Comparison sensitivity of distributed parameter systems

System parameter values can vary from their assumed nominal values. These perturbations may alter the performance of a distributed parameter system from the desired nominal performance to an unacceptable degree. To overcome these undesirable effects it may be possible to utilize feedback control in the system to insure that parameter variations alter the system performance with feedback to a lesser degree than an equivalent open-loop system subject to the same perturbations. New results are developed in the form of sufficient conditions to insure that feedback compensation decreases the effects of parameter variations upon the system dynamics for distributed parameter systems described by linear constant-coefficient partial differential equations which may be nonseparable. The theory is applied to two examples, the most significant of which is that of heat exchange between a moving and a stationary medium such as heating material in a through-passage furnace.