Commutation error compensation method based on DC-link current reconstruction for a coreless brusheless direct current motor without a rotor position sensor
[Objective]The integral commutation error compensation method demonstrates strong performance in suppressing high-frequency noise.However,its effectiveness diminishes at high motor speeds.This paper addresses the limitations of integral compensation accuracy owing to sampling frequency and the presence of commutation misalignment.After analyzing the relationship between commutation error and the DC-link current waveform,a closed-loop control system is constructed using DC-link current characteristics.Consequently,we propose a commutation error correction method based on DC-link current reconstruction.[Methods]Given the negligibly small phase inductance of the coreless stator structure,this study analyzes the symmetry characteristics of DC-link current waveforms.In a commutation cycle,the difference in the area on both sides of the symmetry axis of the DC-link current waveform directly correlates with the magnitude of the commutation error and can be used as a characteristic parameter for commutation error.Moreover,the integration link can attenuate high-frequency disturbances,while higher values provide a more accurate error quantification.To divide the DC-link current with the symmetry axis as the boundary,we combine the three-phase commutation signals to produce a logic signal.By delaying this logic signal and performing an XOR operation on the pre-and post-delay logic signals,we construct a window signal.This window signal can be used as a control signal for two analog switches simultaneously.The DC-link current,once passing through the analog switches,is split into two parts.To avoid the accuracy problem of software integration at high speeds,we obtain the area value of these two signals through hardware depth filtering.These values are sampled by the controller and subtracted to obtain the error characterization parameter.This parameter serves as the feedback to establish the commutation error PI controller.The PI controller calculates and generates the error compensation amount,which is subsequently used to correct the commutation error of the commutation signal through the phase shift module.[Results]Our experimental results demonstrate the efficacy of the commutation error correction method based on the reconstructed DC-link current.We found the following:1)This method,which relies on hardware filtering to obtain the integral,is not limited by the sampling frequency.It delivers high precision and accurate compensation without any overshoot or oscillation during the control process,indicating that the system has good dynamic performance and anti-interference ability.2)Summing the integral of the reconstructed DC-link current for motor current loop control allows us to directly obtain the DC component of the DC-link current.This eliminates the need for additional filtering and conditioning,thus simplifying the hardware circuit.[Conclusions]Compared to traditional methods,our approach circumvents the influence of high-frequency interference during the sampling process of the DC-link current.Simultaneously,the integral value of the reconstructed DC-link current can be accurately obtained through our proposed hardware circuit.This prevents the error compensation accuracy from being affected by the sampling frequency,addressing the shortcomings of the integral compensation method in high-speed scenarios.The proposed method facilitates high-precision closed-loop correction of the commutation signal phase,thereby improving the operational efficiency of the brushless DC motor.
brushless direct current motorsensorless commutationcommutation error compensation
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维普
