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A number of transport vehicles have been fitted with electric traction motors and their inverters. The traction motor is required to continue to operate even if the inverter is under fault conditions. We propose a motor with two controllable rotors for a traction motor, which consists of 2 rotors and 1 stator. In this paper, we propose a fault-tolerant control method for a two-controllable-rotor motor using a 6-phase inverter. The operational principle of the two-controllable-rotor motor is described. The mathematical model under fault tolerant control is shown, and a fault-tolerant control method for the two-controllable-rotor motor is described. The proposed fault tolerant control method is verified by conducting finite element analysis and carrying out measurements on a prototype.

In rotating machinery, the rotor mass unbalance will cause synchronous vibration, in which static unbalance will produce synchronous vibration force, and dynamic unbalance will produce synchronous vibration moment. In order to suppress the vibration moment of the magnetically suspended control moment gyro, a modified dual-channel notch filter (DNF) is proposed in this article. First, the modeling of the rotor system with mass unbalance is performed. Then, the design of modified DNF is carried out. This notch filter uses the equivalent vibration moment calculated by the current and displacement signals as input, and uses the orthogonal characteristics of the moment signals in the X and Y directions to enter the controller at the same time. The stability of the rotor system with a DNF is proven. Finally, the experimental results are given to show that this method can effectively eliminate the synchronous vibration moment in the rotor system.

Accurate and timely fault diagnosis of the rotating rectifier for a wound-rotor synchronous starter/generator is of great importance to improve system reliability. In the generation mode of the system, there is one idle stator winding of the main exciter. The terminal voltage characteristic of the idle stator winding is analyzed, and a novel fault diagnosis method for the rotating rectifier in the generation mode of the system is proposed. In this method, two feature voltages, namely, the maximum peak voltage and any other peak voltage of the idle stator winding terminal voltage are extracted through voltage sequence reconstruction to calculate the feature ratio for fault detection. The corresponding rotor position obtained by an inherent position sensor where the maximum peak voltage occurs is collected to determine the faulty diode location. The experimental results verify the feasibility and effectiveness of the proposed fault diagnosis method.

In the decoupling control process of the outer rotor coreless bearingless permanent magnet synchronous motor using least square support vector machine, the kernel width 2 and penalty factor of the least square support vector machine are difficult to tune, resulting in high kernel space complexity and low fitting accuracy. A new improved genetic algorithm is used to optimize the above parameters. Firstly, the generalized inverse system model of the original nonlinear multiple input output system is fitted online with the optimized least square support vector machine, and the generalized inverse system model is connected in series with the original system to form a pseudo-linear system. And then a linear closed-loop controller is used for control. Simulations and experiments show that the robustness and wide applicability of the original system are guaranteed. The dynamic and static performance of the system are improved, verifying the effectiveness of the scheme.

This paper presents a new interior permanent magnet (IPM) rotor structure/ assembly which inherits from the Halbach magnet configuration and spoke-type IPM rotor to achieve a high saliency ratio and high torque/power density. A higher air-gap flux density and a higher saliency ratio are expected to improve torque density, while the rotor inner diameter can be maximized as much as possible to reduce core material consumption and increase internal space of the rotor. Accordingly, the electromagnetic performance of three motors consists of a unified stator but three different rotors, namely flux-concentrating rotor, Halbach array PM rotor and spoke-type IPM rotor is compared by finite element analysis (FEA). Due to the segmented structure of flux-concentrating PM rotor without magnetic bridges, the mechanical challenges are analyzed in detail for electric vehicle application. The stress analysis on the prototype design with fixing pins to hold the pole pieces validates the structural feasibility at 7200 r/min. Finally, a 72-slot/ 16-pole fractional-slot PM motor with new flux-concentrating rotor is manufactured and tested to verify its performance and feasibility. It can be concluded that the new rotor is superior to the spoke-type IPM and Halbach array PM rotor in terms of torque density and PM utilization.

Accurate rotor position estimation is important to ensure the high-performance operation of position sensorless permanent magnet synchronous motor (PMSM) drives. To suppress the estimated rotor position harmonic error (ERPHE) caused by inverter nonlinearities, flux spatial harmonics, and the current measurement error in high-frequency signal injection based schemes, an adaptive iterative learning control based online suppression method is proposed in this paper. This method constructs a P-type iterative learning rotor position observer with the forgetting factor to obtain the tracking error and generate the compensation value in real time. The stability, the convergence, and the parameter sensitivity of this observer are analyzed in detail. To improve the suppression effect of the ERPHE for different loads and speeds, an iterative learning gain self-tuning strategy is investigated. The proposed method does not require the offline detection and the discrimination of harmonic frequencies, which has strong suppression ability for different harmonic error components. The effectiveness is verified by experiments on a 2.2-kW interior PMSM drive platform.

The present work was based on an experimental study on the aerodynamic performance of a flapping wing rotor (FWR) and enhancement by passive pitching angle variation (PPAV) associated with powered flapping motion. The PPAV (in this study 10o~50o) was realized by a specially designed sleeve-pin unit as part of a U-shape flapping mechanism. Through experiment and analysis, it was found that the average lift produced by an FWR of PPAV was >100% higher than the baseline model, the same FWR of a constant pitching angle 30o under the same input power. It was also noted that the lift-voltage relationship for the FWR of PPAV was almost linear and the aerodynamic efficiency was also over 100% higher than the baseline FWR when the input voltage was under 6V. The aerodynamic lift or efficiency of the FWR of PPAV can be also increased significantly by reducing the weight of the wings. An FWR model was fabricated and achieved vertical take-off and free flight powered by 9V input voltage. The mechanism of PPAV function provides a feasible solution for aerodynamic improvement of a bio-inspired FWR and potential application to micro-air-vehicles (MAVs).

In this paper, a method of simultaneous sensorless rotor position and torque estimation is proposed for interior permanent magnet synchronous machines at standstill and low speed. The proposed method estimates the torque using high frequency inductances identified from the current variations due to high frequency square wave voltage injections in the estimated dq-axeswhich are simultaneously used for sensorless rotor position estimation. The proposed method is not dependent on the fundamental model and has taken the cross-coupling effect into consideration, allowing for low cost and fast torque estimation at standstill and low speed. Both simulations and experiments are carried out to verify the effectiveness of the proposed method.

