Measurement Of Solid Armature’s In-bore Velocity In Series Augmented Railgun

Electromagnetic launch technology utilizes strong electromagnetic force to promote the projectile to achieve high speed. The electromagnetic rail gun is an important research focus of the electromagnetic launch technology. The difficulties of restricting the development of railgun, particularly complex internal ballistics, are related to the in-bore kinematics. Measuring the electromagnetic railgun in-bore kinematic velocity is extremely helpful to solve the difficult problems in interior ballistics and design the launch system.Have now developed some methods based on electromagnetic induction, the Doppler effect or other principles to monitor the in-bore speed, but for the extreme interior ballistic conditions, these methods have different degrees of shortage. The work of this thesis is to measure solid armature’s in-bore displacement, speed and acceleration in series-augmented railgun. B-dot probe, flux ruler and microwave Doppler radar are selected to study of in-bore kinematics experimentally, with focus on B-dot probe method.B-dot probe experiments were performed with the25mm×20mm rectangular caliber railgun. The different B-dot probe signal characteristics of series-augmented railgun and simple railgun were analyzed firstly. The augmentation current in the connecting conductor and outer rail made the probe signal more complex. In order to eliminate the complex influence of augmentation current, the ratio function were introduced, which was the ratio of the B-dot probe integral signal to the current (i.e. the B-dot probe and railgun mutual inductance). The characteristics of the ratio function could determine the moment of the armature to reach the probe position more accurately. With the same launch conditions of previous VISAR experiments, armature B-dot probe and rail B-dot probe experiments were carried out respectively and measured the armature’s discrete displacements. According to the railgun laws of physics, continuous displacement and velocity profiles were fitted. Compared with VISAR experimental results, the B-dot probe method was validated.The flux ruler experiments were conducted still with the25mm X20mm rectangular caliber railgun and different coil size and position were chose for comparison. It was found that the coil position should be away from the connecting conductor at the breech or the muzzle to prevent the influence of corresponding augmentation current. Coil size was determined by spacing and height. Coil height didn’t change the shape of signal waveform. Coil spacing is the key parameters to determine whether the flux ruler is able to output valid signal; the spacing should be much larger than the length of the armature. For exploring the feasibility of Doppler radar, the armature quasi-static experiment and launch experiment were carried out using the30mm×25mm rectangular caliber railgun. Firstly, in order to test the wave-guiding qualities of the barrel, particularly its signal attenuation, quasi-static experiments were performed, accelerating the projectile with mechanical drag. The observed attenuation of the Doppler signal is related to joule losses and dielectric absorption losses. Then, in dynamic launch experiments, the Doppler radar was utilized to monitor the projectile velocity from the breech and the muzzle respectively. Depending on the quality of the electrical contact between rails and armatures, a very good agreement between the projectile dynamics measured by the Doppler radar and the information given by several B-dot signals recorded at several positions along the barrel was obtained. However, with higher charging voltage, the Doppler radar failed to detect the whole interior ballistic process. Doppler radar was also strongly disturbed by high fluctuating magnetic fields. The Doppler radar prototype should be redesigned with a better shielding system.The B-dot probe, flux ruler and microwave Doppler radar experiments laid the foundation for the establishment of in-bore speed measurement system. Complete and accurate kinematic parameters measurement systems will support the in-depth research and design of electromagnetic railgun systems.