Setting up tables

Table inputs in CENOS are a great way to control many parameters in more detail. They allow you to change frequency, time step, inductor inputs and motion based on the time of the simulation.

However, there are some things to keep in mind when using a table as input.

Enabling the table input

To enable the table input, you can click on the dropdown menu on the right side of the input field and select ‘Table’.

This will open the table input field, where you can input all of the parameters.

 

This field consists of multiple parts

1. Time column
2. Value column (in the picture above it is frequency)
3. Button for adding new rows
4. Button for copying the table
5. Button for pasting values

Filling in the table

Next step is to fill the table with values.

It is quite straightforward – you need to know what value you want to have at what time.

For example, if your simulation runs for 10 seconds with 0.1 seconds time step and you want to set the frequency as 10kHz for the first 5 seconds, and then change it to 20kHz after that, the table will look something like this:

A few things to note here:

1. Each frequency value has a start and end time
2. The last row has the time set as the end time of the simulation
3. The table values go from 5 to 5.1 because the time step is 0.1 seconds

Possible issues when setting up a table

An interval has no end time

In the example above you can see that the same value has been set twice – for 0 and 5 seconds, as well as for 5.1 and 10 seconds.

In table format this would look something like this:

If you do not set the end time for each interval, then CENOS will gradually increase the frequency value, so that by the time the simulation reaches 5.1 seconds, the frequency will correspond to the one set in the table:

This works great if that is your goal, but if you were expecting a constant value for an interval, then you should set the start and end times for that.

If you do not set the end time either, CENOS will continue the same pattern – either increasing or decreasing the values which might cause issues:

The time step is too big

When setting up a table, make sure that your time step and table time values are correlating – otherwise you might see some unexpected results.

 

In the above table example, you can see that we have set one row’s time value as 5 and the next one as 5.1.

This is because the timestep is 0.1, so this change will be read correctly.

During the calulation, CENOS will look in the table, see that at 5 seconds it should set 10 kHz, calculate this time step and then at the next time step, which would be 5.1 seconds, it would again take a look at the table and see that the frequency value should be changed.

 

Now, if you have set a bigger time step, for example, 0.5 seconds, then CENOS will take a look at the table at the same 5 seconds, and then at 5.5 seconds, when it will see that the frequency value should be changed.

In this case, the time step would be too large and cause you to have too big of a jump and not catch the table values.

 

A similar thing would happen, if you set the time step as something that does not perfectly divide the table values.

So, if your time step would be 0.4 and the table is the same, then the time when the frequency value would be actually change would correspond to 5.2 seconds, as that is divisible by 0.4.

The last row in the table is smaller that the end time of the simulation

The last row in the table should correspond to the end time. It might also be bigger.

However, if you set the time smaller than the end time, the same thing will happen as with the interval end times.

Let’s say that your simulation will run for 10 seconds, but the last row has the time set as 5.1 – then for the last time steps, the values will follow the same pattern – either increasing or decreasing – and it will cause incorrect results, or even errors, if the values go below 0.