1. A control system comprising: an actuator for positioning a control device comprising a control surface, wherein the actuator positions the control surface in order to control a model state and wherein the model state describes a spool speed; a control law for directing the actuator as a function of a model output, and a closed-loop model processor for generating the model output, the closed-loop model processor comprising: an open loop module for generating the model output as a function of the model state, a constraint on the model state and a model input, wherein the constraint on the model state is based on flow continuity; a corrector output module for generating a corrector output as a function of the model output; a comparator for generating an error by comparing the corrector output to the model input; and a model state estimator for generating the model state as a function of the error, such that the error is minimized; wherein the spool speed has a response time greater than a cycle time of the closed-loop model processor.