Improvement of Control Performances of Linear DC Motor with Needle for a Knitting Machine

Abstract

In this paper, we have studied characteristics and structure of a linear dc motor for a knitting machine. We propose a method to improve control performances. In the method, first, we have designed a two-degrees-of-freedom controller for high accurate and smooth position response. However, there is a limitation of control characteristics only using the controller. Next, using the fact that motion pattern of needle is repetitive at each cycle, we have designed a learning controller. At each trial, set desired signal is modified by the position, velocity, and acceleration errors for next trial, with the aim of progressively reducing the tracking errors. Through the experimental research of the control system, we present the idea that the response delay is a main cause of divergence in the learning control process. To solve this problem, leading of error and filtering compensation simultaneously is a very good method. Unstability which is taken place by the delay time is effectively eliminated. Some satisfactory results are obtained in experiments.