The authors propose an input/output coupling passive electromagnetic interference filter (PEF) for motor drive systems. The input/output coupling PEF uses magnetic coupling and integrates the common-mode inductors connected to the input and output sides of an inverter into a single magnetic component. Hence, this study investigates the attenuation characteristics of the input/output coupling PEF on conducted emission in motor drive systems. The measured results show that the input/output coupling PEF increases the attenuation of conducted emission compared to conventional PEFs over a broad range of frequencies.
DC power generation systems equipped with engine-powered generators and rectifiers are installed in diesel-electric vehicles and series hybrid vehicles. Generally, systems with permanent magnet synchronous machines and full-bridge rectifiers are expected to be energy-efficient and inexpensive. However, it is difficult to increase the output power density of the generator because the generated voltage is limited within the voltage induced by the permanent magnet. In this study, the process of improving the power density of the systems by adding capacitors to form a resonant circuit is described. Subsequently, the characteristics of the systems with two types of resonant circuit were investigated by performing numerical simulations.
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.
Techniques to reduce electromagnetic emission in high-power wireless power transfer (WPT) systems are required because the radiated emission of the WPT must comply with the regulation published by CISPR (International Special Committee on Radio Interference) and ICNIRP (International Commission on Non-ionizing Radiation Protection.) In this paper, a three-phase WPT system, which complies with CISPR 11, group 2, class A is developed. The three-phase WPT system has six solenoid coils on the primary side and six solenoid coils on the secondary side. The use of 12 coils allows radiation noise reduction as the radiation noise is emitted to the opposite direction of the pairs of coils. Moreover, the cross-coupling among six coils on the common side is canceled by adjusting the position of coils. The electromagnetic compatibility of the 22kW prototype is evaluated in a 10 m anechoic chamber according to the CISPR 11 guideline. The prototype fully complies with CISPR 11, class A, group 2 with respect to electromagnetic emission. Moreover, it also complies with ICNIRP guidelines in 2010 at a distance of 340 mm or more from the edge of the coils.
Automation of visual inspection is a critical aspect in industrial fields. Recently, research on anomaly detection using neural networks has been gaining increasing attention. In particular, approaches that use a pre-trained convolutional neural network have exhibited high performance. In this study, we focused on PatchCore, which is a high-performance model, and further improved it using two high-resolution images to accurately detect small anomalies. However, the extracted features (memory bank) consume a large amount of memory and storage; the memory bank is compressed by k-means clustering. Moreover, the inference time was reduced by an approximate nearest-neighbor search using an inverted index. Our method achieved an image-level AUROC of 0.994 on the MVTec anomaly detection dataset. In addition, a pixel-level AUROC of 0.984 was achieved, which is better than that of PatchCore. Furthermore, the compression time was reduced by more than 97% by clustering the memory bank using k-means while maintaining the performance.
This paper proposes a control method for torque ripple using an open-end winding IPMSM driven by an electrolytic capacitor-less dual inverter under grid disturbances. Under grid disturbances, a conventional motor speed range extension method causes torque ripple due to voltage saturation of the main inverter. The proposed control method achieves both an extension of the motor speed range and a reduction of torque ripple under grid disturbances. The proposed method cancels the harmonic voltage generated due to grid disturbances by the output voltage of the compensating inverter. The effectiveness of the proposed method is verified by experimental results using an electrolytic capacitor-less dual inverter and an open-end winding IPMSM under the input voltage distorted by the seventh harmonic voltage. Compared with the conventional method, the proposed method reduces the harmonic currents and the torque ripple by up to 85.6 and 91.0%, respectively, under the distorted input voltage (seventh harmonic, THD 25%). Therefore, the motor drive system using the proposed method can effectively extend the motor speed range, and reducing the torque ripple under grid disturbances.
This paper presents a sensorless approach for contact force estimation and control of piezoelectric bending actuators. A high-accuracy force sensor is generally used to control the interaction force between a manipulator and contact object. In contrast, sensorless control is desired to reduce the cost and installation space in micro/nano-scale working systems. In this study, the contact force is computed according to the mechanical/electrical models under the contact conditions with the environment. A dynamic model including the creep phenomenon is considered for the static mechanical model. In addition, a self-sensing technique is introduced to separate the actuation and sensing voltages, wherein the passive elements are connected in series with the piezoelectric bending actuator. The force is estimated from the model using the voltage applied to the actuator and the voltage across the passive elements as inputs. The parameters used in the model are calibrated through preliminary tests. A feedback control system based on the estimated signal is evaluated from experiments using a piezoelectric bending actuator and different contact objects.
A probabilistic model is proposed to investigate the time-evolution of traffic flow on the circular lane of a roundabout, which is located at the intersection of three approach roads. The circular lane is divided into six cells, and the probability that each cell is occupied by a vehicle is discussed. A six-dimensional vector is introduced to indicate the probability of occupancy of each cell at any particular instant. A set of simple assumptions related to traffic rules are used to derive a linear difference equation that governs the sequential motion of the probability vector. The difference equation is shown to have a uniform equilibrium that is unique and stable. In the case where the equilibrium is replaced by another due to parameter change in relation to environmental fluctuation, several different modes are found in the process of transition to the new steady state.
This paper proposes a genetic algorithm-based image-processing method that enables an intelligent power module (IPM) inserter to be robust to different lighting environments. In a previous study, we developed an IPM inserter based on a 6-axis parallel link robot. The robot grasps the IPM and inserts it securely into the printed circuit board; this process facilitated by three-dimensional visual feedback control from two cameras. Image processing is used to acquire the positions of the IPM pin tips and the holes on the board. However, because the parameters used in the image processing all had fixed values, there were cases where the system could not cope with changes in the lighting environment. To address this issue, in this paper, we propose a method that uses a genetic algorithm to automatically obtain a set of image-processing parameter values that are optimized for the environment. The method also incorporates a proposed technique for speeding up insertion by conventional inserters. Overall, the proposed method can speed up insertion by approximately 40% and achieves a high insertion success rate even when the lighting conditions change.
This paper examines the vertical dynamics of a quadcopter, and presents an approach to achieve better altitude control. The control system includes a multi-sensor-based state observer for estimating vertical speed, a disturbance observer for improving system robustness, and a position controller for tracking the vehicle's altitude with respect to a reference value. This paper clarifies that it is essential to address the model of the propeller actuators to properly guarantee system stability. It was found that the altitude control system is a multi-input multi-output system. By showing the rank-1 interaction between the actuators, this paper derives the condition for the controller that ensures absolute stability of the control system. The condition can be checked conveniently using a graphical test with the Nyquist plot, thereby alleviating the complexity of system design and analysis. The effectiveness of the proposed approach is evaluated by both numerical simulations and real-time experiments. This approach can be easily extended to the motion control of other general multirotor vehicles.
Vector control which is high-performance instantaneous torque control for permanent magnet synchronous motors (PMSMs) has been widely used in industry applications, electric vehicles (EVs), and etc. In addition, to achieve the high-speed operation of these applications, the flux weakening control must be used, and single pulse operation is desirable from the viewpoint of reducing switching loss and increasing the output voltage of the inverter. In the single pulse operation, the voltage amplitude is fixed and the torque must be controlled using only the voltage phase, which results in a strong nonlinearity. For designing a controller, a linearized PMSM model with pre-measured currents of operating point was proposed, however, the torque response sometimes does not match time constant of the designed controller. Here, the authors propose a novel method to design the controller based on the Ferrari's method in which the torque response can be specified. The effectiveness of the proposed controller is verified through simulations and experiments.