I'm trying to build a quadruped robot. I studied dynamics and to get an idea, I read and watched papers and videos related to robots like ALof and StarlETH and some more. But since this is my first project it would be pretty difficult to follow everything and technically I won't be able to, because of no prior experience.
To get to the problem, I'm stuck on choosing an actuation method. I plan to build the thing using aluminum and keep it lightweight. Hopefully 10kg and battery powered. so hydraulics is a no go. Currently I am on the designing stage. I have considered using dc geared motors directly on joints rather than -keeping on hip and transferring via gears and chains- to keep the design simple, but I guess it adds more strain on hip motors with my design. due to budgetary limitations and availability, I'm stuck with motors like XD37GB520 (currently 12v 100rpm but can change it) and no harmonic drivers or maxon motors. but I'm concerned with its ability to hold the weight of the robot. if I try to increase the torque capacity I lose angular velocity.
I have also considered about lead-screw and motor method. but have little or zero knowledge about it. I know that the linear actuation's speed depends on the number of threads per unit length of screw and rpm of the motor, but how should I estimated the torque of the motor and the torque or force that can be expected from the mechanism (something like rated and stall torques of DC motors, I suspect stall torque would just depend on screw joints to the leg links) does the torque of the motor only depend on the friction of the nut?
left: 3 DoFs leg with DC geared motors on each joint top motor is parallel to the drawing-plan.
right: same leg with lead-screw, top screw is in the plane
- So how should I select a motor (torque rating) if I want to implement lead screw and motor?
- if I'm to stick with DC geared on joints, how much minimum rpm should I keep at a joint? (so that I can try to find a motor with that rpm and torque required).
- what is better for this kind of thing dc geared or lead-screw?.
PS: I'm still designing this and I still need to start implementing Matlab or Simulink simulations. So I don't really know which rated torque will be required. I just need to decide on an actuation method to finish the design and move forward.