Electrophotographic process control device which uses fuzzy logic to control the image density

A process control device for electrophotographic apparatus, comprising:

• means for periodically forming a reference image pattern on a photoconductive drum;
• an image density sensor for measuring a density of an image formed on the photoconductive element;
• a scanner for writing read image data representative of a document image on said photoconductive element;
• a neural network responsive to data from sensors including a toner density sensor, a surface electrometer, a drum ammeter, a drum rotation counter, an exposure duration counter, a copy counter, a temperature sensor and a humidity sensor positioned within and in peripheral portions of said electrophotographic equipment for outputting image density data by using image density data from said image density sensor as learning data;
• and
• determining means responsive to the image density data from said neural network and write image data from said scanner for performing a predetermined fuzzy combination operation by using fuzzy rules registered beforehand, and converting a membership function resulted from said operation to a non-fuzzy value to thereby estimate image density between times when the reference image pattern is periodically formed and to determine a toner supply manipulation value.