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seen Apr 29 '12 at 18:19

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Apr
24
comment How do I calculate DC motor speed for a given load?
A DC motor always slows down when the load applied to it increases. The load (weight) in a robot is applied to a DC motor through the wheels. Wheel size affects the load on a motor as if the wheel were a lever arm. If the effect is not linear, what is it? You must take into account that the speed of a motor is not constant, nor is the torque a motor produces. Load determines the torque a motor produces, and it will produce a higher torque at a lower speed. I am asking for help, not trying to tell you anything. How do you work this problem?
Apr
24
comment How do I calculate DC motor speed for a given load?
My point is to include the effects due to torque. A higher load on the motor slows the motor down. My original question was: how do larger wheels - everything else stays constant - increase the load on the DC motors? I "assume" the increased load is linear with the radius of the wheel.
Apr
23
comment How do I calculate DC motor speed for a given load?
Basically, it says that the motor has to work harder for each rotation. As long as I am using the formulas correctly, I am fine. However, if I am not using them correctly I need to know it before I present it to my class. Since the load on the motor goes up with larger wheels, the motor slows down for the larger wheels according to the first formula. My students would have to plug the numbers into each formula to see if the motor slows down more (or less) than the increased movement you get per rotation from the larger wheels. The point is, big wheels on a robot are not always better.
Apr
23
comment How do I calculate DC motor speed for a given load?
I started with the formula from the MIT website (given below by pygmalian): ω = ω0 (1 - τ/τ_0 ) which comes basically from the motor characteristic curve and shows that a shunt wound DC motor speed decreases with an increased load on the motor. I used the same formula to calculate torque load on the motor that ja72 gives in another comment below, τ = rF (F is the weight of the robot, a constant, and r is the radius of the wheel), so the torque required from the motor increases as wheel radius increases. This seems logical, but this is the part I was trying to confirm.
Apr
23
comment How do I calculate DC motor speed for a given load?
Following is the information Alexander asked for. unfortunately, I don't know how to do equations the way ja72 has in his reply, so I have to describe. I am looking for the top speed (after acceleration) of the robot itself.
Apr
21
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Apr
21
comment How do I calculate DC motor speed for a given load?
Thank you for your help, I appreciate the work you are doing to help a stranger. This MIT site is one of the ones I have been using, the formula I used in one of the comments below is the MIT formula (4). I will definitely ask Alexander for his insight.
Apr
19
awarded  Commentator
Apr
19
comment How do I calculate DC motor speed for a given load?
Thank you for your response. I have one more question: How do you convert weight load to torque load on the motor given that motor force is applied at radius r of the wheel? By the way, I am working from a speed vs. torque relationship similar to me.mtu.edu/~wjendres/ProductRealization1Course/…
Apr
19
comment How do I calculate DC motor speed for a given load?
This is not a homework question, this is for a classroom tutorial on robotics that I am making (as a teacher). I want to make sure I am using the right formulas. By the way, I am not trying to make it too complicated, so moment of inertia answers are out.
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19
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19
asked How do I calculate DC motor speed for a given load?