Abstract:Objective To address the strong delay and nonlinearity in the Daqu fermentation process.Methods This study proposes a coordinated control strategy combining a Smith predictor and fuzzy proportional-integral-derivative (PID). By establishing a mathematical model of the fermentation process, the Smith predictor is used to compensate for the delay. Combined with fuzzy rules, the PID parameters are tuned online, achieving precise control of temperature and humidity.Results Compared with traditional and fuzzy PID control, the temperature overshoot is reduced by 23.3% and 4.7%, respectively, while the adjustment time is shortened by 15.81% and 11.53%, respectively. For humidity, the overshoot is reduced by 31.4% and 5.7%, while the adjustment time is shortened by 34.57% and 23.66%, respectively.Conclusion The proposed method ensures that the maximum deviation from the target temperature and humidity curves is less than 2 ℃ and 3% RH, respectively, with the error band stabilizing at ±1 ℃ and ±2% RH. The system demonstrates uniform control performance and strong robustness.