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封闭式栽培是解决中国日光温室传统栽培连作障碍问题的有效途径之一。营养液调控过程的性能指标是封闭式栽培模式的关键。该文针对一种具有二次混肥特性的营养液调控过程进行动态分析并建立模型,使用PID控制算法实现了营养液调控,并对影响因素进行对比试验。试验结果表明,系统达到稳定的时间随出液流量的减小或营养液浓度之和的增大呈现减小的趋势;系统震荡持续时间与超调量随出液流量的减小或营养液浓度之和的增大呈现增大的趋势。由试验结果与分析可知,该带有二次混肥的封闭式栽培系统中最优的出液流量与营养液浓度之和分别为6 m3/h与200 g/L,在此状态下进行PID控制参数整定,得到系统在最优条件下稳定时间为100 s、超调量为3%、震荡持续时间为25 s。表明该带有二次混肥的封闭式栽培系统的营养液调控过程能使用PID算法进行调控,能使系统实现稳定、高效的运行。该研究为封闭式栽培的营养液调控提供了参考。
Enclosed cultivation is one of the effective ways to solve the problem of continuous cropping obstacle in the traditional solar greenhouse in China. The performance index of nutrient solution control process is the key to closed cultivation mode. In this paper, a dynamic analysis of nutrient regulation process with secondary fertilizers and the establishment of a model were carried out. The nutrient solution was controlled by PID control algorithm, and the influencing factors were compared. The experimental results show that the time when the system reaches a steady state decreases with the increase of effluent flow rate or the sum of nutrient solution concentration. The duration of system turbulence and overshoot decrease with the decrease of effluent flow rate or nutrient solution concentration The sum of the increase shows an increasing trend. According to the test results and analysis, the optimal effluent flow rate and nutrient solution concentration in the enclosed cultivation system with secondary compost are 6 m3 / h and 200 g / L, respectively. Under this condition, PID The control parameters are set, and the stability time of the system under optimal conditions is 100 s, the overshoot is 3% and the oscillation duration is 25 s. The results show that the regulation of nutrient solution in the enclosed cultivation system with secondary compost can be regulated by PID algorithm and the system can be operated stably and efficiently. This study provides a reference for the regulation of nutrient solution in closed cultivation.