Anti-vibration Method For Checkweigher Based On Variable Step-size Adaptive Notch Filter

Checkweigher is a kind of complex mechanical structure composed of load cell,shell,moving parts,monitor and control circuit,which has the characteristics of requiring rapid measurement in a short period of time,the measurement environment and the object being measured are not stationary,etc.Vibration interference caused by the relative movement between the moving parts and the shell of the checkweigher results in the consequence that the weighing signal is not a constant value,and any structure has its own natural vibration cha racteristics,mechanical resonance and intense system vibration disturbance will occur if the external force frequency of moving parts coincides with the natural frequency,or there is a vibration source close to the natural frequency in the weighing envir onment.Influence and solutions of system vibration characteristics on measurement accuracy,of checkweigher must be researched in order to ensure accurate weighing under dynamic conditions.Firstly,this thesis analyzes the criterion,development of product,technique actuality and development tendency of checkweigher at home and abroad,discusses anti-vibration applications of adaptive notch technology.Secondly,this thesis summarizes the vibration problem,introduces several typical mechanical vibration s and their causes,and elaborates that the main sources of vibration of the checkweigher include the vibration of the belt roller and the motor.By establishing a dynamic model of a dynamic weighing platform to obtain the inherent vibration characteristics of the checkweigher,and the measurement process of the strain resistance load cell is deduced,the relationship between the vibration of the checkweigher and its influence on the checkweighing results is analyzed.Next,comparing the theoretical checkweighing waveforms,it is pointed out that conventional digital filters have many problems in anti-vibration applications,therefore,the variable step size LMS adaptive notch filter based on improved versiera algorithm is proposed,which is proved to be accurate and superior in filtering vibration interference through simulation research and practical measurements.According to the vibration analysis of the checkweigher,a multi-frequency adaptive notch filter with parallel structure is selected for the system,and the theories of LMS adaptive filtering algorithm and adaptive notch filtering algorithm are explained in detail.Then,according to the requirements of algorithm and project,an embedded ARM-based checkweighing signal acquisition and processing dev ice consisting of a checkweighing signal amplification module,a large tare filtering of weighing platform module,an active low-pass filter module,a checkweighing signal and photoelectric signal acquisition module,a STM32 minimum system module,an interface conversion module and a power supply module is designed,the hardware design of each module is introduced in detail,and the overall embedded software development ideas and implementation process based on our own laboratory device are provided.Finally,the effectiveness and practicability of the method in this thesis for improving the anti-vibration performance and improving the accuracy of checkweighing are verified by checking the scale divisions,minimum capacity,maximum capacity at different speeds and by checking checkweighing performance of the resonance speed.Experimental results show that the verification scale interval is0.5g,which can meet the requirement of category XIII(1).