Articulated arm vs Forklift style arm
 

I was wondering if anyone had any experience with forklift style mechanisms in FRC bots. I would be interested in hearing the pros and cons of such a system when compered to a twin joint articulated arm.

Re: Articulated arm vs Forklift style arm
 

Here are some of the pros and cons we've come up with while narrowing down are choices of a manipulator mechanism.

Forklift Pros:
-We have experience with it
-Simple to do
-Doesn't require a lot of machining

Forklift Cons:
-Not very robust (in our experience)
-Requires upkeep during competition
-Can't change orientation of object (in itself, requires more mechanism to do so)

Articulated Arm Pros:
-Can manipulate object in a variety of fasions

Articulated Arm Cons:
-Power Consumption
-Weight
-Complex

Re: Articulated arm vs Forklift style arm
 

I would suggest looking here: http://thebluealliance.net/ for the 2007 matches. I think doing your research by watching the matches will give you the best idea of what to do. Remember, just because a complicated-looking device works very well from the past, it is no guarantee of what your team can produce. Stay within your capabilities and get the 'bot done early, so you can practice with it!

Good luck!

Re: Articulated arm vs Forklift style arm
 

The biggest con with an arm this year is the 60' rule!

Re: Articulated arm vs Forklift style arm
 

772 has ahad great advantigase with a fork lift and was one of my first ideas when i first saw the game this year ... here is some pictures of the fork lift from 2008 overdrive.

http://photos.sabrerobotics.com/disp...album=45&pos=0

It was extremely strong and could even pic up it elf by doing chin ups on the bar. but was heavy having hains linked from top to bottom a few times.

Re: Articulated arm vs Forklift style arm
 

dont you meen 60in. not 60 feet please get your units right

Re: Articulated arm vs Forklift style arm
 

Make sure you analyze the degrees of freedom of the gripper/forklift/articulated arm manipulator. What degrees do you NEED to perform the task? What degrees will HELP perform the task? What degrees will be EASILY CONTROLLED? What degrees will be EASILY PROGRAMMED (remember repeatability is very important)? What can be EASILY CREATED & TESTED with your team's resources? Turn around time is very important to give the programmers time to work out kinks with autonomous and for the drivers to get some practice in. From there you can decide which rotational and/or which translational degree(s) of freedom will best allow your robot/team to complete the task.

Good luck, I hope this helps!

Re: Articulated arm vs Forklift style arm
 

I Mis-shifted lol

Re: Articulated arm vs Forklift style arm
 

I would say a con for the articulated arm is the complexity of the programming compared to the fork lift. Its only a bit trigonometry, but its not awfully complicated. To make it great is really hard

Re: Articulated arm vs Forklift style arm
 

An arm can't possibly be harder than a fully autonomous robot...

Re: Articulated arm vs Forklift style arm
 

;) I said COMPARED. anyways I was gonna do a very simple mechanism, like the platforms that are like a giant car jack. IDK what they are called, but they are powered with pneumatic actuators. I thought that since they extend to a known distance, I can easily have 2 levels of height. First for the 2nd level and Second for the top. Yea apparently I can not do full automation this year due to the lack of fund... We used it for the 2nd regional, I thought my mentor said we are only doing 1 and that we had enough funds for all the sensors and stuff, apparently not.

I mean great as in: http://www.youtube.com/watch?v=vu6APoC0IOA or http://www.youtube.com/watch?v=5cORKyFr_7E

Re: Articulated arm vs Forklift style arm
 

Elevator is the way to go!

Re: Articulated arm vs Forklift style arm
 

Better yet, use metric units, 213.4 cm. http://www.chiefdelphi.com/forums/sh...ad.php?t=88589

Re: Articulated arm vs Forklift style arm
 

good info were between these ideas to

Re: Articulated arm vs Forklift style arm
 

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

Re: Articulated arm vs Forklift style arm
 

I have experience working with a Forklift, as a deal with them on a day to day basis working in a backroom of a grocery store. So, putting a forklift style mechanism ona robot would be easy to machine. However, it only privides a 3-axis movement. Therefore, taking more time needed to do the task.

As, for an articulated arm? I have been looking at the one we have in our shop. it provides a 6-axis movement but the programming it takes to perform the task is very redundant. It does get the task done in a very timely manner though.

Is there a possible way to combine the forklift style with the articulated arm?

Re: Articulated arm vs Forklift style arm
 

I think it's a clever idea.
Lends itself well to picking up deflated pieces too.

