Simulink PID autotuning problem

Hi, I have tried simple PID auto tuning function, but I'm getting rather strange result. I have attached mdl file, so You can maybe point to me where I'm doing wrong.

Pete

P.S. Sorry if question sounds stupid, I'm a newbie in Matlab/Simulink world

Answer 1

[Arkadiy Turevskiy]

There is nothing wrong or strange with your model. You did not provide op_trim1 operating point that your model uses, so I just initialized the integrator in PID block at 6.37 (I can explain how I did this if you want) - basically to get rid of a large initial transient.

Once I did that, and ran the simulation with your PID gains, I got a reasonable response:

Another note: as gravity is somethign that does not change much, you can just add a constant feedforward term to your controller to compensate for it. Then, even if gravity changes a bit as you change locations, PID will do a good job compensating for that:

Answer 2

[Arkadiy Turevskiy]

Ok, here is how I got that integrator initial condition.

First I added Trim Output Constraint on the "height" signal. To do that, right click on the signal, and specify Trim Output Constraint, as shown below.

Next, launch Linear Analysis Tool:

Now, we want to trim the model:

Click to specify the trim conditions:

All states should be in steady state:

The output (height) should be at 0:

Click "trim". Tool computes the operating condition op_trim1. Examine it to see the value for Integrator in the PID Controller:

All of this can also be done with a few lines of code:

model = 'Proba_3';
opspec = operspec(model);
opspec.Outputs(1).Known = true;
findop(model,opspec)

Answer 3

[jashandeep kaur]

may i know how does auto tunning take place?how does controller calculate the desired values of P and I?is there any method or algo?

Answer 4

[Mudit Verma]

Autotuner not working in my model there is no PId gains showing they are showning 0 and only frequencies are showing in display block

i have attached my model plzz see and give me solution to my prob.