flywheel speeds will result in different shots.
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Unread 15-01-2017, 02:34
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Re: Shooting Motors and wheels

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Originally Posted by YashBrowns View Post
We do have vision tracking though if u that's what you mean by a closed loop
It's not. He's talking about closed-loop speed control.

Open-loop speed control is what you have now. In short, it goes like this:
RIO tells motor: Go this fast

Closed-loop speed control is better for ranging accuracy. It goes like this:
RIO: Motor, go this fast.
Encoder: Hey, RIO, motor is going this fast.
RIO: *checks number from encoder against commanded number* Motor, I need more (or less) speed out of you.
Encoder: Hey, RIO, motor is going this fast.

Repeat.


The reason you want closed-loop is to keep the motor at shooting speed as much as possible--stuff being launched tends to slow wheeled shooters until it leaves the "muzzle".
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Unread 15-01-2017, 11:42
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Re: Shooting Motors and wheels

Quote:
Originally Posted by YashBrowns View Post
We r just have it hooked from wires to battery
This is not ideal.

As a first whack, OK (despite the very big lack of safety), but now at least get a big fuse or circuit breaker in there.

Very much preferred at this stage - a week in - is to have the RoboRIO controlling it through a motor controller. This way you can:
1. Adjust the speed very finely so accuracy is spot-on
2. Use a speed sensor on the motor or wheel to (try to) keep the wheel speed constant, so ball #12 goes to the same spot as ball #1.
3. Get a better idea of what you will see in reality when the robot is actually doing the controlling (The motor controller doesn't give as much voltage to the motor as a direct connection might).

All of these point more towards success. Yes they require effort, but do you want to win or watch?
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Unread 15-01-2017, 12:00
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Re: Shooting Motors and wheels

So looking up an encoder will control the speed of the wheels and motor which will help increase accuracy
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Unread 15-01-2017, 12:45
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Re: Shooting Motors and wheels

Quote:
Originally Posted by YashBrowns View Post
So looking up an encoder will control the speed of the wheels and motor which will help increase accuracy
Tell us what language you plan to use to code your robot and you may get more detailed advice and help.


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Unread 15-01-2017, 14:15
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Re: Shooting Motors and wheels

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Originally Posted by Ether View Post
Tell us what language you plan to use to code your robot and you may get more detailed advice and help.


We r using c++ most likely
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Unread 15-01-2017, 17:25
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Re: Shooting Motors and wheels

For quick prototyping we wire up a motor controller in between the battery and the motor (and an in-line automotive fuse) and then use the thrifty throttle from Andymark to control the motor controller. This allows students to vary the speed of the motor to try various experiments. At $29 it's a lot cheaper than tying up a robo-rio for this and it's a lot quicker to set up.
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