Study On Electromagnetic Coilgun Projectile Position Detection Technology

As a new generation of advanced launch technology, electromagnetic launch technology uses the electromagnetic power to promote the projectile. The emitter can reach hypervelocity, to meet the requirements of future battlefield with higher range,shorter time of flight and stronger killability. There is an optimal trigger position in each stage of driving coil of multi-stage electromagnetic coil gun. If the switch is triggered too early or too late, the efficiency of electromagnetic emission will be reduced. If the trigger position of driving coil is advanced, it will provide reverse tension to transmitter coil. If the trigger position of driving coil is lagged, it will shorten the effective acceleration time of the emitter, and reduce the outlet velocity of the emitter. To trigger the driving coil accurately, improve the accuracy of emitter position detection is needed.The driving coil is triggered when the emitter reach the optimal position.Analyze the advantages and disadvantages of different electromagnetic launch technology position detection method at home and abroad. According to the scattering of emitter material surface in the hemisphere space distribution which satisfy the bidirectional reflectance distribution function(BRDF), the innovative work in this paper is as follows:First, the principle of coil gun position detection based on BRDF is analyzed, and the relation between the emitter location and photoelectric detector output voltage is deduced, and position detection system model is established. The BRDF value of the aluminum alloy surface is measured, according to the single reference measurement method. The mathematic analytical model of aluminum alloy surface scattering characteristics is build. Build the model of position detection system and make simulation in Trace Pro, get a series of discrete data points of light flux received by the detector when the emitter move to different position. Compare with the theory curve,the method is proved to be correct.Then, analyses the principle of the coil gun and system equation. Through the electromagnetic field simulation software, make static and dynamic simulation.Analyses the optimal trigger position in each stage of driving coil of three-stage electromagnetic coil gun. The control strategy based on BRDF position detection is put forward.Finally, the overall structure of the coil gun position detection system is designed.Extract the signal amplitude received by photodetector through the Lab VIEW platform,and display the result in the upper computer. Design the experiment by dragging the emitter, and compare the experimental results with theoretical curve, the feasibility of this method is verified. The method provide a new train of thought for theelectromagnetic coil gun position detection in the future.