24-01-2015 20:13

cmrnpizzo14

Re: pic: Captain Whidbey's Proswishper is walking down the stairs!

I love the battery shifting idea! I would be a little nervous of something happening and it disconnecting mid match but I think that it is a really ingenious and clever solution to the CoG problem that many teams will face this year.

Is it essentially a smaller scale mechanism like this: https://www.youtube.com/watch?v=g-vi...njfEn4l1LE jj

24-01-2015 21:57

asid61

Re: pic: Captain Whidbey's Proswishper is walking down the stairs!

First off, I hope you have the weights of everything in CAD.
Second, moving the battery might not be enough to shift the COM to lift, say, a six stack without tipping. If you have COM in in CAD, disregard.

What size stacks are you planning to make? If you are going 6 stacks, how are you lifting them onto the step?
Do you have plans to get cans?

25-01-2015 00:56

nathannfm

Re: pic: Captain Whidbey's Proswishper is walking down the stairs!

Are you saying you plan to have 2 redundant mechanisms on your robot or did you simply CAD (maybe build) both and will see which one you prefer?

25-01-2015 02:12

eedoga

Re: pic: Captain Whidbey's Proswishper is walking down the stairs!

The back lift mechanism is for doing a three tote autonomous...The front lift mechanism is for driving and manipulating totes in any orientation...Not planning on lifting a 6 tote stack...Three at most which we know will slow us down, but we are hoping to make up for that by contributing a 3 tote autonomous. We are hoping to be part of a team...not the whole shebang...

As for the COG...We can also tilt both lift mechanism back over the center of the robot which will hopefully help out a bit...We are using the Dart actuators for that which we know is overkill, but...

As for weight, we still aren't sure...We made some changes after CAD and are doing some other things to lighten the load...IE replacing bolts with rivets and 8020 with square tube... We will post more later next week when we have a better idea as to what the whole thing will weighs.

Honestly we are sort of really hoping with fingers crossed that this works out like we hope it will...

Edoga

25-01-2015 08:47

g_sawchuk

Re: pic: Captain Whidbey's Proswishper is walking down the stairs!

This is essentially the exact robot design that I wanted to do, minus the genius battery shifter. Well done.

26-01-2015 08:42

RunawayEngineer

Re: pic: Captain Whidbey's Proswishper is walking down the stairs!

I'm happy to see a battery counterbalance. When I saw the CoG issues that were going to come up, a shifting battery was one of the first things I thought of - but I wasn't sure that a team would take the risk of making their robot's heart mobile.
I would have thought that this approach would be most beneficial to a team going for a 6 stack since that is the worst case scenario for CoG shift. Is it to address the issue of tipping, or is it to distribute weight on the wheels? How significantly does it control CoG?

26-01-2015 12:21

eedoga

Re: pic: Captain Whidbey's Proswishper is walking down the stairs!

To be honest...We currently don't know...

Our CAD model (Autodesk Inventor is way off currently...Mostly because of imported parts that aren't accurate and post design revisions. We need to redo a lot of our modeling in order get a more accurate understanding of what is happening when we move the battery.

We also don't have an accurate measure of our current robots weight. We broke our scale and need to fix it or get a new one before we can get things accurately figured out in order to do the math.

The idea of moving the battery came from the original plan/community request to use Mecanum wheels. In the past we have had trouble with robots being off balance which makes it difficult to get the robot to move sideways.

We had originally planned on moving the battery to help balance out the weight on the wheels.

To help with COG while lifting heavy loads of totes we are leaning the tote stack in a bit over the robot in conjunction with moving the battery. We are hoping to move the COG over the contact patch by leaning the stack.

We also don't plan to lift major loads. We plan to stick to three or four totes at the most, though bigger lifts may prove necessary as things go on.

Edoga

26-01-2015 13:39

RunawayEngineer

Re: pic: Captain Whidbey's Proswishper is walking down the stairs!

Thanks for the reply. I wish your luck with your scale troubles.
I'm sure you've considered this, but for the benefit of anyone reading - this is one of those scenarios where you have a really clever idea, but you still have to figure out if it actually helps you or not.
Luckily, there are a couple ways to figure it out. The math will give you a numerical answer with reasonable accuracy. However, the number might not tell you as much as you would hope: if it improves evenness of weight distribution by 15%, is that worth the investment to make it work? Still, if the numbers show some truly unimpressive numbers, that is an early way to dismiss an idea.
I think you might be better off just testing it out: put the battery in one spot, have your driver try it out - then move the battery and try again. Of course this requires you have a mostly complete robot already.

26-01-2015 14:16

eedoga

Re: pic: Captain Whidbey's Proswishper is walking down the stairs!

At this point we are so committed to the concept that we might as well go with it unless we have a weight issue, which we will know in about a week...

Now a good thing is if we are underweight...We can add weight to the battery tray which would increase its effect...Though that is unlikely given the size of the robot.

Edoga