Dc Motor parameter identification - Need a tip

Other Hardware Motors, Mechanics, Power and CNC
1

Hello guys, I am building a system to quickly and efficiently ident. the parameters of a dc motor.
I am applying signals using simulink signal generator that are applied to the motor by the arduino and I read current and velocity data.
Im am using this H-bridge and it works very nice, the motor responds very well to the pwm control ;D
http://www.hvlabs.com/hbridge.html

  • The motor is brushed 11A peak and 30.2V max

The thing is, Lets say I apply a square wave, full on, full off, 1 sec each.

My question is, should I use fast stop ? or just let the motor by itself slowly reach zero velocity? What mode would give me more precise parameter values ?

Fast stop would make me read a surge current when it goes from full on to full off but it stops as the voltage goes to zero.

Normal mode just letting the motor inputs open won't give me any current readings but I will have velocity values while it slowly stops.

So guys, I tried searching but I didnt find any concrete answer that I could settle with.

What are your opinions ??

Best rewards,
Marcos Moura.

2

Which motor parameters are you trying to measure?

There's the normal motor constant (torque/current or volts/angular-velocity),
There's MoI, Theres the electrical time constant and the mechanical time constant
(which can be inferred from the others). No-load current. Series resistance.

Things hard to measure automatically are rated speed and power since they depend
on bearings, thermal dissipation and so forth.

3

The normal motor constant, Ke kt
Winding resistence Ra
'' ''inductance La
Dampling B
Enertia J

This is the model I have in simulink but I also output the current not just the velocity as in this model:

The goal is to take the input signals and resulting velocity/Current data and do some curve fitting.
Later I will learn and try to incorporate non linear models.

But for now that is the goal, a linear approximation model of the motor ;D
Then it can also be used to calculated accurate PID controller gains.