Articulated arm vs Forklift style arm

[IKE]

Originally Posted by sircedric4

For those with electrical arm and elevator experience, how do you keep your arm or forklift in the position you want it without power. How do you make the up and down appear so easy and controlled?

We have built a couple big arm bots and 1 forklift. There is a really good article with pictures of our 2007 bot in the Behind the Design book. It also discusses the controls. On both the 2005, and 2007 machines, we had a high axis arm with a large drive sprocket. We also used a 3-4" lever off the back of the arm and tied multiple loops of bungee. The bungee was very very tight. For 2005 there was approximately 200 lbs of downforce on those joints. make sure the bungee is fresh for that year (it degrades quickly especially if stressed). Also, when operating in cold environments, the bungee will stiffen. Warm it up to room temp before operating your arm otherwise funny stuff might happen.
The resolution with the shoulder joint was not the best due to the locking pins in the dewalt, and the use of FP motors which burn up in stall very easily. Because of this we had a forearm on both of those bots that would adjust relative to the shoulder position. Ideally you want angular feedback right at the actual joint for rotation. This will give you true position vs. using a sensor in teh chain loop that will have a little error from chain lash.

I don't remember what we used as the drum brake for our elevator in 2008. In fact, I am not sure that we had one.

[TheGreatPhil]

Originally Posted by Tom Ore

We're thinking of using static electricity to pick up the tubes. The programmers are trying to figure out how to make the robot shuffle it's feet on the carpet.

Good luck with that, if you really want to go with static electricity I'd recommend using capacitors to build up charge.

[TEE]

Originally Posted by TheGreatPhil

Good luck with that, if you really want to go with static electricity I'd recommend using capacitors to build up charge.

I think he was joking

[Snowbotics]

Originally Posted by davidcone315

My team is considering using a vacuum to pick up the tubes instead of an arm, does anybody think that is a bad idea?

My team has personally experimented with suction in the 2007 game and we were met with great disappointment and in the end failure to that idea.

[keehun]

Originally Posted by Snowbotics

My team has personally experimented with suction in the 2007 game and we were met with great disappointment and in the end failure to that idea.

Team 2502 has a mentor that is a salesman at a pneumatics company and deals with all sorts of pneumatics and industrial extruded materials.

He brought in his kit of vacuum products with all assortment of cups (standard to weird shaped ones) and all sorts of valves and vacuum modules and items of that nature and we tried everything. It held on to the tubes REALLY well and even held tightly when shook... But once we put our hand to one of the father places of the tube and pushed it, it just popped right off.

Also, air consumption, we thought, would be an issue to keep the seal tight for the entire 2 minutes.

[pfreivald]

Originally Posted by keehun

Also, air consumption, we thought, would be an issue to keep the seal tight for the entire 2 minutes.

This is generally my objection to pneumatics.

If you are repeating the process over and over, you're chewing through your batteries via the compressor. If you're not, then why are you including pneumatics when a motor or servo can do the same job?

I long for the day that the electric solenoid -- so darn useful in industry -- is finally allowed in FIRST.

[Timmur]

The problem with a vacuum is the power it will take and that you need to apply a complete suction to most of the surface for a hold. also if the intake of air is not completely covered that means less pressure and less of a grip. This competition calls for speed so there is going to be some bumping no matter what. That suction might not hold. If you still plan for all this and do vacuum successfully then i tip my hat to you. good luck to all this year!

[Nemisis]

This entire week my team and i have been designing and searching for ideas just like most everyone but we've found that watching the championship games from 2007 show some great bots with incredible designs that use the articulated arm with a claw and the forklift idea that was mentioned. We've pretty much settled on the arm idea but engineered our own claw. My suggestions would be to watch some videos and study up a bit. Also with the new updates that have been set into play could possibly help! Like for instance the 84' diameter now no longer 60'. So it might be somethin to consider maybe! Best of Luck to all!

[arkangle]

An arm would pick it up faster but u would have to position more to pick the tube up than with a forklift. so i would go with a forklift. hope this helps.

Team 639

[riptide]

Sometimes when asking for advice it is hard to make a good decision based others people’s opinions, as there are so many of them. A great tool for sorting out the opinions and making a sound decision is to create a decision matrix.

On the left hand side are all of the your possible decision alternatives or options. Next enter the determining factors or requirements that you are interested in along the top. You then need to decide the weight (scale 1-10) for each factor.

The final entries are for your opinions (scale of 1-10) of what your think a given factor ranks or meets your factor or requirement.

By multiplying the rank by the weight and totaling up all the factors for each option, it is easy to see what option will meet you requirements.

Example:

[adam the great]

Maybe a combination of mechanisms would fit this game best. Try combining an elevator lie system with a movable wrist extended from it. that way you can alter the height and pick up from the ground if necessary (we will see). and this way you can concentrate on getting certain goal heights or whatever you want to do from there.