This solution given by Jovan is a good way to plot the signals that you require in the report.
An alternative, in case you don't wish to replace your plots by using the attach_figure function and to attach them as they are, is using the allure package and the allure.attach.file function.
With this function, you can attach files, like .png format, in your Allure report. In a quick test that I tried, the attached figure is also shown on the PDF report.