problem in control system

[roboyoyo]

I design a velocity control with DC brush motor, constant magnet and PID controller
The velocity I measure with Hall Effect sensor
My problem is that I don't have the motor parameters to build transmission function with the PID controller
Anyone know how I can receive transmission function with step response input ?
Maybe I can receive the transmission function with bode diagram ?
If the answer is yes then who I can do it
Or How I can receive the DC brush motor parameters in empirical way
This motor doesn't has datasheet
The parameters that I need to know are :
L – Induction
T – Torque
K – Voltage constant
b – Restraint coefficient
J – Inertia torque
Is a measure device that can do it existent ?
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[LvW]

Perhaps the following may help:

As a good first - and in many cases sufficient - approximation you can assume that the step response of the dc motor (number of revolutions over time) follows a standard second order system with two time constants T1 and T2.
If you measure this step response you can identify both time constants roughly by using the asymptotic lines crossing the time axis (T1) and the maximum speed line (T2), respectively. Then T1<T2.
Thus, you have the denominator N(s)=(1+sT1)(1+sT2) of the transfer function. The numerator is determined by the motor constant K (number of revolutions per volt).
This gives you the motor transfer function in the s-domain expressed by motor speed H(s)=K/N(s).
To transform this transfer function into the domain of the revolution angle you simply have to multiply by 1/s (integration in the frequency domain).

 

[roboyoyo]

Thanks LvW,
Can you give more explenation about this method
I will glad to recieve more comments and more methods

 

[LvW]

Sorry, but I don't know which additional information is needed.
I mentioned the step response (to be measured) and the procedure to derive both time constants (approximately).
I think, that's all I can say about this subject.