Yukio Honda

Motor design considerations and test results of an interior permanent magnet synchronous motor for electric vehicles

This paper describes the high performance motor design of an interior permanent magnet synchronous motor (IPM motor) for electric vehicles. The authors examined the differences in motor characteristics based on how the magnets were embedded. For this comparison, they set conditions so that the volume of magnets remained constant, and they used both computer simulation and experiments with a prototype motor. As a result, they were able to develop a double layer IPM synchronous motor, which has two layers of magnets embedded lengthwise in the radial direction in the rotor. The q-axis flux path can be expanded by using an IPM rotor with magnets divided into two layers with the separation lengthwise at the rotor radius. An evaluation of prototype motors confirmed that a double-layer IPM motor produces a 10 percent or more increase in the torque generated compared to a single-layer IPM motor using the same current. Also, the high efficiency operating region (min. 90%) was a minimum of 10% wider than the single layer IPM motor. However, reluctance torque of a double layer IPM motor with concentrated winding cannot be designed as high as that of a similar motor with distributed winding. This is because the inductance difference between the d and q-axes cannot be sufficiently increased in this former. Here, it was learned that a concentrated winding is inferior to a distributed winding both in terms of generated torque and the constant power region size.

Highly efficient brushless motor design for an air-conditioner of the next generation 42 V vehicle

In the past few years, worldwide awareness of environmental problems has grown dramatically. The idling stop and 42 V battery system has attracted large attention for next generation vehicle. In order to adapt to idling stop, air-conditioning compressors are required to be changed to electric-motor driven from gasoline engine driven. This paper discusses the optimum design of a high speed and high efficiency brushless motor for a compressor of the 42 V operated vehicle. The compressor motors require high efficiency at high speeds. Therefore, turning attention to an IPMSM which guarantees structural strength, improved techniques such as an optimal method of designing a magnet layout that minimizes iron loss, and concentrated winding technology using rectangular wire that minimizes copper loss have been developed. As a result, a method of designing IPMSM that offers high efficiency of 94% at 15,000 min/sup -1/ and is suitable for the 42 V vehicle has been established.

The performance comparison of SPMSM, IPMSM and SynRM in use as air-conditioning compressor

This paper reports results on the performance comparison of highly-efficient reluctance motors, in which performance was compared in use as an air-conditioning compressor. The compared motors were a SynRM (synchronous reluctance motor), SPMSM (surface permanent magnet synchronous motor), IPMSM (interior permanent magnet synchronous motor) and a conventional IM (induction motor). It was found that the IPMSM was superior in terms of efficiency, and SynRM was the lowest cost. Its efficiency was also higher than the typical IM.

High performance synchronous reluctance motor with multi-flux barrier for the appliance industry

Advances in power electronics and machining mean that reluctance motors have now become the focus of new studies. Research and development is pursuing two different tracks. One targets what is referred to as a switched reductance motor which uses a pulse signal to drive a salient-pole rotor. The other targets a synchronous reluctance motor (SynRM) which uses a sinusoidal wave to drive a rotor which is constructed with several flux barriers. The stator winding of the latter is of the same specifications as that used in an induction motor or a brushless motor which utilizes permanent magnets. It also carries the merit of effectively utilizing a conventional inverter due to the sinusoidal wave drive. For what regards rotor construction of this type of motor, Lipo, Miller, Boldea, Yagati and others have enthusiastically researched an axially laminated construction which features layers of electromagnetic iron plate in the rotors axial direction for the purpose of improving saliency ratio. However, many of these have not clarified the relationship between flux barrier construction and motor efficiency. This paper reports on simulations and experiments using a prototype, in which flux barrier construction and design optimization were investigated in consideration of machining distortion and other factors, as part of studies into making a highly efficient multi-flux barrier SynRM. It is also reported that the prototype model proved to be 6% more efficient than an induction motor with the same inverter drive.

