Study on Data-Driven Approaches for the Automated Assembly of Board-to-Board Connectors

The mating of the board-to-board (BtB) connector is rugged because of its design complexity, small pitch (0.4 mm), and susceptibility to damage. Currently, the assembly task of BtB connectors is performed manually because of these factors. A high chance of damage to the connectors can also occur during the mating process. Thus, it is essential to automate the assembly process to ensure its safety and reliability during the mating process. Commonly, the mating procedure adopts a model-based approach, including error recovery methods, owing to less design complexity and fewer pins with a high pitch. However, we propose a data-driven approach prediction for the mating process of the fine pitch 0.4 mm board-to-board connector utilizing a manipulator arm and force sensor. The data-driven approach uses force data for time series encoding methods such as recurrence plot (RP), Gramian matrix, k-nearest neighbor dynamic time warping (kNN-DTW), Markov transition field (MTF), and long short-term memory (LSTM) to compare each of the model prediction performances. The proposed method combines the RP model with the convolutional neural network (RP-CNN) to predict the force data. In the experiment, the proposed RP-CNN model used two final layers, SoftMax and L2-SVM, to compare with the other prediction models mentioned above. The output of the data-driven prediction is the coordinate alignment of the female board-to-board connector with the male board-to-board connector based on the value of force. Based on the experiment, the encoding approach, especially RP-CNN (L2-SVM), outperformed all prediction models as mentioned above with an accuracy of 86%.