This paper presents the development of a 48V integrated starter generator (ISG) for mild hybrid vehicles. The motor needs to satisfy power and torque performances requirements under the 48V system voltage as well as the passenger vehicle's specific requirements, such as acoustic noise and layout space. Several processes have been explored to obtain a 48V ISG such as the pole number selection process, the electromagnetic design approach for reducing acoustic noise, and a novel position sensor topology. By using the developed technologies, a 48V ISG motor is designed, built, and tested. Furthermore, the developed motor is demonstrated to achieve 180Nm, 15kW exceeding the 95% motor efficiency with acoustic noise reduction design and thin axial motor length.

Machine learning techniques, including Gaussian processes (GPs), are expected to play a significant role in meeting speed, accuracy, and functionality requirements in future data-intensive mechatronic systems. This paper aims to reveal the potential of GPs for motion control applications. Successful applications of GPs for feedforward and learning control, including the identification and learning for noncausal feedforward, position-dependent snap feedforward, nonlinear feedforward, and GP-based spatial repetitive control, are outlined. Experimental results on various systems, including a desktop printer, wirebonder, and substrate carrier, confirmed that data-based learning using GPs can significantly improve the accuracy of mechatronic systems.

The zero moment point (ZMP) is a measure for realizing dynamic motion in legged robots. An important concern in ZMP-based motion control is the measurement of the ZMP itself. General humanoid robots use sensors attached to their feet to measure the reaction forces. However, this method is not applicable for wheel-legged mobile robots because it is difficult to attach force sensors inside the wheels. Therefore, this study proposes a method to determine the ZMP based on the relationship between the load and resonant frequency of the tires. The resonant frequency of the tires depends on the tire pressure. First, the relationship between the load and resonant frequency is confirmed by a frequency analysis and experiments on the wheel joints. Second, a method used to estimate the ZMP based on the relationship between the load and resonant frequency is described. Third, an online estimation technique for the ZMP is described. Finally, factors other than the vertical force that affect the frequency characteristics of the wheel are discussed. The average of the root-mean-square errors from the sensor value in the online-ZMP estimation results is 0.0361 m, which is sufficiently smaller than the typical stability margin of the support polygon of the robot.

In this paper, a model predictive control (MPC) based time-varying delay compensation system is proposed. The proposed method uses a prediction model that estimates the future state of a remote plant to compensate for the delay in remote control. Because the amount of the delay is not known before transmission, the local prediction model needs to assume the maximum delay when the delay varies. However, most packets arrive within the maximum delay time. Therefore, this study proposes the utilization of early-arrival packet to generate a reference trajectory for model predictive control at the remote side. To achieve this, we propose a method to deal with the variable horizon for model predictive control. In addition, the proposed method predicts the state of the remote plant considering the controller on the remote side; therefore, it is possible to predict the state with a higher accuracy than the conventional method. The performance of this method in comparison with the conventional method is evaluated by numerical simulations and experiments.

A torque vectoring differential (TVD) enhances the cornering performance by generating a torque difference between the left and right wheels. For electrified vehicles, a TVD with a two-motor-torque difference amplification mechanism (TDA-TVD) is proposed, and it generates a greater torque difference than an Individual-wheel-drive (IWD) system under the same power output from the traction motors. However, owing to the complex gear reduction system including planetary gears and driveshafts, TDA-TVD has problems with the vibration of both the driveshaft torque and the yaw rate while cornering. To deal with these problems, a detailed dynamic model of TDA-TVD is first derived in this study. Secondly, a decoupling compensator is designed to achieve independent drive for the left and right wheels so that any motor drive algorithm designed for IWD systems can be applied. Thirdly, a vibration suppression controller is designed. Then, simulations and experimental evaluations using a real vehicle with the TDA-TVD are performed. The experimental results show the effectiveness of the vibration suppression of driveshafts and yaw rate.

This paper presents an observer-based sensorless drive system for the position control of the permanent magnet linear synchronous motor (PMLSM). To achieve the purpose of position control and maintain the stability of the global system, the drive system is designed using the sum-of-squares (SOS) method. With the help of the SOSTOOLS toolbox, the control algorithm can be established without the need for complicated mathematical derivation. First, to apply the SOS technique, the motor model is treated as a fifth-order polynomial dynamics model. Based on this model, the state estimation of the full order Luenberger observer is studied. The feedback gain of the observer is obtained in polynomial form rather than a constant, thus making the observer nonlinear and time-varying. Compared with existing studies, the SOS observer construction requires no additional assumptions and no adaptive mechanisms to cope with changes in velocity. By combining the SOS method with the Lyapunov analysis, the observer-based control system is systematically developed to ensure the stability of the global system. The experimental results verify the proposed control scheme.

