Abstract：The counter-rotating axial-flux hybrid-excitation permanent magnet machine (CR-AFHEPMM) is a novel special-purpose motor for direct-drive counter-rotating propeller systems. Unlike conventional counter-rotating machines, the CR-AFHEPMM reverses the air-gap magnetic fields on both sides via the field-regulation winding, enabling unbalanced-load operation at the two mechanical ports. However, no relevant control strategy has been reported for this machine. Considering the complex operating environment of counter-rotating propellers, uncertainties such as sudden load changes directly act on the rotors. Moreover, the manufacturing and assembly processes of axial-flux machines tend to affect air-gap uniformity, leading to torque harmonics dominated by low- and medium-order components. These factors increase the risk of misalignment between the two rotors of the CR-AFHEPMM. This paper investigates a dual-rotor control strategy and employs a cascaded linear active disturbance rejection controller (CLADRC) to enhance the system’s disturbance-rejection capability, thereby ensuring stable operation under unbalanced loads. Firstly, a mathematical model is established to analyze its operational states under various conditions. Subsequently, a control strategy combining dual-rotor position-difference control with vector control is proposed for the CR-AFHEPMM. To mitigate medium- and low-frequency disturbances arising from complex operational variations and manufacturing/assembly tolerances, the CLADRC is introduced to enhance the position-difference-based field-regulation system, thereby improving disturbance-rejection capability and dual-rotor synchronization accuracy under unbalanced load conditions. Furthermore, the influence of controller parameters on disturbance estimation performance is analyzed. Experimental results show that the proposed control strategy ensures synchronous opposite-direction rotation of the two rotors under complex conditions, including asymmetric load operation, sudden load changes, and synchronized speed regulation. Compared with the conventional PI controller and LADRC, the CLADRC yields smaller position-difference fluctuations and shorter settling times during transients. During acceleration tests, the overshoot of position difference is reduced by 60% and 46.15% relative to the PI controller and LADRC, respectively. During deceleration tests, the reductions are 50% and 43.75%. Moreover, CLADRC significantly reduces steady-state position-difference fluctuations in the CR-AFHEPMM across different loads and speeds, thereby further improving the robustness of dual-rotor synchronization. The following conclusions are drawn. (1) The proposed position-difference control strategy enables stable operation of the CR-AFHEPMM system. (2) The adoption of CLADRC improves the dynamic performance of the CR-AFHEPMM system. (3) CLADRC significantly reduces position-difference fluctuations during steady-state operation of the CR-AFHEPMM.
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2026, Vol. 41 
