Why the different response of two Simulink models?
4 views (last 30 days)
Show older comments
Here is a follow-on question to this original question:
I have two different models of a buck converter (see attached). In the first, the feedback summing junction has a negative sign forming the error signal and the PWM comparator after the PID uses "<". In the second, the feedback summing junction has a positive sign, and the comparator uses ">=". I fully expected the two models to produce the same response, but the second model has over twice the overshoot. Saturation limits of the PID made no difference. Can anyone provide a simple explanation of why the different response?
0 Comments
Answers (1)
Sabin
on 24 Jan 2024
The two structures are not the same. A PID controller is designed to take an error signal as input, which is the difference between a setpoint (the desired value) and a process variable (the measured value). The controller then calculates the output required to minimize this error by adjusting a control element. This is what the first structure is doing. In the second structure, the PID will try to minimize the measurement-setpoint, as the measurement starts from 0 it means the controller will see as input -setpoint and will try to drive it to 0. The controller will overcompensate or undercompensate because it is not receiving a proper error signal which in this case leads to increased overshoot. However, in a some situations the controller will have stability issues.
0 Comments
See Also
Categories
Find more on PID Controller Tuning in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!