纬编针织机编织过程中三角振动响应特性

Vibration response characteristics of cam in knitting process of weft knitting machine

纬编针织机编织过程中工作状态及故障的实时检测对提高其编织性能和稳定性具有重要意义,为解决单一品种执行器工作状态实时检测通用性差,无法保证纬编针织机终端控制环节准确等问题,结合纬编针织机编织过程中织针与三角的动作工艺,搭建其编织过程三角振动响应特性测试平台,得到在不同转速和不同针法下三角振动响应特性(振幅、频率)与转速、出针方式的数学关系。结果表明,测试平台可适用于各品种纬编设备,且可从设备的控制终端——织针的出针方式实现其编织过程中工作状态及故障的实时检测,对从振动层面提高纬编针织机稳定性具有一定借鉴意义。

Objective The existing research primarily focuses on real⁃time detection of the working status of a single species of actuator,resulting in poor generality and inability to ensure the accuracy of the terminal control process in the weft knitting machine.This study investigates the forced motion characteristics between knitting needles and cam during the knitting process,providing theoretical and experimental evidence for the real⁃time detection of the working status and faults in the weft knitting equipment from a vibration perspective.Method Combining the actual weaving process of the weft knitting machine,which involves the knitting needle impacting the cam and undergoing forced motion along the cam track,a testing platform was designed to investigate the vibration response characteristics of the cam during the weaving process.PZT(piezoelectric ceramic)was attached to the surface of the piezoelectric cam,creating a′cam+PZT′coupling system.Vibration characteristic curves of the coupling system were obtained at different rotational speeds and knitting techniques.Results The vibration characteristics(amplitude,frequency)under different rotational speeds and knitting techniques,as well as their mathematical relationship with the rotational speed and needle selection method,yield the following three results for fault diagnosis and online detection of weft knitting equipment from a vibration perspective.Firstly,the moment when the knitting needle strikes the cam,the vibration signal experiences a rapid increase in amplitude,reaching its maximum value within a short timeframe(approximately 200 microseconds).The amplitude then gradually diminishes to zero.Importantly,the decay time period remains consistent and can be considered negligible compared to the needle selection cycle.This finding holds true irrespective of the impact velocity(Fig.3).When the weft knitting machine is in the fully selected needle state,the needle selection frequency is equal to the vibration frequency detected by the"cam+PZT"coupling system.Conversely,when employing an n_(1)×n_(2)knitting technique,the needle selection frequency becomes n_(1)+n_(2) times the vibration frequency detected by the"cam+PZT"coupling system.These results highlight the relationship between needle selection and the vibration response of the knitting apparatus(Fig.4-8).The maximum value of the vibration signal detected by the"cam+PZT"coupling system exhibits a linear increase in relation to the rotational speed of the cylinder for different knitting techniques.Notably,this behavior remains independent of the specific knitting technique utilized,emphasizing the importance of rotational speed as a contributing factor to the vibration characteristics(Fig.9 and Fig.10).These results provide essential insights into the vibration⁃based real⁃time detection of working status and faults in weft knitting equipment.They pave the way for developing efficient fault diagnosis and online monitoring systems for weft knitting machinery.The findings contribute to the advancement of the weft knitting industry by improving the accuracy and reliability of detecting and addressing operational issues in real⁃time.Conclusion The vibration attenuation characteristics of the"cam+PZT"coupling system can be utilized to detect faults during the weaving process for impact frequencies below 5 kHz.This implies the potential for implementing fault detection mechanisms based on the vibration decay pattern of the coupling system.Understanding the relationship between needle selection frequency and vibration frequency across different knitting techniques allows for the diagnosis of jacquard weaving faults.The consistent patterns observed in needle selection and vibration frequencies provide insights into specific needle selection methods.Additionally,the correlation between the maximum value of the vibration signal and the vibration speed enables real⁃time monitoring of rotational speed in the weaving process.This offers a means to assess the timeliness and stability of rotational speed in weft knitting machines.In summary,these conclusions highlight the practical applications of the results,including fault detection,jacquard weaving fault diagnosis,and online monitoring of rotational speed in weft knitting machines through vibration analysis.