Cones falling off mobile goals

So when I deploy a mobile goal with cones on it, the cones fall off depending on how many cones are on there. Anyone know how to solve this problem?

What type of lift do you have? Because if you have a DR4B with a chainbar/4bar then you can hold the top of the stack to keep the stack together. :slight_smile:

Yes, I have a dr4b with a chainbar, but I want to be able to do it purely by code just incase.

Less power for a slower deploy maybe? Our team has the deploy power lower than the uptake power.

Do you know what the specific issue is?

Yes, due to the acceleration of the mobile goal lift, the mobile goal hits the ground hard causing it to knock the cones off. A slower deploy might help a bit, but the mobile goal lift will still accelerate causing the mobile goal to hit the ground hard

You will need to have a potentiometer installed on the MoGo lift to tell you its angle/position.

As it gets close to the ground you will need to reduce motor power by, let say, a half. When it gets even closer - reduce it to a third, and when potentiometer reads a value corresponding to the full out position you cut it to something like 10 or 5 power units.

This way not only it should solve your ground impact issue, but reduce the stress on the motors and MoGo lift’s mechanical components. You will need to do the same power reduction for the top position as well.

While some of this stress can be alleviated through correct programming as stated in the above posts, there is also a huge mechanical factor to this. Make sure your mogo intake uses screws to connect the linkages (not axles, as they have more play), and that the mechanism overall does not have too much give. Too much give allows the weight of the mogo to shift the entire mechanism around depending on what position it’s in, so it may not go down perfectly parallel to the ground because of the mechanism’s give, which would case the front of the mogo to hit the ground first, which is even worse than hitting it down hard, as now there is an angle that the cones want to fall off at.

Thanks for the idea, but the mobile goal does go down parallel to the ground, its nothing with hardware, but more on the programming side is what I need help with

I believe @technik3k has already solved the problem for you. Just make a P loop or something

summarizing what @technik3k said, you need a P from PID to control power and allow your mogo to sorta “coast” down to where it needs to go

You could also put rubber bands that stretch out when you deploy your mogo lift to help slow it down

Simple P was not enough for my team, because P will never reverse the power and, to sufficiently slow our mobile goal, we require some power in the reverse direction. We used PD, with a ridiculously high kD (100 x kP).

How would you tune the PID constants with lifts? I know how to tune them for drives.

Add rubber bands so it raises faster and drops slower. That’s the simplest solution in my opinion. Other than that making a slower release or bigger ratio on the lift could help. Also make sure the mobile goal is staying as strait as possible when releasing because that will eliminate a lot of rocking when the mogo hits the ground.

Exactly the same way?

Yeah, do it the same way. Adjust it until it works for you.

Just play around with them until it works. I’d start with 0.049 for the P and tune it from there.