How we can avoid the un wanted pulses generated at the output of the PID controller

[FSK]

Sir

  I am controlling the level of a  water at desired postion. I  am using PID  controller. The values are tuned and i got the simulated  reult at the out put . But now problem happened  that  some unwanted pulses are generating at the out put of the PID controller. Can any bode help regrds this please.......

Regards

FSK

[nyc_(is_out_of_here)]

duplicate post  http://forums.ni.com/t5/LabVIEW/How-we-can-avoid-the-un-wanted-pulses-generated-at-the-output-of/td...

one place is enough for asking this question

[nathand]

NYC - you linked back to this post, rather than to the duplicate posted in the Instrument Control board.

FSK - can you attach your code, and a graph of the unexpected output or something similar?  Otherwise there's not enough information to help.

[nyc_(is_out_of_here)]

duplicate post   http://forums.ni.com/t5/Instrument-Control-GPIB-Serial/How-we-can-avoid-the-un-wanted-pulses-generat...

[FSK]

NATHAND

     I have seen the pulses generated at the output by observation  .when  I am simulated the code no pulses are generated but when I am implemented in the  system I am getting this pulses. This is  observed when there is change  in  the value of the sensor.

[nathand]

That's still not a lot of information to work with. Does your simulation match your real system well? Have you tried tuning the real system, or are you using gains derived from simulation? Is there noise in the teal system that is not present in the simulation? Derivative control in particular is very sensitive to noise, if that is your problem consider using PI control only.

Again, it would help if you could graph your process variable, setpoint and output showing these spikes.

[FSK]

Nathand

 I am using PID coefficients which derived from  the simultaneously derived for simulation is same as with model of the system except with sensor  and actuator. Actuator used in the real system is solinodvalve  and  sensor output is not linear with  measured value.

[FSK]

Nathand

 I am using PID coefficients which is derived from simulation.  the real model and  simulated sutem are   same  except with sensor  and actuator. Actuator used in the real system is solinodvalve  and  sensor output is not linear with  measured value. 

 Ther pid coeffiecents are

p=60.7616469938741
i=5.89072520625225
d=-219.965319877913 and 

  system transfer function fort the simulation is

T(s)=0.0217/(17.45s+1)

[nathand]

Well, clearly the simulation and the real system are not the same, or your controller would work the same way.  If you can't provide any data showing what's happening, I can't do much to help.  I'm not a theory person - I don't care what your theoretical transfer function is, if it doesn't work in the real system then it's not very helpful and you should tune using the real system if possible.

Are you running the simulation in LabVIEW, or in some other environment such as Matlab?  If you're simulating in another environment and then trying to use those same tuning parameters, make sure that the forms of the PID and the units are the same.  I assume you're using the LabVIEW PID toolkit.  The time units are minutes (not seconds) and it's in standard form, where the integral gain is actually the proportional gain divided by the integral time (in minutes), and the derivative gain is the derivative rate multiplied by the proportional gain.

[FSK]

Nathand

   Sir  i will give the data tommorw as today the lab will not open for us. Sir how i can tune the real system.

 I am calculating the PID coeffiecents( P I D values )  using by the simulink model and calculated the  Kc Ti and Td  values using the formula. then applied in the simulation.