Minor loop feedback
Minor loop feedback is a classical method used to design stable robust linear feedback control systems using feedback loops around sub-systems within the overall feedback loop. The method is sometimes called minor loop synthesis in college textbooks, some government documents. The method is suitable for design by graphical methods and was used before digital computers became available. In World War 2 this method was used to design Gun laying control systems. It is still used now, but not always referred to by name. It is often discussed within the context of Bode plot methods. Minor loop feedback can be used to stabilize opamps. (Wikipedia).
