ABSTRACT
A feedback loop exists in a model when a connection emanating from a branch point is directed or fed back into the original direction of signal ¦ow, reentering a prior block in the ordered sequence of block operations. An algebraic loop results when the output of a block operation is used as a part of the very same input to the block; e.g., output y = u1 + u2 involves the inputs u1 and u2, but input u2 = f(y). That is, the block output is a function of its input, as expected, yet that input is a function, although usually indirectly, of the same block’s output. The feedback loop and algebraic loop are essentially equivalent in the context of using model diagrams to represent mathematical equations.
