Estelle,
The immediate issue here is the controller, not the machine model. The current and speed are not regulated as you are intended due to fundamental control implementation errors. For example, due to the SR Flip-flop in the modulation path you end up with an effectively fixed duty cycle of 0.9 @ 5 kHz. The settings for the Relay block are to toggle at +/-1 A but the current reference is restricted to 0-0.2A meaning the current cannot be regulated within that window.
I would recommend systematically reviewing your controller to ensure each portion behaves as expected.
Regards,
Bryan