Wound rotor induction motors (WRIM) are widely used in a vast number of high output power industrial applications due to their capability of reaching high start torques while maintaining low inrush currents. Nonetheless, these machines are very prone to require early maintenance, and the possibility of presenting rotor winding asymmetry failures is high due to their more complex rotor circuit. Although some recent works have proposed techniques that overcome the drawbacks of conventional methods, an additional research effort for the development of alternative approaches able to enhance their performance and reliability is desirable. In this work, a new method for the diagnosis of rotor asymmetries in WRIM is presented. The proposed methodology is based on a feed-forward neural network (FFNN) feed by suitable fault severity indicators, which rely on the maximum energy density of higher order harmonics (amplified by the failure) at strategic regions of the time-frequency maps obtained from stray flux signals under startup transient. Experimental results for three different levels of rotor asymmetries in a 11 KW WRIM prove the reliability of the enhanced proposed system in comparison to conventional approaches that only rely on the main sideband fault-harmonic amplitudes.

In rotor dynamics, blades are normally modelled as a slender beam, in which elastic deformations are coupled with each other. To identify these coupling effects, new rigid-flexible structural model for helicopter rotor system is proposed in this paper. Finite rotations of the whole blade (on flapwise, lagwise, and torsional) are described as three global rigid degrees of freedom. The nonlinear deformation geometrics of the beam is built on geometrically exact beam theory. New expressions for blade strain energy, kinetic energy, and virtual work of various kinds of external forces are derived as functions of finite rotations and elastic deformations. To quantify the coupling characteristics, following the definition of coupling factor in electromagnetics, a new coupling factor between two modal components on each mode is introduced in modal analysis. Simulations show that the new structural model is highly capable of solving static and dynamic problems in rotor dynamic and the maximum deformation that moderate deformation beam theory can predict might be 15% of beam length. After the new coupling factor is applied to study structurally coupled characteristics of rotor blade, it can be concluded that closeness of natural frequencies likely indicates considerable coupling between corresponding DOFs in structure.

This paper presents and evaluates a dual rotor axial flux permanent magnet motor for electric aircraft applications. Several features, including grain oriented electrical steel (GOES), magnet segmentation, and wires with rectangular cross-sections, are used to improve torque density and efficiency. Rather than simply optimizing the motor by itself, this paper evaluates the tradeoffs between motor performance and its interfaces with the drive, thermal management system (TMS), and mechanical structure. This information can be used along with similar analyses of the drive, TMS, and structure to select a design that achieves the system-level optimal performance. The paper uses finite element simulations to characterize tradeoffs between active mass, efficiency, fundamental frequency, power factor, axial forces on the rotors, and cooling surface area. Several designs exceed 95% efficiency at takeoff with less than 8 kg of active mass. While high pole counts, a large outer radius, and short stator teeth tend to optimize the magnetic performance at takeoff, this can reduce cruise efficiency, reduce the surface area through which the TMS can extract heat, increase the fundamental frequency the drive must supply, and increase the structural mass required to support the rotors. Additionally, designs with 20 °C cooler magnets were simulated to evaluate the impact of a more effective TMS, but the improvements in magnetic performance were relatively small.

In this paper, a novel dual-rotor multiple-winding machine (DRMWM) is proposed for the continuous variable transmission (CVT) in hybrid electric vehicles (HEVs). First, a mathematical model of the proposed machine is constructed by using the harmonic modeling method (HMM). Then, on the basis of the magnetic field analysis, the operating principle of the DRMWM is deduced. By introducing multiple windings with two different working harmonics, namely the permanent magnet (PM) harmonics, and the magnetic gear (MG) harmonics, the proposed DRMWM can cope with various operating conditions of HEVs. To further obtain optimal performance, a finite element analysis (FEA) and multi-objective genetic algorithm II (MOGA-II) combined sequential optimization is carried out for the proposed DRMWM. The proposed optimization method is proven to be more computationally efficient compared to the global optimization method. Finally, a prototype is manufactured and tested in various operating modes. The results validate the simulation and analytical method predictions. Also, it proves that the proposed DRMWM is suitable to work as the CVT in HEVs.

Vibrations impose negative impacts on the effectiveness and public acceptance of helicopters. Active rotors with trailing-edge flaps have been proved to be an effective way to actively eliminate helicopter vibrations. For the existing control algorithm based on offline system identification, the transfer functions of an active rotor under different flight conditions are pre-requisites to implement closed-loop vibration control. In this study, a three-bladed active rotor with improved trailing-edge flaps is designed, and wind-tunnel tests are conducted to identify the transfer functions of this active rotor using frequency sweep and phase sweep methods. The experimental results demonstrate that these transfer functions are insensitive to the variation of flight speeds: the amplitude of the transfer function varies slightly, while the phase delay almost remains unchanged. In addition, this finding is validated through closed-loop vibration control tests with the active rotor. The transfer function obtained from the hover test results is also applicable to closed-loop vibration control tests under the forward flight conditions. This will dramatically simplify the implementation and operation of an active rotor.

Surge is one of the main factors affecting the stability of the centrifugal compressor. This article investigates surge disturbance suppression of active magnetic bearing (AMB)-rotor systems in magnetically suspension centrifugal compressors. An active disturbance control method is adopted to make the rotor stably levitate under surge disturbance. First, the dynamic model of the magnetic bearing rotor is established and simplified into a single-channel model. Second, a third-order linear extended state observer (LESO) and a linear active disturbance rejection controller are designed. The performance analysis of the controller shows that the estimation error accumulation of the observer is bounded and the estimation errors decrease with the increase of the observer bandwidth. Furthermore, the variable differential parameter added in the differential link of the controller can flexibly adjust the system damping. A method of tuning parameters for linear active disturbance rejection control (LADRC) is proposed to suppress surge disturbance while satisfying the stability of the system. Finally, the results of the experiment demonstrate that the proposed scheme is effective in suppressing the large-scale vibration effect of the surge disturbance on the rotor, and the magnetically suspended centrifugal compressor (MSCC) can run stably with low amplitude under the modified surge and mild surge.

