Load characteristic of dc generator (dc machine block)

Hello, I want to plot the load characteristic (Vload,Iload) of a dc generator using the dc machine block in simulink. Two things most concern me: 1.)How can I create and add a magnetization curve in the dc machine block? 2.)How can I change the load current (Iload) through simulation? To plot the load characteristic I want to begin with zero load current and increase the load current until I reach the nominal value of the load current. For every value of the current I want to plot the load voltage. I accept every possible solution that may not include the dc machine block, or include matlab code. This is a very important university project.

Thanks in advance

[Tamir Suliman]

the simulink model screen shot photo is not really clear would it be possible to upload the file to test it ?