Another Arduino Robot Arm

Just done a basic write up of my Arduino robot arm, its very basic but I'm going to expand on the code to do inverse kinematics with it.

Arduino Robot Arm

Interest arm - kinda like a SCARA arm; I am curious, though - you mention in your blog post that existing arms were too expensive? Unless a SCARA arm was your goal, why not the OWI-535 Edge arm? It only costs $50.00 US...

Although you would need to figure out how to add feedback to it for positioning, and it isn't as easy to interface to the motors as servos are (you would need an h-bridge per motor on the arm).

There was a guy here on the forum, though, who did interface an Arduino to it (sans position feedback)...

:)

Hi cr0sh - Check out my blog - I was the guy who interfaced the Arduino to the Edge robot arm. :slight_smile:

Its cheap yes, but you can’t do anything precisely or repeatable here’s the link

Arduino and Edge Robotic Arm

So rather than hack the arm by adding position feedback (would have been wheel encoders) seemed more logical to build an arm from scratch that I can now reliably program. £15 for 3 servos is all it cost to build :slight_smile:

Cool little arm. I wanted to make my own too, but what is stopping me is all the calculations needed to make it move right.

I got absolutely no idea on how to do it, and after a lot searching I found some formulas, but don't understand them. :(

Might just start with a copy of your arm.

inverse kinematics and trigonmetry - I'll post up all the code to control it when I've got it working :)

Only thing I would advise is use something stronger than foamboard and maybe get some more precise (and expensive) servos.

I am planning on using lexan (same material mythbusters are using for their blast screens), and some pretty expensive digital servo's (can be connected to usb and adjusted), that should give a pretty good result, i think/hope

I like you you fitted a bolt to the servo itself :-) Very neat modification which saves a lot of work.

skumlerud - yeh fitting the bolt removed the need to worry about brackets, not sure on how much weight it'll take but if you add in some washers and possibly epoxy the bolt in as well it should hold a decent weight.

bld - That lexan stuff is great, I did mine with the foamboard so i could test it without wasting decent materials, only thing is cutting the materials, I have a dremel-a-like which should be fine, how are you planning to cut it?

I am going to use one of these My experience is that dremel is way too fast for cutting lexan, it is great for engraving it though.

Hi cr0sh - Check out my blog - I was the guy who interfaced the Arduino to the Edge robot arm.

/facepalm - I guess I should've checked!

;D

Its cheap yes, but you can't do anything precisely or repeatable here's the link

Yeah, without a way to add feedback, you're pretty much outta luck. I actually bought one of the Edge arms, but haven't done anything with it yet (it was too neat to pass up). I would like to add feedback to mine when I get around to it, but I figure someone will beat me to it before I do. I am not sure it is even possible without "frankensteining" it.

:)

IK Arduino code is here -> http://www.circuitsathome.com/mcu/programming/robotic-arm-inverse-kinematics-on-arduino

Hi,

I’m building one ATM, but have no pics yet. The biggest problem is the arm swing due to its inertia and weight (the arm is supported by two servos).

Here are the inverse kinematic functions:

You only need sqrt() and acos(). You can use rad2deg() to convert values to degrees.

Hope it helps.

Álvaro

I've actually written most of the IK in Processing which will control the arm (or any other). I did it by using simplified trigonmetry - i'll post this up as soon as I have it working.

skumlerud - yeh fitting the bolt removed the need to worry about brackets, not sure on how much weight it'll take but if you add in some washers and possibly epoxy the bolt in as well it should hold a decent weight.

If you epoxy an aluminum plate to the bottom of the servo it should be more that strong enough. A bit more work than just drilling a hole in the plastic, but still much easier than fabricating a bracket.

You can put a brace point opposite of the servo horn just using low temp hot glue. The below nut/nail attach points hot glued to the servo base did not detach when subjected to a 10 pound force in both shear and tensel. Arm parts can be made from very thin plywood wood or the large craft sticks.