This paper focuses on the rare-earth magnet reduction on interior permanent magnet (PM) motor based on the consequent pole rotor design. The motor design is targeted for the two-wheeler traction application with demanded constant power region consideration. The reference design is based on a 6 kW and 8-pole V-shape interior PM (IPM) motor with a constant power region between 3000 rpm and 9000 rpm. This paper develops a guidance for rotor magnet design to minimize the cogging torque while maintaining the torque output. However, due to the asymmetric rotor magnet, the equivalent direct axis flux permeance on consequent pole rotor should be higher than conventional IPM rotor. Because of the reverse saliency whereby the direct axis inductance is greater than the quadrature axis inductance, the better constant power field weakening control is expected. All the design process is verified based on finite element analysis (FEA), and the proof-of-principle prototype is fabricated and verified with the respect of back electromagnetic force (EMF).

This paper presents a fast and easy-to-implement acceleration-based parameter identification method for designing limited-angle servo motor drives. First, the servo motor model and position control scheme are introduced. Since controller gains are closely related to mechanical parameters, the impact of parameter mismatch on controller design is analyzed, showing that accurate parameters lead to better control performance. Conventional methods require designing the position or speed controller first and then estimating the actual parameters, which makes it hard to determine the gain of the controller before knowing the parameter. Therefore, this paper proposes an acceleration-based parameter identification method that directly identifies the parameters, which are then used to design the controller. To address cost and space limitations, an acceleration estimation technique is employed instead of installing an accelerometer. Finally, the accuracy of the parameter identification and the improved position control performance are experimentally validated.

This study aims to develop an easy-impement method for bearing health condition monitoring and predicting. Unlike traditional diagnostic methods with vibration sensor signals, this study utilizes motor current signature analysis (CSA) as a condition monitoring method to avoid cost and installation issues. Furthermore, the proposed anomaly detection approach can diagnose with just healthy samples, addressing the issue of insufficient fault samples in fault model training and classifying. This method introduced the complex autoregressive (CAR) model to identify the inherent pattern of health current. It can separate the nonsteady part in motor current caused by irregular vibration of damaged bearing. In addition, to enhance the robustness and accuracy of prognosis, this study uses the projected recursive least squares (P-RLS) for real-time prediction. It is shown to have better performance compared with traditional Bayesian-based methods by limiting the boundary of estimation. To verify the effectiveness of the proposed method, two different data sets are used for evaluation.

This paper examines the management of motor torque in electric bikes (E-bikes) while accounting for various external resistances. In the case of assist electric bikes, the electromagnetic torque generated by the permanent magnet motor can be manipulated to lessen the amount of pedaling torque required from cyclists. However, the overall torque required during riding is influenced by external resistances such as the cyclist's weight, air resistance, friction from the road, and the incline of the road. It's important to regulate the motor torque based on these riding conditions. The primary motion characteristics of an electric bike are analyzed in this paper to determine motor assistance torque. To address the dynamic effects of both pedaling torque and wheel acceleration, four torque control methods are proposed. By aligning the motor torque in the opposite phase to the pedaling torque, fluctuations in acceleration can be minimized. These torque control methods are evaluated through simulations of electric bikes across various resistances. Additionally, an experimental setup is constructed to validate the findings from these cycling simulations.

This paper designs a CubeSat reaction wheel for high-precision angular momentum control. For aerospace applications, the reaction wheel (RW) must provide sufficient momentum range under a rigorous weight limitation. To minimize the motor weight, a permanent magnet (PM) motor is developed with several design considerations. A novel four phase spherical motor structure and the vector control algorithm is proposed in this paper. The novel spherical motor design aims to replace three single axis 1 DOF RW motors by one 3 DOF spherical RW motor on the satellite attitude determination and control system (ADCS). According to the simulation result, the vector control can provide continuous torque through proposed current regulation, and the rated momentum of 60 mNm-sec and rated torque 5 mNm can be achieved to satisfied the demand of 6~30U satellite.

This paper improves a flux-based position sensorless drive for surface permanent magnet (PM) machines. On the basis, the rotor position is obtained from the spatial information in the magnet flux. The flux estimation is realized based on the integration of EMF voltage. In this paper, several implementation issues on the flux estimation are considered to improve the position sensorless drive. First, the machine phase voltage is measured for the flux estimation. By obtaining the actual inverter voltage outputs, the inverter deaditme effect is negligible on the flux and position estimation. Second, a modified integration is proposed to remove the flux estimation drift due to the voltage offset. Because the flux linkage is theoretically independent to the rotor speed, the signal-to-noise (SNR) ratio of postion estimation greatly increases at low speed. According to experimental results, the PM machine sensorless drive is improved at ~6% rated speed among the spaital signal SNR and drive dynamic response. More importantly, the overall current regulation bandwidth can be increased to 1kHz which is compatible to standard encoder-based drives.

