[Simulink] Create chirp signal in trigger subsystem block

Hello everybody

I want to create a chirp signal that only run when I press the push button like this:

https://ch.mathworks.com/matlabcentral/answers/847085-how-can-i-model-the-waiting-time-in-simulink?s_tid=srchtitle

In the link above, the signal is the sine signal, therefore the file can run smoothly. However, when I change to chirp signal, this can not run because the sample time of chirp signal is not inherited:

I want to ask how can I create a chirp signal that only run when I want?

Thank you very much

Edit 1: Sorry for the confusion, I want to replace the Enabled Subsystem by the Triggered Subsystem.

I have attached the file. The Matlab release is 2022b.

Edit 2: The reason I want to use the Triggered Subsystem is because I want the signal starting to run when I press the button (ON). If I use the Enabled Subsystem, the signal will start to run at the begining of the simulation and will show on the scope when I press ON. Please correct me if I wrong. Thank you very much.

Edit 3: I have put the 3 blocks: Enabled Subsystem_sine, Enabled Subsystem_chirp and Triggered Subsystem_chirp for you to compare.

Edit 4: I have put the 4 blocks: Enabled Subsystem_sine, Enabled Subsystem_chirp, Triggered Subsystem_chirp, Enabled Subsystem_Signal_builder for you to compare.

Edit 5: I have updated the file so that it's easier to understand. I will use the signal builder to build a more specific signal so that it's easier to see what I want.

First, I run the simulation for 3s when the swich is OFF:

After 3s, I press the button to ON:

You can see the result in the picture below:

What I want is the signal start rising at 3s as the red line in the picture below:

I hope it's more clarify.

[Angelo Yeo]

Can you share your model and tell us which release you used? It's best to reproduce the issue with the model.

[madhan ravi]

Like @Angelo Yeo mentions it"s better to know the release. I had no problems running the model in 2023b from the link and replacing it with chirp signal block, didn"t check it for Enabled Subsystem. Note: in the link Enabled Subsystem was used and you are using Triggered Subsytem.

[Nguyen Ngoc]

Thank for your reply, I have updated my question with the file

[madhan ravi]

Enabled subsytem should suffice your use case.

By the way, you are using r2021b not r2022b.

[Nguyen Ngoc]

The reason I want to use the Triggered Subsystem is because I want the signal starting to run when I press the button (ON). If I use the Enabled Subsystem, the signal will start to run at the begining of the simulation and will show on the scope when I press ON. If you let the button at OFF and run for 3s, then press ON, the signals show in the scope will be the same. I want it to start when I press ON, which mean the signals must be different. Please correct me if I wrong.

[madhan ravi]

I am not sure what you are referring to. You can hold your states or reset it in the Enabled subsytem.

[Nguyen Ngoc]

Thank for your reply, I will be more specific.

I have updated the file so that it's easier to understand. I will use the signal builder to build a more specific signal so that it's easier to see what I want.

First, I run the simulation for 3s when the swich is OFF:

After 3s, I press the button to ON:

You can see the result in the picture below: (please ignore the legend: Enabled subsystem_chirp; it should be: Enabled subsystem_signal_builder)

What I want is the signal start rising at 3s as the red line in the picture below:

I hope it's more clarify.

Answer 1

[R]

Hi Nguyen,

Thank you for providing your model and the output to explain your case.

As you correctly identified, the ‘Chirp Signal’ block in Simulink doesn't inherently adhere to a sample time and executes at the Simulink runtime. To address this, refer to the attached model (Image for reference):

Your requirement can be met if you know how much of a delayed start you want to assign the chirp signal. Refer to ‘Delayed Chirp’ subsystem in the attached model, which employs a ‘Transport Delay’ block to buffer the input signal by a defined delay. In the model, I set it to 3 seconds and as a result in the `t_delay_chirp` signal plot, you can observe it starting at 3s in the Scope output below:

The enabled subsystem that you used is demonstrating the right behavior. It retains the previous value (0 initially), until the button is pressed- where it enables the output from the subsystem. Refer to the plots of `enabled_chirp` and `normal_chip` is identical until the trigger is enabled after around 3 seconds.

Depending on your specific needs, you can choose between the two available options and modify your approach accordingly.

[Nguyen Ngoc]

Thank you, can you save the simulink file into the older version? I'm using the Matlab 2021b.

[R]

Sure, I've edited my answer to include the model saved in MATLAB R2021b. Hope this helps!

[Nguyen Ngoc]

Thank you