A brushless DC motor (BLDCM) is a kind of nonlinear system with multivariable coupling.Under certain conditions, chaos and other non-linear dynamic phenomena will occur and bring adverse effects to the motor itself and the drive system.However, in existing research on chaotic mechanism of BLDCM, the chaotic phenomena caused by the disturbance of load torques are seldom involved.However, in practical engineering applications, the disturbance in the load of the motor is extensive.To analyze the non-linear characteristics of the BLDCM caused by this disturbance, a disturbance variable was added to the d-q axis mathematical model of the BLDCM.Then, a non-autonomous system model of 5-D BLDCM was constructed by using time scale and linear affine transformations.First, the non-linear dynamic characteristics of the system caused by the torque disturbance were analyzed by calculating the dissipation and equilibrium points of the system.Second, the chaotic dynamic behavior of the system under load disturbance was discussed through Lyapunov exponent and bifurcation graph.Finally, the accuracy of the model and analysis was verified through experiments.Results show that when the frequency of the disturbance component of the load increases from 0 Hz to 100 Hz, the system experiences various motions, such as stable, period doubling, paroxysmal chaos, and periodic.This study provides a theoretical reference for further exploring the engineering physical characteristics of the BLDCM under load disturbance and searching for an improved control method.
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