In recent years, a technology for the preservation and reproduction of human motion has been in demand in the fields of manufacturing and human support. An efficient method for this purpose is the use of a motion-copying system. This system deals not only with the trajectory but also with the strength of human motion. However, there are several problems associated with this system. One of them is that the saved motion is not reproduced completely when the environmental location in the motion-loading system is different from that in the motion-saving system. For real-world haptics, a reproduction method that considers the relationship between human motion and the environment is necessary. In this paper, a motion-copying system based on acceleration information is proposed. In the proposed method, human motion is treated as the acceleration information. As a result, motion reproduction is realized even when the environmental location is different, because the acceleration information does not depend on the initial position. The validity of the proposed method is confirmed by experiments.
This paper presents a novel strategy for torque ripple minimization with instantaneous current feedback compensation for switched reluctance motors (SRMs). The authors have already proposed suitable reference current profiles and a control algorithm to obtain an instantaneously flat torque of an SRM and confirmed the effectiveness of the algorithm by performing experiment in the low-speed range. In the high-speed range, however, the winding current cannot track the reference current owing to the lack of necessary voltage. In this study, mathematical analyses on the inability to trace the current profiles are performed. A new current control with compensation of the current profiles with instantaneous feedback is proposed. The validity of the proposed control is demonstrated by the experimental results.
Terminal voltage of a synchronous generator drops with an increase in the generator current because of the large inductance in the generator, called synchronous reactance. This paper proposes the use of an active series compensation device named magnetic energy recovery switch (MERS) for improving engine generator performance. The MERS can compensate for the voltage drop caused by the synchronous reactance and it can control the load voltage more quickly than the auto voltage regulator can control the excitation current. Thus, the MERS can improve the generator efficiency and transient over power characteristics.
Blimps have some advantages, for example, that they do not need driving forces to float and can move in three-dimensional space. However, it is not easy to control them since they are underactuated systems with nonholonomic constraints. Some papers have presented control technologies, but the technologies need impractical conditions. Furukawa et al. presented a blimp control technology by considering a nonholonomic situation, but it cannot be used to control blimps in the presence of wind disturbances. This paper introduces a wind-observer-based control approach that involves the consideration of wind disturbances. A controller based on the proposed approach can generate a driving force in the direction opposite to that of a wind disturbance and help a blimp move against the wind.
This paper proposes a new current control method for interior permanent magnet synchronous motor (IPMSM). In the case of AC motor control, two axis current feedback control is performed to control the voltage amplitude and phase. When the inverter voltage is saturated, current control is achieved by controlling the voltage phase. Conventional techniques require switching the mode of the control system from variable-voltage mode to voltage-saturation mode. However, in conventional techniques, the transient voltage saturation occurs by switching the control system. The proposed method achieves the current control in variable voltage mode and voltage saturation mode without switching the control system. Moreover, the current response is not affected by the rotor speed. The numerical simulation results and experimental results confirm the effectiveness of proposed current control method.
This paper presents a reverse-recovery analysis of parallel-connected pin diodes using a physics-based device model. Since the pin diode model is based on a physical equation, the excess carrier distribution in the drift layer is estimated. A precise device model enables us to understand the transient characteristics of the parallel-connected pin diodes. We investigated the reverse-recovery characteristics of parallel-connected pin diodes by using a physics-based pin diode model. A difference in the wiring inductance or device temperature between the two pin diodes causes a transient current imbalance. Complicated reverse-recovery current waveforms are observed under both conditions—a difference in the wiring inductance and a difference in the device temperature. They result from a difference in the starting time of forming each depletion layer between the two pin diodes. Simulation results are in good agreement with experimental ones within an error of 10% in terms of the reverse-recovery loss. We find that a precise physics-based pin diode model is very useful when designing a power electronics apparatus.
We have been developed a small and highly efficient axial gap motor whose stator core is made of a soft magnetic core. First, the loss sensitivities to various motor design parameters were evaluated using magnetic field analysis. It was found that the pole number and core dimensions had low sensitivity (≤ 2.2dB) in terms of the total loss, which is the sum of the copper loss and the iron losses in the stator core and the rotor yoke respectively. From this, we concluded that to improve the motor efficiency, it is essential to reduce the iron loss in the rotor yoke and minimize other losses. With this in mind, a prototype axial gap motor is manufactured and tested. The motor has four poles and six slots. The motor is 123mm in diameter and the axial length is 47mm. The rotor has parallel magnetized magnets and a rotor yoke with magnetic steel sheets. The maximum measured motor efficiency is 93%. This value roughly agrees with the maximum calculated efficiency of 95%.
This paper proposes a strategy based on constant dc-capacitor voltage control for a current balancer in single-phase three-wire distribution systems. The proposed control strategy involves the use of only the constant dc-capacitor voltage control block commonly used in active power conditioners for the calculation of the compensation current. No calculation block is required to obtain the reactive and unbalanced-active components. Thus, we provide the simplest possible control strategy for the current balancer. The basic principle of the proposed control method is discussed in detail and its validity, which is confirmed by a digital computer simulation using PSIM software, is shown. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of unity are obtained on the secondary side of a pole-mounted distribution transformer while unbalanced load current conditions with a lagging power factor are retained.
This paper addresses an avoidance problem of robot joint limits in visual servoing. Many robotic systems are practically subject to some physical constraints. In particular, violation of joint limits can deteriorate control performance and lead to the breakdown of the system. Redundancy appears frequently in the visual servoing formulation. To this redundancy, the authors introduce the maximal admission function. Consequently, both avoiding joint limits and exploiting joint range of motion effectively are achieved in visual servoing. Here, we consider a moving object as the target of visual servoing. In visual servoing, the case of a moving object is more severe than the case of a stationary object. The effectiveness of the proposed scheme is validated experimentally. The obtained results are also evaluated through a comparison with the conventional schemes.
Many software tools for magnetic field analysis give us distribution of magnetic flux density between Halbach arrays of permanent magnets. However, we need easier calculation tools in an early stage of development. This paper proposes an equivalent magnetic circuit method with high accuracy for field magnets provided with dual Halbach arrays.
This paper describes a high-speed switching method of MOSFETs applied to a chopper. By employing a set of auxiliary switch and diode in parallel with a load, the turn-off time can be reduced, which makes a high frequency drive possible. It was confirmed through experimental tests that an actual duty cycle of the main MOSFET was effectively improved by the proposed method, especially in a low-load range.