Application of dynamic programming algorithm in winter heating control of greenhouse

In order to solve the immaturity of decision-making methods in the regulation of winter heating in greenhouses,this study proposed a solution to the problem of greenhouse winter heating regulation using a dynamic programming algorithm.A mathematical model that included indoor environmental state variables,optimization decision variables,and outdoor random variables was established.The temperature is kept close to the expected value and the energy consumption is low.The model predicts the control solution by considering the cost function within the next 10 steps.The two-stage planning method was used to optimize the state of each moment step by step.The temperature control strategy model was obtained by training the relationship between indoor temperature,outdoor temperature,and heating time after optimization using a regression algorithm.Based on a typical Internet of Things(IoT)structure,the greenhouse control system was designed to regulate the optimal control according to the feedback of the current environment.Through testing and verification,the optimized control method could stabilize the temperature near the target value.Compared to the threshold control(threshold interval of 2.0°C)under similar weather conditions,the optimized control method reduced the temperature fluctuation range by 0.9°C and saved 7.83 kW·h of electricity,which is about 14.56%of the total experimental electricity consumption.This shows that the dynamic programming method is feasible for environmental regulation in actual greenhouse production,and further research can be expanded in terms of decision variables and policy models to achieve a more comprehensive,scientific,and precise regulation.

Influence of sprinkler irrigation droplet diameter, application intensity and specific power on flower damage

To determine the main parameters of droplet strike damage and avoid flower injury due to the unsuitable practices during sprinkler irrigation, an indoor experiment of irrigation droplet impact on cyclamen was conducted.The influences of different parameters such as droplet diameter, application intensity, specific power on flower strike damage was analyzed using Image Pro-Plus software to compute strike damage area and define damage level by sense-analysis. The results showed that a damage area of < 1% represents a safe irrigation level, 1%–3% slight damage level, 3%–6% moderate damage level, and > 6%heavy damage level. Equations of application intensity,specific power with sprinkler irrigation time and flower injury ratio were regressed against parameters which cause impact damages. The results indicated that specific power has a significant correlation with injury, and flower damage area increased as the increasing of the value of specific power for the same irrigation time. Application intensity was also correlated with injury when the droplet diameter was larger than 1 mm. When the duration of sprinkler irrigation was 1, 5 and 10 min, the threshold of impinging damage of application intensity was 25.30, 5.01 and1.64 mm·h^(–1) and the specific power was 0.467×10^(–3),9.340×10^(–3) and 3.110×10^(–3)W·m^(–2). These results provide a reference for determining the suitable values of sprinkler properties in operation design.