A novel visible light communication system for enhanced control of autonomous delivery robots in a hospital

Control systems for Autonomous mobile delivery robots have been described before. However, the control they provide is limited, leaving potential for serious errors. The current mobile robot systems concentrate on position accuracy and operational function but leave open management of safety hazards such as entering the dangerous and not intended areas as stairway. In order to increase the safety of the robot, it is as important to work with sensors installed in the external environment as the sensors installed on the robot. For this purpose, visible light communication (VLC) is a promising device to be used with the robot system. VLC creates an in-house GPS system by installing special LED lights that can replace standard lighting in key locations in the hospital. We have developed an in-hospital transportation robot, called HOSPI in which the control system has been enhanced by combining the navigational sensors of the robot and a VLC using installed lighting in the building. By using VLC, robots can obtain more information about the environment. As the first step for the practical application of VLC to robot system, we use VLC to overcome problems in conventional localization approaches, and to provide an additional line of defense in the case of catastrophic failures. This paper also describes experimental and actual operational results in detail of robots equipped, in an actual hospital, with the described process.

Optimum design of highly efficient magnet assisted reluctance motor

Permanent magnet motors have attracted a lot of attention for their potential energy saving. However, they are only used for certain applications because of expensive magnets. This paper discusses the optimum design of the low cost and highly efficient magnet assisted reluctance motors with a minimum amount of magnets. The motor considered in this study is a multi-flux barrier reluctance motor with assisted permanent magnets. The configuration by which permanent magnets are embedded to the innermost side of the rotor to obtain maximum output with the minimum amount of magnets was evaluated through simulation and experiments with a prototype motor. As a result, we established a method for designing motors capable of realizing the same efficiency as permanent magnet motors with only one-fourth the amount of magnets. In our experiments, we achieved a high efficiency of 94.4% with a 750 W motor.

Novel noise improvement technique for a PMSM with concentrated winding

The vibration of concentrated winding motors tends to be higher than distributed winding motors. This phenomenon is caused by the projection of radial stress. Hence, an effort has been made to reduce the vibration of the concentrated winding motors considering its radial stress. In this paper, it is shown that for the concentrated winding motors the radial stress becomes partly large which leads to deformation of the stator core. Therefore, the air gap length where radial force is large has been enlarged. It has been found that the radial stress in the air gap becomes smooth by enlarging the air gap partly and consequently, the vibration of the motors can also be reduced.

Rotor design and control method of synchronous reluctance motor with multiflux barrier

To design the rotor of a synchronous reluctance motor with multiple flux barriers, the studies of the number of barriers, bridge width and other elements are important. It is found that a 6-layer configuration is best in terms of efficiency. In performance tests, a prototype efficiency is 6[%] higher than a conventional inverter-driven induction motor. The rotor also rotate at speeds in excess of 10,000 [r/min] because magnetic and nonmagnetic parts were built into a single body made of alloy.

Recognition of 3D dynamic environments for mobile robot by selective memory intake and release of data from 2D sensors

We have developed an autonomous mobile robot to perform in-hospital transportation. When an autonomous mobile robot moves in a hospital, it needs to detect and avoid such obstacles as beds, wheelchairs, patients, visitors, and hospital staff. These obstacles move and often have overhanging parts that cannot be detected by only 2D sensor which measures horizontal surface. The robot, therefore, must recognize obstacles in a three-dimensional space on a real-time basis. Appropriate and practical 3D sensors for actual use are not available, and 3D recognitions using 2D sensors such as 3D-SLAM are not fast enough to collide with moving object. This paper proposes a method that recognizes the three-dimensional environment around a mobile robot using a laser range finder at its front for measuring the horizontal surface and three additional range finders at the left and right sides and the front top position to look down and detect three-dimensional obstacles. The information is integrated by data fusion into the memory. The features of this method include memorization of the obstacle positions with overhangs and removing the memorized position of the moving obstacles from the memory by selective memory intake and release of data from 2D sensors. This paper also describes experimental and actual operational results in detail about the robot equipped with the developed process in real hospital.

High performance design of an interior permanent magnet synchronous reluctance motor for electric vehicles

We have examined the optimum rotor design of an interior permanent magnet motor (IPM motor) for electric vehicles. By using double-layer magnets embedded into the rotor with the layers separated in the direction of the rotor radius, we have been able to construct a rotor that takes greatest advantage of reluctance torque, resulting in a 10 percent torque increase over the conventional IPM motor, which uses only a single-layer of magnets in the rotor.