There is an increase in the popularity of small spacecraft because they are expected to introduce large opportunities in the space industry. However, there are two issues with increased use of small spacecraft: enhancement of cost-effectiveness and improvement in the mission failure rate. This study defines the battery state as the most important parameter in spacecraft operations because it directly relates to the health status of the spacecraft. We propose solving problems by introducing high-accuracy in situ state estimations for real-time operation mode selection and on-ground future state estimations of the battery in spacecraft operations planning by utilizing a suitable numerical model. The high-accuracy in situ state estimations allow us to minimize operational margins for battery protection, improve the efficiency of each spacecraft, and achieve safe spacecraft operations. The combination of a model-based system development approach and numerical optimization methods helps establish an efficient autonomous mission operations planner system to maximize mission duration. This enables us to reduce the human resource costs for spacecraft operations. This study addresses two topics: battery and spacecraft modeling, and establishing a mission operations planner system. The details of the system and battery modeling considering temperature dependence are explained using parameter identification results from the experiments. The design policy of the mission operations planner, which utilizes the battery status as the threshold of the operations and constraints, is explained via numerical optimization details. Numerical and experimental case studies are performed to evaluate the proposed method and show its effectiveness.

This paper proposes a new convergence acceleration method specialized for the magnetic field analyses of synchronous machines based on the time-periodic explicit-error-correction (TP-EEC) method. The proposed method constructs an auxiliary equation for error correction in the dq rotational reference frame to convert a fundamental harmonic component into a DC component. This conversion enables us to perform error correction using the TP-EEC method at intervals of an arbitrary number of time steps. The effective time intervals for error correction were investigated using practical interior permanent magnet synchronous motor (IPMSM) models. Moreover, DC superimposed problems, such as PMSMs with an open-end winding, were examined. Numerical results verified the effectiveness of the proposed method, and smaller time intervals could significantly improve the convergence characteristics of the transient analysis when high-order harmonic components were small. Furthermore, by adopting a 1/6 period as the time interval for the proposed method, a steady-state solution could be obtained precisely, even in a time-periodic problem that included many high-order harmonic components.

Currently, electrification for vehicles such as battery electric vehicles (BEVs), plug in-hybrid electric vehicles (PHEVs), fuel cell electric vehicles (FCEVs), and hybrid electric vehicles (HEVs) has received considerable attention, owing to the urgent need to reduce CO2 emissions created from transportation and the energy dependency on crude oil. Honda has set a target whereby two-thirds of total global sales should come from EVs by 2030. A traction motor is an essential component of electrified vehicles. Generally, interior permanent magnet synchronous motors (IPMSMs) are used as traction motors owing to their high torque and power density, high efficiency and ease of use. The design of rotors, which consist of magnets and electrical steel sheets, is important for IPMSMs because their average torque, efficiency, quietness, as well as cost depend on it. We have developed a novel rotor, which allows for a degree of freedom in the shape of the magnets. In the proposed rotor, first, the shape and position of the magnets are determined parametrically under manufacturing constraints. Then, the shape of the electrical steel sheet is determined by the ideal flux-line using maximized Lq-Ld. This involves combining q-axis flux and flux shape optimization for a practical design of the rotor. We also reduced torque ripple by considering the magnet position and dimple design. Rotors that are used in electrified vehicles are rotated at a maximum speed without gearing; therefore, the rotor must be designed by taking into consideration not only the magnetic forces but also the centrifugal ones. Therefore, we studied a mechanical simulation by optimizing magnetic performance while limiting maximum stress and displacement. We also developed a new production process for a C-shaped sintered and hot-deformed magnet.

This paper proposes a control method to suppress vibrations in a double-star winding permanent-magnet synchronous motor (PMSM). The double-star winding PMSM, which has two three-phase windings, can be used to improve reliability and torque ripple cancelation. A 6th order torque ripple is canceled by providing a phase angle of 30° to the mechanical angle between the two windings. A temporal 12th order radial force vibration causes a breathing mode vibration, which uniformly deforms the stator core in a double-star winding PMSM. The breathing mode vibration is suppressed by superimposing the 6th order current. In this study, the temporal 12th order and spatial 0th order radial force, which causes the breathing mode vibration, was reduced by 86.3% by superimposing the 6th harmonic current via simulations. The radial acceleration was experimentally measured on the surface of a motor. The temporal 12th order radial acceleration on the motor surface exhibited a reduction of 66.5%.

The paper proposes a novel estimation method for a mechanical two-mass system. The concept of a multi-layer estimator is proposed to improve the estimation quality of the system states, especially for unknown initial conditions of the drive. The proposed estimator has two layers. The first layer consists of two individual Kalman filters, whereas the second layer is based on aggregation mechanism to calculate the final states of the plant. The proposed layers comprise a multi-layer Kalman filter (MLK). The investigated drive has a changeable value of the load-side inertia. To ensure the desired responses of the drive, an adaptive-control structure based on a proportional-integral (PI) controller with an additional feedback loop is implemented. The simulation and experimental results illustrating the effectiveness of the proposed MLK in an open- and closed-loop configuration are presented. The MLK guarantees a considerably more accurate estimation quality than a classical single estimator.

