Time dependent matrix entry

Good day,

I've got a repeating sequence block with a 1x2-matrix for the durations of the output values. I however need to change these values, each entry, according to a ramp function that implements a linear increase. Below is a setup of the model I currently have in Simulink.

Any idea on how I can achieve this?

Answer 1

[Jon]

Under source blocks in the Simulink library there is a block called Ramp. It seems like this should work for your purpose.

[Christo van Rensburg]

Hi John,

I'm familiar with the ramp block and have implemented it elsewhere in the model. The real trick is to get the "Ramp" block to work/feed into the "Repeating Sequence" block.

If you have any help regarding that matter it would be greatly appreciated.

Thanks

[Jon]

I'm still not completely clear on what signal you are trying to generate but I'm now thinking it is a sequence of ramps with linearly increasing amplitude. Is this closer to what you are looking for? I construct the signal as a product of a repeating sequence and an increasing stair case.

Also, you could alway construct some arbitrary waveform in MATLAB and then feed it in using the from workspace block.

[Christo van Rensburg]

Hi John,

So the "Repeating Sequence" block in my case outputs a square waveform with a constant frequency/period. I need to increase the frequency (or decrease the period) as the simulation progresses.

The waveform I'm after looks like this:

[Jon]

I think you could get what you are looking for using a chirp (sine wave with linearly varying frequency followed by a sign block to turn it into a square wave. Note that the chirp frequency can either increase or decrease. You set the initial and final frequencies. Also if you need to phase shift it you could insert a delay.

[Jon]

I now see you want the square wave to go from say 0 to 5 rather than -1 to 1. You can just add 1 to the output of the sign block (using a sum block and constant) and then scale it with a gain block.

If you need the on and off (low and high values) duration to be different, you can offset the chirp signal (add a constant) before you apply the sign function.

[Christo van Rensburg]

Hi John,

So I actually managed to figure it out on my own using the blocks shown below:

So what happens is:

• Using a "Variable Pulse Generator" block to generate pulses with the frequency specified by the preceeding blocks.
• I then simply add the appropriate gain (5).
• Finally, each signal is delayed by a time stamp according to my requirement with the "Transport Delay" block.

But thanks once more for your time and effort to help me get to the bottom of this!

Christo