摘要
在对设施蔬菜生产中使用的水肥一体化设备进行智能灌溉控制设计中,监测混肥罐和回液桶中液位高低是非常必要的。现有液位检测普遍采用机械开关式液位浮子,工程实践中发现当进出水口与浮子过近,或者水纹波动显著时,浮子上下剧烈抖动会导致水泵随浮子的抖动而经常启停,对于启动电流较大的泵容易造成损伤。本文在软硬件设计中采用了计数器数字滤波电路以及单片机定时器中断,设计了一种替代简单液位浮子的实用智能液位开关。为了检验该设计的性能,在同等条件下,进行了不同液面、不同压力和水流量的对比试验。试验结果表明,计数脉冲发生电路中充电电阻和放电电阻为4.7 kΩ时,滤波后的输出信号比现场实际的数控信号时间迟延了2.11 s,经数字电路滤波后的输出信号已经完全消除了宽度小于2 s的所有干扰信号,并且具有很高的稳定性。迟延时间与计数电路、计数脉冲发生电路有关,通过电路设计调整滤波脉宽可使输出信号有效地滤除干扰成分。同时,利用该方法也可以根据不同工况,如不同功率的水泵设定不同参数滤除干扰信号,提高智能液位开关适用性。
It was necessary to monitor liquid level in both mixing fertilizer tank and recycle tank respectively to design the integrating equipment of water and fertilizer in the intelligent hydroponic control system for facility vegetable production. In practical engineering project,the liquid level floater is widely used for the existing liquid level detection. The effect of the floater can be disturbed by some conditions,such as waterlines fluctuation when the floater was too close to inlet or outlet. Shaking up and down of the floater result in pump to start and stop intermittently,which will damage the pump with great starting current. To solve these problems,the counter was used to design digital filter circuit and MCU timer interrupt respectively in the hardware and software. In order to test the performance of the new intelligent liquid level switcher,the comparison experiments of different depths,pressures and water flows were carried out under the same conditions. The results show that this method can effectively filter out interfering signal. When both the charging resistance and discharge resistance of the counting pulse generating circuit are 4. 7 kΩ,the filtered signal delayed 2. 11 s after the fact output signal. The effective output signal was cleared off disturbing signal under 2 s by digital filter circuit and kept high stability.The delay time is related to the counting and pulse generating circuit,so different disturbing signals canbe declined by configuring filter plus width in circuit design. On the way of software design,timer programming method was used in microcontroller considering width of the wave curve to detect the status of ports at certain intervals. The algorithm was introduced to remove disturbance and improve the efficiency of SCM. The method can be used to filter out the interference signal by setting different values according to the actual situation,such as different power pumps so the smart switcher can be more feasible.
出处
《农业机械学报》
EI
CAS
CSCD
北大核心
2015年第S1期108-115,共8页
Transactions of the Chinese Society for Agricultural Machinery
基金
国家自然科学基金资助项目(31301240)
土壤植物机器系统技术国家重点实验室开放课题基金资助项目(2014SKL03)
关键词
水肥智能调控系统
液位浮子
抖动
数字滤波器
智能开关
Water and fertilizer integration system
Liquid level floater
Jitter
Digital filter
Intelligent switch