This paper focuses on the voltage modulation method to reduce the switching frequency and proposes a voltage-integral-based reference tracking modulation (VIRTM) method. The proposed method calculates an evaluation function by considering the factors of the switching frequency. Thereafter, the proposed method outputs the voltage vector based on the evaluation function and reduces the switching frequency. The switching frequency of the conventional discontinuous pulse width modulation (DPWM) and that of the proposed VIRTM are evaluated by using simulations and experiments based on feed-forward and feedback control systems. From the results, the usefulness and effectiveness of the proposed method are confirmed.

To realize automated drive of a vehicle, more reliability to the motor drive system is required. The three phase dual winding permanent magnet motor drive using two inverters with corresponding voltage supplies is one of the potential candidates for the reliable motor drive system. With the respective voltage supply and winding connected to the inverter, the two motor drive systems are electrically independent. Thus, even if when a failure occurs in one of the systems, the other system can continue the motor drive. However, there is an issue: a voltage drop in one of the voltage supplies reduces the sinusoidal wave region of the drive system as the rotor of the motor is common in the two windings and the back electromotive voltage in the two windings are the same. The motor drive method that enlarges the applied voltage without causing high harmonics under the voltage supply unbalance in the three phase dual winding permanent magnet motor is proposed in this paper.

This study presents a wideband small-signal model for common-mode inductors (CMIs) based on the stray capacitance estimation method. The proposed model can be used to calculate the small-signal characteristics of CMIs over a wide band of frequencies by substituting the stray capacitance values in the model are considering the frequency dependence of the complex permeability. The common-mode (CM) impedances of the fabricated manganese zinc-ferrite and nanocrystalline CMIs are measured using an impedance analyzer to validate the proposed model. Comparisons between the results of the measured and calculated CM impedances for the fabricated CMIs show that the proposed model enables the calculation of the CM impedances of CMIs over a wide frequency range from 1kHz to 100MHz.

This study discusses a multilevel cascaded linear amplifier that includes multiple H-bridges. The amplifier operates the MOSFETs in the switch mode and active state. The MOSFETs in the switch mode change the voltage level to reduce the ripple voltage, which is filtered using the MOSFETs in the active state. Thus, the conversion efficiency of the amplifier is improved. The MOSFETs in the switch mode also control the charging state of the capacitor on the DC-side of each H-bridge to maintain the DC capacitor voltages. The amplifier can perform real power conversion with one DC voltage source as it can regulate the DC capacitor voltage of each H-bridge. Moreover, DC capacitor voltages are regulated at various values to further reduce the ripple filtered by MOSFETs in the active state. Lastly, DC capacitor voltage control was verified through a experiment using three H-bridges, and the measured conversion efficiency of the amplifier with unequal DC capacitor voltages was 87.9%.

This paper presents a new configuration for the concentrated windings of permanent magnet motors in order to reduce the torque ripple. There are limited choices for the concentrated windings in conventional permanent magnet motors when selecting the numbers of poles and slots, which results in winding factors for harmonics that cannot be zero and the corresponding torque ripple remains. Unlike conventional concentrated-winding motor, whose teeth are all wound with one coil, the proposed concentrated-winding motor has some teeth with multiple coils wound around. The number of turns for each coil can be optimized to reduce its winding factors for harmonics to nearly zero so that the corresponding torque ripple could be significantly reduced. Prototypes of the conventional and proposed motors were constructed, and the experimental results are compared. Simulation and experimental results confirm the torque reduction effect of the proposed concentrated-winding motor.

In this paper, a new type of axial gap motor, named the “flux-modulating hybrid-field consequent pole motor (FHCM)”, is proposed. To enable flux modulation, the FHCM comprises rotor iron pieces sandwiched between two stators, the armature, and field poles. The field poles comprise permanent magnet poles, iron poles, and ring field windings. The magnetic flux of the field poles can be adjusted by varying the field current. The electromagnetic performance of the FHCM, including the air-gap magnetic flux density, back-electromotive force, torque, and torque ripple, was theoretically analyzed, and the results were verified through three-dimensional finite element analysis and experiments. By utilizing the inner space of the machine, the proposed FHCM could achieve a higher torque density than that of the conventional flux-modulating hybrid field motor.

In this study, we propose a novel pulse-width modulation (PWM) method to reduces common-mode noise. The proposed method includes a 120-degree dormant two-phase modulated three-phase inverter that the comparative carrier of one of the two modulation phases. This configuration is easy to implement because it uses a triangular-wave carrier comparison. In an experiment using a three-phase inverter, the common-mode current was reduced by approximately 60%, and in particular, the carrier frequency component was reduced to approximately 1/10 that of the conventional sine-wave comparison PWM.