Re: Articulated arm vs Forklift style arm
 

Go back and look at the 2007 and 2010 games for suction related devices. Many teams used suction in 2007 to pick up tubes, as well as last year to hang on to the soccer balls. Obviously 2007 may have some direct correlations, so start there. If I remember correctly Team Voltage had a pretty nice suction system in 2007 (Team 386).

-Brando

Re: Articulated arm vs Forklift style arm
 

After all, the deflated pieces are still in play. But, we need to devise a way to place the cylinder on an axel and raise it so we can angle the hose, and lift it higher to reach the middle and top rows

Re: Articulated arm vs Forklift style arm
 

As a team that has very successfully implemented a vacuum, I would caution you from using a vacuum to pick up these tubes. Instead look back at 2007 and look at the mechanisms that were most effective, particularly in acquiring and retaining the pieces.

Re: Articulated arm vs Forklift style arm
 

we had orginally had four ideas for an arm. the hook idea was disposed of right off the bat. are idea that made it to prototyping was an inside expander. our vacum idea like that similar to team 230's is now back for protyping. any thing recomeneded for the inside expander?

Re: Articulated arm vs Forklift style arm
 

i was thinking of doing a fork lift type arm but was wondering how important it would be to be able to pick the pieces of the ground. if it is important than the arm would have to be far more complex than i originally thought.

Re: Articulated arm vs Forklift style arm
 

The forklift style is a better choice in my opinion. Yes it isn't has fancy or complex but it doesn't matter. You simply lifting tubes up to a certain height. It would also be able to repair something on a forklift style arm. It is also very easy to design and to create. Now of course we are considering creating a system (suction or rollers) to keep the objects in place so you may want to consider that as well.

Re: Articulated arm vs Forklift style arm
 

I have to agree with you here. We used a suction device in 2007 and while it was successful, to a certain degree, in picking up the tubes, it was difficult to maintain a grip on it while being defended. It all depends on your contact point and surface area for the suction device, but I would suggest looking at devices that did work very well in 2007. Take a look finals videos on the blue alliance for devices that worked under extreme defense.

Re: Articulated arm vs Forklift style arm
 

This is my teams second year in FRC, so we can't look back to rack n' roll. but, what would you suggest for a manipulator instead, a suction device would be efficent for picking the tubes off of the ground, but i do think that a forklift that raises 10' would work for placing the tubes on the scoring grid

Re: Articulated arm vs Forklift style arm
 

Check out Team 47's bucket from 2007. (Now Team 51)

Re: Articulated arm vs Forklift style arm
 

"This is my teams second year in FRC, so we can't look back to rack n' roll."

Sure you can, go the the blue alliance web page and watch the video's

http://www.thebluealliance.net/

Re: Articulated arm vs Forklift style arm
 

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.

Re: Articulated arm vs Forklift style arm
 

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.

Re: Articulated arm vs Forklift style arm
 

What if one were to design a forklift that could still pick up things off the floor, over the top of the bumpers, without use of a motor to articulate their grabber?

Hmmm... :D

Re: Articulated arm vs Forklift style arm
 

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.

Re: Articulated arm vs Forklift style arm
 

If you look earlier in this forum someone on I think the first page posted a link to some pictures of a 2008 robot with a fork lift that would solve that problem easily

Re: Articulated arm vs Forklift style arm
 

Hey for everyone whose considering an arm, check the rule update! the 60"diameter has been changed to 84"!!

Re: Articulated arm vs Forklift style arm
 

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! :)

Re: Articulated arm vs Forklift style arm
 

60" is only the starting configuration after the match has started you can go as high as you want

Re: Articulated arm vs Forklift style arm
 

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! :)

Re: Articulated arm vs Forklift style arm
 

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

Re: Articulated arm vs Forklift style arm
 

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.

Re: Articulated arm vs Forklift style arm
 

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.

Re: Articulated arm vs Forklift style arm
 

Really?

Hmm.

I think we need to setup a party between our teams at your shop sometime after you build it... :p

Re: Articulated arm vs Forklift style arm
 

Nevermind... We came up with something even better. :D

Re: Articulated arm vs Forklift style arm
 

Arm pros:
simpler
more robust
lighter

Lift pros:
easier to score on the pegs
can raise lift in safe zone without having to leave the zone

As a team that did the lift back in 05. I can say that it takes a lot of upkeep and in many ways is not worth it. on the other hand that was one of our best robots all time. I couldn't find any pictures of the lift but if I do I'll post them

Re: Articulated arm vs Forklift style arm
 

Here's my teams 'bot from 2007. You'll want to watch from about :37-1:27

http://video.google.com/videoplay?do...5109075900959#

Re: Articulated arm vs Forklift style arm
 

I think he was joking :rolleyes:

Re: Articulated arm vs Forklift style arm
 

Not to crash your party, but since we are doing that, I can't wait to see how you do it at FLR!

