First, this article describes the features of motors used in drones. The discussion by the members of the investigating R&D committee on small motors and their control technology to satisfy service robots requirements has shown that the requirements for drone motors include "the durability and failure resistance" to avoid crashes, "the long-time drive", and "the weight reduction". Therefore, next, this article explains the methods for failure resistance, long-time drive, and weight reduction for the drone motors.
Multirotor unmanned aerial vehicles have been applied to inspections such as wall crack detection and topographical survey. In a multirotor flight, rotors cause aerodynamic interference and change rotor thrust, and additional thrust control is required to compensate for flow interference. Thus, multirotor design considering aerodynamic effect is essential to improve multirotor performance and realize safe flight for future planned applications. In the article, first, we briefly introduce the development history of multirotor aerial vehicles. Second, we show wind tunnel experiment results to understand the effect of rotor-to-rotor flow interference on multirotor control in-flight conditions.
This paper presents mechanisms to extend the flight performance of multicopter-type drones and their flight control. A single-axis tilting mechanism or a dual-axis tilting mechanism that enables the change of the thrust direction on each rotor is introduced, and the dynamic model of the drones, including the tilting mechanisms, is discussed. The multicopter-type drones can achieve independent position and attitude control, and flight in arbitrary attitudes by tilting mechanisms. This paper describes flight applications of the drone with single-axis tilting mechanisms and the flight demonstration of the drone with dual-axis tilting mechanisms.
We propose the bridge inspection system using a small size two-wheeled multi-copter. The multi-coper has two-wheels of the size 25 cm and can go into narrow space on bridge bearings. We also develop both a wheel driving system to move accurately at low speed on the ground in the narrow space and a camera gimbal device capable of controlling remotely to take close-up images of the bearings. Some field examinations in a water part of the river show that the system is useful and practical for a bridge inspection. Finally, we present an autopilot control system for inspection of bearing parts in bridges by using two-wheeled multi-copters.
In order to improve the method of soundness inspection of railway bridges, remote inspection techniques using drone robots have been developed by Railway Technical Research Institute. Drone robots have been developed to perform inspections of concrete structures while running beneath the underside of bridge girder using self-propelled crawlers. The systems using a drone robot can conduct close-up shooting, reinforcement explorations and hammering test of the under-side and side surfaces of concrete structures. In addition to those, it can also analyze the measured image data and sound data with AI diagnostic techniques.
In Japan, in order to ensure the safety and security of the use of Unmanned Aircraft, from June 20, 2022, Unmanned Aircrafts such as drones must be equipped with a remote ID function, which is the license plate of Unmanned Aircraft. Therefore, it was necessary to make the remote ID function available in the market promptly. We have developed, verified and evaluated an external remote ID device product, confirmed that it complies with the standard, and launched the first model-registered product on the market. As a result, the remote ID function has become available on many Unmanned Aircraft on the market as planned.
We aim to develop an X–Y linear synchronous motor where 360° rotational motion around the Z-axis is possible. We considered “rotational force characteristics around the Z-axis that use alternating magnetic fields orthogonal to the X–Y linear synchronous motor.” The stator of the linear synchronous motor has two pairs of three-phase field windings positioned orthogonally to each other. A two-pole permanent magnet and an iron core comprise the rotor (mobile element). We demonstrated the rotating magnetic field around the Z-axis generated by an alternating magnetic field intersecting on a plane. Further, we used magnetic field analysis to evaluate the rotational force characteristics working on the rotor. We also considered the impact of the position of the rotor magnetic pole on the output characteristics. We experimented with a prototype to evaluate the validity of the analytical result. The experimental result showed that a rotational drive force could be generated 360° around the Z-axis.
This paper proposes a novel hybrid-type permanent magnet motor (HPMM) that simultaneously applies ferrite-PM (Fe-PM) to reduce the amount of NdFeB permanent magnet (Nd-PM) used in electric vehicle traction motors. Conventional HPMM can be divided into parallel type (P-HPMM) and series type (S-HPMM). P-HPMM is advantageous for PM torque improvement because it can obtain high PM flux linkage, but there is a problem in that Fe-PM is demagnetized due to the strong magnetic flux of Nd-PM. S-HPMM is the way to fundamentally solve these problems. However, it is difficult to improve PM flux linkage compared to P-HPMM. Therefore, in this paper, a novel rotor topology that can effectively generate reluctance torque by improving S-HPMM is proposed. The target motor is the 2018 NISSAN LEAFTM traction motor. The proposed motor has the same torque density as the target motor, while reducing Nd-PM usage by 38%.
In order to maintain the motor's body size and increase its power, Interior Winding Synchronous Motor is being considered. A magnetic composite material is applied to the yoke of Interior Winding Synchronous Motor. Until now, magnetic composite materials have been applied to transformers of DC-DC converters driven in the MHz band. However, magnetic composite materials in the kHz band and high flux density range used in Interior Winding Synchronous Motor have not been examined. Therefore, magnetic composite materials suitable for IWSM was examined by changing materials of magnetic powder. As a result, the relative magnetic permeability improved up to twice at maximum. Furthermore, iron loss was reduced by 94.4% as compared with the conventional magnetic composite material. When applied to Interior Winding Synchronous Motor, the efficiency was improved by 0.3% and the loss was reduced by 18.7%. Magnetic composite materials for IWSM should be selected from magnetic powders with large particle size, low coercive force, and high saturation flux density.
In recent years, as progressing a declining birthrate and a growing proportion of elderly people rapidly, the burden on caregivers is increasing. To reduce the physical burden of caregivers, various power-assisted systems have been developed for housing care. We have also developed an electrical power-assisted lift for transferring. However, there are some issues to overcome to improve the operability of the system.
The purpose of this paper is to improve the operability of the power-assisted lift for transference assistance, where the smoothness control is applied to reduce impact force at the mode change. Friction compensation based on a rolling friction model is also introduced. The effectiveness of the proposed power assist system has been verified by experiments using a prototype of a transferring lift.