How to get the signal output of a PID controller as a voltage

So I am trying to closed-loop model a PMDC motor in Simulink, using a PID controller to control the voltage input through the angular speed of another motor's rotor. The motor has an input of 36V.

I am told that I need to use a motor driver to act as a bridge between the motor and the controller. However, in simscape I don't think that there is a driver for a PMDC motor (there are drivers for other motors BLDC, stepper, etc.). So I tried to make my own driver using a controllable voltage source block from simscape, however, the output from this block is the same as the output from the PID. So I fed this through a gain of 36/PID signal value.

But then I tried to check what would happen if a constant block was used with 36 as its value and the results are the same, therefore, this means that my makeshift driver doesn't work. Here is what I made:

I wasn't sure how to work with the controllable voltage source so I just put the resistance and the inductance of the motor acorss this voltage source.

Any help would be much appreciated. Thanks a lot!

[Mathieu NOE]

hello

in its simplest form, a driver acts just as a power (audio) amplifier, so it's simply a gain block

for example you can normalize your PID so that it outputs remains within +/- 1

putting then a gain block with gain = your power supply voltage (36 V) , will create an out put that swings between 0 and 36V amplitude.

[Tb]

This was very helpful, however, how would you normalise the output of the PID?

[Mathieu NOE]

you can add a saturation block after the PID (limits at -1 and +1)

[Tb]

Hello agian, I tried this, but doesn't this just remove any values outside of the range 1 to -1, doesn't this mean that information outside this range is lost. I tried this and the output of the PID never stabalises, hence it can't be tuned, is there any other way to "normalise" the output?

Thanks.

[Mathieu NOE]

the saturation block will just limit the output to stay with +1/ -1 limit

if input > 1, output = 1 and the same if input < -1, output = -1

now maybe because you introduce the driver as a fixed gain of 36, the loop gain has changed , so you must probably reduce all the gains from your PID in the same amount as you have increased the loop gain

that is basic feedback loop gain adjustement (trace the bode plot of your system first)

there is no reason not to be able to tune a PID for a PM motor

[Tb]

Ok, I have tried this again, but I think I am making some silly mistake, is there any way I can send you the model to have a look if possible?

[Tb]

The following is the simulink model of the PID, for some reason this system doesn't stabalise:

I am summing this signal as there is a second pid being run in parallel with this one and I want the total signal to control the voltage. Here is the result of PID output:

As you can see this is not what I am expecting, this is with gains of 1 1 and 0 for the PID. So it is not tuned. The H-bridge attaches to the motor.

Thanks

[Mathieu NOE]

can you share your simulink model ?

[Tb]

Hello, I have solved the issue, thank you for the help

[Mathieu NOE]

good news !!