Simulink Signal Builder: Change of Variable

In short, I'm designing a cruise control system and I want to simulate the profile of a "hill". It makes more sense to model the hill as a function of position rather than time. It's a closed loop model, so I have a "velocity" node. I figure if I add an integrator from this node to to a custom variable, and use that custom variable as the axis of signal builder, then I will get the model I am looking for.

Any way to do this? Or alternatives?

Answer 1

[sanidhyak]

Hi @Andrew Sager,

I understand that you are working on a cruise control system and want to model a "hill" as a function of position instead of time using Simulink Signal Builder.

Based on your question I am assuming that you are using Simulink R2018b. In this version the “Signal Builder” block supports only time as the independent variable, which limits direct implementation of position-based profiles.

To achieve your goal, you can follow the below steps:

1. Use an “Integrator” block to convert the velocity signal into position.
2. Then, instead of “Signal Builder”, use a “1-D Lookup Table” block.
3. Configure the “Lookup Table” to take position as the input and define the “hill” profile by mapping position to elevation.
4. Connect the “Integrator” output to the “Lookup Table” input and use the table's output in your cruise control logic to simulate the “hill” effect.

You can also use “Scope” blocks to visualize the velocity, position, and “hill” elevation during the simulation.

This approach models the “hill” as a function of position rather than time.

If you are using Simulink R2021b or later, you can also explore the “Signal Editor” block, which offers more flexibility, though it still primarily uses time as the independent axis.

For further details on the “Lookup Table” block, refer to the official documentation:

• https://www.mathworks.com/help/simulink/lookup-tables.html

I hope this helps.

Cheers and Happy Coding!