How to achieve uniform mixing of highly viscous fluids with low energy consumption is a major industry demand and one of the hot spots of mixing research. A typical multistage rotor-stator mixer (MRSM) equipped with a distributor was investigated to disclose the effects on the mixing performance and power consumption for highly viscous fluids via numerical simulation, considering the influence factors associated with different geometric parameters of both MRSM and the distributor. The mixing index and power consumption are used to evaluate the performance of the mixers. The dimensionless correlations for the mixing index and the power consumption are established considering the factors including the flow rate, rotor speed, the number of mixing units. Adopting the optimized mixer with the distributor (X1-T1), the mixing index increases to 0.85 (obviously higher than 0.46 for the mixer T1 without a distributor), meanwhile the corresponding power consumption is about 1/5 of that of T1 achieving the same mixing effect. It illustrates that the distributor can significantly improve the mixing of highly viscous fluids in the MRSM without the cost of large power consumption. These results would provide a guidance on the design and optimization of multistage rotor-stator mixers in industrial applications.

It is recognized that the rotor with a shielding cylinder (SC) is one of the effective measures to restrain the rotor eddy current loss (RECL) for high-speed surface-mounted permanent magnet synchronous motors (PMSMs). At present, the RECL of PMSMs with multilayer composite rotor structure is mainly analyzed by the finite element method (FEM), which has obvious shortcomings in time-consumption and the mesh generation of the thin SC. In this paper, a multi-layer subdomain analytical model for calculating the RECL of high-speed PMSMs with both non-ferromagnetic retaining sleeve and SC is proposed by taking the effects of eddy current reaction, stator slotting and current harmonics into account. Moreover, the 3-D distribution coefficient of eddy current in the SC is derived by the equivalent impedance method and the effects of temperature on the conductivity of the SC and RECL are obtained through equivalent thermal network model. Based on the analytical model, the SC parameters are calculated to obtain the variation ranges when the RECL is minimum. Finally, the C-shape core experiment was built up to verify the correctness of the multilayer analytical model under different shielding layer conductivities and thicknesses.

In the docking process of aeroengine rotor parts, docking accuracy that indicates the gaps between the end faces is strictly required. A key issue is improving docking accuracy using automated docking equipment. In this paper, a systematic study is carried out on the error modeling and compensation of a novel six-degrees-of-freedom (6-DOF) docking equipment for aeroengine rotors. First, a new model for indicating the main indexes of docking accuracy is proposed. Then, the error model of a specially designed 6-DOF docking equipment is established based on a modified Denavit Hartenberg method with five parameters. Subsequently, two error compensation methods are proposed. Based on the above models, a docking accuracy simulation algorithm is proposed using the Monte Carlo method. Finally, verification experiments are conducted. The results show that, for the maximum values and standard deviations of the gaps between the rotor end-faces in the actual and target positions and attitudes, i.e., main indexes that represent docking accuracy, the deviation rates between the simulation and experimental results are less than 20%. The modeling methods have referential significance. The decline rates of these values are 50–65% when using the two proposed compensation methods. The compensation methods significantly improve the docking accuracy.

Platelet rich fibrin (PRF) is an autologous blood concentrate, that supports tissue regeneration. The effect of the centrifuge rotor angle in the fabrication of PRF is still not fully elucidated. The hypothesis of this study is: When applying the same g-force {relative centrifugal force (RCF)} and centrifugation time, PRF components and bioactivity are not modified using either a swing-out or fixed angle rotor. For this purpose, peripheral blood samples (five donors )were used to gain solid matrices (710 xg, 8 minutes) and liquid (44 xg, 8 minutes) PRF matrices using three different centrifuges (one fixed angle as a control; and two different swingout rotor centrifuges). The physical characteristics of the solid PRF were measured to evaluate the clot formation and cellular distribution. Liquid PRF was used to evaluate the cell number, bioactivity and influence on primary human osteoblasts and fibroblasts in vitro. Solid PRF clots were significantly larger in the group of fixed rotor centrifuges compared to either of the two evaluated swing-out rotor centrifuges. No differences were observed when evaluating the cellular distribution within the solid No statistically significant differences were documented in the cell's density in liquid PRF samples (platelets, lymphocytes, neutrophils, eosinophils, and basophils) among the differently gained PRF samples. No statistically significant differences were documented for the released growth factors (VEGF, EGF, TGF-β1) over 7 days. Primary human osteoblasts (pOBs) and primary human fibroblasts (pHFs) viability after treatment with PRF conditioned media showed no statistically significant differences between the evaluated groups. However, the number of adherent cells treated with PRF obtained with the use of the fixed angle rotor was significantly higher when compared to those treated with PRF obtained by using the swing-out rotors. The presented results confirmed that regardless of the centrifuge rotor used, the components and bioactivity of solid and liquid PRF matrices are modified by the applied RCF and centrifugation time. These findings are of great importance for highlighting the essential role of adapting the centrifugation protocols when using different centrifuges and to correctly report the used centrifugation protocols in scientific research to allow for reproducible results.

To obtain an accurate rotor position is an important part of sensorless control of permanent magnetic synchronous machine (PMSM) since PMSM is usually operated under speed varying conditions. However, the existing methods cannot provide a satisfactory tracking performance under harmonic polluted condition in wide operating range, which degrade the position detecting accuracy. In this paper, a recurrent neural network (RNN) based phase detection method is used for rotor position estimation of PMSM. To tackle the nonlinear problem in wide operating range of PMSM, RNN is used as a nonlinear dynamic system to establish the mapping relationship of the voltages of stator and rotor position. The proposed method can also provide frequency-adaptive filtering capability to remove the affect of harmonic. To validate the method, a comparison simulations with conventional SRF-PLL method are carried out under speed varying and harmonic disturbances conditions. The results confirm the effectiveness of the proposed method.

The suppression of harmonic vibration of active magnetic bearing (AMB) rotor system depends on the speed signal. Aiming at the problem of harmonic vibration suppression when the speed measurement sensor fails, a dynamic model of the AMB-rotor system including mass unbalance and sensor runout is established. This paper analyzes the main sources of harmonic vibration force, and proposes a double-input filter based on adaptive frequency estimation. The characteristic that the displacement output signals of the radial X- channel and Y- channel of the rotor are orthogonal to each other can be used to quickly and accurately estimate the actual speed of the rotor adaptively. At the same time, the harmonic components of the control current are also compensated. Finally, the effectiveness of the proposed harmonic vibration suppression method with adaptive frequency estimator is verified by the simulation and experiments.

