This paper presents a novel single-phase inverter equipped with a buck-boost-type power decoupling function that is suitable for PV generation. The proposed buck-boost-type power decoupling circuit relaxes the increase of the DC-bus voltage of the PWM inverter compared with the conventional boost-type power decoupling circuit. This prevents the increase in switching and conduction losses caused by the high voltage rating switching devices. Another feature of the proposed inverter is a power decoupling control method based on a single-phase p-q theory. Because the proposed power decoupling method reduces the low-frequency ripple current flowing at the DC input, the electrolytic DC-bus capacitor is replaced by a small film capacitor that has a longer lifetime. The effectiveness of the proposed system is verified through simulation and experiments using a 200W experimental setup.
Bilateral control is one of the control methods for teleoperation system. The presence of network delays between a master robot and a slave robot makes the design of the bilateral control system challengeable. This is because network delay seriously deteriorates the performance and could make the system unstable. The authors' previous research proposed a compensator to stabilize the against network delay and a control system to attain reproducibility. However, operationality is remained as a problem. In this paper, to attain almost same performance as the system without time delay, allocations of high pass filter are studied. High pass filter is implemented to remove the undesirable operational force in low frequency area. By allocating high pass filter correctly, operationality is improved while maintaining stability and reproducibility. The validity is confirmed by numerical analysis and experimental results.
In this paper, a gate driver supply, which supplies power to multiple gate drivers, is demonstrated. Robust isolation is required in the gate drive supplies of a medium-voltage inverter in order to drive high-voltage switching devices such as insulated-gate bipolar transistors. The proposed isolation system achieves isolation with transmission coils mounted on printed circuit boards. Furthermore, the isolation system transmits power from one transmitting board to six receiving boards. In the conventional system, the number of receivers is limited to one. In contrast, multiple receivers are acceptable in the proposed system. These characteristics help reduce the of the isolation system for the gate driver supplies. This paper presents the fundamental characteristics of the isolation system. The equivalent circuit of the proposed system can be derived by applying the equivalent circuit of a wireless power transfer system with a repeater coil. In addtion, a design method for the resonance capacitors is mathematically introduced using the equivalent circuit. It is verified that an isolation system with multiple receivers can be designed using the same resonance conditions as an isolation system with a single receiver. Moreover, the isolation system is experimentally demonstrated. It is confirmed that the isolation system transmits power with a maximum efficiency of 46.9% at an output power of 16.6W beyond an air gap of 50mm with only printed circuit boards.
Mobile haptic devices are being studied extensively because they have great potential for use as information transfer devices. Amemiya et al. proposed a method for haptic feedback with a slider-crank mechanism that uses an asymmetrical drive. We have recently proposed a haptic device that uses a small two degree-of-freedom (2-DOF) oscillatory actuator. Using this actuator, we were able to reproduce the same asymmetric acceleration as the one achieved by Amemiya. However this waveform is dependent on the mechanical structure of the slider-crank mechanism and thus it is not necessary to use it for our actuator. In this paper, first, the relationship of the properties of the asymmetric acceleration to haptic perception is investigated by conducting experiments on volunteers. Next, by applying a genetic algorithm to the optimization method, an optimized asymmetric acceleration waveform is created. The effectiveness of the method is demonstrated by the power consumption of our actuator and the ratio of correct answers given by the volunteers.
In this paper, a time-adaptation control for motion reproduction is proposed for adapting to variations of environmental location and toward advanced manufacturing process. The method has the highest priority on eliminating force error; by lowering the priority on time correspondence, the reproducibility of contact motion is improved. Concretely speaking, the proposed method matches the force response value with its command under contact motion, by introducing a difference between save time and reproduction time. By using this method, even when the environmental location is changed, it is possible to reproduce the same reaching velocity at the moment of first contact. Then, the force error in the reproduced motion is suppressed immediately. In recent years, not only production speed, but also product quality must be ensured in a manufacturing site. In an actual manufacturing site, because materials are natural objects, properties, such as the size of an object, are different in different lots. Therefore, a control method that can adapt to variations of environmental location is effective for achieving high-quality manufacturing.
Electric vehicles (EVs) have been intensively studied over the past decade, owing to their environmentally-friendly characteristics. However, the miles-per-charge of typical EVs is lower than the cruising range of typical internal combustion engine vehicles. To increase miles-per-charge, the authors' research group has proposed a series of control systems, including Range Extension Control Systems (RECS) and Range Extension Autonomous Driving (READ) systems. In this paper, by considering the load transfer, slip ratio, motor losses, a READ system is proposed that optimizes the velocity trajectory and the front and rear driving-braking force distribution ratio; these techniques help reduce the consumption energy of the autonomous vehicle. The effectiveness of the proposed method is verified by simulations and experiments.
