Closed-Loop Control Systems Containing a Digital Computer

A discussion is given of the concepts of delay and distortion in feedback loops, with special reference to some of the special features incurred by digital control. Simple examples are given. Various approximations are presented for the ``starred´´ transfer function in terms of the original analog transfer function, both in signal order to facilitate stability computations for digitally controlled loops, and also to illustrate the dependence of the properties of such loops on the analog and digital parameters.