Weft density has been considered as one of the most effective factors on woven fabric construction and it is influenced physical and mechanical fabric properties. Therefore, we developed a closed loop control system in a weaving machine. The manipulator element was take-up roller rotation speed. The weft density was measured by means of a special computational image processing routine. The PID control algorithm used to calculate the desired modification of take-up speed. However, the existing variable delay on the sensing weft density variation by the measuring system causes the conventional PID control system to have been disabled in providing robust action, so the control system was utilized by the Smith predictor to modify control behavior. To adjust control parameters, the function of the weaving machine has been investigated and a simulated model of the weaving process was constructed. The result of set point tracing and regulatory control in various tests indicated satisfactory performance of our new system.A. Almasi Zefrehyee was with the Textile Engineering Department,

Controlling the weft density in the course of weaving is of great importance in technical textiles production. In this study, a closed loop control system was designed and implemented in a weaving machine. Moreover, a PID algorithm was used in the control system. The control action starts by taking a picture from the fabric near the cloth fell. A machine vision system was prepared to calculate the number of weft yarns per inch. Based on the measured weft density, the take-up roller speed was adjusted by changing the supply voltage to the take-up motor. Because of the variable delay between the weft density measurement and cloth fell, the normal PID control system was not able to provide a robust action, and thus, a Smith predictor was utilized to modify the control behavior. The results of set point tracing and regulatory control action indicated the satisfactory performance of our novel system in various tests.