Hi, I’m having a bit of trouble for sizing the motor for a robot. I read the tutorials on this website and saw the calculator too.
But I think I’m having an issue with theory VS practice.
The robot I want to build will weight 100kg. I understand that to size the motor I need know the wheel size, friction coefficient of the ground, wind resistance and desired acceleration. But let’s leave those values unknown for the moment.
I know that, as a cyclist, my legs can generate 100W of power to push 80kg (my bike and myself). Therefore, I assume that a 200W motor would be sufficient for my 100kg robot. But then I see ebikes being sold with 500w motors. But that’s probably just to get a better acceleration right? Can someone confirm if this logic is right? The robot doesn’t need high accelleration. I’m looking at moving to a speed of 1m/s If it’s right, then it sounds like if I use 2 X 200W ebike motors (so 400W total), I would probably be able to build a 100kg robot regardless of the values of those unknown variables.
Hi,
I don’t know alot about robotic, so maybe I am wrong with the engine, but at school (I study in electromecanic) we learn that an engine have a number of rpm with and without charge. Its usually written on it.
T= P/(2* pi* N/60) ( or you may see the formula in hz instead, T= P/ (2pief) where f is the frequency in hertz ( hz)
So Torque, aka the maximum possible charge( in newtons-meters = Power ( in watts)/ ( 2* pi* Number of turn per minutes ( rpm) ( the N its rotational speed exactly in english when I google ( I am from quebec) I put number of turn because I translate from french ( number= nombre)/ 60.
So if you take an engine with 100 watts at lets say 1000 rpm for exemple. 100/(2* 3.1415* 1000/60)
100/ ( 104.71666)
0.9549 Newton-meters
( I ask the question at an AI and its the answer I get)
On earth the gravity its around 9.81m/s², so if you calculated the force F= MA ( force= masse(kg) Acceleration (9.81 m/s²) if you take 1kg it would be 9.81 newton meter if you put the weight ( masse) into a 1 meter rotation axis.
F= 100kg * 9.81 >= 981 N (newtons.)
I hope I help you a little with my answer. O and if you find the exact formula the theory and practice are really close, but to make it simple sometime just double your theory number by 2 and you will be closer.
