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Motor torque selection

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newInRobotics:

--- Quote from: mado on May 14, 2013, 12:18:09 PM ---how to calculate the required torque?

--- End quote ---
m = 65kg
a = 1.5 ft/s2
v = 3.14 ft/s
D = 0.5 ft
r = D / 2 = 0.25 ft

F = m * a = 65kg * 1.5ft/s2 = 29.718N
T = F * r = 29.718N * 0.25 ft = 2.2645116 Nm

C = pi * D = 3.14 * 0.5 ft = 47.8536 cm
f = v / C = 3.14 ft/s / 47.8536 cm = 2 Hz
RPM = f * 60 = 2 Hz * 60 = 120

Theoretically, to achieve desired velocity and desired acceleration You need 1 motor with RPM = 120 and T = 2.2645116 Nm, however in real world You have friction, errors and the like, so add at least 25% to compensate for that, so what You are looking for is RPM = 150 and T = 2.8306395 Nm. If You have 2 driving motors, then divide torque value by 2 for each motor, if You have 4 driving motors, then divide torque value by 4 for each motor.

P.S. Derived torque value only applies to acceleration on flat ground, not a slope. If You want to find out required torque to accelerate on a slope You have to include gravity into equation.

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