PID Controller rise time question

[Physicist3]

In optimising the PID controller produced on Simulink, my controller has a step voltage of 100V and I am not sure if the rise time is the point where the response curve first reaches (or crosses)this point, or if it is the point where it hits the first overshoot peak?

 

[Floid]

Usually 10% - 90% of desired value (so if stepping from 0 to 100V the time it takes to go from 10V to 90V) is used for rise time. For control you could also use 0 -100% (0 to 100V). Doesn't really matter as long as your are consistent with the measurement so that you can compare results as you tune your controller. Do not measure past the 100% mark though (don't include overshoot peak) because as you tune your system you probably will try to reduce the overshoot.

 

[Physicist3]

Thanks for the reply. I've managed to tune it so that the steady state error is 0.025 above the step voltage. Does this mean that the overshoot is also 0.025 as the sse is above the line so the system has technically overshot?

 

[milesyoung]

Have a look at this:
Underdamped response

Does that help?

 

[Physicist3]

Thats really helpful thanks :)