Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001
· In real systems we expect that certain events will occur that are not part of our system model.
· In this case we assume that the system control is happening as expected, and we add in a new disturbance input.
· The block diagram below shows one of these systems, with a disturbance injected between the controller and the process.
· Notice that in the above form we are reducing the problem by finding differences (basically a partial differential solution) which will be a good approximation when the disturbance is not too fast or large.
· We can develop an equation for the controller, based on the desired system response to the disturbance,
· The closed form expression can be calculated by replacing the desired transfer function,
· These systems are often called regulators, and can be used when a system is subject to unexpected noise. Examples of possible applications would include plumbing systems, electrical power supplies, etc.