Control system for accurate granular feeding using a screw feeder

Many modern manufacturing industries use granular materials as raw materials. A highly accurate feeder is needed to supply granules to processes in order to maintain the quality of products. There are various types of feeders depending on the purposes and the nature of supply materials. Improvements in current high accuracy feeders and/or control systems are required. In this study, a screw feeder together with a control system, including a flowmeter as a sensor, is discussed. Tow types of flowmeter are used. One is an impact-type flowmeter in current use. The other is a prototype strain-gauge-type flowmeter developed at the author's laboratory. The characteristics of the flowmeters, such as speed of response and the difference of response depending on the nature of supply granules, are examined. A control system using the flowmeters as the detecting element in order to supply fixed quantities with high accuracy was constructed. A self tuning regulator (STR) scheme is applied to the system as the control method. The results show that the strain-gauge-type flowmeter is more sensitive as a detecting element. Good response waves were obtained for a step reference input and a disturbance input.