This is a bipedal robot concept using Torxis servos, which are very expensive, but the torque ratings I hope will allow for taller humanoid projects. The big concern is how everything is held together: in the CAD, I'm using 6061-T6 aluminum for custom servo mounting plates to be made on a CNC or milling machine (seen in grey), all held using 10-32 bolts. Also I have no welding experience, so that's kinda out of the picture unless I find a cheap service, which I doubt I will find.
As of now, I'm going to store this away until Summer. Right now, I don't have the money to pay for the servos and the other tools I might need to make this thing (hence the forum post about funding expensive robot projects). Furthermore, I haven't even built a robot yet; jumping the gun to pursue something as complicated as a large-scale humanoid robot is something perhaps no one should do as a first robot.
Any questions, feel free to ask and I'll try to answer as best I can. If any one has an idea how to improve structural stability, that would be great. Finally, if anyone wants a CAD model, then reply and I will send a .STEP file.
Make a biped is hard … imagine a large scale one! hehehhh
My first robot project was a humanoid biped (https://www.robotshop.com/letsmakerobots/node/32034)… at that time I had only micro servo motors. I learned that with some adjustments we can enhance the strength of a small servo motor.
So… I suggest that before you spend so much money on these servo motors, consider this alternative: you can use giant scale servo motors (for example: https://www.robotshop.com/en/hs-805bb-giant-scale-servo-motor.html) and make some linkages, some kind of levers, which will potentiate the torque of the servos, and you will save much money! You also will need smaller batteries; the control method will be easier, since this servo motors works like common ones.
And… I guess with that giant scale servo motor I mentioned before (which have 24.7 Kg-cm of torque), combined with linkages and levers, you will have more strength than the Torxis servos mounted directly in the joints… of course it will need some calculations…
And consider using PLM (parallel leg mechanism/parallel linkage mechanism): it makes the robot more stable and you save two servo motors (one in each leg).
Not math, but more like analytical thinking, since I don’t really have actual values to do math, but it looks like if you have a parallel linkage you are basically reducing the amount of force that is applied on the servo.
Don’t have a good camera on me to show my thinking, but my logic was that the downward force of gravity can be split into two components perpendicular to each other and with one vector parallel to the leg. The other vector would be ignored in terms of torque because it is pointing into the servo arm, and it would be the other that would have to be overcome by the servo in order to produce movement.
My physics knowledge is a little rusty after a year, but like you said: using linkages would not only reduce the number of servos, but perhaps even the torque that the servo has to apply against the weight of whatever goes on the legs.
So perhaps Torxis servos are not needed (haha, like I could afford 12 of them). So it looks like back to the drawing board, but I have until Summer, and I’ll definitely take a look at your humanoid project for some ideas ;)
