Gan Zhang's research while affiliated with Southeast University (China) and other places

This paper proposes a 12-stator slot/4-rotor pole (12/4) synchronous reluctance (SynRel) machine with integral slot concentrated windings (ISCW), a segmented stator, and a skewed rotor, namely the 12/4 ISCW machine. The proposed 12/4 ISCW machine exhibits comparable torque performance when compared to the case of adopting an integral slot distributed winding (ISDW) with the same total stack length. A comparison study is conducted on the 12/4 ISCW machine, a 24/4 ISDW machine, and 6/4 fractional slot concentrated winding (FSCW) machines. Then a torque prediction method and a continuous maximum torque per ampere (MTPA) control based on the polynomial fitting model (PFM) are proposed for SynRel machines, to provide fast and accurate calculation of the real-time inductances and torque. Magnetic saturations are also considered in the PFM, which is why the PFM has great potential in the maximum-current-per-torque control of SynRel machines. Finally, a prototype of the proposed 12/4 ISCW SynRel machine is manufactured and experimental validations are carried out.

In many robotic applications, the joint is required to have a small volume, low weight and high torque output. In this paper, based on the finite element analysis (FEA), a 36-slot 40-pole outer rotor surface-mounted permanent magnet (OR-SPM) motor with concentrated winding is designed for the exoskeleton robot. The fractional slot concentrated winding (FSCW) is employed to reduce end winding height, leading better portability. Since the motor is relatively flat, the 3D end effect is critical to the electromagnetic performances. Special attention is paid to 3D end effect during the multi-objective optimization of the OR–SPM motor. In order to increase the ending torque output, the planetary reducer is located between OR–SPM motor and load, and then system level optimization covering motor and reducer is carried out to achieve best torque output. In addition, the force impendence control method with parameter self-adaptive capability is proposed to improve user experience of the exoskeleton robot, where the key parameters in the algorithm vary according to different actions of the exoskeleton. In addition, the inertia of load is calculated using the parameter identification based on least squares method. Finally, the prototype of the joint is fabricated and tested to validate the above FEA results and control method. The user experience of the exoskeleton robot is also covered.

This paper proposes a quasi-cylindrical function contour rotor to reduce the windage loss and torque ripple (cogging torque) of stator-permanent magnet flux-switching (SPM-FS) machines, where the rotor tooth top contour conforms to the function y = ax <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and the overall appearance of the rotor is quasi-cylindrical. Firstly, three conventional rotors and one new rotor are introduced, and the difference in the modulation process between the four rotors are investigated based on the general air-gap field modulation theory (AFMT). Then, the advantages of the proposed rotor are verified from the perspectives of time-averaged torque amount reduction and torque ripple. It is found that the function contour can reduce the torque ripple (cogging torque) by about 76∼90%, while the quasi-cylindrical appearance can reduce the windage loss by about 66% at 10,000rpm. Surprisingly, the proposed rotor maintains a high convective heat transfer capacity of the air within the air-gap, which is beneficial for the machine's heat dissipation. Von Mises stress and deformation analysis verify the mechanical reliability, and manufacturing process of proposed new rotor is introduced. Finally, experiments are carried out to verify the validity of the rotor.

For the brushless doubly-fed reluctance machine (BDFRM), a composite rotor featuring salient pole reluctance and short-circuited coils is applied to efficiently improve the cross-coupling capability and magnetic field modulation effects, where the short-circuited coils induce symmetrical multi-phase current and then establish the corresponding additional magnetizing magnetomotive force to modulate the source one. This paper investigates the modulation behavior and evaluate the modulation capability of the composite modulator from the perspective of the magnetic field conversion mechanism. The modulated airgap harmonic phase shift phenomenon in space caused by the short-circuited coil modulator is firstly observed, resulting in the reduction on the effective magnetic field conversion factors in the BDFRM with conventional symmetrical composite rotor. The phase shift mechanism is revealed for the first time, then an asymmetrical composite modulator configuration is proposed to eliminate the phase shift so as to enhance the rotor cross-coupling capability and improve torque performance. A BDFRM prototype with the asymmetrical composite modulator is designed and manufactured for experimentation. Theoretical predictions are verified by 2-D finite element analysis together with experiments.

