Why I can't tune/design PID for a stepper motor with lead screw modelled with simscape?
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Hello,Would you please tell me how to tune the PID controller for a stepper motor with a lead screw modelled with Simscape?
I want to add a driver model by introducing a closed loop. I used the "tune" button inside the PID block. I tried to linearize the model and find the p and i values. That was unsuccessful too. Kindly teach me how to tune a PI for this simple model in Simscape. Thank you.
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Sam Chak
on 23 Dec 2024
Hi @MOKHTAR
I am unfamiliar with the graphical model design using Simscape. However, if you can provide the performance specifications and the mathematical model (preferably differential equations with code) of the stepper motor with lead screw, I may be able to investigate whether it can be controlled by a PID controller.
Answers (1)
Aravind
on 24 Dec 2024
It seems you're trying to use the "PID Tuner" app to automatically tune a PID controller in a Simulink model with Simscape elements, but encountering some difficulties.
After reviewing your model, there don't appear to be any major errors. One possible reason for the linearization issue could be the selection of initial conditions. Linearization occurs around an operating point, so choosing the right operating point is crucial. You might try asking the "PID Tuner" app to linearize the model at different simulation snapshots, such as at 2s, 3s, or 5s, when the system reaches a steady state. This approach can help the "PID Tuner" app successfully linearize the model and design a PID controller.
Another reason for linearization failure could be model fidelity and accuracy. Ensure that your Simscape model is accurate and that its parameters closely match real-world values. This will aid the "PID Tuner" app in finding a better operating point, linearizing the model, and designing a PID controller.
Additionally, I noticed that your model includes disturbance forces affecting the lead screw's motion. When tuning a controller, it is best to exclude disturbances, as they can interfere with the linearization process. Consider removing these disturbances or setting their values to zero before using the "PID Tuner" app.
Here are some resources to help you further:
- Reasons for Linearization Failure: https://www.mathworks.com/help/slcontrol/ug/plant-cannot-be-linearized-or-linearizes-to-zero.html
- MATLAB Answer on Plant Linearization Failure: https://www.mathworks.com/matlabcentral/answers/135228-pid-tune-plant-cannot-be-linearized-why
- MATLAB Answer on PID with Simscape Components: https://www.mathworks.com/matlabcentral/answers/467606-why-i-can-t-tune-design-pid-for-a-vehicle-modelled-with-simscape
I hope this helps resolve your issue.
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