Simulation, design and experimental validation of a passive magnetic damper for ultra-fast actuators

Abstract: A contact system driven by a high energetic Thomson actuator requires to be decelerated from full speed down to zero. The forces originated from the interaction between a stationary copper tube and a moving array of magnets combined with plastic or ferromagnetic material are used to generate eddy-current damping. Five different configurations of small but strong (N52) neodymium magnets and spacers were benchmarked for simple free-fall damping. A comparison between experimental results and simulations (using COMSOL) has shown that the most effective damping is reached by two consecutive permanent magnets with opposite magnetization directions ,separated by low-carbon content steel concentrators(SN - Fe concentrator- NS). The proposed damper design is the result of the balance between various parameters such as magnet orientation topology in the array, spacer material and its dimensions, copper tube thickness and the air gap between copper tube and array. Furthermore, the design was scaled up and an actuator-drive system was added to perform more realistic tests, which demonstrated the damping effectiveness on a fast moving armature actuated by a Thomson coil energized by a capacitor bank. All models in the simulation predicted the damping effect in advance. Investigations were conducted with two cases: (1) A solid copper rod was supposed to pass through the magnet array; (2) A plastic shaft was applied to support the magnet array. Finally a damping prototype with a plastic shaft was built for completing damping tests. The results of these tests validated the numerical model with a high degree of accuracy.