To suppress high cogging torque and torque ripple of stator-permanent magnet flux-switching (SPM-FS) machines, three functional-contour salient pole rotors (FSPRs) are proposed and designed, where the rotor tooth top contours conform to y = k | x |, y = ax <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and y = A cos( bx ) respectively. Firstly, with the help of finite element analysis, optimal geometrical parameters of FSPRs are obtained with minimum torque ripple. Then, the torque ripple suppression rates at unit torque loss of these FSPRs are analyzed by comparing with the initial values from output torque, torque ripple, and cogging torque. Further, considering that the functional-contours of salient pole rotors are easily affected by manufacturing errors, rotor single-tooth three-points model and stator inner circle deviation model are established on the typical manufacturing errors in both stator and rotor. A finite manufacturing error combination is obtained by Latin Hypercube Sampling, based on which the manufacturing error sensitivity of three FSPRs is discussed. Finally, prototypes with three FSPRs and initial rotor are tested to verify the cogging torque suppression capability of three FSPRs. Also, the manufacturing error analysis provides a reference for robustness design and industrial application of SPM-FS machines employing the FSPRs.

The very close d-axis and q-axis inductances of the flux-switching permanent magnet (FSPM) machine make it even similar to a surface-mounted permanent magnet (SPM) machine, especially those with fractional slot and concentrated windings (FSCW), which is usually applied in a light-power situation where small size and high power density are desired. Based on finite element analysis (FEA), the FSPM machine with 6-slots/5-poles (5 pole pairs) is designed for light servo applications and further compared to an SPM machine with 9-slots/8-poles (4 pole pairs), covering electromagnetic, thermal, and mechanical behaviors. The rotor skewing of the FSPM machine is also studied. Finally, the prototypes of the FSPM and SPM machines are manufactured and experimental measurements are carried out to validate the FEA results.

Parameter sensitivity analysis is usually required to select the key parameters with high sensitivity to the optimal goal before the optimization is carried out, especially for flux-switching permanent magnet (FSPM) machines where lot of design parameters should be considered. Unlike the traditional studies on parameter sensitivity, which are generally experience- or statistics-based, and are time-consuming, this paper proposes a parameter sensitivity analysis method of a FSPM machine based on a magnetic equivalent circuit (MEC), which enables the parameters’ sensitivities to be evaluated by their exponential in the nondimensionalized equations, thus providing a fast and accurate way to obtain the parameter sensitivities. Thereafter, the influences of modular manufacturing methods on magnetic performances are discussed, and the robust design approach for the FSPM machine is introduced, which aims to achieve the best machine stability and robustness by setting boundaries on design dimensions when taking into account the manufacturing tolerances. Experimental validations are also presented.

In this paper, the 12-slot/4-pole (12/4) synchronous reluctance motor (SynRM) with concentrated windings is proposed for low-cost hybrid vehicles. The non-linear magnetic equivalent circuit (MEC) model of the 12/4 SynRM is built to obtain the main electromagnetic characteristics such as coil flux, inductances, torque, etc. The magnetic saturation is also counted in by the MEC. Results calculated by MEC are validated by 2D finite element analysis (FEA). Then, aiming at larger average torque, lower torque ripple and lower total harmonic distortion (THD) in phase voltage, the parameter optimization method of the SynRM is proposed based on the Taguchi method and the MEC model. The proposed Taguchi-MEC method enables a fast optimization with satisfactory accuracy. Finally, the motor prototype is manufactured, and experimental validations are carried out.

Flux-switching permanent magnet (FSPM) machine suffers from high output torque ripple due to its special doubly salient structure and high air-gap flux density, causing undesired acoustic noise and vibration. In this paper, by analyzing the physical nature of output torque ripple, output torque ripple suppression methods of FSPM machines from both rotor and stator sides are proposed with the aid of magnetic field modulation theory (MFMT). According to harmonic modulation mechanism, air-gap PM field can be modified by revising harmonic content of rotor and stator modulation functions, and consequently three concepts, including cos-shaped edge rotor (CSER), cos-shaped edge stator (CSES), and double cos-shaped edge (DCSE), are proposed and implemented to suppress output torque ripples due to cogging torque and harmonic torque ripple of FSPM machines. Finally, finite element analysis (FEA) and experiments are conducted to verify the proposed approaches. The results reveal that the CSER method exhibits the most effective suppression effect.