The Exoskeleton

I have been literally immersed in a virtual reality. Working at a small scale forces you to adjust your senses and perception of self. Then you suddenly realize that somehow your fingers are too big, your body too clumsy, your eyesight not good enough to deal with a Lilliputian world. Fortunately our cyborgian self comes to the rescue and we make use of the many attachments and extensions that makes us makers of things, creators of our own destiny. (I might believe that someday...)

All the mechanics are functioning, at least by hand and in individual servo tests. It has been very hard to deal with some problems, most of which have to do with balance and friction, not of the marionette which is very fine, thank you, but of the mechanical elevator that raises and lowers most of the machinery so that the head can turn, the body express and the arms move while at the same time the Creator changes its position , kneel, stand up etc.

This problem is not so evident at first, specially if you are used to manipulate a puppet or marionette. Since your hand has a mind of its own it is hard to consciously realize tha amount of intelligence that it has to deal with all these complicated maneuvers. As you move the "plane" controller, pull the strings etc, you hand raises and lowers automatically and compensates this movement by tilting, rolling or yawing the controller.

Arm control assembly

Potentiometer as high precision encoder

However, when you have a fixed structure that supports the controllers it becomes evident that you need more than one motor to actuate on any given movement, because each movement influences the rest. Of course, as Dwiggins taught us, you should let gravity do most of the work, since she knows all about the laws of physics, but then there is the issue of correspondance, economy, efficiency and why not, elegance of design. Simpler is better. The complexity of simplicity.

Detail of the servo with its sturdy mounting plate

Assembled arm control with lead counterweight

Lead counterweight and potentiometer encoder

Give me a big enough lever...

The real servos finally arrived! here is the Hi-Tech HS-805BB Mega Giant Scale Servo being tested. I simply attached one of the many great horns and plates that it comes with to my fish-line spool, using its own screw and voilà! 19.8 / 24.7 kg*cm (4.8V/6V) of torque! It is temporarily held in place with straps as you can see because as you can imagine the square holes of the Vex plates don't line up with anything but their own stuff (I promised I would stop bitching about it!)

For the rest of the controls I am using the HS-645MG UltraTorque Metal Gear Servos that have 7.7 / 9.6 kg*cm (4.8V/6V) of torque, very much on the safe side.

On the left of the picture you see Vex's red optical encoder which I planned to use to determine the position of the continuous rotation motors that lift the arms, but again, not even the extremely versatile Make controller could recognize the simple signal. I am sure it can be done but why waste time. I ordered a set of high-res 10 turn potentiometers that are not only more precise but can "hold" the last position even when the power is turned off.