An Adaptive Sliding-Mode Observer-Based Fuzzy Proportional Integral Control Method for Temperature Control of Laser Soldering Process

In the process of electronic packaging, laser soldering exhibits advantages such as noncontact, minimal thermal affected zone, and rapid soldering process. Additionally, the precision of temperature control in laser soldering process is crucial as it determines the quality of the solder joints. However, the uncertain time-variant parameters and the unknown time-varying bounded disturbances make it challenging for high-precision temperature control to achieve high-quality solder joints. To address parametric uncertainties and disturbances, an adaptive sliding-mode observer-based fuzzy PI (ASMFPI) control method is proposed. In ASMFPI, an adaptive sliding-mode algorithm-based observer is designed to estimate temperature variations caused by uncertainties and disturbances, aiming to improve the accuracy of the temperature model. An observer-based compensation is employed to enhance the temperature control precision. Then, a fuzzy proportional integral (PI) control algorithm is adopted to guarantee the track performance and robustness of the closed-loop system. Experiments and comparisons are conducted on a laser soldering machine to validate the effectiveness of the proposed method. The results demonstrate that the designed observer significantly improves the accuracy of the thermodynamic model. Furthermore, comparisons of ASMFPI, well-tuned PI, and feed-forward PI methods indicate that ASMFPI exhibits superior temperature tracking performance compared to the other two methods.