| Most of the materials are in the form of bags,bottles or cans to facilitate their storage,transportation and use.Therefore,the filling machine is an indispensable device in the automatic filling production line.Filling machinery is a kind of product in packaging machinery,which is widely used in medicine,food,beverage,daily chemical,oil,pesticide and other special industries.Weighing liquid filling machine is a kind of filling machinery.How to ensure the required weighing accuracy in the case of rapid weighing has become the focus of domestic and foreign scholars.Therefore,it is of great significance to design and develop a liquid filling dynamic weighing control system which can achieve high-precision weighing within a predetermined time.In view of the problem of mutual influence and contradiction between weighing accuracy and weighing speed existing in high-precision liquid filling dynamic weighing control system,this paper takes weighing liquid filling machine as the research object,mainly studies two key technologies: adaptive noise cancellation weighing signal acquisition and processing and two-stage filling control online correction.The main research contents are as follows:1)By consulting the relevant literature and enterprise research,this paper analyzes,summarizes and summarizes the development of filling machinery,weighing signal processing technology and filling control technology at home and abroad,which has done a good job in the research and development of liquid dynamic weighing control system.2)Combined with the actual working conditions,according to the filling technical index requirements of the subject,the demand of high-precision liquid filling dynamic weighing control system is analyzed,the research contents are analyzed and summarized,and the corresponding overall scheme is designed.3)Research on adaptive noise cancellation weighing signal processing technology.Combined with the actual working conditions,by analyzing the main sources of noise,aiming at the non-stationary and random characteristics of dynamic weighing signal and noise signal,an adaptive noise cancellation weighing signal processing method is proposed.This method attenuates or suppresses the influence of the noise signal produced by the vibration of the load cell itself,the change of the impact force when the material falls in the filling process and the external random interference by canceling the noise signal in the dynamic weighing signal.This paper focuses on the structure of adaptive filter,the principle and algorithm of adaptive noise cancellation,and the method of obtaining reference noise signal.Through simulation experiments,the denoising performance of adaptive LMS algorithm,adaptive NLMS algorithm and adaptive RLS algorithm is compared and analyzed.Finally,the adaptive NLMS algorithm is selected as the adaptive noise cancellation algorithm of the dynamic weighing signal in this subject,and the realization is realized A stable and reliable weighing data acquisition and processing is realized.4)Research on online correction technology of two-stage filling control.Combined with the double control filling valve of the weighing liquid filling machine,in order to give consideration to the requirements of feeding speed and feeding precision,the control strategy in the filling process is analyzed and studied,and a control strategy of two-stage filling with the opening and closing of the double control filling valve is proposed.The mathematical model of the dynamic weighing filling process is studied,and the rough control method is determined The optimal switching point of the fine feeding stage maximizes the feeding speed,analyzes the shortcomings of the existing filling control technology,and proposes an online correction method of the closing advance based on the improved iterative learning control algorithm to improve the feeding accuracy.Finally,experiments show that the improved iterative learning control algorithm has good adaptability.5)In view of the above key technologies,the hardware selection and design of high-precision liquid filling dynamic weighing control system are carried out,and a prototype device is built to verify the effect of adaptive noise cancellation weighing signal acquisition and processing and two-stage filling control online correction in the filling process.The results show that the high-precision liquid filling dynamic weighing control system can ensure the high-precision weighing within the specified time,and meet the effect of weighing 500 g materials within 12 s and weighing accuracy within 1 g. |
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