PID parameters calculation (Kp,KI, KD)

Hi ALL

         I am Mohd sulaiman, I am working on Position control of the
BLDC motor using the microcontroller. I have to implement the PID
controller in Microcontroller through coding. My worry is mainly about
the calculation of Kp,KI and KD constants. If you know how to
calculate them or have a document which talks about the determination
of these parameters. please let me know and how actually did you
calculated PID values in your project. please give me the details not
the implementation part. If any one wants to know full details of my
project I will give them in order to solve the problem.

                               Thanking you,
With Regards
Mohd sulaiman

you cannot calculate everything, you have to try the
basic parameters. Take a look to your motor to determine
the speed loop first. What is the rpm/volt operating 
voltage and what is your amplifier gain? This will 
give a rough result for your proportional value. 

No try to operate your system with this value and see,
that the result will be an oscillating system. Therefore
go down with the Kp value to about 1/2 or 1/10 of the 
first estimated value. After this add more and more Ki
until the system does not oscillate any more. The more 
Ki you have, the higher the gain is allowed. What is 
feasable depends from the motor power and final load and
inertia to move. If operation is almost ok, you can try 
to add KD to increase acceleration but you will see, 
that high KD make the system unstable again.

If this speed loop is ok, you can start trying the position
loop. Of coarse you can take a look in the theory of 
schoolbooks but practially you always have to analyze your
mechanic first. http://home.t-online.de/home/janvi/pid/pid.htm
(sorry, my page is in German only)