This study systematically investigates the aerodynamic interactions of a two-rotor system with a front rotor and an aft rotor aligned with the direction of flow. The rotors are 5.5 ftdiameter fixed-pitch rotors operating at approximately 12 lb/ft2 disk loading, representative of large eVTOL aircraft. Fluid flow is simulated using the commercial Navier–Stokes solver, AcuSolve, with a detached eddy simulation (DES) model. Simulations were performed nominally at 40 kt edgewise flight for nine cases corresponding to three values of longitudinal hub–hub separation (2.5R, 3R, 3.5R) and three values of vertical offset (0, 0.25 R, 0.5 R ). Aft rotor performance was compared to an isolated rotor operating in the same conditions in order to quantify the effects of rotor–rotor interaction. For the cases where the aft rotor is closest to the front rotor (2.5R longitudinal offset, zero vertical offset), the aft rotor produced 8.4% less thrust and required 13.4% higher torque than a rotor in isolation. When vertical rotor separation was increased, interactional aerodynamic effects decreased. For a 2.5R longitudinal offset, increasing the vertical offset to 0.5 R decreased the lift deficit to 4.6% and the torque penalty to 6.8%. Increasing the longitudinal offset to 3.5R (while keeping the vertical offset at zero) also reduced interactional aerodynamic effects, but reductions in lift deficit and torque penalty were smaller than those observed with 0.5R vertical offset. Reducing disk loading was found to strengthen interactional aerodynamic effects, with an 11.5% thrust deficit at 6 lb/ft2 compared to 9.0% at 12 lb/ft2. An increase in flight speed also increased interactional aerodynamic penalties from 5.4% thrust deficit at 20 kt to 12.2% at 60 kt. The increased interactional aerodynamic penalties with the reduction in disk loading and increase in flight speed were both attributed to an increase in wake skew angle and the resulting decrease in separation between the aft rotor disk and front rotor wake.

In order to solve the problems of high cost and large volume of the displacement sensors in magnetic bearings, an improved quantum particle swarm optimization (IQPSO) algorithm optimized cubature kalman filter (CKF) prediction model was proposed for a six-pole radial active magnetic bearing (AMB). Firstly, the structure and operation principle of the AMB are introduced, and the mathematical model of the suspension force is derived by the equivalent magnetic circuit method. Combined with CKF, the prediction model of the six-pole radial AMB is established, and the state prediction values obtained by the prediction model at the time of updating stage are optimized by the IQPSO algorithm, and the rotor displacement self-sensing technology is achieved. Then, the simulation system is constructed, and the simulation analysis of floating and anti-interference are carried out, which show the prediction ability and anti-interference performance of IQPSO algorithm optimized CKF prediction model is stronger than standard prediction model. Finally, the verification experiment is carried out on the experimental platform, which proves the feasibility of the method.

As a new type of flux modulation machine, line-start permanent magnet vernier machine (LSPMVM) has drawn more and more attention. Thanks to the rotor starting winding, the self-starting capability of which can be acquired without applying the inverters. As a result, the system reliability has been improved and cost can be decreased, which is promising for industrial applications, such as pumps and fans. In order to extend the family of LSPMVMs and select the preferable topologies meeting the different requirements, four LSPMVMs, including V-shaped LSPMVM, consequent-pole U-shaped LSPMVM, dual-stator spoke LSPMVM and consequent-pole surface-mounted permanent magnet (SPM) LSPMVM, have been proposed in this paper. And the steady state performance, starting and synchronization capability are comprehensively analyzed and compared, where the regular commercial line-start permanent magnet synchronous machine (LSPMSM) is used as a counterpart. It is found that all the proposed LSPMVMs can acquire the higher torque density. Especially, the V-shaped LSPMVM and consequent-pole U-shaped LSPMVM have the highest torque density, while the consequent-pole SPM LSPMVM can be a better candidate where the low cost is desirable. Finally, the prototype of V-shaped LSPMVM has been manufactured, where experimental results match well with finite element analysis (FEA).

In this study, the rotor loss as well as the temperature variations due to the static air‐gap eccentricity (SAGE) and the rotor inter‐turn short circuit (RISC) in synchronous generators is presented. Different from the previous studies, this study investigates the loss/temperature changes under not only the single SAGE fault and the single RISC fault but also the combined faults (CF) that are composed of these two single faults. Detailed formula derivation on the hysteresis loss (HL) and the eddy current loss (ECL), together with the rotor temperature rise due to varied fault types and different operating conditions, are first carried out based on a theoretical analysis of the magnetic flux density (MFD) variation. Then, 3‐D finite element analysis (FEA) and experimental verifications are performed on a CS‐5 prototype generator that has two poles and a rated rotating speed of 3000 rpm. It shows that the occurrence of either SAGE or RISC will increase the rotor loss and temperature. Comparatively, the single RISC fault overweighs the single SAGE fault in the rotor temperature increment, while the combined fault overweighs both of these single faults. In the same fault cases, the rotor temperature will have the highest value under full‐load operation.

Stator- and rotor-side voltage source inverters (VSIs) (VSI-S and VSI-R) of a double-inverter-fed wound rotor induction machine (DI-WRIM) drive individually feed 1-p.u. power each, to extract 2-p.u. power at a 2-p.u. speed. This feature of the DI-WRIM drive is explored, in this article, to model this drive as two virtual cage rotor induction machines (CRIMs). The VSI-S connected to the stator is emulated as one VSI-fed CRIM with the rotor short circuited, while the VSI-R connected to the rotor is emulated as another VSI-fed CRIM with the stator short circuited. The mathematical modeling of the DI-WRIM drive as two virtual CRIMs, in the synchronous reference frame, is presented by considering the angle between the stator and rotor currents ( $\gamma$ ) as a medium of coupling between the two virtual CRIMs. The proposed mathematical model of the DI-WRIM is used to demonstrate the performance of the drive in a current-oriented control (COC) technique. In the COC technique, the VSI-S is controlled in the stator current-oriented frame and the VSI-R is controlled in the rotor current-oriented frame. The proposed model and technique is tested on a 4-hp WRIM drive and the experimental results are also presented to demonstrate the satisfactory performance of the drive.

