Design and Verification of Metal Foreign Body Detection Device for Harvester Based on Eddy Current Effect

Highlights Prevent metal foreign bodies from scratching the intestines of animals and damaging the harvest cutter. Highly integrated design of acquisition circuit. Application of electromagnetic simulation to verify the feasibility of the principle of eddy current effect. Establishment of Support Vector Machine Multi-Classification Algorithm Model. Abstract. Aiming at the problem that the metal foreign bodies mingled in the silage cause damage to the gastrointestinal tract of animals and livestock, as well as irreversible damage to the rotary cutter of the harvester, a metal foreign body detection and sensing device for the harvester feeding drum composed of multiple single coils and signal acquisition units was designed to realize real-time detection and alarm of metal foreign bodies during harvesting. The sensor adopted a monolithic design with high integration of the signal acquisition circuit, which has a strong anti-interference ability. First, the electromagnetic simulation model was established. According to the simulation analysis of the eddy current effect, when the metal foreign object enters the alternating magnetic field, the energy will be lost, and the equivalent impedance of the coil will change accordingly. Then, the existence of the metal foreign body can be determined by detecting the equivalent impedance Rp of the coil. Next, we adopted a support vector machine multi-classification algorithm to train the detection device. In this process, different sizes of metal (copper, aluminum, and iron) were used, which can effectively improve the sensitivity and accuracy of metal foreign body detection. Finally, the sensor was installed on the test stand for multi-scene simulation experiments. The results show that the metal detection sensor can quickly identify the existence of metal by detecting the equivalent impedance Rp based on the eddy current effect; at the same time, the size of this sensor for metal foreign body detection is limited to 0.6 mm in diameter, 12 mm in length, and 100 mm in maximum detecting distance. Keywords: Eddy current effect, Equivalent impedance, Harvester, Metal foreign body, Support vector machine.