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A non-singular fast terminal sliding mode control (SMC) strategy with a new piecewise reaching law (PRL) of permanent magnet synchronous motor is presented to reduce the steady-state buffeting in this paper. A speed adaptive regulator is designed to make the motor work stably at the lowest speed value under the limitation of the DC bus voltage condition when the motor starts non-normally or with locked rotor, and a disturbance observation is introduced to further improve the anti-interference ability of the control system. The experiment test is carried out. Compared with the experimental results of traditional SMC, the buffeting suppression of the control system using non-singular fast terminal SMC with PRL is reduced by 66.7%, 57.9% and 60% at 20 rpm, 30 rpm and 40 rpm under no-load condition, respectively. The buffeting suppression and the dynamic stability time of the proposed method are reduced by 52.3% and 53.3% under load condition, respectively.

Since the complicated decoupling control strategy of single winding single directional magnetic circuit (SDMC) in linear rotary motor (LRM) limits its application, its control system is carried out based on space vector pulse width modulation, voltage predicted model and the active disturbance rejection control (ADRC) without considering decoupling control in this paper. The SDMC-LRM can be translated to different three-phase permanent magnet synchronous motors working with different electromagnetic parameters by adjusting the nine-phase windings connection form, which causes that the traditional control system with constant control parameters is not suitable for this system with changing motor parameters. In order to solve this problem, the radical basis function neural network algorithm is adopted to optimize the parameters of ADRC when the winding connection form is changed, which not only can simplify the parameter determination progress, but also can enhance the robustness of the control system. The different motion statues with different winding connection forms are concluded, and the dedicated control system simulation model and experimental platform are established to verify the control strategy with different winding connection forms.

In order to improve the torque density of doubly salient permanent magnet (PM) machine (DSPMM), two different DSPMMs (topologies I and II) with NdFeB PM materials embedded in the stator yoke are presented, and the working magnetic circuits of both topologies contain the main magnetic circuit and auxiliary magnetic circuit through the magnetic barrier beside the PMs, which can improve the air gap flux density and the torque density effectively. The optimization designs of two DSPMMs are analyzed by establishing the equivalent magnetic circuit (EMC) models at no load and load conditions. Another two traditional DSPMMs (topologies III and IV) are taken as the comparison objects, and the best optimal structure parameters of the four topologies are decided by genetic algorithm. A prototype of topology II is manufactured, and the electromagnetic performances of the four DSPMMs are revealed. It is observed that the electromagnetic performances of topology II analyzed by EMC method are in agreement with the results analyzed by finite element method and test results, and the torque of topology II is larger by 148.1%, 27.72% and 245.5% than that of topology I, III and IV, respectively.

In order to improve the drilling efficiency and accuracy of drilling robot, a linear rotary drilling motor (LRDM) is proposed with U-type stator and toroidal winding structure. The stator sections are staggered, which can use the motor space effectively. The asymmetric air gap flux density (AGFD) phenomenon of LRDM is found based on the initial magnetic field analysis by finite-element method (FEM). According to flux tube principle, the variation law of the amplitude of the asymmetric AGFD of the LRDM is derived, which can be used to realize the optimization design with less computation time. The cogging torque, detent force, torque, and thrust are taken as the optimization objectives, and the optimal values of the structure and electromagnetic parameters are obtained. Then a prototype is manufactured. The electromagnetic characteristics of the proposed motor are analyzed and verified by FEM and experimental test.

Compared to the conventional frame motor, the frameless motor (FlM) has lower torque ripple and higher power density, which becomes the ideal selection in the robotic field. In this article, a novel permanent magnet (PM) FlM is proposed, which has a modular three-teeth stator structure and toroidal windings. The air gap flux density and cogging torque are analyzed by analytical method (AM), and back electromotive force (EMF) and torque of the PMFlM are calculated by magnetic circuit method, which can be used to achieve the best parameter values of PMFlM. The torque density of PMFlM is improved by increasing the axial length of the rotor and PM poles. A PM synchronous motor (SM) with toroidal winding and air gap in the stator pole (topology II) and traditional PMSM (topology III) are designed. A prototype is manufactured, and the electromagnetic characteristics of PMFlM are analyzed by both the experimental test and finite element method (FEM). While the three topologies have the same volume, the amplitude of the back EMF and the torque density of PMFlM are improved by 55.7% and 35.8% compared to those of topology II, respectively. The torque density of PMFlM is larger by 3.5% than that of topology III.