Reverse pedal operational property in front crosswind flight condition is a potential hazard for accidents involving loss of tail rotor effectiveness (LTE), which is closely related to the main rotor (MR) wake interference on the tail rotor (TR). As understanding of this interaction is vital for the early warning strategy development, the MR wake influence effect on TR thrust and the effect of helicopter yaw stability are examined in this study. For this purpose, the comparison of TR thrust and flow field with wind azimuth and speed in front crosswind environment was performed by experiment and CFD simulation, respectively. Test campaign was performed at a 5.5 m × 4 m wind tunnel in the China Aerodynamics Research and Development Center using a high-position bottom-blade forward-rotating TR and a counterclockwise rotating MR to address the TR thrust under wind speeds of 8–22 m/s with 50°, 60°, and 70° wind azimuths. The influence of MR disc loading was also contrasted. CFD analysis was used to gain insight into the flow physics responsible for the interference effect. It was conducted with unsteady Reynolds-averaged Navier–Stokes simulations, where the MR using the actuator disk approach and the TR blade rotation was modeled via a sliding mesh method. Results indicated that the MR disc vortex has a remarkable interference effect on the TR aerodynamic performance characteristic and that the effect is sensitive to the wind speed, wind direction, and MR disc loading. The observed yaw instability is considered to be related to the lesser inflow introduced by the MR disc vortex due to the change in the relative position of the disc vortex filament and TR with the wind azimuth. The increase in TR thrust at moderate wind speeds is due to the increase in leading edge dynamic pressure caused by the opposite swirl direction of the disc vortex contrasted to the TR. The MR disc loading affects the TR thrust due to the change of disc vortex strength and position.

Motor current signature analysis (MCSA) has become the most widespread test for detecting rotor cage faults as it can provide remote, on-line monitoring. Although MCSA has been successful, many cases of false indications have been reported in the field. False negative indications, where MCSA fails to detect the fault due to load variation, low slip operation, error in speed estimate, and non-adjacent broken bars, is considered serious as it can lead to unexpected motor failure. This has triggered research on alternative monitoring techniques for reliable detection of rotor faults with flux monitoring being one of them. In this paper, a new test method based on time-frequency analysis of the airgap flux is proposed and verified. Experimental test results are given under load variation, low slip, and non-adjacent broken bar conditions to support the claims on the reliability of the proposed method for cases where MCSA produces false negative indications.

This article investigates the influence of start rotor position on three-phase short circuit (3PSC) current in dual three-phase surface-mounted PM (DTPSPM) machines. For DTPSPM machines with symmetrical winding configurations, the 3PSC analytical model considering PM flux linkage harmonics is developed. It shows that the variations of 3PSC peak current with start rotor position mainly repeat every multiple of /3 in an electrical period due to the 5th and 7th harmonics. The start rotor positions causing the largest 3PSC peak currents heavily depend on the harmonic magnitudes and phases. Then the 3PSC analytical model for DTPSPM machines with asymmetric mutual inductances in one winding group is developed. It shows that the variations of 3PSC peak current with start rotor position mainly repeat every multiple of . For winding configurations with smaller Mac, Mbc, and Mab, start rotor positions causing the largest d-axis peak current are about /6+k, /2+k, and 5/6+k (k=1, 2, 3), respectively. To obtain the largest q-axis peak current, such start rotor positions are about 7/24+k, 5/8+k, and 23/24+k (k=1, 2, 3). In addition, the influence of rotor speed and asymmetric level is discussed. Finally, finite element simulation is performed and experiments are conducted to validate the theoretical analysis.

The influence of rotor position error generated by resolver on electromagnetic noise of permanent magnet synchronous motors (PMSMs) is analyzed in this paper. The motor noise is mainly caused by the electromagnetic force acting on the surface of stator teeth or permanent magnets. Firstly, the influence of rotor position error on current harmonics is deduced theoretically. The spatial and temporal characteristics of the electromagnetic force are then analyzed. The results show that the rotor position error will introduce extra sideband frequency harmonics to the current and electromagnetic force. This will lead to more abundant noise harmonics. The field-oriented control (FOC) model and the electromagnetic finite element model (FEM) are then established to simulate the influence of rotor position error on current harmonics and electromagnetic force. Finally, a test is carried out to capture the phase current and noise spectrum. Both the simulation and test results are consistent with the theoretical analysis results. This study can give a reference to the source identification and optimization of acoustic performance for PMSMs in electric vehicles.

A wave rotor is suitable for compact and efficient pressure-exchange between gas flows. This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate the unsteady pressure waves. The experimental and CFD results showed some slopes in the circumferential pressure distributions, and the slopes indicated the traces of specific unsteady pressure waves. Such traces varied regularly if the rotational speed varied within a range from −11% to +11% off the baseline value, but they were seriously disturbed if the rotational speed varied by −45% from the baseline value. It verified that a pressure wave in a wave rotor tended to keep its pressure ratio and propagation velocity unchanged if the rotational speed varied by a small extent, and that the pressure wave could not keep its propagation patterns if the rotational speed varied by a large extent. Because of the pressure wave behaviors, the wave rotor demonstrated specific regulations of the rotational speed effects on its operational states.

In this paper, the design and control of a new coaxial tilt-rotor (CTR) unmanned aerial vehicle (UAV) are presented. The CTRUAV is an electric-powered UAV with a special configuration, which is composed of two pairs of tiltable coaxial rotors and a rear rotor. A CTRUAV prototype has been designed by 3D CAD software and constructed according to the designing scheme. The dynamic model of a CTRUAV is derived by utilizing the Euler-Lagrange equation, which considers the special features of the coaxial rotors and air drag forces on the CTRUAV. An adaptive controller is developed to realize motion control for the CTRUAV. The adaptive controller includes two sub-controllers: an inner-loop attitude controller and an outer-loop velocity controller. The stability of the resulting closed-loop CTRUAV system is analyzed via the Lyapunov method. Finally, several simulations and real flight experiments are implemented to validate the effectiveness of the developed CTRUAV.

