Forwards and Backwards Ball Pickup

[Brandon_L]

Originally Posted by bEdhEd

It is well known that an effective rolling ball pickup that has two rollers needs to have the top roller in front of the bottom roller in order to pick up this year's game ball with few or no problems.

But do you really need a top and bottom roller?

[bEdhEd]

Originally Posted by Brandon_L

But do you really need a top and bottom roller?

It all depends on what you're trying to do. For us, we are trying to grab and lift the ball up with an arm mechanism to launch it, and pick up both sides so two rollers can be useful.

With a robot has a one roller over-the-bumper-intake, or most robot designs that I could think of for that matter, two rollers wouldn't be as necessary.

[Chris is me]

I don't think if you can solve this problem you should take on the complexity of a double sided intake. I know what you're trying to do and it seems tempting to pickup from both sides but I think once you abandon double sided pickup you'll find it's a lot easier to package everything anyway.

To answer your question: I bet a properly sized chain linkage could angle your claw such that it's pointing "down" on either side of the robot. Doesn't even need an extra motor if you do it right.

[bEdhEd]

Originally Posted by Chris is me

I don't think if you can solve this problem you should take on the complexity of a double sided intake. I know what you're trying to do and it seems tempting to pickup from both sides but I think once you abandon double sided pickup you'll find it's a lot easier to package everything anyway.

To answer your question: I bet a properly sized chain linkage could angle your claw such that it's pointing "down" on either side of the robot. Doesn't even need an extra motor if you do it right.

I would have to say that if a back/front intake requires an extra motor compared to one that is one sided, it isn't worth doing. Our design is simple (to my own standards, at least), easy to build, and requires no extra motors or power sources, so we want to give it a shot

[Chris is me]

Originally Posted by bEdhEd

I would have to say that if a back/front intake requires an extra motor compared to one that is one sided, it isn't worth doing. Our design is simple (to my own standards, at least), easy to build, and requires no extra motors or power sources, so we want to give it a shot

I've been working on a similar design concept (a well packaged claw on an arm pivoting about the center of the robot). What ultimately drove me away from using two rollers and thus picking up on both sides wasn't the extra motor requirement. For this design I wanted the rollers to articulate out of the way to allow for a clean fire from some spring force. With passive forks on the bottom instead of rollers, actuation for this motion became a lot simpler and lighter. If you're thinking something else entirely, then carry on.

[bEdhEd]

Originally Posted by Chris is me

I've been working on a similar design concept (a well packaged claw on an arm pivoting about the center of the robot). What ultimately drove me away from using two rollers and thus picking up on both sides wasn't the extra motor requirement. For this design I wanted the rollers to articulate out of the way to allow for a clean fire from some spring force. With passive forks on the bottom instead of rollers, actuation for this motion became a lot simpler and lighter. If you're thinking something else entirely, then carry on.

We do have a plan for our rollers to pivot out of the way for clean shot, so what you're thinking is what I'm thinking.. Even if a two roller back/front intake is not entirely practical, if my team can pull it off, and if it provides negligible problems and setbacks, i'd keep it for the fact that nobody else wanted to or couldn't do it, and therefore adding some cool factor.

[1493kd]

Having two intakes could also come in handy if you are trying to catch the ball. We are working on something along these lines. How well it works out is yet to be seen.

I appluad/enjoy it when teams do out of the box things that may or may not be of great benifit. As long as you are learning and having fun then that is all that matters. IMO

[bEdhEd]

Originally Posted by 1493kd

Having two intakes could also come in handy if you are trying to catch the ball. We are working on something along these lines. How well it works out is yet to be seen.

I appluad/enjoy it when teams do out of the box things that may or may not be of great benifit. As long as you are learning and having fun then that is all that matters. IMO

Exactly my opinion. I'd rather have my team have some challenging fun trying out stuff that few others are trying, because I find going the easier or more practical way a bit boring. I run into this all the time when I judge for FLL and VEX. Hardly any teams in these programs ever use sensors on their robots, because they tell me it's just easier that way. It may be true, but sensors are in every bit of technology we use daily, and when I judge teams that use sensors, and tried the harder way, I can tell that those students have learned more than the ones who tried the minimum, or the easier way.

