Design a closed control loop for speed regulation of the separately excited DC motor for the following set of disturbances?

a. Step disturbance in reference speed from 50% rated speed to rated speed. (perform this at the no-load condition).
b. Step disturbance in input voltage from 80% of the rated voltage to 100% ((perform this at the no-load condition)).
c. Step disturbance in load from no-load to 50% of full load. (Perform this at rated speed and rated voltage conditions).