Re: Articulated arm vs Forklift style arm
 

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?

Our students built a four-link arm in the off-season for a game they made up. (We simulated a build season with them to get them ready for this season) They used one of the locking Dewalt transmissions and a CIM to drive the arm and while going up was good, controlling the down was difficult. We did try to do some balancing, but overall, once the brakes released on the Dewalt, the arm was too quick going down to control nicely.

My question to the veterans with really successful mechanisms, is how do they control their arms and forklifts so nicely? Do you build custom worm gear drive trains, or use really inefficient gearboxes to establish the same level of control going up and down? For balancers do you use torsion springs or gas shocks?

Re: Articulated arm vs Forklift style arm
 

Fork-Lift
Pros:
- Compact, even in the scoring zone
- Consistent positioning in the y & z axes in relation to the scoring
- 1 Sensor can determine multiple positions
- Extremely simple to adjust height for minor corrections

Cons:
- Must be very rigid to prevent torsion & binding when the lift is at maximum height
- Generally heavier due to (typically) multiple stages
- Requires upkeep every match -- PROPER tension on cabling, cabling remains on pullies, ensuring the winch hasn't jumbled the cabling, etc
- If linear slides are used, they limit the ability to powder-coat (not a con for most in FRC, however in the real world this is a consideration since EVERYTHING must deal with corrosion if it's a long-lasting product -- so we teach it to our students as well)

Rotating Arm
Pros
Simple to build if it's 2 joints
Very easy to program so long as the joints are geared slowly enough (standard PIDs)
No need for a braking mechanism if it's geared enough (due to lightweight game piece this year)

Cons
- The drivers have to be different distances from teh scoring pegs depending on how high the arm is
- It must be 2 joints to reach a game piece on the floor (most 2007 designs make the bumper configurations illegal under 2011 rules)
- Different orientations of the shoulder joints may cause undesiered re-orientations of the game piece -- in 2007 many teams took advantage of it (see 330's diagram in the Behind the Design book) yet this year that's a bit more difficult (IMO).

Re: Articulated arm vs Forklift style arm
 

In a nutshell: Balancing. Make sure your arm is counterbalanced either through stored energy or weight and it will be a lot easier to hold up.

I've heard some people say they use a PID loop for this purpose and some people say not to, depends on who you ask...

Re: Articulated arm vs Forklift style arm
 

Suction devices will not work, even if you generate enough power to keep hold of the tube, it will make the rest of your robot lose speed and power. Besides, the slightest collision knocks the tube off of the vacuum. So either way, it is not efficient

Re: Articulated arm vs Forklift style arm
 

Our team has an idea for a dual conveyor belt system that pulls in the tubes, then it flips the tubes so they are vertical. At which point a telescoping arm with a hook grabs the tube and lifts the tube up so it can place it on a scoring grid.

Re: Articulated arm vs Forklift style arm
 

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.

Re: Articulated arm vs Forklift style arm
 

I suggest you look to team 1771 in 2008 picking up a 48 inch trackball that weighed orders of magnitude more than a tube:
http://www.thebluealliance.net/tbatv.../2008arc_qf1m1

I'll go a step further. I will bet you a steak dinner (this is the accepted bet on our team, to be collected at an away-regional or competition) that not just 1, but several teams do a vacuum system, do it well, and consistently win matches with their robots.

Nearly every idea we brainstorm in our team meetings ends up being implemented by someone successfully on the field. That includes the ones we've decided not to use because of some perceived technical problems - like vacuum in '08, a dumper bot in '09 (but you'll need to be able to shoot at different angles so a turret is perfect!), and linear-motion kicker in '10 (binding killed ours).

Re: Articulated arm vs Forklift style arm
 

I'll take that bet. See you in St. Louis. :P

Re: Articulated arm vs Forklift style arm
 

We actually made a 3 pronged suction claw and it worked pretty darn good but we still shot the idea down. But the tubes did stay connected to it while jostling the holder.

Re: Articulated arm vs Forklift style arm
 

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.:cool:

Team 639

Re: Articulated arm vs Forklift style arm
 

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: