Repeat a reference curve?

Brian Balvin

Posted on 11.01.2018 23:05

I am setting up a teststand to use a time reference curve to that will then need to be output as a CAN message to another module. We have a reference curve setup for a 15minute duration, but need to repeat continuously until failure shutdown conditions are met.

Looking for any guidance on how to make the curve repeat once it has hit it's last setpoint. Seems there should be a way to utilize a custom block in the sequence, but I am unsure where to start.

Note, using a Dewe 43. An attractive alternative (if possible) would be the ability to import my reference setpoints

Anže Baš
Software Test Engineer I
Posted on 12.01.2018 11:54

Hi Brian,

unfortunately in the current state of the time reference curve you aren't able to repeat the signal. I will add a request to our feature wish list for a repetition check box, but that could take some time to implement.

Maybe you could do a workaround with the sequencer, where you would regulate a control channel using the calculation and delay blocks to make your reference curve. But the sequencer is asynchronous and the curve wouldn't be linear - the changes would be step shaped.

Another possible workaround would be to create a very long datafile with arbitrary AO channel, that looks like your time reference signal is simulation mode and then use that file for the "Reference curve type -from data file" option of the time reference curve. That will however require you to make a very long file.

Please tell me which option would be best for you and try to explain it a little more into detail.

Brian Balvin

Posted on 12.01.2018 14:54

Thanks for the quick response. I am working down the path of using the sequencer today and will see how that goes. Stepped changes will be fine for these cycles.

I had wondered if there was a way I could make a 15 minute data file of my curve, and seeing if the sequencer should use that and then reload and repeat it, but it doesn't look like that is an option.

Anže Baš
Software Test Engineer I
Posted on 15.01.2018 08:54

Attached you can find an example setup and sequence file of how you can make a repeatable reference curve using the sequencer. Unfortunately like I mentioned earlier, the transition is stepped.

The simple example that I created only has 9 points from 1 second to 9 seconds as can be seen in the setup file. I then used the mod formula option to get a repeatable sequence of 10 steps, which I used in the sequencer to change the reference value depending on its current value. The control channel from the user inputs module can be single value or asynchronous. To make it synchronous you need to use it in a formula (in the example Reference2 channel) and change the timebase in the Time axis tab (left side of formula form) and set it to Sync.

If you have any additional questions about the setup and sequence, I'll gladly help.

Attached files:
Brian Balvin

Posted on 16.01.2018 22:07

Thank you for the help, it is much appreciated!

I ended up making a subroutine in sequencer that was a pattern of simple calculations (control x = speed value) followed by a delay of 30sec. I repeated this pattern for all the speed values needed to get my 15 minute cycle. In the main sequence I have this repeating 4000 times (gets me to 1000hrs, we will likely shutdown at some point in this) We are using a digital out to shutdown the teststand if certain conditions are met, so even if the stand shuts down, the control cycle will continue.

I actually needed to do this over 3 teststands, with independent control of each, so my actual sequence routine is quite a bit more complex.

Anže Baš
Software Test Engineer I
Posted on 17.01.2018 06:57

No problem, I'm happy to assist you. Like I said in an earlier reply, the request for a repeat checkbox in the time reference curve was added to our feature request list and hopefully it will be added in the near future.

Login to reply to this topic. If you don't have account yet, you can signup for free account .
This website uses cookies to ensure you get the best experience on our website. Learn more