# help needed PID control calculations(BRUSHLESS DC MOTOR CONTROL)

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Hi ALL,

I am mohd sulaiman. I am working on Brushless dc Motor
position control.In my application we are controlling the motor using
the dsp processor from TEXAS i.e TMS320LF2407A. my design have been
completed now i have startedd to write the code for the application.

I have doubt regarding the implementatation of the PID
and PI control in software and how do we determine the Respective
constants of the PID or PI controller. could any one explain on what
parameters of the motor they are dependent and how do we determine
them.

With Regards
Mohd sulaiman

Re: help needed PID control calculations

You're familiar with analog control loop theory ?
Open loop response and closed loop response of the system ?
If your sampling frequency is far above the bandwidth you can
proceed if it was analog, else you have to pull it over
to the digital domain by the means of the Z-tranform.

Rene
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Re: help needed PID control calculations
look in microchip's site, they have an application note. It goes into all the
theory.

Re: help needed PID control calculations

Z-transform is the discrete version of the lapplace transform.  If
your sampling frequency is too low, you are cutting off the high
freqency responses.  That's true for both digital and analog.

Let me try some simpler terms.  Basically, any analog wave form can be
modeled in a sequence of fundamental frequencies.  If you pick n of
the important ones, you can simulate the characteristic of the system
with N differential equations, or a Nth order matrix.  Then your
system is in the form of
Y(t) = M(t)X(t) + A(t), where M(t) is NxN and A(t) is Nx1
You just need a do some matrix calcuations (computer can do that very
well).

If you need additional details, please email me (epl).  I don't think
other people want to bother with these details.

Re: help needed PID control calculations(BRUSHLESS DC MOTOR CONTROL)
On 5 May 2004 22:17:07 -0700, snipped-for-privacy@hotmail.com (Sulaiman
mohd) wrote in comp.arch.embedded:

Have you already looked at the applications notes for motor control
available from the web page
http://focus.ti.com/docs/prod/folders/print/tms320lf2407a.html ?

This one has source code available:
http://focus.ti.com/docs/toolsw/folders/print/sprc112.html

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