I am using 3 PI controllers in "Subsystem". When i used Kp and Ki values given in a paper im getting horiible results. So i tried tuning option and i tried different operating points also. It always showing "linearizes to zero". Why is it so?
MATLAB: Cant i tune this simple electrical system? “The plant model in the PID loop linearizes to zero” Please help!!!!!!!!!!!!!!!!!!!!!!!!!!!
electricallinearisation errorpid tuning
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The plant is linearized, but the linearization at t=0 is a gain of zero. Most likely this happens due to initial conditions in the model. You can ask the PID Tuner to linearize the model at a simulation snapshot of say t/2, when everything comes to steady state.
When you do that, the PID Tuner successfully linearizes the model and designs a PID controller.
Here are the snapshots of the steps using R2014a.
Hi Minjae,
Even if the dynamics equations are fine, some nonlinear systems are difficult or impossible to linearize. A possible way is to use data to estimate a model of the system.
The workflow is as follows:
- In the PID Tuner tab, select Identify New Plant.
- The Plant Identification tab will open. Select Get I/O Data, then Simulate Data so to generate identification data by simulating the model.
- It will open the Simulate I/O Data tab, where you specify the input data (for example a step function) used for the plant identification.
- Click Run Simulation. Then, click Apply and Close.
- Then, the Plant Identification tab will open showing the results of the plant identification. Once in there you can modify the response by moving or adding factors (for example delay, zero, integrator).
- Select Apply. It will create a new variable in the Data Browser section of the PID Tuner.
- Go to the PID Tuner tab, select Step Plot: reference tracking plot. Here the PID is using the new identified plant. You can still improve the system response by moving the sliders.
- Click Update Block and simulate the model with the new PID parameters.
Hope this can help to solve your question.
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