Understanding Motor speed, torque, voltage

[Ether]

Originally Posted by AriMindell

How are speed and torque related?

Torque vs speed at the spec voltage is commonly modeled as a straight line connecting the stall point (stall torque @ zero speed) at the spec voltage to the free speed point (zero torque @ free speed) at the spec voltage.

So the equation of that line would be:

T = T_s*(1-N/N_f)

... where T is torque, T_s is stall torque at the spec voltage, N is speed, and N_f is free speed at the spec voltage.

Values for Stall Torque and Free Speed of FRC-legal motors are published every year.


Let's say the spec voltage is 12 volts (it is for most FRC motors).

If the applied voltage "V" is not equal to 12 volts, the equation can be generalized by using the approximation:

T=T_s*(V/12-N/N_f)

Originally Posted by AriMindell

I calculate the angular acceleration (alpha) of the attachment, then add alpha(*dt) to the angular velocity (omega), and omega*dt to the position (theta).

I added the red part.

This is called Euler integration. Given all the other tolerances in the model, it's probably adequate for what you are doing. But for students who may be interested in learning about it, the Midpoint Method is a better way to do numerical integration that is quite easy to implement in Excel. You can find a discussion thread here.