Research Of Robust Control Methodologies For Loom Warp Tension Control

Whether the warp tension of a loom during the textile process is constant or not has a significant influence on fabric qualities. Thus, the effectiveness of warp tension control is the key point of the standards of textile weaving. The research of novel warp tension control techniques is therefore of great importance.First, this paper introduces the background and values of warp tension control. The achievements of domestic and international researchers about numerous kinds of advanced control techniques are summarized, and the merits of sliding mode control and adaptive sliding mode control are described.Second, through the dynamical analysis of warp’s movement from a warp beam to a fabric beam along with shedding motions and beating-up motions, a plant model of warp tension control from control input signals to system output signals is obtained. In order to simulate realistic conditions, a sinusoidal signal with reasonable frequency is utilized to represent the external disturbance existing in the system.Third, a random noise signal is added to the output tension signal to mimic real sensor output, and a low-pass filter is adopted to filter high-frequency noises. A PID controller and a conventional sliding mode controller are designed for the same plant model and the system stabilities of them are verified, respectively. For the aim of alleviating chattering phenomenon, which is a common drawback of sliding mode based controllers, a boundary layer control technique and a low-pass filter are utilized. Comparison results demonstrate that the sliding mode controller is superior to the PID controller due to its capability of handling the parametric uncertainties in the plant model and compensating for the external disturbance.Last but not least, in order to increase the accuracy of the controller to compensate for the external disturbances, an adaptive sliding mode controller is designed for the same plant model, and the stability of the control system is verified according to Lyapunov principles. Simulation results indicate that the proposed adaptive sliding mode controller possesses superior control performance and smaller tracking errors since it is not only of strong robustness to deal with the parametric uncertainties existing in the plant model, but also capable of adaptively estimating the external disturbance and compensating for it more precisely.