In the process of establishing a bearingless induction motor (BL-IM) traditional dynamic model, the magnetomotive force of rotor winding, the influence of suspension winding on torque, and the influence of torque winding on radial force are ignored. To solve the problem of insufficient accuracy in the traditional analytical model, based on fixed-pole rotor structure designed by the research group, which comprehensively considers the effect of suspension winding, torque winding and rotor winding, an optimized dynamic model is proposed. Firstly, the spatial variation equation of air gap under rotor eccentricity is established, and the composite magnetomotive force of three sets of windings according to the law of magnetic circuit is deduced, and the analytical model of magnetic co-energy in air gap is bulit. Secondly, using virtual displacement theorem to find partial derivative, the torque and radial force analytical model are obtained. Thirdly, the optimized BL-IM dynamic model is established. Finally, FEA (Finite element analysis) simulations based on controlled variable method prove the accuracy of optimized dynamic model and the change trend of torque is verified with respect to suspension current, phase difference between suspension current and torque current, as well as rotor eccentricity.

This study investigates the instabilities of the interstage flow between a rotor and a stator in turbomachinery and evaluates their impact on the fan noise. By viewing the interstage flow as the so...

This paper investigates the influence of static and dynamic rotor eccentricities on electromagnetic performances, including air-gap flux density, back electromotive force (EMF), electromagnetic torque, cogging torque and unbalanced magnetic force (UMF), of a 2-pole/3-slot permanent magnet (PM) motor considering eccentricity ratio, eccentricity angle, and rotor initial angle. Both finite element analyses and experiments show that in a 2-pole/3-slot PM motor, the static rotor eccentricity leads to unbalanced magnitudes and phase angles of fundamental back-EMFs of three phases but does not change the harmonic contents, while the dynamic rotor eccentricity will not cause unbalance in three phase back-EMFs but affects the harmonic contents of back-EMFs and their phase angles, which causes asymmetric positive and negative half-periods and corresponding even harmonics of phase back-EMF waveform. In addition, both static and dynamic rotor eccentricities have negligible influence on the average torque, but result in large torque ripple, cogging torque, and UMF.

The influence of static eccentricity (SE) and dynamic eccentricity (DE) on the electromagnetic forces in internal- and external-rotor permanent magnet synchronous motors (PMSMs) is investigated in this paper. Firstly, the analytical model of the electromagnetic force is derived. By introducing the eccentricity coefficient, the influence of eccentricity on the electromagnetic force is then analyzed. The results show that SE change the spatial component of the electromagnetic force in internal-rotor motors while the frequency remains unchanged. While for the external-rotor motors, both the spatial order and frequency of electromagnetic force are affected by SE. Contrary to SE, DE introduces additional spatial components and sideband frequency harmonics to the electromagnetic force of internal-rotor motors. For external-rotor motors, only the spatial order is changed. In addition, axial-flux PMSMs suffer from extra unbalanced bending moment (UBM), which is a unique feature that differs from traditional radial-flux PMSMs. The expression of UBM caused by eccentricity is further derived. Finally, the theoretical analysis is validated by the simulation and test results respectively. This study will benefit the researchers and designers in terms of source identification and reduction of acoustic noise in PMSMs.

The decrease in aerodynamic performance caused by the shock-induced dynamic stall of an advancing blade and the dynamic stall of a retreating blade at low speed and high angles of attack limits the flight speed of a helicopter. However, little research has been carried on the flow control methods employed to suppress both the dynamic stall induced by a shock wave and the dynamic stall occurring at high angles of attack. The dynamic stall suppression of a rotor airfoil by Co-Flow Jet (CFJ) is numerically investigated in this work. The flowfield of the airfoil is simulated by solving Reynolds Averaged Navier-Stokes equations based on the sliding mesh technique. Firstly, to improve the effect of a traditional CFJ on suppressing rotor airfoil shock-induced dynamic stall, an improved CFJ—a CFJ-sloping slot is proposed. Research shows that the CFJ-sloping slot suppresses the shock-induced dynamic stall more effectively than a traditional CFJ. Moreover, the improved CFJ can also suppress the dynamic stall of rotor airfoil at low speed and high angles of attack. The improved CFJ proposed in this paper is an effective flow control method that simultaneously suppresses the dynamic stall of the advancing and retreating blades. The mechanism of the improved CFJ in suppressing the dynamic stall of the rotor airfoil is studied, and a comparison is made between the improved CFJ and the traditional CFJ in terms of dynamic stall suppression at high and low speed. Finally, the effect of improved CFJ parameters (the jet momentum coefficient, the position of the injection/suction slot, and the size of the injection/suction slot) on shock-induced dynamic stall suppression is analyzed.

Rotor-step straight skewing is a common method to reduce electromagnetic vibration of permanent magnet synchronous motors (PMSMs). However, the difference of the radial electromagnetic forces received by different axial positions of the stator caused by the elastic-plastic material is generally ignored in the theoretical analysis to determine the skewing structure, which makes the vibration suppression effect of the structure far less than expected in practical applications. Take a 48-slot 8-pole interior PMSM as an example, this paper compares the suppression effects of rotor-step straight skewing and rotor-step zigzag skewing when the elastoplasticity of the stator material is considered. It is pointed out that the rotor-step zigzag skewing can overcome the limitation of the straight skewing in restraining electromagnetic vibration in practical application. Based on the theoretical formula and multi-physical field simulation, the selection rules of the rotor-step zigzag skewing angle and segment number are summarized. Finally, the rationality and effectiveness of the simulation method are verified by experiments on the prototype.

Compared with the fundamental loss, the harmonic losses become very complicated because of the coupling between the power supply harmonics and the motor harmonics. For dispose of this problem, a multi-slice 2-D finite element model considering the interbar currents and a fast rotor harmonics identification method is employed to identify the harmonics of the rotor current density and flux density of the inverter-fed induction motor (IM). Considering the complex coupling phenomenon of time-space harmonics, a two-term iron model with piecewise-defined variable coefficients (PVCIL model) and a finite element analysis (FEA)-based copper loss method are then used to calculate the iron and copper loss components of the inverter-fed IM. Finally, based the introduced methods, both the electromagnetic field and different losses terms of the same 5.5 kW IM inverter-fed under different load and supply conditions are calculated and analyzed. The experimental validation of those two losses calculation methods is performed on a 5.5 kW IM with different operating conditions. The results obtained in this paper can provide theoretical basis for targeted harmonic elimination and loss reduction in the design phase of the inverter-fed IM.