This paper analyzes current sampling issues on the saliency-based position sensorless drive for permanent magnet (PM) machines using the pulse width modulation (PWM) voltage injection. On the basis, PWM voltage with the switching frequency is persistently injected into the machine. The rotor position is estimated through the spatial signal from the PWM voltage reflected current ripples. Because the rotor position is estimated every PWM cycle, multiple transient currents instead of single average current should be sampled per PWM. It leads to the issue on the selection of current sampling points with respect to different PWM patterns. In this paper, an asymmetric current sample is proposed for the position estimation using PWM voltage injection. By directly sampling phase currents during the injection period, the better signal-to-noise ratio (SNR) of position signal is concluded comparing to conventional symmetric current sample. In addition, shunt resistors are typically installed for the current sensing in inverters at low cost. A modified PWM control is also proposed for the position estimation compatible with low-side shunt current sensing. According to preliminary experimental results, the position estimation error is decreased using the proposed asymmetric current sample for the inverter with Hall-effect current sensors. More importantly, the inverter with low-side shunt sensors can be used for the saliency-based drive using the proposed PWM voltage pattern.

This paper proposes a high-precision permanent magnet (PM) motor primary used for the small satellite attitude control. A radial-flux type motor is designed to achieve the high demanded smooth torque production for satellite applications. On the basis, a slotless stator is used to improve flux harmonics by removing the stator steel component. Several design methods are proposed to increase the torque output while minimizing the ripples under the slotless topology. First, leakage fluxes caused by slotless stator are reduced by designing the radial-flux distribution with dual rotors. In this structure, two rotors can be used respectively for flux transmitter and flux receiver to concentrate the flux linkage across air gap. Second, rotor magnets are designed with Halbach array for the sinusoidal magnet flux distribution. Halbach array results in more torque production at low ripples. In this paper, finite element analysis (FEA) is used as the simulation tool for the motor design. A prototype is fabricated for the experimental evaluation.

Stator turn fault is commonly found in variable-frequency PM machine drives which using PWM techniques, and this paper analyzes electromagnetic response of permanent magnet (PM) synchronous machines exposed to this fault under two different stator windings configurations. In this paper, two stator windings are modeled and compared to determine which has better fault tolerant capability. When the machine is operated under turn fault, the windings with separated neutral points (NP's) has lower torque ripple caused by fault reflected flux harmonics. Besides, average torque output is less affected by the turn fault because of decreasing circulating currents in windings. Analytical models based on equivalent circuits are developed to predict the machine flux and torque property. All developed analytical models are verified by the finite element analysis (FEA).

This paper improves the position sensorless drive by directly measuring machine three-phase voltages. On the basis, the machine phase voltage is obtained based on the digital integration of phase pulse width modulation (PWM) voltage. The capture modulator in existing drive microcontrollers (MCU's) is used for the PWM voltage measurement. Comparing to existing phase voltage measurement, no separated A/D converter and communication hardware are required because PWM pulses are directly measured using MCUs. However since the capture based on TTL logics receives only digital signals, a preprocess circuit is developed to convert AC PWM line voltages to equivalent digital signals. According to experimental results, a 150MHz sampling rate for phase voltage measurement is achieved based on the proposed capture-based voltage measurement. Although the physical limitation of back electromotive force (EMF) estimation still results, the stability of proposed sensorless drive greatly improves at low speed. The proposed sensorless drive is suited for non-salient permanent magnet (PM) machine where the saliency-tracking position estimation is not possible.

This paper evaluates the fault detection performance of stator winding turn-to-turn short in the inverter-fed permanent magnet (PM) machines based on the high frequency (HF) voltage signal injection. On the basis, a HF pulsating-type AC voltage is injected on the direction of d-axis with respect to the rotor-referred synchronous frame. Once turn short occurs, a fault reflected current signal results due to the change of inductance on the faulty phase. Comparing to prior turn fault detection techniques using synchronized voltage or current signals for the torque production, this HF fault reflected current signal is immune to the speed variation. In addition, the torque load only affects the inductance saturation but not the change of phase and magnitude. It leads to a reduced impact on the load to the HF fault reflected current. It is possible to monitor a minor turn fault (2~3% turn short per phase) at different operating conditions. A salient PM machine with designed turn-to-turn short is built to verify the proposed fault diagnostic method.