Preliminary Ideas

I've been researching, brainstorming, and sketching this and that, from what kind of movements I want to have and what I can actual accomplish. At this time, I think it's best if I try to plan for everything and as I build I can scale back...

To begin, I'll focus on the head and neck area (I'll also try to get some of my sketches up eventually). The different movements I would want in my ideal WALL-E would be:

Eye Lense Zoom - Inner element would move back and forth and also be able to stop in any position between. This would most likely be accomplished by a low power stepper motor and lead screws.

Eyebrows - This should be a simple open and close mechanism using servomotors.

Eye Tilt (Roll) - Each eye should be able to tilt up and down and stop in any position between. I'm thinking about using servomotors but I'm worried about the torque output vs. the weight of the eyes. Servomotors would be more compact than other actuators but I may have to resort to using lead screws or double pneumatic cylinders connected to a stepper motor which is better described in the next section...

Head Tilt (Pitch, Roll) - The real WALL-E has a ball socket joint at the base of the head but no way to actuate it. Disney's version seems to be using two micro linear actuators in addition to the ball socket joint but I can't tell what type of actuator it is. Others have used a pan/tilt bracket using servos but I want to try and mimic Disney's version using pneumatic cylinders. I'll probably use single acting pneumatic cylinders and connect the air line to another pneumatic cylinder. I want to do this because I don't want to add a compressor... this method would be similar to the syringe operated hydraulic excavator hobby kits they have out there. I'll probably have to add a T joint and valve in case I need to release pressure or recharge the lines. With these three points (ball socket joint, two pneumatic cylinders) I should be able to give pitch and roll to WALL-E's head.. I'll probably integrate the control with an accelerator mounted in WALL-E's nose.

Head Rotation - At the base of the ball and socket joint in the neck, I'm thinking about using a servomotor or a stepper but I need to determine what kind of torque I need for this application. Also, there's not much room in WALL-E's neck so we'll have to see...

Neck - From the base to the ball socket joint, there are going to be three pivot joints. These joints will be controlled using belts and pulleys similar to the a lot of robotic arms. There just isn't enough space to have motors at each joint but if I can fit pneumatic cylinders, I might go with that. With pneumatic cylinders or the belt/pulley method, I'll be able to have a lot of the weight out of the neck and inside the body which is a definite plus.

Well that's that for the head and neck movements... if I can, I want to add at least one wireless camera to WALL-E's eyes but I'm not sure the one camera I looked at will fit inside. It's a common 2.4 GHz 9V camera but with the two glass elements, I don't know if I'll be able to see anything in the end...

In other news, I have a spare Arduino Mega that I could use but I'm thinking about using that for the front solar charge panel and using a Maple from Leaf Labs or Beaglebone for the main controller. We'll see. For the drive system, I'm looking to use two NPC 2212's along with Dimension Engineering's Sabertooth 2x60 ESC. Depending on the final weight of WALL-E, I might have to change that as well.

Well, time to do some more sketches before sleeping...