Adaptive Gain Sliding Mode Observer for Sensorless Control of Brushless DC Motors

Traditional sliding mode observers' fixed gain and sign function leads to system oscillations and stability issues. This paper proposes an improved novel sliding mode observer(SMO) strategy for brushless DC motor control. On the one hand, in order to reduce chattering caused by the discontinuity of the traditional sign function, a new approach law is designed on the basis of the traditional power-law approach law, which improves convergence speed while reducing chattering. On the other hand, A self-adaptive gain is proposed to replace the fixed gain of SMO based on current error, ensuring the stability of the control system in various situations and improving the accuracy of speed observation. Then, based on the observed linear back electromotive force, the motor speed and rotor position are obtained, achieving sensorless control. Finally, the effectiveness of this strategy was verified through simulation.