Theoretical Research And Design Of Magnetically-suspended Needle Selection Device For Knitting Machines

Textile industry is one of the important pillar industries and key export-oriented industries, with large economic scale and huge employed population. Knitting industry has played a very important position in the entire textile industry, but the current high-end knitting machines are almost entirely dependent on imports, because our country can not break through the technology of core device. Currently the core needle-selection mechanism of conventional weaving machine is multi-level mechanical transmission, and the performance of knitting needles is constrainted by the driving principles and the mechanism, so it is difficult to further improve the performance since it is affected by the bottlenecks.Based on the analysis and study of the conventional needle-selection technology and the principle of magnetic suspension technology, this paper has proposed a new type of suspension model, electromagnetic-permanent magnetic suspension, and introduced it into the needle-selection mechanism. It has also proposed the theory of axial magnetic-suspension type needle drive. The core of this theory is to impose the electromagnetic force directly on the knitting needles, to enable the drive principles of "zero transmission" from conventional "multi-level transmission" for knitting needles.This paper has proposed electromagnetic-permanent magnetic suspension according to the basic principles of needle-selection technology and magnetic suspension technology, built a mathematical model and transfer function for this suspension mode, analyzed the relationship between various parameters and initially established the basic suspension theory. Meanwhile, the generating process of friction heat and electromagnetic heat of suspension needle device is analyzed by using finite element software. Since the air gap between the suspension needles is variable, force conditions of needles at different air gaps and current are also analyzed in this paper. So the force law of needles and the impact on suspension mode due to power coefficient are obtained. The paper has also discussed how to improve the material and wear resistance of conventional needles, and put forward performance requirements and preparation methods for new knitting needle materials. Finally, the application form of cylindrical capacitance displacement sensor in the needle device has been studied and the selecting method of coating materials and design theory of the controller are also proposed in this paper.The theory of magnetic suspension needle drive method proposed in this paper is helpful for the breakthrough on key device of the knitting machines and independent key technology development in China. And the proposed theory of electromagnetic-permanent magnetic suspension can provide reference and theoretical support for the magnetic suspension technology applications in other fields.