Fundamentals of feedback control applied to microcomputer instrumentation design

Feedback control is widely used in applications which range from simple control of room temperature to very sophisticated control of space flight. This paper describes some fundamentals of feedback control as they apply specifically to microcomputer based medical devices. A classical controller is described in its analog and digital implementations. Reference is made to methods for adjusting or tuning the controller for specific applications. Successful applications of adaptive or self-tuning control are discussed. Examples of feedback control include systems to control arterial blood pressure by the infusion of sodium nitroprusside, systems to control arterial carbon dioxide concentration by mechanical ventilation and systems to control depth of anesthesia by controlled anesthesia delivery.