Uncalibrated visual positioning using adaptive Kalman Filter with dual rate structure for wafer chip in LED packaging

•Sensitivity analysis of variable visual calibration parameters in LED packaging.•Visual sampling delay compensation based on dual rate sensing structure.•Real time and precise estimation of variable calibration parameters in two cases.•Improving of wafer chip positioning effect and working efficiency in LED packaging. In the LED packaging, the changes of calibration parameters will affect the positioning effect of wafer chip and eventually result in the quality degradation of packaging process. Moreover, the frequent visual calibration processes will reduce the production efficiency. Accordingly, an uncalibrated visual positioning method for wafer chips is presented and applied for LED packaging in this paper. Firstly, the calibration model of LED chip visual positioning system is established. After sensitivity test based on calibration model, two typical cases of calibration parameters variation in LED packaging are given and analyzed. Then, the Kalman Filter is used to online estimate the variable calibration parameters, where two kinds of state vectors are designed for the two cases respectively. To accelerate the convergence and heighten the robustness, an adaptive design is introduced to improve the iterative process of Kalman Filter. Considering the influence of real time problems in visual signal, a dual rate structure is proposed to compensate the visual delay and realize the time synchronization for the multi-rate sensing. Based on the presented adaptive Kalman Filter with dual rate structure, an uncalibrated visual positioning control system is designed and verified by simulation. Finally, the chip positioning experimental results demonstrate that the proposed method can effectively improve the positioning effect of wafer chips and the working efficiency in LED packaging, which can be applied in practical production.