I'm not trying to say that teams who may exclude difficult or unproven designs are not always learning as much as teams who go a different route, but the teams who dare to do something different will probably learn something that the cautious teams will not.

[atucker4072]

Having a way to pick up from both sides does have its advantages. I see what you are going for now. You are going to want a good balance between torque and speed in my opinion. Or you can keep your loader light enough so that you can have a reasonable amount of speed. I don't think it would be a good idea to have a way to pick up from both sides but have it take a while for it to get to each side. That's why I said why no just turn.

[Sparkyshires]

I'm gonna go ahead and post the unpopular opinion: why have a two sided pickup? There's only ever going to be one ball on the field, so long as you just keep track of it it really isn't necessary. Even if you're worried about the rebound, just have the robot turn 180 degrees be part of the shoot sequence. It's just gonna add more complication and an ounce more flair to teams when they try to appeal to scouters.

All in all, personally not worth it.

[Abhishek R]

Originally Posted by Sparkyshires

I'm gonna go ahead and post the unpopular opinion: why have a two sided pickup? There's only ever going to be one ball on the field, so long as you just keep track of it it really isn't necessary. Even if you're worried about the rebound, just have the robot turn 180 degrees be part of the shoot sequence. It's just gonna add more complication and an ounce more flair to teams when they try to appeal to scouters.

All in all, personally not worth it.

Not an unpopular opinion. That's probably the majority opinion, actually, it's much simpler for most teams.

[Kernaghan]

Just an idea: build an intake on one side, and spend the same time you would have taken to build a double sided intake, practicing.

Again just pure opinion, but I think we will see good robots with lots of practice beat amazing robots with little practice.

[bEdhEd]

Originally Posted by Kernaghan

Just an idea: build an intake on one side, and spend the same time you would have taken to build a double sided intake, practicing.

Again just pure opinion, but I think we will see good robots with lots of practice beat amazing robots with little practice.

I understand where you're coming from, and the amount of practice a team has determines the robot's performance, but we plan on building two robots like we have our past two seasons anyway, so we have all the time after build season to practice our drive team too. As long as I am their drive team mentor, I will always assure that both our drive teams have adequate practice to perform above the standard.

And if we don't build a second robot, well, let's just do everything to make sure two get built.

[bEdhEd]

Originally Posted by atucker4072

Having a way to pick up from both sides does have its advantages. I see what you are going for now. You are going to want a good balance between torque and speed in my opinion. Or you can keep your loader light enough so that you can have a reasonable amount of speed. I don't think it would be a good idea to have a way to pick up from both sides but have it take a while for it to get to each side. That's why I said why no just turn.

We have a tried and true system for having speed AND torque without compromising either. We call it the "battle axes" because they are arcs whose center points are on the axis of rotation, and have chain along the arc length, with a sprocket rotating on a motor mounted on the arm. It's basically a rack and pinion system, but curved. We put this on our 2013 robot last year since we had a long arm that not only held all four disks in a line, but also had two 6" AM performane wheels at the very end for shooting. This is a pic of what they look like.


http://www.chiefdelphi.com/media/img...16ffd890_l.jpg

The diameter is about a foot, so it's like being able to drive the arm with a 12" sprocket , and only using 2 FP motors.


We intend on using this type of system again this year for a full rotation. Our heavy arm last year took about a second to get from down to top position, and we plan on having the same success with it this year. Turning around and rotating the arm should both take about the same amount of time.

The big advantage I forgot to mention is that during autonomous mode, we will be able to grab balls from behind us without turning, in the likely event that a robot has an unreliable, ineffective, or no autonomous mode. Just have the ball touch the other robot, and have the ball right behind our robot, and have programs for one two, or all three ball autonomous modes. If an alliance member is a goalie, they can place the ball behind us when it's in between the truss and the zone line, and we will never have to remove a ball from the beginning of the match.

My team would not prefer to turn around during auto, but rather go forwards and back, and reduce the chance of bumping into an alliance partner during auto if anything goes wrong during this period of the match.