This study focuses on the nonlinear dynamic behavior of a marine rotor-bearing system coupled with vibration isolation structure under ship rolling motion. After considering the effect of the nonlinear oil film force and the ship rolling motion, a mathematical model is established based on Lagrange's equation. By employing a numerical method, the dynamic steady-state response of the system is analyzed, such as the orbits of the rotor and its Poincare maps, spectrum waterfall diagram, and the displacements and frequency spectrum diagram of the raft frame. We also studied the effects of the rotor speed, the amplitude and frequency of ship rolling on the marine rotor-bearing system coupled with isolation structure under ship rolling motion. The results indicates that response of the rotor shows obvious nonlinear dynamic behaviors such as amplitude jumping, bifurcation and chaos due to the influence of the nonlinear oil film force and the ship rolling motion. As the rotor speed increases, the motion of the rotor experiences the process of quasi-periodic and chaos vibration. Both the amplitude and frequency of ship rolling have effects on the amplitude of the rotor and the raft frame. Moreover, the rotation angle of the raft frame is greatly influenced by the amplitude and frequency of ship rolling, and it is necessary to control the vibration attitude of the raft frame.

Numerical studies were performed to investigate the mechanism and potential of several active rotors for reducing low-frequency in-plane thickness noise generated by rotating blades. A numerical method coupling the blade element theory, prescribed wake model and Fowcs Williams-Hawkings (FW-H) equation was established for rotor noise prediction. It is indicated that the excitation force on the blade tip can generate anti-noise that to partly cancel the in-plane thickness noise with an appropriate actuation law. Results from the phase, frequency and amplitude sweeps show that the excitation force direction and actuation law are the crucial factors affecting the noise reduction, which determine the noise reduction area in the elevation and azimuth directions, respectively. The active trailing-flap rotor can generate the in-plane excitation force, but because of large lift-drag ratio the anti-noise is mainly from the vertical lift, which is caused by flap deflection similar to a variable camber airfoil. For the harmonic control rotor and active twist rotor, the excitation force is also attributed to the vertical blade lift. The vertical force can reduce the noise near the rotor plane, it will also cause the noise increase in most other areas. Finally, two new active rotors were proposed to generate the in-plane chordwise and spanwise excitation force. With the modified actuation law, the noise in most areas around the rotor was reduced, which improved the acoustic characteristics of rotor significantly.

Recently, electric power generation from direct-drive counter-rotating wind turbine has gained considerable attention. Consequently, employing an efficient and a high power density electric generator is important. In this regard, flux switching permanent magnet generator with double-sided structure is one of the potential candidates for this purpose due to its features like inherently magnetic gearing effect, high power density, high reliability, and robust rotor structure. In this regard, rotor structure of double-sided flux switching permanent magnet generator is one of the most important factor which can highly affect the machines performance due to the fact that, rotor geometry is the main part in the flux switching procedure of double-sided flux switching permanent magnet generator. Consequently, this paper presents a comprehensive analysis of counter-rotating double-sided flux switching permanent magnet generator with segmented rotor and laminated rotor in which a bridge is located between adjacent rotor poles. The finite element simulations and experimental tests results showed that the proposed generator with laminated rotor gained from the higher power density in comparison with the segmented one whereas in the case of segmented rotor, the torque ripple is lower.

In this study, the lock-in phenomenon of Tip Clearance Flow (TCF) instabilities and their relationship to blade vibration are investigated numerically on an axial transonic rotor with a large tip clearance. The capabilities of simulating instability flow and lock-in phenomenon are verified on a transonic rotor and a NACA0012 airfoil by comparing with the test data, respectively. The lock-in phenomenon is first numerically confirmed that may occur to TCF instabilities when its frequency is close to the blade vibration frequency. The lock-in region becomes wider with the vibration amplitude increasing, and it is also affected by modal shapes. For the rotor at the simulation conditions in this study, the bending mode results in a wider lock-in region than the torsional mode. In the lock-in region, the phase difference between the Tip Clearance Vortex (TCV) and the blade vibration changes with the flow condition and the frequency ratio of the blade vibration and the TCV instabilities. The frequency of the TCV instabilities reduces with the mass flow decreasing. Therefore, reducing mass flow and increasing frequency ratio have similar effects on the TCV phase, which causes a significant variation on the unsteady pressure amplitude in the blade tip area. Thus, the aerodynamic damping changes significantly with the TCV phase. The aerodynamic damping displays a nonlinear relationship with the vibration amplitude, and it changes from negative to positive with the vibration amplitude increasing at the same frequency ratio. The negative damping is mainly provided by the tip area of the blade. For unlocked conditions, the period of the TCF instabilities fluctuates over time, and it cannot be directly separated by their frequency features. Inter Blade Phase Angle (IBPA) also has an important influence on the feature of the TCV instabilities. The occurrence of frequency lock-in also requires “appropriate” IBPA. For the examined working conditions, the frequency lock-in occurs under 0 ND (Nodal Diameter), but not under 8 ND. However, no matter 0 ND or 8 ND, the phase of TCV always locks onto the IBPA at the examined conditions.

The Halbach array structure rotor of the aero motor can satisfy the requirements of high power density and high air-gap flux for aeronautical motors. The size parameters of the rotor are determined by the power rating of the motor based on an analytic method. Producing a Halbach array structure is difficult. Comparison and analysis of the structure of the aero motor show that the overall structure of the rotor adopts a three-axial-section classic Halbach-array hollow structure, and the rotor magnetic steel adopts a discrete structure of 4 blocks per pole and a single 45 degrees magnetisation mode, which reduces the processing difficulty of the rotor magnetic steel. The finite element method was used to analyse the magnetic flux density distribution of the aeronautical motor under various working conditions. The results show that the motor can produce uniform air-gap flux density at various working conditions and present good sinusoidal periodicity. Furthermore, the axial segment did not produce obvious magnetic flux leakage. Finally, considering the eddy current loss of the stator under the rated power-generation condition with high-frequency magnetic field, we conducted coupling analysis of electromagnetic and heat flows to verify that the thermal characteristics of the rotor magnetic steel material could meet the requirements for the aero motor.

