Measurement of Solid Armature's in Bore Velocity Using B-Dot Probes in Series Enhanced Railgun
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摘要: 采用磁探针（B-dot）测电磁轨道炮内弹道速度的方法是，基于电枢经过探针线圈时引起感应磁通变化的原理，测出系列的电枢位移-时间离散点后拟合成电枢位移曲线，然后对位移曲线时间微分得到速度曲线。在串联增强型轨道炮中，磁探针感应磁通需考虑外轨及内外轨道连接导体中电流的影响，而磁探针输出的微分信号积分后除以电流，将得到一个与电流无关、只随电枢与探针相对位置变化的比值函数。电枢磁探针或轨道磁探针的比值函数在电枢经过时分别取最大值或中值，因此比值函数的此种特征可用来判断电枢到达相应探针位置的时刻。在双轨串联增强电磁轨道炮上设计了3发条件相同的实验，分别利用电枢磁探针和轨道磁探针并结合激光干涉测速方法（VISAR），测试并拟合了位移、速度曲线。比较结果发现三者一致性较好，拟合的炮口速度与测试速度接近。磁探针尺寸及位置、轨道及电枢中的电流分布以及杂散电磁干扰等，是影响磁探针测速精度的主要因素。Abstract: The solid armatures displacement and velocity can be obtained by arranging B-dot probe arrays along the barrel of a series enhanced railgun. The moment of armature arrival can be determined by an evident change in the differential signals of B-dot probes while armature passing by. However, it is difficult or even impossible to pick up the arrival moment directly because of not only armature movement but also current variety, especially for the series enhanced railgun with currents in outer rails and connecting conductors. To eliminate the influence of current variety, the ratio function is introduced, which is the ratio of the differential signal integral to the current. The ratio function of armature B-dot probe will reach a maximum when the armature arrives, while the one of rail B-dot probe will reach the median. Three shots with same initial conditions, which adopted armature probe, rail probe and VISAR respectively, were carried on a series enhanced railgun. The well agreement with each other about displacement and velocity waveforms indicated that method and measurement were valid. The accuracy of B-dot method is mainly affected by probe size and position, railgun current distribution and electromagnetic noise.
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Key words:
- series enhanced railgun /
- in-bore velocity /
- B-dot /
- ratio function /
- solid armature
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