Intelligent control of microassembly process based on in-process monitoring of pressing force

To realize an automated and intelligent microassembly process, a method has been developed to monitor the position of the shaft in the plate of the high-precision spindle motor to reduce the shaft high and the shaft low problems. The shaft low occurs when the shaft is stuck in the plate lower than the setting tolerance due to the large tolerance of the shaft and the small tolerance of the plate. While the shaft high appears, the shaft is pressed through the plate over the setting tolerance due to the small tolerance of the shaft and the large tolerance of the plate. The plate is expanded to reduce the shaft low before microassembly by preheating technique at the experimentally simulated temperature. The force sensor is utilized to monitor the pressing force. A method proposed to reduce the shaft high introduces the reference voltage as the threshold value, which is obtained by taking the differentiation of the in-process pressing force. A slope detector is developed to calculate the output voltage and the motor driver of machine is controlled when the obtained output voltage is larger than the reference voltage. It is proved that the shaft high and the shaft low are well controlled and reduced regardless of the geometries of the shaft and the plate.