Research On Measurement Mechanism Of Projectile Speed In Bore Based On Environmental Magnetic Field

In the field of artillery ballistics,the rotational speed of internal ballistic projectiles is an important indicator for the design of artillery and projectiles.It is also an important basis for inferring the degree of wear between the projectile and the inner wall of the chamber,and the ablation of the inner chamber of the barrel.However,due to the constraints of the internal surface structure of the artillery barrel,the highly dynamic movement of the projectile,and the complex and harsh environment in the bore of the projectile during the launch process,it is difficult to obtain the rotation parameters of the internal ballistic projectile.At present,there is still a lack of direct measurement of the internal ballistic projectile speed.Methods and means.Aiming at the difficulty of testing the rotation parameters of internal ballistic projectiles,this paper proposes a method to directly measure the rotational speed by using the disturbance of the internal ballistic magnetic field during the movement of the projectile in the bore.Combining the characteristics of the internal structure of the artillery bore and the projectile launching process,the method of measuring the speed of projectile based on electromagnetic induction is discussed.The basic idea is to directly measure the rotational speed of the internal ballistic projectile by measuring the perturbation information of the magnetic field in the barrel during the movement of the projectile.First,based on the analysis of the internal structure of the general artillery barrel,the shielding law of the tube wall to the geomagnetic field when the geomagnetic field and the artillery barrel are at different angles,as well as the perturbation effect of the rifling in the artillery barrel and the projectile on the magnetic field are investigated.As an example of the barrel model of the Chinese W1986-122 mm howitzer,the distribution of the environmental magnetic field in the gun bore is analyzed.In order to realize the measurement of the perturbation information of the magnetic field in the bore by the missile-borne measurement system,the magnetic field distribution of the projectile’s trajectory at different detection distances is simulated and analyzed.The simulation results show that the magnetic field distribution curve of the projectile rotating with the rifle shows a single peak characteristic;as the detection distance increases,the magnetic field fluctuation difference becomes smaller and smaller;when the detection distance is 15 mm,the magnetic field fluctuation difference is about200 n T.Based on the above simulation and analysis results,with the goal of improving the sensitivity of weak magnetic detection,this paper designs a magnetic aggregation microstructure that can amplify weak magnetic signals by 6.78 times;based on magnetoresistive sensors,a suitable missile-borne speed measurement system is designed;at the same time,according to The characteristics of the projectile speed signal.In a strong noisy environment,the Hillport-Huang transform method based on wavelet denoising is used to obtain the instantaneous frequency of the signal,and then the projectile speed parameters are calculated.Through the experiment of simulating the movement of the projectile in the barrel,the feasibility of this research method is verified,and the method and idea are provided for the direct measurement of the speed of the ballistic projectile in the artillery.