On-Line Micro-Weighing for Sterile Preparations Based on Error Compensation of Laminar Wind

High-precision micro-weighing is an important means to maintain the accuracy of powder filling volume in the pharmaceutical industry. However, the laminar wind used to keep the production area sterile causes weight misalignment continuously. This paper makes attempt to adaptively compensate the net weight errors brought by the dynamic laminar wind. We found an irregular fact that it is hard to use a uniform probability distribution to represent this net weight errors on all production lines. First, a criterion of window maximum mean discrepancy (WMMD) was set up to obtain the irregular distribution, then a production line adaptive error compensation method (AEC) was proposed by the WMMD-based distribution learning, to drag the interfered weight back to the actual net weight cleverly. Experiments carried out on two actual production lines, obtaining improvements of RMSE from 13.06 mg to 1.99 mg and from 10.48 mg to 0.62 mg respectively, prove that our method is workable to suppress the laminar wind.