A ramp block going backwards?

Hey people!

I am using a ramp block in Simulink driven into an m-function. I am checking the signal every time the m-function is executed and sometimes the ramp value is decreasing.

How can be this possible?

Many thanks.

[Azzi Abdelmalek]

How are you checking the signal in the m-function?

[Dani Tormo]

Saving the ramp value in a persistent variable.

Answer 1

[Guy Rouleau]

You are probably using a variable step solver. Variable step solvers often need to take steps backward to ensure they respect the specified tolerance.