PID Controller rise time question

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Discussion Overview

The discussion revolves around the definition and measurement of rise time in the context of PID controller optimization using Simulink. Participants explore various interpretations of rise time and its implications for controller tuning.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether rise time is defined as the moment the response curve first reaches the target voltage or when it hits the first overshoot peak.
  • Another participant suggests that rise time is typically measured from 10% to 90% of the desired value, emphasizing the importance of consistency in measurement for comparison purposes.
  • A different participant notes their steady state error (sse) of 0.025 above the step voltage and inquires if this indicates an overshoot, suggesting a potential relationship between sse and overshoot.
  • A later reply provides a reference to an underdamped response, possibly to clarify the behavior of the system in relation to rise time and overshoot.

Areas of Agreement / Disagreement

Participants express differing views on the definition of rise time and its measurement, indicating that the discussion remains unresolved regarding the most appropriate approach.

Contextual Notes

Participants have not reached a consensus on the definition of rise time, and there are assumptions regarding the measurement methods that have not been fully explored.

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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?
 
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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.
 
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?
 
Thats really helpful thanks :)
 

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