Sensorless Control of High-Speed BLDC Motor for Vacuum Cleaner Using Sliding Mode Observer

This paper presents a sensorless control method of a high-speed BLDC (Brushless DC) motor for vacuum cleaners using a sliding mode observer. For vacuum cleaners, motor parameters are susceptible to change due to the harsh environment such as high temperature and high speed. Although sliding mode observers (SMOs) are more robust to parameter variation than back-EMF observers, the chattering from the signum function in the SMO decreases the sensorless performance over a wide speed range. Although sigmoid function can reduce the chattering effect, it is still difficult to achieve convergence and chattering cancelation together. In the proposed method, a variable acceleration is introduced for sigmoid function to maintain the convergence and chattering reduction in the full speed range. The optimal acceleration slope of the sigmoid function is applied in the designed SMO according to the estimated speed. The suitability and effectiveness of the sensorless control with SMO to which the proposed variable sigmoid function is applied was verified through experimental results.