How do I make a robot skeleton?

April 9, 2008 9:17 AM

I'm trying to build a robot and I need some help creating the support that all the motors and what not are going to rest on. Also, any other tips on mechanical engineering for this electronics guy would be very helpful.

I'm building a robot head which is basically a round ball sitting on a platform. The ball has to spin circularly, but also tip up and down. I'm a digital circuit fellow, so I'm fine with all that part, but I have very little idea how to deal with the mechanical portion of the robot.

I'm thinking to buy a plastic globe and mount all the machinery I will need inside. The problem there is that all my servo motors and so on have to be inside this plastic ball. For that, I will need to keep them in position using some type of framing system.

I'm thinking wood, because it's basically the only material I know how to cut and form. Is there anything better than that?

I also thought of using something like the old erector style screw on metal rods, but those do not seem to be created anymore. I have very little idea about mechanics, so I'd really appreciate any helpful tips in this direction.

Lego mindstorms or any other prefab kit is not an option because I have a particular design in mind that will not fit into any predefined mould. I need the freedom to basically create the skeleton myself with minimal hassle.

Thanks!

posted by markovich to Sports, Hobbies, & Recreation (4 answers total)

Maybe Grant Imahara's book Kickin' Bot will help.
posted by onhazier at 9:38 AM on April 9, 2008

Wood or thin pieces of aluminum are both good choices. Aluminum will be a bit thinner, but is as easy to cut and drill as wood. Keep in mind that 90 degree (L-shaped) aluminum is especially strong, it won't twist. Get lots of L brackets, plenty of nuts and bolts and go crazy!
posted by bprater at 9:45 AM on April 9, 2008

Off the top of my head, you are going to want to know lots of things.

First off, the motors will have lag and sensor drift. They will generate torques and forces and accelerations that are generally non-linear. Mounting is one problem, but controlling them is another.

Second, if you are going to be writing a program to control the motors digitally, your task will be much simplified if you can generate the inverse kinematics of the joint(s) in question. You'll need lots of data about the motors and the design to do this, and there is a fair amount of linear algebra that goes into computing the jacobian(s) required.

As for materials, wood works OK - but is harder to work with the sturdier it is, and must be quite bulky to have good strength. Plastics can sometimes be stronger and better, but can non-trivial to form and deal with. Same with metals.

Hope this helps some. I don't have time right now to point you to some books, but that should get you started.
posted by Pogo_Fuzzybutt at 9:50 AM on April 9, 2008

Here are a couple links from the current Nuts and Volts magazine:
Lynxmotion, home of the Servo Erector Set
Integrated Ideas & Tecnologies metal fabrication
posted by Fins at 6:30 PM on April 9, 2008