基于动态摩擦因数反演的直线推进电磁能装备的运动特性

In the working process of linear propulsion electromagnetic energy equipment, friction between the armature and rail due to high-speed sliding is one of the important factors affecting its motion characteristics. However, realizing real-time and in-situ friction coefficient measurement is challenging under extreme electromagnetic, thermal, and mechanical shock conditions. Therefore, the friction coefficient between the armature and rails is fixed as the empirical value in the current research. The actual motion characteristics of the armature fail to be accurately captured because the potential impact of its dynamic changes on the Performance of the System is ignored. This paper proposes a method based on the dynamic friction coefficient inversion of motion characteristics.Firstly, a nonlinear mapping relationship between the armature velocity with the armature-rail friction coefficient and the rail inductance gradient during the armature motion is deduced from the observable data measured by the electromagnetic propulsion experiment and the armature kinetics forward model. Then, the inversion model for the armature-rail friction coefficient and rail inductance gradient is established using the improved dynamic particle swarm optimization (DPSO). The computational velocity is corrected in real-time by the measured velocity of the armature to obtain the spatiotemporal characteristics. The friction coefficient between the armature and rails Starts to decrease rapidly with increasing armature velocity, then the decreasing trend slows down and finally tends to a stable value.Then, the model for transient electromagnetic, thermal, and mechanical coupling is established. Motion characteristics of the equipment are analyzed when the friction coefficient is dynamic (DFC) and constant (FFC). Herein, the friction coefficient between the armature and rails is segmented according to velocity, and the Parameters of each velocity segment are determined using the nonlinear least Squares fitting method. The results show that the dynamic change of the friction coefficient increases the armature current density, magnetic density, and temperature at the same velocity, which greatly affects the temperature of the armature-rail contact surface. A high current density and magnetic induction are necessary to produce enough Lorentz force to overcome the increased friction caused by the dynamic changes in the friction coefficient. Therefore, the simultaneous increase of friction heat and resistance heat causes the temperature difference on the contact surface of the armature rail to increase gradually under DFC and FFC conditions. The temperature difference reaches 522 °C at 0.75 ms.Finally, an experimental platform for the linear propulsion electromagnetic energy equipment is built to measure the armature velocity and the magnetic induction strength at the rail. Considering the dynamic friction coefficient, the armature velocity and the magnetic induction intensity are close to the measured values, and the calculation accuracy of the model is high, verifying the correctness of the theoretical analysis.