Abstract: A method and apparatus for adjusting a variable parameter of a dynamic system in response to a signal representative of the system performance so as to optimize system performance with respect to that parameter. A first signal related to system performance is extracted from the dynamic system and is thereafter coupled to a plurality of performance index blocks, each of these blocks for operating on this signal according to a different predetermined characteristic transfer function. The output level from a selected performance index block is periodically sampled and the sampled level is compared with a previously sampled level to provide a positive or negative difference signal. A first pulsed signal is formed wherein pulses and zero levels are respectively representative of the incidence of opposite polarity levels in the difference signal.