Research On Control Technology Of High-precision Dynamic Yarn Feeding Stepping Motor For Circular Weft Knitting Machine

The rapid development of knitting industry creates opportunities for the development of knitting machinery,but also challenges the manufacturing process and control accuracy of knitting machinery.Circular weft knitting machine is one of the representative types of knitting machinery,and there are problems(such as flaws in horizontal stripes,loop length changes and holes)in the products knitted by the circular weft knitting machine.According to literature at home and abroad and factory investigation,uneven yarn tension control is the main reason for the flaws in knitted fabrics,and the above problem is mainly caused by insufficient control accuracy of stepping motor.Therefore,this thesis takes the stepping motor as the research object,and studies the control algorithm,hardware system and software program of the stepping motor.A simulation model and an experimental platform of the stepping motor are built,and the design scheme of control technology of high-precision dynamic yarn feeding stepping motor of circular weft knitting machine is preliminarily realized.The main research contents are as follows:First,the problems of large speed fluctuation of tension motor and insufficient control accuracy of needle cylinder motor of the existing circular weft knitting machine are studied.Taking stepping motor as carrier,self-adaptive PI controller and speed damping controller are designed to accelerate the tracking response,reduce the steady state speed fluctuation and improve the yarn tension control performance,and a sliding mode position controller is designed to precisely control the needle cylinder motor.Second,the hardware circuit of circular weft knitting machine is designed.On the basis of the determination of the overall scheme of the control system of circular weft knitting machine,the speed and position of the stepping motor can be controlled with high precision by designing the main control circuit,power supply circuit,drive circuit,detection feedback circuit and communication circuit.Third,the software program of circular weft knitting machine is designed.The modularized and delaminated concept is adopted for the design of software program.The main program and four subprograms(i.e.interrupt service subprogram,detection subprogram,speed damping algorithm subprogram and sliding mode position algorithm subprogram)of the system are designed.Finally,the control system of two-phase hybrid stepping motor is simulated and experimented.A simulation model is built through MATLAB,and the PI control algorithm is introduced for comparison,and the results are analyzed.An experimental platform is built and the experimental verification is carried out on the platform.On this basis,the yarn tension is tested on the circular weft knitting machine and the quality of the products is tested.According to the results,the good results of the control system are achieved,the design requirements can be met,and the excellent performance of the control system is reflected fully.