Optimization And Control Research On The Heating System Of Evaporative Coating Machine Substrate

Evaporative coating technology is widely used in decoration,communication,optics,and semiconductors because of its advantages of simple processing and low environmental impact.In this technology,substrate temperature is a critical factor that affects coating quality,so controlling the temperature of the substrate surface during film formation is crucial.The temperature control of the substrate has two main aspects:maintaining substrate surface temperature uniformity and controlling the surface temperature rise of the substrate.A decrease in substrate surface temperature uniformity can lead to poor film quality and lower product yield.Due to the nonlinear,hysteresis,and time-varying characteristics of the substrate heating system,the controller must have fast response speed and strong stability.This study focuses on the substrate heating system in the evaporation coating machine and investigates the control method of substrate temperature rise and the uniformity of substrate surface temperature.The following are the primary research findings:(1)The substrate heating system was modeled and simulated using the COMSOL finite element simulation software.The simulation results indicated that the system reached steady state at 6000 seconds.Following the steady state period,the temperature within the effective heating zone exhibited a radial trend of increasing and then decreasing,with a maximum temperature difference of 16.8℃.These results suggest that the substrate heating system suffers from poor temperature uniformity and a prolonged heating time in the effective heating zone during steady state operation.(2)The impact mechanism of the heating power of the heat source on the substrate temperature uniformity and the heating efficiency of the system was studied.It was found that the conventional fixed-power heating method had problems such as long heating time and uncontrollable substrate surface temperature.To address these issues,this study coupled the PID algorithm with the heating system’s heat source and conducted simulations.The simulation results showed that the system reached steady state at 2000 seconds,and the heating efficiency was significantly improved.However,the system still exhibited overshoot and low temperature control accuracy.(3)The impact mechanism of the heater structure on the temperature uniformity of the substrate surface was studied.The effects of the layout of the heating wire,heating distance,and reflection distance on the temperature uniformity of the substrate were investigated using a single-variable method.The parameters of the heater structure were optimized using the Nelder-Mead simplex method of gradient-free optimization algorithm to reduce the temperature difference in the effective heating area.The optimization results showed that the maximum temperature difference was reduced by41% compared to the original value,with a maximum temperature difference of 9.91 ℃.Based on this,experimental tests were carried out on the substrate heating system,and the results showed a 6% deviation between the experiment and simulation,verifying the reliability of the model and the feasibility of the optimization.(4)The substrate heating system is identified as a first-order pure lag link by model identification,and the transfer function of the system is determined by the step response method.In response to the current problems of large overshoot,slow response speed,and low control accuracy in the substrate heating system,three temperature control strategies based on Smith prediction PID,fuzzy PID based on Smith prediction,and Smith prediction fuzzy PID based on particle swarm optimization algorithm are proposed.Simulation analysis of the above three control strategies is conducted using the Simulink module,and the results show that Smith fuzzy PID based on particle swarm optimization algorithm has the fastest response speed,The highest control accuracy.This study uses finite element analysis to simulate and analyze the temperature field of the substrate heating system.The simulation model is combined with the PID control algorithm and the gradient-free optimization algorithm,significantly improving the heating efficiency of the system and the uniformity of the substrate surface temperature.The feasibility of the optimization is verified through experiments,providing guidance for the research of coating technology and the actual production of coating equipment.Additionally,this study combines intelligent algorithms with modern control theory to achieve precise control and adjustment of the substrate temperature,providing a new approach and method for the temperature control of coating machines.