Model-free predictive current control (MFPCC) that only needs the input and output data of the system can eliminate the influence of the motor parameters mismatch. In the conventional finite control set MFPCC (FCS-MFPCC), the delay and distortion that exist in the current variations update can affect the future current prediction and the current tracking performance. This article studies an improved current variations updating mechanism to improve the update frequency. Based on the ultralocal model, the current variations corresponding to the different voltage vectors can be updated at every control period. Then, the stator currents can be predicted with the accurate current variations, and the optimal voltage vector can be selected by minimizing the cost function without using motor parameters. Besides, a sliding mode observer is designed to observe the ultralocal model's parameters fast. Furthermore, the two voltage vectors and the optimal duration are introduced to improve the current tracking performance. Meanwhile, in order to guarantee the accuracy of the future current prediction, the current compensation strategy is studied to revise the current estimation. Finally, the effectiveness of the proposed FCS-MFPCC strategy is verified through the simulation and experimental results.

Traditional active disturbance rejection control (ADRC) is not adequately capable to deal with current disturbances including periodic harmonics of permanent magnet synchronous motor (PMSM). Thus, an improved ADRC with a cascade extended state observer (CESO) based on quasi-generalized integrator (QGI) is proposed to attenuate the periodic and aperiodic disturbances in the current loop. In the proposed strategy, a CESO with two cascaded levels is designed to enhance the estimation accuracy of aperiodic disturbances and decrease the steady-state observation error of periodic harmonics. The QGI is embedded into the second cascade level of CESO to improve its estimation accuracy harmonic disturbances. With the periodic harmonics accurately estimated, the subsequent improved ADRC based on feedback control law can effectively enhance the rejection of such disturbances. The theoretical analysis is comprehensively conducted to investigate the disturbances estimation performance, stability, disturbances rejection capability and robustness, while the parameter tuning strategy is studied based on the control bandwidth. Finally, the effectiveness and superiority of the proposed scheme are verified on a PMSM bench through the experiments.

Permanent magnet synchronous motors (PMSMs) are widely used in the field of industrial servo control, especially in high-precision applications. Owing to the periodic torque ripple caused by the cogging torque, flux harmonics, and current offsets, the speed output of the system has a periodic ripple, which affects the control accuracy of the servo system. The conventional proportional–integral controllers cannot reject torque ripple and are highly dependent on motor parameters. This limits the control performance when a PMSM is used as a high-precision servo system. Thus, this paper proposes a combination of model predictive control (MPC) and iterative learning control (ILC) to not only speed up the response time of the system but also effectively reduce the speed ripples. MPC updates the predictive model in real time through feedback and evaluates the system output and control rate according to the cost function. It obtains an optimal control sequence for the next moment and has good parameter robustness and fast response. ILC records the speed of ripple signals over an entire cycle and then uses those signals to compensate for the control signal in the next cycle. It is capable of reducing the periodic speed ripples. The experimental verification of the schemes was conducted on a digital signal processor–field programmable gate-array-based platform. The experimental results obtained confirm the effectiveness of the proposed MPC–ILC scheme.

A control strategy that combines a novel reduced-order vector resonant controller and a generalized active disturbance rejection control (ROVR-GADRC) is proposed in this article to suppress the current disturbances containing periodic harmonics of a permanent-magnet synchronous motor (PMSM). First, the ROVR controller is designed, which integrates the advantages of both the complex coefficient filter and the vector resonant controller. Compared with the existing resonant control methods, the proposed ROVR can separate and extract the positive and negative sequence harmonics, and avoid the phase delay and peak point simultaneously. Second, a generalized extended state observer is introduced to enhance the suppression of low-frequency disturbance. Then, the composite control strategy is developed. Besides, the stability, disturbance rejection performance, parameters configuration, robustness, and tracking performance of the proposed ROVR-GADRC are comprehensively analyzed. The proposed current controller simultaneously performs harmonics suppression of specific phase sequence and other unknown disturbances attenuation. Finally, the feasibility and effectiveness of the proposed method is verified on a PMSM platform through the experimental results.

It is well-known that there is a trade-off between robustness to disturbances and measurement noise sensitivity in the active disturbance rejection control (ADRC) framework based on extended state observer (ESO). To this end, this article proposes a novel variable structure ADRC (VSADRC) for permanent magnet synchronous motor (PMSM) speed control to enhance the disturbance rejection and the noise suppression simultaneously. In this technology, a variable structure ESO (VSESO) with two-stage interconnected observer is proposed to avoid directly employing noise-contaminated signal, in which the extended disturbance differential is appended to achieve higher-level disturbance estimation. By doing this, at low frequencies, the magnitude curve slope is 40 dB/dec for the VSESO and 20 dB/dec for ESO, while at high frequencies, it is –40 dB/dec for the VSESO and –20 dB/dec for ESO. Furthermore, the stability and output characteristics of the proposed strategy are comprehensively investigated. It is revealed that the superiority of the studied scheme in disturbance rejection and noise suppression. Finally, the experimental results verify the feasibility and effectiveness of the proposed VSADRC.