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Unread 06-30-2017, 01:22 PM
PatrickW PatrickW is offline
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pic: Swerve Module, 2910 Off Season

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Unread 06-30-2017, 05:02 PM
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Re: pic: Swerve Module, 2910 Off Season

Love the spinning bevel gear! Make sure to keep those front 775Pro vents fully exposed for the best results.

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Unread 06-30-2017, 05:28 PM
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Re: pic: Swerve Module, 2910 Off Season

Looks really cool! 2 775pros and a bag per module seems like a lot to me (not many pdp ports left), but the designs look really cool! One question- what is the purpose of the second gear that has a little yellow thing off the top? What is the yellow thing? Looks kind of like an encoder shaft, and if so I am curious why you opted not to use the Versaplanetary Integrated Encoder for your turning.

I really love how space efficient your modules are, and love the design! Great job!!
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Unread 06-30-2017, 06:50 PM
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Re: pic: Swerve Module, 2910 Off Season

what's the reason behind a BAG motor for turning rather than using another 775? Is it size?
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Unread 06-30-2017, 07:39 PM
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Re: pic: Swerve Module, 2910 Off Season

Quote:
Originally Posted by SpruceyBrucey View Post
what's the reason behind a BAG motor for turning rather than using another 775? Is it size?
BAG motors have a much lower RPM than the 775pro, thus requiring less of a reduction to have a module that turns reasonably. This can potentially save weight and such depending on how you treat it.
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Unread 06-30-2017, 07:54 PM
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Re: pic: Swerve Module, 2910 Off Season

Quote:
Originally Posted by marcusbernstein View Post
One question- what is the purpose of the second gear that has a little yellow thing off the top? What is the yellow thing? Looks kind of like an encoder shaft, and if so I am curious why you opted not to use the Versaplanetary Integrated Encoder for your turning.
The little yellow thing with a gear on it is one of the US Digital MA3 absolute encoders available from AndyMark. The primary reason I choose not to use the Versaplanetary Integrated Encoder was because the output shaft of the Versaplanetary is not a 1:1 ratio to the rotating part of the module. The way it is geared, the steering encoder is a 1:1 ratio with the rotating module. With the 1:1 ratio, the output of the absolute encoder will directly correspond to the steering angle of the wheel. It just makes it a little bit simpler to program and eliminates the need to have the modules pointed in a certain direction when the robot is turned on or something to that effect.

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Originally Posted by SpruceyBrucey View Post
what's the reason behind a BAG motor for turning rather than using another 775? Is it size?
A 775 can be used as the steering motor. It fits fine and you should be able to get the reduction need with the 2 stage versaplanetary and the 3:1 from the toothed belt. I just though it would significantly overkill power wise.
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Unread 06-30-2017, 08:00 PM
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Re: pic: Swerve Module, 2910 Off Season

Quote:
Originally Posted by SPang View Post
BAG motors have a much lower RPM than the 775pro, thus requiring less of a reduction to have a module that turns reasonably. This can potentially save weight and such depending on how you treat it.
We actually used a 775pro over the BAG this year and ran it at 6-8V. So there isn't that big of a difference between the two. If anything at 6V the 775pro is @ 9-10k rpm. I only see reduction mattering if your making a custom steering setup and want it to be more compact.

With the Vp's your going to have to do a 2 stage reduction and at that point you can achieve whatever gearing you want from 12:1 to 100:1! So your not gaining anything using a BAG over a 775pro and vice versa (maybe weight?)
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Unread 06-30-2017, 08:09 PM
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Re: pic: Swerve Module, 2910 Off Season

[quote=PatrickW;1691100]The little yellow thing with a gear on it is one of the US Digital MA3 absolute encoders available from AndyMark. The primary reason I choose not to use the Versaplanetary Integrated Encoder was because the output shaft of the Versaplanetary is not a 1:1 ratio to the rotating part of the module. The way it is geared, the steering encoder is a 1:1 ratio with the rotating module. With the 1:1 ratio, the output of the absolute encoder will directly correspond to the steering angle of the wheel. It just makes it a little bit simpler to program and eliminates the need to have the modules pointed in a certain direction when the robot is turned on or something to that effect.

