PID adaptive cruise control

I am following guideliness for this project like:

http://brettbeauregard.com/blog/2011/04/improving-the-beginners-pid-introduction/

And for tuning:

https://www.google.com/amp/s/www.electronicshub.org/pid-controller-working-and-tuning-methods/%3Famp

I’ve been searching the internet for more than 2 weeks before asking the question here... And like i said if there are faults in my programs which i dont see the tuning methods will never work. Like in the link i gave it says:

  • increase P til oscillation
  • increase I til it slowy goes to the setpoint, this may reult in overshoot
  • increase D to reduce the overshoot

So i follow all the steps, but my overshoot never reduces...