An adaptive control method for the covers on the south roof of Chinese solar greenhouses: A case study of insulation blankets

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The Chinese solar greenhouse (CSG) enables farming activities in colder conditions and extends the harvest time. It is a crucial component of Chinese agricultural facilities. Rolling/unrolling the cover on the south roof is critical for modifying the greenhouse environment and improving the production efficiency of CSGs. However, since the structure of CSGs is constantly being updated, the existing winding equipment is inadequate because it causes deformation of covers. This study used as insulation blankets an example to proposed an adaptive control method of the rolling cover of CSGs. Deformation and force analysis showed that the fundamental reason for the deformation of the insulation blanket and the winding mechanism was the uneven load distribution in the length direction. A segmented winding mechanism and multi-motor scheme were used to reduce the deformation of the insulation blanket. A fuzzy proportional–integral–derivative (PID) control algorithm was developed to adjust the speed of the slave motors adaptively to roll/unroll the insulation blanket. The simulation results showed that the shorter winding mechanism resulted in lower torsional deformation. Experiments using a scale model demonstrated that the proposed double-motor scheme and fuzzy PID control method provided good performance for rolling/unrolling the insulation blanket. The double-motor scheme can significantly improve the operation efficiency of rolling insulation blankets. The running time of the double-motor scheme was 12.81% lower than that of the single-motor scheme, the average absolute position deviation was 41.95% lower, and the average absolute standard deviation was 44.51% lower. The proposed fuzzy PID control strategies enable the closed-loop control of the deceleration motor and the adjustment of the displacement deviation to reduce the deformation of the insulation blanket according to the feedback received from the slave motor. Unlike the conventional PID control, the fuzzy PID control automatically adjusts the system parameters to eliminate the system error. The control accuracy and stability of the fuzzy PID method have reached a good level, and the applicability is better than that of the conventional PID method. In the scale model experiments, the average position deviation remained within ±1 mm, and the average standard deviation was 1.32 mm. The proposed adaptive control method for the cover on the south roof of CSGs is highly suitable for practical applications. The study also provides application examples and theoretical references for the automation of rolling covers in greenhouses worldwide.