Indeed. But why do you need to hook it up during the training? Why not just train it all virtual then print it?
So I implement something like an accellerometre, using computer vision instead.
What I need, every time the robot moves, is the new camera position+orientation, and the floor plane underneath it's position+orientation, with those two things, I can get it to walk along.
But I plan on doing more than that, I actually want it to be able to fight another robot, so I can have robot wrestling with it, so the computer vision is more complete than that, what I'll be implementing.
Its me being tricky, not putting angle sensors in it, you don't have to omit those, its easier if you have the angles of the leg hinges known.
So, why do I need the actual physical response from the specific body itself?
Its because I have N physical properties (constants, like gravity, friction, and hinge motor force) I need to brute force, to match the virtual simulation to something closer to reality.
Its actually probably not exact even at best (the virtual physics compared to the actual physics), and it'll show the fact by being a little uncoordinated, and it wont be able to do really amazing tricks, but it'll be able to possibly wrestle and pin down, as long as its not being "too tricky a skateboarder" how it does it. (Just does it simply.)
Because the internal workings of the body is apart of the physical properties as well, that go into the N constants for the physics simulator, I need to actually run it with the body, and also the body has to be supported by the software as well. so if there is a type of gear, or motor being used, the physics simulator has to be able to support it. (So a dc motor robot, is slightly different than this thing, which runs off cranks and levers.)
You could think the simulator is really hard to write, but something approximate is really easy, if you know the basics of virtual ragdoll systems you can omit alot of maths! alot of it can be discarded, but it does make it less realistic, but as long as you keep the angular momentum that would help.
If you want to read about the physics engine Im going to use, its similar to these->
They make it look really tough to learn, but something a little less realistic, but still the basic gist, is really easy if you just think about it on a page by yourself, get the basics down, they dont tend to help you in that area on the internet. (Thinking for yourself, its more of a psychological motivation type lecture, its a bit different "meta-learning".)
Its like that car and soft body box thing, except its a stick-insect instead, and i just add internal forces, other than that exactly the same code.
I spose... if you didnt worry about the exact motors/linkage/gears used, it probably could be fully virtual. the other physics constants would be the same no matter what the body.
But I bet it would synch slightly better, if I custom did it with the single specific body itself, because theres alot of factors involved, and if I do it in the exact body it would possibly get a more accurate result taking into account the extra unknown factors involved.