How to remove the noise in PID iteration loop ?

I have some noise in my PID loop , I had tried using IIR filter but it doesn't get removed. My code is correct in some way but still while using correct P , I , D parameters my target is not followed at higher speed.. please provide me any suggestions. I am using only MATLAB for the coding.

[Aquatris]

Is your issue noise or tracking performance? What part of the plot do you want to improve? What does the plot show in x- and y-axis? Is the plot simulation or experiment? What kind of system is it?

[Usman]

Actually it's both... y-axis gives the speed of the vehicle, x-axis is the time of the driving cycle...

[Aquatris]

The noise does not seem to be present at all times, but only at particular point, where tracking performance is also detoriated. I am gonna assume disturbances acting on the system did not change between times 0 to 1800 (seconds?). The noise and tracking performance looks like a hardware issue. One issue can be your motor is not capable of running smoothly at speeds higher than 80 (rpm?) or your power source is not capable of supplying the required voltages for that speed. At the last part though, it does look like your motor speed is saturated. You might be hitting the maximum speed capabilities of your motor.