Abstract: To satisfy the requirements of miniaturization for attitude control unit in distributed small satellite system (DSSS), a reaction flywheel system based on axial-flux motor is presented. The three-dimensional distribution of air-gap magnetic field is analyzed by using the finite element method (FEM). A computational model for back-EMF of the motor is established based on the printed circuit board (PCB) winding. The multidisciplinary design optimization method is applied to optimize the main structure size of the flywheel rotor to minimize the weight of the flywheel system while meeting the requirements of strength, stiffness and the air-gap flux density under the premise of using sequential quadratic programming (NLPQL). The total mass of the flywheel rotor is decreased from 0.899 kg to 0.741 kg (namely reduced by 17.6%) after optimization. A flywheel prototype is designed based on the optimal results and the no-load performance is tested. The results show that the maximum error between the calculated and measured values of back-EMF is 9.7%, which verifies the correctness of the design method and provides an important reference in the miniaturization design of reaction flywheel system.

Key words: Axial-flux motor, Distributed small satellite system, Finite element method, Optimal design, Reaction flywheel