Modulo plots

Modulo plot

This type of plot is dedicated to observing the change in a value for a variable across a period over cycles. The X-axis can be the time period or a variable representing the cyclic changes in the system. One of the most common applications is to analyze physical quantities in a rotary machine, such as pressures in an internal combustion engine over the four-stroke cycle.

We will illustrate this using the ModuloPlot.ame demo from the Tutorials directory.

Open the model and go to Simulation mode.

Modulo plot setting parameters

setting parameters for a Modulo plot

Setting parameters for a modulo plot

Procedure

1. Open the Plot Circuit settings through the Tools > Advanced menu.

Figure 93: Plot circuit settings

2. Define the Modulo variable. In this example we select the angular position of crank.There are two methods to do this:

Drag and drop the variable from the Variables pane to the Use a variable field.

Click the Choose button. This opens a dialog that lists all the components and their variables. Expand the components to display their variables, or use the Search field at the top to filter the list. Select the checkbox next to the variable you want to add and click OK.

When a variable is selected, its title is written in bold, while the alias of the component is written in grey. You can click once on the Use a variable field to highlight the component on the sketch, and double-click it to highlight the component and center the view on it.

3. Define the Default period, and the Default offset.

Displaying a Modulo plot

displaying a Modulo plot

Once you have performed a simulation run, you can display a Modulo plot in the following ways:

Procedure

1. Right-click on a variable in the Variables or Watch variables view.

2. Select Plot > Modulo.

Or

Procedure

1. In a standard plot window, select Tools > Create modulo plot.

2. Click on your original graph to select it.

Or

Procedure

1. From the Simcenter Amesim Analysis toolbar, click the arrow next to the Plots button and select the Modulo tile.

An empty Modulo plot window opens.

2. Drag and drop a variable from the contextual Variables window.

When you select one of these options, the Modulo plot is displayed in a new plot window:

Understanding a Modulo plot

Modulo plot understanding

A Modulo plot contains two rows. The upper row represents the evolution of the variable over the full duration of the simulation, and the lower row displays the selected period or cycle.

understanding a Modulo plot

To select a cycle:

• use the slider, or,

• use the arrows in the Cycle field.

Results

Figure 94: Select a cycle

Click the cursor replay button from the toolbar to display the replay cursor coordinates. The modulo value is shown in the value boxes.

On the first graph, the modulo value of the value box corresponds to the value of the modulo variable at the current time. On the second graph, it is the modulo value, between 0 and the period.

Note

This information is even more interesting in an XY Modulo plot because in this case, the modulo variable value cannot be read on the X axis.

Figure 95: Cursor replay

When you start the replay, you can see that when the time reaches the end of a cycle, the next cycle is activated automatically.

Note

If you have two or more items on your graph, you can switch it to an XY curve. Please refer to the XY curve section for more information.

The result is a 2D line plot of the variation of the Y item(s) versus the X item for each cycle.

Stacked cycles

Modulo plot stacked cycles

stacked cycles

You can superimpose the Modulo plots for the whole simulation by using the Stacked cycles option:

Note

If the modulo plot window has several columns, the activation of the stacked cycles is performed on all graphs.