Let's Make Robots!

Robotic Arm Control

I have built a robotic arm. You can see it in the robot section. It is called IPTUPED.

Now that it is built i can only prgram it to pick up something that is in the same time. I need a new control method.

Due to the fact that i am pretty new to this i need some ideas. Basically i am asking you guys if you can help me find a good method. I have seen wii and arduino, nd rc. I need a good tutorial online somewhere that can help me control it. So far i have only been able to find a method that can control 2 servos. I am using 4 and maybe 5 in the future. Thanks for any help.


By the way. Can you view the videos, i cant on this browser???

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Actually, that is correct. There is a 100ms pause in there and we are stepping 1 each time. We have say, 200 "clicks" to make a full sweep of the servo. That's 100ms * 200 steps = 20000ms. 20,000 milliseconds = 20 seconds. Yup, that's pretty slow.

That "pause 100" could probably go down to pause 10 or even pause 5 --or could even be removed. --Try different pauses and see what you like.

Ok, It seems I may need to redesign my project. 1. It works very slowly and in the next few days i will mess around with the speed of things. 2. I need a heavier, stronger base due to the fact the current one is failing. - think about wood innate an idea in mind 3. Stronger servos. The shoulder and base servos are too weak. A. I have a plane supporting the base by take pressure off of the servo. B.possibly adding a second servo at the shoulder on the opposite side? - would that work? C or I have a design in my head that would decrease the weight of the whol arm - what's ur opinion? New design or a second servo?

Second servo would be fine --just be sure that they both point the same direction. Don't point the 2 output shafts to eachother. In this case, one would be backward and funny code would be needed. Instead, point both servos the same way and connect them together with a "Y" wire. 

--Sorry, I just figured out your question. It is the rotate servo that is giving you problems. Yes, mounting the whole arm on top of a single servo horn is not going to work. I would suggest a lazy-susan bearing from the hardware store. They are metal, ball-bearing and less than 10 bucks. I think the smallest (from the regular hardware store) is a 4" which should be about right. You will need to figure out a cleaver way of attaching your rotate servo to this new base --but now, all it has to do is rotate the thing, not bear the weight.

What I said above goes for the first "main" joint (the sholder) --this is where the double-servos go.


This just jumped in my head --servo math and strength for your arm...

A "standard" servo is around 44 oz/in. Take a servo and stick an arm on it that is exactly 1" long. Now tie a string on to that arm and hang a weight on that string. A "standard" servo could lift 44 oz using this 1" arm. If the arm is 2" long, the servo would only be able to lift 22 oz. If the arm is 4" long, the servo could only lift 11 oz.

--This should give you an idea of how long and heavy your arm can be with the servos you got. Just look up the specs for your servos and you can figure out how strong they are from there.

Why try to make your servos do all the work?

If you "spring load" all your joints to the balance point when fully extended horizontally, then the only work your servo / motor has to do, is lift whatever weight is in your gripper. Springs are much cheaper, smaller, and easier to program than servos:-)

This is the elbow joint of one of my arms, there are 2 springs at the pivot point to counterbalance the weight of the lower arm.

This is a different view of the arm.

There are also 2 springs visable on the top side of the gripper to ensure it opens reliably.