Contact-force control of propeller-driven systems achieves aerial tasks that require contact motions with objects. Conventional contact-force controllers for propeller-driven systems utilize a contact-force feedback controller. Although the feedback gain should be high to achieve high target tracking performance, a high gain causes a large overshoot. This paper therefore proposes a novel contact-force controller which utilizes an airframe's velocity and an airframe's acceleration. An estimated acceleration and an estimated velocity of the airframe are fed back to the contact-force controller. A rotor angular velocity is utilized to estimate the acceleration. The validity of the proposed controller is verified through frequency analysis, simulation, and experiment.

This paper proposes a search algorithm using particle swarm optimization (PSO) with virtual pheromone for swarm robots. Swarm robots are attracting attention in disaster relief works to search for victims. The search algorithm involves a combination of global and local searching. The conventional search method consists of random walk as the global search and PSO as the local search. However, random walk is not efficient in complex environments. For efficient searching, PSO with virtual pheromone is used for the global search. The virtual pheromone drives the swarm robots to an unsearched area, dose not need map data, and has low calculation cost. In addition, it is not necessary in the proposed method to switch algorithms between global and local searching. The validity of the proposed method was confirmed from the simulation results.

There has been an increasing interest in biological effects owing to magnetic field exposure, because wireless power transfer systems for electric vehicles are expected to be widespread in the 85kHz band. Therefore, it is necessary to develop a magnetic field generator and evaluate the biological effects through experimental verification. In particular, the exposure area needs to be expanded for the development of magnetic field generators to offer sufficient number of exposure subjects. This paper presents the design procedure of a two-winding inductor for expanding the exposure area of a magnetic field generator. Two-winding inductors connected in series and in parallel are shown, and circuit configurations using these inductors are presented. It is revealed through impedance analysis that the difference in circuit parameters restricts the operable frequency band in a magnetic field generator with a two-winding inductor connected in parallel. The two-winding inductor connected in parallel can expand the exposure area to 321% of that of a conventional magnetic field generator. Moreover, the validity of impedance analysis is confirmed through the experimental verification rated at 100V.

The electric railway is an environment-friendly transportation system. An energy-saving operation with a low cost and high energy-saving efficiency is often considered to further decrease energy consumption. An Automatic Train Operation (ATO) system has the advantage of energy-saving because a train can be controlled by an on-board computer. However, many railway lines are still being operated by drivers and controlled via manual operation in addition, energy managements often become difficult for drivers and operators. Therefore, a study of energy-saving manual operation is desired. Energy verification of a manual operation is difficult because an adequate experiment has several constraints and trial periods are limited. Moreover, it requires a considerable amount of time and effort. In this study, an energy evaluation system is developed to calculate the energy consumed by a train when a driver manually operates it through adding an advanced calculation device to a conventional railway simulator. Consequently, the evaluation system contributes to carry out simple experiments with a short duration.

There are no ground fault protection devices in the AC circuit between the rectifier transformer and rectifier of DC electric railway substations. Therefore, the ground faults in the AC electric circuit are expected to be protected by overcurrent relays or DC ground fault overvoltage relays (64P) installed in the upper system. However, these protections are inadequate, so we examined methods to detect ground faults in the AC circuit between the rectifier transformer and rectifier. Thus, it was found that the ground fault current included a third harmonic current that was absent when there were no ground faults. Therefore, we created a prototype device to extract the third harmonic current, and confirmed that ground faults in the AC electric circuit between the rectifier transformer and rectifier could be detected by artificial ground fault tests.

Feature values of the current are rapidly becoming online indicators of faults in motors and load equipment. Diagnosis by analysis of the stator currents is called motor current signature analysis (MCSA). Compared with vibration analysis, this method can be applied without sensors, and additional long wiring. MCSA detects incidents peculiar to motors, such as bearing failures and rotor bar faults, before breakdown. In this study, we introduce relationships between the failures and current features. The MCSA sometimes has difficulty in identifying anomalies and there is the possibility of false-positive results; hence, we propose some solutions to these problems.

This study proposes a control method for a dual inverter to extend the output speed range of an interior permanent magnet synchronous motor with open-ended windings. The secondary inverter with a floating capacitor for the dual inverter supplies reactive power to the motor. In the proposed method, the reactive power required to drive the motor is calculated using an inductive voltage-limiting ellipse, and the d-axis current reference value and output voltage of the secondary inverter are determined. In the proposed control method, the primary inverter of the dual inverter supplies the effective power to the motor to expand the output speed range. The experimental results indicate that the output speed range is significantly improved and the constant torque region is expanded by approximately 41% compared with that in the conventional method.

Three-phase voltage-fed inverters are used for numerous applications, such as HEVs, EVs. These inverter systems require further improvements in terms of conversion efficiency, cost, size and reliability. On the other hand, dual inverter systems for open-winding motors are garnering attention. This paper, proposes application of pulse-voltage-injection two-phase pulse width modulation (PWM) scheme to dual inverter systems that drive open-winding motors. From the simulated results, it is confirmed that the voltages and currents in the open-winding motor are of higher quality than those in the conventional three-phase PWM scheme or the reference-shift two-phase PWM scheme.

Laborsaving is a major issue in production. In an automotive production line, a yard that is used as a temporary storage for vehicles before shipping. The vehicle-loading robot that operates autonomously has been proposed to automate the alignment of vehicles in the yard instead of human driving. In this study, the dynamic wireless power transfer system that includes the structure of the roadside for the vehicle-loaded robot is proposed. It is proven that the transmitter coil has enough durability for the load of the robot weight using simulation and actual measurement. It is also shown that the reinforcement bars of the road structure cause considerable eddy current loss even with stainless steel. This is similar to loss by coil resistance. This system achieves a 1.8kW dynamic wireless power transfer with an automated coil detection system and a frequency control system, under factory conditions.

This article introduces the policy and main research activities of Yamazaki Laboratory in Chiba Institute of Technology.