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I am interested in constructing an robot which will be responsible for supporting a 200 pound load. There will be four wheels and the diameter of the wheels are 8 inches. The robot will be required to accelerate 5 meters per second. How do I go about determining the required torque for the motor of each wheel? Do I assume each wheel holds 50 pounds since the weight is 200 lbs and there is 4 wheels?

user15588486
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  • This is my catch-all thread for this kind of question since it gets asked so often. Your question is better specified than most, but is still missing critical specifications: https://engineering.stackexchange.com/questions/31501/how-can-i-calculate-the-power-and-torque-required-for-the-motor-on-a-wheeled-rob – DKNguyen Nov 03 '21 at 04:38

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Right, we could calculate the torque as 1/4 of the total torque on each wheel.

let us say your robot weighs 100lbs and convert the acceleration first

$$\alpha=5m/s^2=(\frac{3.28ft*5m}{1m})=16.4ft/s^2$$

$$F=m\alpha = (100lbs+200lbs)16.4ft/s^2=4,920lbsf$$

$$4920/4= 1230lbsf\ per\ wheel$$

$$1230*4in=4920lbs.in \ torque\ per\ wheel$$

kamran
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    On level ground, and if rolling friction were not a thing... – DKNguyen Nov 03 '21 at 04:55
  • @DKNguyen, sure. i was just trying to get the most basic algorithm across. otherwise what if the robot needs to turn and swing its arm. it can quickly become complicated. – kamran Nov 03 '21 at 05:12
  • The 200 lbs load is force or mass? – r13 Nov 03 '21 at 14:41
  • @r13, I understood it as mass. I should have used lbm maybe. – kamran Nov 03 '21 at 15:41
  • Thanks for the clarification. I was thinking W=mg. – r13 Nov 03 '21 at 16:46
  • How does friction on axles and gears influence this? Is there some calculation, or is a better strategy just to add some small amount to the calculated torque value to account for real life energy losses? – WhisperingShiba Nov 03 '21 at 23:50
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    @WhisperingShiba, the static and dynamic friction factor is neede, the gear efficiency, the overturning moment of the robot to determine how much of its weight is supported by each wheel is needed. I think a nominal 15-20% extra torque is reasonable. – kamran Nov 03 '21 at 23:57
  • @kamran I believe the actual unit for mass in the imperial system is slugs. Which no no one ever uses. So it's like...Force (lbs) = Mass (slugs) x Acceleration – DKNguyen Nov 04 '21 at 05:04