Adaptive process controller for electrophotographic printing

A adaptive process control apparatus for controlling a plurality of image parameters in an electrophotographic printing machine is disclosed. A toner area coverage sensor detects value of density values for a composite toner image representing a toner reproduction curve and generates a plurality of corresponding signals. A toner concentration sensor detects a level of toner concentration and generates a corresponding signal. The signals from both sensors are conveyed to a linear quadratic controller and compared to target image parameters, wherein control signals are generated based upon the difference between the two sets of inputs. An identifier also receives the signals generated by the sensors, along with the control signals corresponding to the difference between the two sets of inputs. The identifier then modifies the target images to compensate for changes in image quality due to material aging or environmental changes.