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Comparison of Outer Rotor Radial Flux and Axial Flux PM Motors for CMG Application

Control moment gyroscopes (CMG) are used in modern satellite applications for attitude control of satellites. The volume and mass of the instruments is very important in such applications. In this context, integrating the mass of the CMG, on the stator of the motor, promises to save space and mass. Radial-flux outer-rotor motor is a promising configuration in that respect. In this paper, using such a PM motor is considered for control moment gyroscope applications. The design of the motor must be made such that the specifications, such as accelerating torque, steady-state torque and temperature rise constraint should be taken into consideration, while the mass and volume are kept at minimum. This is a difficult problem to solve. This paper presents an approach for designing the motor to meet these criteria. The findings indicate that the outer-rotor, radial-flux motor based CMG has important advantages and while the mass of the CMG can be reduced to 2/3 of the reference design, the volume is reduced to 1/5 of the reference design.