Periodic torque ripples caused by current harmonics seriously affect the control accuracy of the Permanent magnet synchronous motors (PMSMs). A conventional approach to reducing current harmonics is the use of a proportional-integral resonant controller in the current loop. Nonetheless, harmonics can still cause steady-state errors. Furthermore, the PI-based control structure is sensitive to parameter mismatches and uncertain disturbances, which will decrease the tracking performance of the current loop. To overcome the drawbacks of the traditional control method, a hybrid robust resonant control strategy was developed in this study. First, a vector resonant controller was enhanced by introducing fractional-order calculus (denoted as the fractional-order vector resonant (FOVR) controller in this article) so that it can suppress harmonic components more effectively. Then, a robust internal mode controller (Robust-IMC) was designed to improve the robustness and dynamic response and further reduce the current harmonics. Finally, by combining the FOVR controller and Robust-IMC, a control method-FOVR-Robust-IMC was designed as the robust control law to ensure satisfactory robustness and harmonics suppression performance. Meanwhile, the stability and robust stability of the developed control strategy were also analyzed. The results demonstrated that the proposed FOVR-Robust-IMC effectively reduced the harmonic components and improved the robustness to parameter mismatch.

This paper concentrates on a robust resonant control strategy of a permanent magnet synchronous motor (PMSM) for electric drivers with model uncertainties and external disturbances to improve the control performance of the current loop. Firstly, to reduce the torque ripple of PMSM, the resonant controller with fractional order (FO) calculus is introduced. Then, a robust two degrees-of-freedom (Robust-TDOF) control strategy was designed based on the modified resonant controller. Finally, by combining the two control methods, this study proposes an enhanced Robust-TDOF regulation method, named as the robust two degrees-of-freedom resonant controller (Robust-TDOFR), to guarantee the robustness of model uncertainty and to further improve the performance with minimized periodic torque ripples. Meanwhile, a tuning method was constructed followed by stability and robust stability analysis. Furthermore, the proposed Robust-TDOFR control method was applied in the current loop of a PMSM to suppress the periodic current harmonics caused by non-ideal factors of inverter and current measurement errors. Finally, simulations and experiments were performed to validate our control strategy. The simulation and experimental results showed that the THDs (total harmonic distortion) of phase current decreased to a level of 0.69% and 5.79% in the two testing environments.

Permanent magnet synchronous motors (PMSMs) have attracted great attention in the field of electric drive system. However, the disturbances caused by parameter mismatching, model uncertainty, external load and torque ripple seriously weaken the control accuracy. The traditional adaptive sliding mode control (ASMC) methodology can address slow-varying uncertainties/disturbances whose frequencies are located at the bandwidth of the filter used to design the adaptive law well; however, it has been barely discussed with respect to the periodic situation. In this paper, we extend the ASMC arrangement to periodic case to suppress the torque ripple by using a series-structure resonant controller. Firstly, a typical SMC is designed to force the tracking error of speed to converge to zero and obtain a certain capacity to disturbance. Then, the improved adaptive law is incorporated to estimate the lumped disturbance and torque ripple. The improved adaptive law is enhanced by embedding the resonant controller, which can obtain a better estimating result for torque ripple with repetitive feature. Finally, simulation and experimental results with PI, SMC and proposed methods are compared to verify the effectiveness of the developed controller.

This paper proposes a novel method for harmonics and disturbance suppression in permanent magnet synchronous motors (PMSMs) used in photoelectric tracking and measuring systems. The approach introduces a trigger-resonant-robust-current controller with a two-degrees-of-freedom structure (TR-RC-2DOF), composed of trigger-type resonant (TR) and robust current (RC) controllers. First, a trigger mechanism is developed to automatically engage the resonant controller when the current error falls below a certain threshold. Compared with the proportional-integral resonant (PI-R) controller and the PI-R controller with a low-pass filter (LPF), the proposed TR control strategy significantly reduces overshoot and oscillations while ensuring a fast convergence of the tracking error. This advantage contributes to optimizing the dynamic response. An improved filter is then introduced, incorporating the TR controller. A harmonic suppression term is added to the modified filter, forming a two-degrees-of-freedom (2DOF) structure with the original RC controller. The composite controller, with its cascaded design, allows for independent optimization of dynamic response and robustness, thereby enhancing disturbance suppression while maintaining satisfactory dynamic response. Finally, comparative simulations and experiments are conducted using MATLAB and a laboratory setup to validate the superiority of the proposed control method. The experimental results demonstrate that the TR-RC-2DOF controller outperforms the PI-R, PI-R with LPF, PI-TR, and RC control strategies in terms of transition performance, robustness against parameter mismatches, and harmonic rejection.

As Moore's Law is gradually reaching its limitation, traditional CPU-centric computing architecture cannot meet the ever growing computational requirements, especially in large distributed data centers. There is a growing consensus in the industry that the future architecture is a data-centric fabric which can better integrate the function of computation, storage and network. In order to reduce the pressure on CPUs in data centers and further facilitate the transformation of the entire architecture towards higher flexibility and efficiency, this paper presents a SmartNIC-based offloading framework for storage pooling (SOSP) by leveraging the functionality of SmartNICs to offload both the local and remote storage services from CPUs. Our experiments show that the SmartNIC-based solution SOSP can increase the I/O random Read/Write operation performance by around 20-25% and 13-15% respectively, and at the meantime, free up host CPU cores by saving 16.7% virtual cores compared to the solution without using SmartNICs.