PID Controller in Simulink question

Can i apply a series of values as Kp Ki and Kd values instead of just one single value. Like lets say it starts from 1,2,3.. and after the last value it stays at that value till end of simulation.

Answer 1

[Paul]

Set the 'Source' parameter to 'external' as in doc for PID block. The you can calculate the gains external to the block as functions of time however is needed and feed the gain values into the block as inputs.

[Manikanta Aditya]

Thanks Paul for your reply, but could you explain with more details of the steps to follow, please?

[Paul]

Not without more information about what you don't understand. Do have a Simulink model? Does that model include the PID block? Is that Source parameter set to 'external'? Etc. Where are you getting stuck?

[Manikanta Aditya]

I do have PID Controller block, and the parameter is set to external too, but My question is like how to apply a series of values as Kp Ki and Kd rather than a single value in the block parameters? Like lets say it starts from 1,2,3.. and after the last value it stays at that value till end of simulation.

[Sam Chak]

Hi Mani, I think you want to apply the time-varying gain function, Kp(t) = Staircase function, which can be easily constructed by visualizing how the gain jumps from one value to another, using a few Heaviside functions, kᵢ·θ(t – Tᵢ).

[Paul]

@Manikanta Aditya

Use the blocks available in Simulink to compute Kp (and the others) as whatever function of time is desired.

Do you really want the Kp gain to start at 1 and then keep increasing by 1 at a fixed rate? If so, what is that rate? If not, what is the actual function of time that is Kp(t)?

[Manikanta Aditya]

I want to increase by a set of values instead of one value, so I want to know about this, like I want like the below mentioned

% Create a PID controller block.
pid_controller = pid(1, 1, 1);

% Create a list of KP values.
kp_values = [1, 2, 3, 4, 5];

% Create a list of KI values.
ki_values = [4, 5, 6, 7, 8];

% Create a list of KD values.
kd_values = [7, 8, 9, 10, 11];

[Sam Chak]

I see now, you are not using Simulink. So you want to hold the last value of each gain?

But I think that the pid() function does not accept time-varying parameters. However, you can possibly use the time-sampling approach or event-triggered method to update PID controller

kp_values = [1, 2, 3, 4, 5];
ki_values = [4, 5, 6, 7, 8];
kd_values = [7, 8, 9, 10, 11];
kp_values(end)

ans = 5

ki_values(end)

ans = 8

kd_values(end)

ans = 11

pid_controller = pid(kp_values(end), ki_values(end), kd_values(end))

pid_controller =
 
             1          
  Kp + Ki * --- + Kd * s
             s          

  with Kp = 5, Ki = 8, Kd = 11
 
Continuous-time PID controller in parallel form.

[Manikanta Aditya]

Thanks @Sam Chak!, It was helpful

Answer 2

[Sam Chak]

Hi @Manikanta Aditya

If you set the PID controller block to have external inputs for the control gains as advised by @Paul, then the configuration should look like the following block diagram. However, I'm unsure how you intend to set up the filtered derivative, since yours has only Kd.

[Manikanta Aditya]

Got it, thanks @Sam Chak