Research On Contact Bounce And Its Influencing Factors In Reed Systems Of Aerospace Relay

Aerospace relay, a main kind of electronic components used for control, information transmission and circuit switch in national defense weapon equipment system and aerospace system, is widely used in national defense military engineering, communication and industrial automation, etc. The reliability of electromagnetic relay in its long-term continuous working in aerospace directly affects the reliability of the national defense arming system and aerospace system. However, the contact bounces of electromagnetic relay, with incapable avoidance, are the main cause of electric abrasion and material erosion which consequently reduce the reliability of the relay and its working lifetime. The research on the reaction mechanism and properties of the contact bounces has its significance for improving relay's lifetime. Based on the researches both home and abroad, a study of contact bounces and its influencing factors in reed systems of aerospace relay in three aspects - theoretical modeling, simulation analysis and experimental investigation - is presented in this paper.Firstly, the continuous and discrete systems models of reed system were built based on Euler beam theory. It is proved that the limit of the flexibility coefficient of discrete systems is their corresponding Green's function while the difference points are infinite increasing and the difference step tending to zero. And the two models could be unified and have similar qualitative properties of their natural frequency and mode. As consequence, the solving programs of the natural frequency and mode of reed system were created. Using the mode analysis and numerical calculation, the dynamic models of two different reed systems of aerospace relay - the pushrod-driven and the direct-driven - are established.Secondly, based on multi-body dynamics theory, a simulation investigation on flexible body dynamic of contact system of aerospace relay is performed by using ADAMS. Considering the reed system constructions and taking the pushrod-driven as an example, the influence degree on several characteristic parameters - the maximum kinetic energy of moving contact, the maximum bouncing displacement, the maximum dynamic contact force, the total bouncing time, the maximum impact speed and coefficient of restitution - of the influence factors which contains the length, width and thickness of reed, size of contacts, driving force, location of pushing rod and the reed material, is analyzed. The sensitivity analysis of the significant factors is also performed. Consequently, two sets of experiment apparatus using CCD sensors are designed to simulate actual closing process of relay based on laser triangulation principle. Three experiments are carried out on the experiment apparatus to analyze the how the factors influencing contact bounces. The experiments are the relay driving simulation device experiments for researching the influence of reed length and origin clearance between contacts, the orthogonal experiments of reed shape parameters in direct-driven reed system for synthetically evaluating the influencing degree of some factors, and the spring driving simulation device experiments considering driving force and loads separately for researching the influence of the characteristic factors on the dynamic performance of contact bounces under different loads.In the end, the contact bounce model of some kind of aerospace relay is verified. The electromagnetic numerical model of the relay is established in ANSYS. The simulation results in ANSYS, combining with the dynamic simulation of contact bounce in contacts system model in ADAMS, are compared with the theoretical calculating and experimental results. The conclusion of the comparison is that the contact bounce model is valid.