An efficient seeding state monitoring system of a pneumatic dibbler based on an interdigital capacitive sensor

Abstract

Multiple and missed seedings cannot be fully avoided when a pneumatic dibbler is used in the field, so the sowing state should be judged using a sowing monitoring device. However, traditional sowing detection devices cannot be used with a pneumatic dibbler. To solve this problem, this study proposes a real-time monitoring system for the seeding state of a pneumatic dibbler based on an interdigital capacitive sensor. First, a sensor is designed based on the structural and operational characteristics of a pneumatic dibbler. Then, the output capacitance of the sensor is determined using a Pcap02 micro-capacitance acquisition chip and analysed by the correction model of temperature and humidity and the prediction model of cotton seed weight, which can determine the weight of cotton seeds accurately. Finally, the seeding state is determined based on the multiple and missed seeding thresholds of the corresponding varieties. The bench performance of the proposed system is verified experimentally using an interdigital capacitive sensor, a micro-capacitance acquisition system, and an experimental prototype dibbler. The experimental results show that the measurement error of the capacitance is within 1%. Meanwhile, the measurement error of the prediction model of the cotton seeds grain weight is less than 3%, inferring that the proposed micro-capacitance acquisition system can meet the measurement requirements. The bench experiment has proven the accuracy of the proposed system in the missed seeding experiment. In the normal seeding experiment, the proposed system can achieve a misjudgement rate of less than 3%. Namely, in this experiment, normal seeding can be misjudged as missed seeding or multiple seeding due to the difference in the grain weight of cotton seeds. Further, in the multiple seeding experiment, the proposed system’s misjudgement rate is less than 4%. Multiple seeding can be misjudged as normal seeding because the cotton seed combination quality is slightly higher than the multiple seeding judgment threshold and the measurement error of the seeding monitoring system. Therefore, the proposed monitoring system can meet the structural and operational requirements of a pneumatic dibbler and realise an accurate judgement of the seeding state. The proposed system can not only achieve good accuracy and stability but also has an important significance for the precise sowing of cotton.