A model of the warp dynamics on power looms

Abstract

In some types of power looms, the tension on the warp (lengthwise strands of yarn) is regulated by matching the rate at which yarn is unwound from the beam (yarn supply roll) to the weaving rate. This paper reports a simulation study of one such type of loom in which the regulator permitted too much variation in tension and under certain conditions became unstable. The study uses a nonlinear model of the warp dynamics derived from fundamental principles of elasticity theory and rigid-body equilibrium. The mathematical model is ill-suited to the application of the general methods of control theory. A simulation approach was therefore chosen; it uses a Continuous System Modeling Program (CSMP) operating on a PDP 11/40 computer. The model was successfully calibrated using experimental data from the shop and was validated by comparing its output with manufacturer's data. An extensive study of the warp dynamics under various operating conditions was completed with only two man- months of work. Knowledge gained in the study led to a simple, retrofittable modification of the loom. Its purpose was to improve the control of warp tension and to eliminate the instabilities. It was analyzed by simulation, built in the shop, installed, and found to work well. It is now incorporated in the manufac turer's standard machines.