A quarter century after he developed his model, John Robinson continues to proselytize to process engineers about his dryer control system.
Robinson began developing the algorithm for his control system in the late 1970s, while working at a wood veneer manufacturing facility. At the time, the dry bulb temperatures of a dryer's heated air, the speed of the product through the dryer and steam pressure were the variables used to control moisture content. But the actual levels were never known until the process was complete. The result was a broad bell-shape curve indicative of significant variation in moisture content. If the temperature drop in the dryer's air was known, Robinson reasoned, a model could be built for a feed-forward control system to automatically adjust feed rate and heat input, regardless of the initial moisture content, thickness or type of product.