# Characteristics of Electric Field Induced by Oscillating Metal Underwater Vehicle
## 1 Introduction  
As an important source of target exposure, ship electric fields have the advantages of being unable to be completely eliminated, strong anti-interference ability, and obvious line spectrum characteristics. They are often used for underwater target detection and underwater weapon fuses [1; 2; 3; 4; 5]. With the escalating conflict of international maritime rights and the progress of countries around the world in ship noise reduction and demagnetization, the detection of electric fields in water targets has attracted much attention. Domestic and foreign research teams have achieved many results in detection, identification, and tracking positioning, greatly enriching the application of underwater electric fields in underwater target detection [6; 7; 8; 9; 10; 11; 12]. In recent years, various types of underwater vehicles such as UUVs(Unmanned underwater vehicleS), AUVs(Autonomous Underwater Vehicle), and underwater gliders have developed rapidly due to their advantages such as low cost, small platform volume, flexible deployment, and strong environmental adaptability [13; 14; 15; 16; 17]. Among them, high-speed underwater vehicles such as supercavitating torpedoes, small submarings, high-speed ships, and anti-submarine high-speed aluminium can achieve a basic speed of 100 m/s; their maximum speed can instantly reach underwater sound speed [18]. This type of vehicle can be equipped with various sensors for target detection according to mission requirements, so it is widely used in the military and civil fields. Underwater vehicles are generally made of metal, and when they move underwater at a uniform speed, the metal hull will inevitably cut the magnetic field lines of the Earth's magnetic field and generate an electromotive force, which will generate an induced electric field in space. Considering the application platform, the interference generated by its motion mainly has two aspects: one is the platform's own movement cutting the induced electric potential generated by the geomagnetic field through the seawater to form an induced electric field; the second is that the movement of the platform causes the electric field sensors and wires to cut off the geomagnetic field generated by the induced electric field. Since most metallic moving objects/motion targets are encapsulated in air bubbles during high-speed underwater navigation, the induced electric field formed by their leakage into seawater has relatively little effect on the electric field measurements. This paper focuses on the analysis of the induced electric field generated by wire cutting in the geomagnetic field, including the induced electric field generated by the cutting of the metal moving platform and the induced electric field caused by the vibration of the platform. The development of underwater vehicles and electric field detection technology provides a new approach for the detection of underwater targets. Combining electric field detection with underwater vehicle detection can achieve better target detection results, fully leveraging the advantages of electric field detection and underwater vehicles. In reference [4], to solve the problems of obtaining electric field signals and detecting targets in deep and distant seas, the electric field detection system was combined with ocean buoys to analyze the interference electric field characteristics of the measured data of deep-sea electric field detection profile buoys. The results showed that the electromagnetic valve of the buoy platform would interfere with the electric field sensors installed nearby. Through the adaptive threshold line spectrum energy sum detection method, the detection probability was high and the false alarm rate was low. Suitable for application on buoy detection platforms, it can fully leverage the advantages of electric field detection and buoy detection.