This paper aims to gain insight into the nonlinear modal characteristics and the possible influence of the modes on the responses for the practical dual-rotor system with rub-impact in aero-engine. The finite solid element method combined with a constraint stiffness model produced by rub-impact is introduced to build the governing equation of the complicated nonlinear dual-rotor system. In order to deal with the efficiency and numerical divergence in the process of solving the nonlinear modes of this large-scale nonlinear system, an analysis strategy is proposed by integrating a two-layer reduction technique into the harmonic balance method. The effectiveness of the analysis strategy is validated by applying to a simple rotor system, which can easily obtain the theoretical result. Based on the modeling method and analysis strategy, the modal characteristics of an aero-engine dual-rotor system with rub-impact are revealed. The results show that the modal frequency of the dual-rotor system increases when rub-impact occurs and has the feature of interval, which allows us to obtain the critical speeds of the rubbing system by traditional Campbell diagram. The rotation direction is an important factor since it can not only affect the gyroscopic effect but also change the friction effect of the rub-impact. It is found that the modal frequencies of the counter-rotation dual-rotor are less than those of co-rotation condition. More importantly, the forward modes of the counter-rotation dual-rotor may be instable when rub-impact occurs at a certain rotor, while the corresponding modes under the co-rotation condition are always stable. Furthermore, by analyzing the rubbing response of the dual-rotor, it is found that the modal characteristics have an important influence on rotor’s response. The instable forward modes existing in the counter-rotation dual-rotor may lead to the divergence of the response when passing the corresponding critical speed.

One of the major challenges of diagnosing rotor symmetry faults in induction machines is severe modulation of fault and supply frequency components. In particular, existing techniques are not able to identify fault components in the case of low slips. In this paper, this problem is tackled by proposing a novel approach. First, a new use of singular spectrum analysis (SSA), as a powerful spectrum analyser, is introduced for fault detection. Our idea is to treat the stator current signature of the wound rotor induction machine as a time series. In this approach, the current signature is decomposed into several eigenvalue spectra (rather than frequency spectra) to find a subspace where the fault component is recognisable. Subsequently, the fault component is detected using some data-driven filters constructed with the knowledge about characteristics of supply and fault components. Then, an inexpensive peak localisation procedure is applied to the power spectrum of the fault component to identify the exact frequency of the fault. The fault detection and localisation methods are then combined in a recursive regime to further improve the diagnosis’ performance particularly at high rotor speeds and small rotor faults. The proposed approach is data-driven and is directly applied to the raw signal with no suppression or filtration of the frequency harmonics with a low computational complexity. The numerical results obtained with real data at several rotation speeds and fault severities, unveil the effectiveness and real-time feature of the proposed approach.

In this paper, the authors presented various insights into theoretical and experimental analysis carried out in past, to understand the vibration characteristics of a misaligned rotor-bearing system. The literature presented by various researchers was reviewed methodically. Firstly, the literature review based on theoretical vibration analysis of misaligned rotor system with emphasis on finite element method has been presented. Secondly, various vibration-based analysis methods and the description of experimental measurement techniques have been discussed in detail. Apart from the above, distinct tools used for the detection of fault analysis of the rotor system is also reviewed systematically, which may be useful for preventive maintenance of the rotating machinery used in several industries.

Due to the rotor unbalance of the magnetically levitated turbo-molecular pump (TMP), this paper presents a novel high-precision field balancing method based on regular control mode without trial weight. Firstly, the static/dynamic unbalance vector expressions of the magnetically levitated rotor are analyzed and derived in polar coordinates frame. Secondly, according to the synchronous currents and displacement responses of the rotor at a fixed speed, the correction weight can be solved by the double-plane correction method based on equivalence principle of the magnetic forces. Then, in order to reduce the deviation between theoretical and actual value of the magnetic bearing parameters, this paper proposes a second correction method by correcting the conversion coefficient matrix from online identification procedures. The proposed method, which can eliminate the errors introduced by the oversimplification of dynamic model in regular control, is especially suitable for the magnetically levitated rotor system with strong gyroscopic effects and asymmetric structure. Finally, the experimental results on a magnetically levitated TMP prototype validate the effectiveness of the proposed method. Compared with the original unbalance of rotor, the synchronous current amplitude declined by 99.0%, and the synchronous displacement amplitude also declined by 96.1% with the proposed method. A high-precision field balancing has been achieved.

Fault detection of a rotating rectifier for a wound-rotor synchronous starter/generator (WRSSG) without a rotor position sensor in the stationary state is necessary for a successful engine start. Based on high-frequency (HF) voltage injection, a novel fault detection method of the rotating rectifier for the WRSSG in the stationary state is proposed. The rotating HF voltage is imposed on the stator windings of the main machine, and the HF feature current signal extracted on the stator windings of the main exciter is used for fault detection. In this article, the HF current signal in the main exciter with the rotating rectifier under different working conditions is analyzed first. To obtain the HF response current on the stator windings of the main exciter, the HF model of the WRSSG is analyzed. Through the Fourier series, the HF feature current signal together with fault detection is achieved. Compared with the existing fault detection methods, the proposed method shows no dependency on the rotor position information. Experimental results verify the feasibility and effectiveness of this method.

The significant nutation will degrade the stability of high-speed magnetically levitated turbo-rotor system. This article presents a damping optimization method to suppress the nutation mode. The proposed method consists of two parts: nutation compensation and damping optimization. The nutation compensation with the cross-channel displacement signal is designed in detail to increase the damping force of nutation mode in the first part. The root locus of the closed-loop rotor system is used to analyze the effect of damping compensation. The control parameters are iterated to configure the pole of the nutation mode with the goal of making the rotor system have the optimal damping ratio at the nutation mode. Finally, simulation results show that the nutation damping ratio of the rotor system with the proposed method is greater than 0.658, and the experiment results on a magnetically levitated turbomolecular pump prototype validate that the proposed damping optimization method can effectively suppress the nutation mode and its power spectrum level is below $-$ 60 dB over the entire speed range.