Rotational speed control of magnetic coupling with variable damping method

Abstract

Permanent Magnetic Coupling (PMC) is used in underwater vehicle to transmit torque from the motor to propeller without leakage and friction. Output rotational speed stability of PMC is an important index indicating the PMC output makes smaller vibration. To improve the stability of the output rotational speed, PMC dynamic characteristic was analyzed based on Lagrange equation in this paper. The dynamic characteristic was indicated by the angular phase generated by the master rotor and the slave rotor. The angular phase varied with the damping coefficient, torsional rigidity and rotational inertia of PMC. These parameters' influence on the angular phase was analyzed and the results revealed the rules between these parameters and the angular phase. Based on the rules, a variable damping method was proposed to control the angular phase. The angular phase changed smoothly with this method that was used to design a variable damping controller based on electromagnetic damping effect principle. This method was verified by theoretical calculation and finite element analysis (FEA). Finally, a novel variable damping PMC was designed to improve the output rotational speed stability of PMC.