The rotor structure of a quadruple-axis aircraft model motor directly affects its moment of inertia. Moment of inertia, a physical quantity characterizing the rotational inertia of an object, is closely related to the rotor's mass distribution and axis position. Reducing moment of inertia can significantly improve the motor's response speed and dynamic performance, making quadcopter models more agile in tasks such as attitude adjustment and trajectory tracking. This goal needs to be achieved by optimizing rotor material selection, geometric design, and mass distribution strategies, while also considering key indicators such as motor efficiency, heat dissipation performance, and structural strength.
The choice of rotor material is fundamental to reducing moment of inertia. Traditional motor rotors often use high-density metal materials, which provide sufficient strength, but their large mass leads to a high moment of inertia. Modern quadruple-axis aircraft model motors tend to use lightweight, high-strength materials, such as carbon fiber composites or aerospace aluminum alloys. Carbon fiber composites have only one-quarter the density of steel and possess excellent specific strength and specific stiffness, significantly reducing rotor mass; aerospace aluminum alloys, through alloying and heat treatment processes, reduce density while maintaining strength. The application of these materials fundamentally reduces the rotor's moment of inertia, laying the foundation for improved motor dynamic performance.
Optimizing rotor geometry is a core method for reducing moment of inertia. External rotor motors, by attaching magnets to the outer casing, concentrate the rotor's mass at the outer edge far from the shaft. While this allows direct propeller driving, it results in a large moment of inertia. Improvement solutions include using thin-walled cylindrical structures or streamlined designs to reduce the radial thickness of the rotor and decrease the mass distribution radius; or employing lightweight structures such as hollowed-out sections or ribs to reduce material usage while maintaining structural strength. Internal rotor motors can reduce moment of inertia by reducing the rotor diameter and increasing the axial length, thus bringing the mass closer to the shaft. For example, designing the rotor as a slender cylinder can reduce the mass distribution radius and significantly decrease the moment of inertia.
Precise control of mass distribution is a key technology for reducing moment of inertia. Finite element analysis (FEA) and topology optimization methods allow for refined design of the rotor's mass distribution. FEA (Functional Analysis) can simulate the stress and deformation of the rotor under different structures and identify areas of redundant mass. Topology optimization can automatically generate the optimal material layout scheme, minimizing mass while meeting strength requirements. For example, removing non-load-bearing materials from the rotor surface or using a variable-density design to concentrate mass towards the shaft can effectively reduce rotational inertia. Furthermore, adjusting the arrangement of magnets, such as using a segmented or skewed pole layout, can optimize mass distribution while ensuring magnetic field performance.
The design of the rotor and stator has a synergistic effect on reducing rotational inertia. As the stationary part of the motor, the stator's mass distribution also affects overall rotational performance. Reducing stator mass or optimizing its structure can indirectly reduce the rotor's rotational inertia requirement. For example, using distributed windings or a flattened stator design can reduce stator mass and shorten the air gap between the rotor and stator, thereby improving motor efficiency and response speed. Simultaneously, optimizing the stator-rotor gap can reduce magnetic reluctance and frictional losses, further reducing the impact of rotational inertia on motor performance.
Improved manufacturing processes are essential for reducing rotational inertia. Precision machining technologies such as CNC milling and EDM ensure the accuracy of rotor geometry, preventing uneven mass distribution caused by machining errors. Surface treatment technologies such as anodizing and sandblasting can reduce rotor mass while improving its corrosion resistance and wear resistance. Furthermore, integrated molding technologies such as die casting and injection molding reduce the number of connectors and fixing structures during rotor assembly, thereby reducing the contribution of additional mass to rotational inertia.
Reducing rotational inertia requires a balance between motor performance. Excessively pursuing low rotational inertia may lead to insufficient rotor strength, decreased heat dissipation, or deterioration of magnetic field performance. Therefore, optimized design must comprehensively consider multiple dimensions such as rotational inertia, efficiency, torque, and temperature rise, achieving optimal overall performance through multi-objective optimization methods. For example, when using lightweight materials, structural reinforcement design is needed to compensate for strength losses; when optimizing mass distribution, it is necessary to ensure that magnetic field performance is not affected.
Reducing rotational inertia through rotor structure improvements in quadruple-axis aircraft model motors requires coordinated efforts from multiple aspects, including material selection, geometry design, mass distribution control, stator fit, manufacturing processes, and performance balancing. These improvements not only enhance the dynamic response of the motors but also improve the flight stability and agility of the quadcopter model, providing technical support for its applications in aerial photography, racing, reconnaissance, and other fields.