Seems like you can save some parts, complexity with your pulley/gear combo part, and potentially weight (dependent on how much a vp encoder vs you encoder +3d prints weigh) by just using an integrated encoder. The software end is pretty simple, just multiply or divide the encoder input by the ratio it's running on. The VP integrated encoders can do both absolute and relative sensing, so it should be just as easy to program with the multiplier, and simplify your design a bit.
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Unread 06-30-2017, 08:27 PM
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Re: pic: Swerve Module, 2910 Off Season

Quote:
Originally Posted by marcusbernstein View Post
Seems like you can save some parts, complexity with your pulley/gear combo part, and potentially weight (dependent on how much a vp encoder vs you encoder +3d prints weigh) by just using an integrated encoder. The software end is pretty simple, just multiply or divide the encoder input by the ratio it's running on. The VP integrated encoders can do both absolute and relative sensing, so it should be just as easy to program with the multiplier, and simplify your design a bit.
If you turn the module while the robot is off, the encoder cannot keep track of the true angle of the module. If the ratio is 3:1 for example, turn the module 1/3rd of a rotation while the robot is off. The absolute encoder will still report zero, but the module will be in a majorly different position.
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Unread 06-30-2017, 09:31 PM
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Re: pic: Swerve Module, 2910 Off Season

Quote:
Originally Posted by nickbrickmaster View Post
If you turn the module while the robot is off, the encoder cannot keep track of the true angle of the module. If the ratio is 3:1 for example, turn the module 1/3rd of a rotation while the robot is off. The absolute encoder will still report zero, but the module will be in a majorly different position.
Typically a hall effect sensor can be used to zero the module, and the quadrature portion of the integrated encoder used for rotation tracking to be gear-ratio independent. I would still do this with absolute encoders, as I've had issues with them moving for one reason or another before. I am 100% certain somebody will chime in with a "but that never happened to us! You must have done something wrong" and I agree- I'm sure that it's possible to do that. But it's not guaranteed that it'll work. The integrated encoder with a zeroing mechanism is hard to make fail, by comparison. Just make sure you always trigger the hall effect in the same direction or hysteresis can throw you off.
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Unread 07-01-2017, 01:32 AM
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Re: pic: Swerve Module, 2910 Off Season

Quote:
Originally Posted by nickbrickmaster View Post
If you turn the module while the robot is off, the encoder cannot keep track of the true angle of the module. If the ratio is 3:1 for example, turn the module 1/3rd of a rotation while the robot is off. The absolute encoder will still report zero, but the module will be in a majorly different position.
This is 100% correct and is the main reason I choose not to use the VersaPlanetary encoder (or any absolute encoder turning with the VersaPlanetary output shaft).

When you turn the robot on the VersaPlanetary encoder would know the absolute position of the versaplanetary output shaft. The problem is that the module will be at 1 of 3 possible positions. Without an additional limit switch or encoder or something to know which of the 3 possible positions the module is in, you will need to make an assumption. An example of such an assumption would be that all the modules are generally pointed in the forward direction.

I don't want to add the complexity of an additional sensor, and I also don't want to rely on the drive team having the wheels facing a certain direction when the robot is placed on the field. That's why I choose to have a single absolute encoder 1:1 with the rotation of the module.
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Unread 07-02-2017, 06:39 AM
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Re: pic: Swerve Module, 2910 Off Season

Quote:
Originally Posted by asid61 View Post
Typically a hall effect sensor can be used to zero the module, and the quadrature portion of the integrated encoder used for rotation tracking to be gear-ratio independent. I would still do this with absolute encoders, as I've had issues with them moving for one reason or another before. I am 100% certain somebody will chime in with a "but that never happened to us! You must have done something wrong" and I agree- I'm sure that it's possible to do that. But it's not guaranteed that it'll work. The integrated encoder with a zeroing mechanism is hard to make fail, by comparison. Just make sure you always trigger the hall effect in the same direction or hysteresis can throw you off.
This is also very easy to achieve with a passable limit switch. (basically the button is pressed as a certain spot on the module passes it, but allows the module to continue past it in both directions.) Always zero it moving the same direction though to account for even the slightest mechanical slop.
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Unread 07-02-2017, 08:59 AM
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Re: pic: Swerve Module, 2910 Off Season

I think you might be underestimating the 775 pro here. I think you might also be underestimating the impact of using 12 motors on a drivetrain.

I'd suggest you compare the current draw and the max torque of these two modules at a similar wheel speed. (That methodology because you'll never hit top speed, but you can use that torque to push.) You might find that one of your modules is twice as powerful as the other, but impractical on an electronic level
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Unread 07-03-2017, 11:57 AM
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Re: pic: Swerve Module, 2910 Off Season

What do you have pipe clamped to the top of the one 775? A shaft encoder? If so, is this custom or did you get it somewhere?
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Unread 07-03-2017, 12:18 PM
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Re: pic: Swerve Module, 2910 Off Season

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Originally Posted by cbale2000 View Post
What do you have pipe clamped to the top of the one 775? A shaft encoder? If so, is this custom or did you get it somewhere?
Looks like this
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