One of the most vital skills of daily life is the ability to stand from a sitting position. This study aims to use musculoskeletal model simulation to create an optimal sit-to-stand motion without causing stress to the knee joints while activating the weak muscles. Numerical optimization was performed using the musculoskeletal model by applying the multiobjective genetic algorithm. The numerical optimization results indicate that by placing the feet under the chair prior to standing (not bending the upper body visibly forward) during the sit-to-stand movement, it is possible to reduce stress on the knee joints and muscles. To validate this optimized sit-to-stand motion, we performed two experiments. First, we calculated a correlation value between simulation and experimental results relative to muscle activity, and verified that there is a significant correlation. Next, two types of sit-to-stand movements performed by five healthy male subjects were analyzed: spontaneous sitting-to-standing and imitated sitting-to-standing using the optimized motion. The experimental results confirm that the imitated movement reduces the knee joint's maximum torque.
This paper proposes a method that uses model-error feedback to improve the steady-state performance of a communication disturbance observer (CDOB) and a controller design based on the stability theorem with a Lyapunov-Krasovskii functional. The conventional CDOB faces the problem of a steady-state error due to model error, and the stability of a system with time-varying delay is not guaranteed. To solve the issue, the controller based on the mixed H2/H∞ control problem is introduced. The paper presents a solution that uses a controller design based on the Lyapunov stability theorem and model error feedback.
Simultaneous localization and mapping (SLAM) is a very popular technique which is used to develop autonomous mobile robots. We have developed an autonomous mobile robot that can perform the SLAM based solely on information it gathers with a laser range finder. Path planning using the A* algorithm is proposed to help the robot determine the shortest path while avoiding obstacles and minimizing travel distance and rotation. In addition to the standard eight adjacent cells present in conventional A* algorithms, the proposed path planning method allows the eight cells that may be reached via the knight move to be defined as additional adjacent nodes. As a result, the achieved path is smoother than those obtained via more conventional methods, as has been experimentally verified.
The literature concerning human assistive robots typically focuses on “wearable” devices, with the aim of reducing the muscular effort required of patients during movements. This paper describes the design of an orthosis for assisting patients during sit-to-atand (STS). The newly developed device generates a hip joint torque and reduces the muscle activity required of the wearer. The device makes use of non-linear springs called stiffness adjustable tendons (SATs), to simulate the behavior of human tendons, and to exploit their ability to store energy when in motion and to return it at a later time. A series elastic actuator (SEA) was adopted to create the device. A position reference is designed to realize an assist control without a force sensor. EMG sensors are used to verify the effective reduction of muscle activity required of the wearer during the STS.
This paper proposes a method for suppressing the vibrations that occur under load conditions in trochoidal reduction gears. For the proposed suppression method, a general-purpose vibration-suppression control system based on a disturbance observer is constructed without the use of a load-side sensor or the individual values of the reduction gear. The proposed method is shown to effectively improve the accuracy of the trajectory tracking. This paper proposes a new model for calculating the angular transmission error caused by a deformation of a trochoidal gear under load conditions. Using the state observer designed along with this model, the shaft torsional vibration produced under load conditions is estimated. The experimental results validate the proposed angular transmission error model and confirm the improved accuracy of the trajectory tracking.
Integrated magnetic components for interleaved converters have been developed in order to fulfill the demand for high power density and high efficiency in power conversion systems. The close-coupled inductor and the loosely coupled inductor methods for interleaved converters are well known as attractive techniques to downsize magnetic components or improve the power conversion efficiency. Moreover, the integrated winding coupled inductor has already been proposed. However, the advantages of the interleaved converter with the integrated winding coupled inductor over the other methods have not been fully elucidated. Consequently, this paper analyzes and evaluates the integrated winding coupled inductor, specifically, the characteristics of the inductor ripple current and the magnetic flux in the core. The analysis shows that the integrated winding coupled inductor provides attractive features compared with the other methods. The effectiveness of the integrated winding coupled inductor is discussed from theoretical and experimental points of view.
An induction heating system is proposed as a new circuit topology for induction-heating cookers that can be used with all metals. This system has a fixed number of work coil turns that switch the inverter between full-bridge or modified half-bridge configuration according to the cookware material and power setting. When heating cookware made of a low-resistivity material such as copper or aluminum, the inverter is switched to the half-bridge configuration; when cookware made of a high-resistivity material such as iron or magnetic stainless steel is heated at high power, the inverter is switched to the full-bridge configuration. The buck converter, which is placed in the stage before the inverter, controls the DC link voltage to adjust the power. In addition, the boost converter placed in the stage before the buck converter is switched between passive filter and active filter modes to reduce the harmonics of the commercial input current and hence improve the power factor. Tests confirm the power conversion efficiency of the inverter and boost and buck converters as well as the power control characteristics of the inverter. High efficiency over a wide power range when heating an iron pan was also confirmed.