This paper discusses a problem regarding a communication disturbance observer (CDOB) for a system through variable time delay. A CDOB is a method of compensating the effect of time delay. According to a few reports, it has been verified that a CDOB compensates the effect of constant time delay. However, the most recent studies reported that a system with a CDOB exhibits steady-state error, which is caused by variable time delay and modeling error. Therefore, this paper discusses the cause of this problem by focusing on the estimation error in communication disturbance. Additionally, we propose the introduction of a scaling gain to the output of a CDOB to resolve this problem. We derive steady-state error using a transfer function, and the proposed method is able to suppress the error.
In a teleoperation system with communication delay, the contact information on the slave side is transmitted to the master side with time delay. Hence, an operator may misunderstand that the slave has not contacted an object and may add more force. Eventually, excessive force by the slave may collapse the object. This paper proposes model predictive control with a variable dumping method to prevent collision on contact in a teleoperation system with time delay. The prediction method considers the distance to the object on slave side, and variable dumping is implemented on the master side. The proposed method is evaluated through numerical simulations and experiments.
Direct torque control (DTC), one of the known PMSM drive systems, can realize maximum torque-per-ampere (MTPA) control and flux-weakening control by yielding an optimal target magnetic flux. In this paper, an armature reaction flux control that can achieve MTPA control and flux weakening control is proposed for PMSM control systems using DTC. The proposed control focuses on the equivalence of the reactive power, which is an inner product of the stator magnetic flux vector and a current vector. In order to achieve MTPA control, the proposed control focuses on the rotor flux and current phase information and corrects the reference flux such that the rotor flux vector and current vector intersect each other orthogonally. Furthermore, flux weakening control is also achieved by correcting the reference flux in order to shift the current phase to produce the desired stator voltage. The effectiveness of the proposed control is experimentally confirmed.
A method that estimates the parameters for a bilateral filter, based on the distribution distance of the images, is proposed. This study presents a method to estimate a sub-optimal set of parameters in a reasonable execution time by using a local search method with adequate initial values. The image quality is slightly degraded when sub-optimal parameters are used, and therefore a second method is proposed to compensate the parameters to achieve better image quality. Parameter estimation time was reduced from 398 s (brute-force method) to 0.15s (proposed local search method) with a 2.8GHz Xeon processor. When the compensated parameters are used, the image quality was approximately equal to the optimal result.
This paper proposes a switching pattern of a reduced switching non-isolated buck-boost DC/DC converter using series voltage compensation for a DC power interchange system. The proposed method uses a capacitor as an energy buffer in the circuit in order to reduce the current through high breakdown voltage switches. Moreover, the losses in high breakdown voltage semiconductor switches decrease. In order to estimate the effect of the proposed method, the 990W prototype is tested. In the experimental result, the efficiency of the proposed method is higher than that of the conventional method. The analysis results show that the switching loss and conduction loss are reduced using the proposed method.
In this study, a traction drive electric motor was designed with a new magnet-free motor design technique where electromagnets are generated on a rotor by utilizing changes in the spatial second harmonic of the magnetic fields. To apply the proposed technique to electric motor design, balancing the rotor and stator magnetomotive force is important. This paper presents design methods for adjusting the rotor and stator magnetomotive forces. A test motor was designed with these design methods and evaluated using a motor bench. The analytical and measurement data indicated that the proposed motor performed comparably to magnet motors.
This paper proposes new, efficient current command determination methods that allow torque generation with minimum copper loss for permanent-magnet synchronous motors with double independent three-phase windings (DIW-PMSMs). The double windings are not necessarily identical, but can have different characteristics. When one of the windings is designed for high torque at low speed and the other for low torque at high speed, the resulting DIW-PMSMs can have an ability of wide-range high-efficient drives. In order to translate wide-range high-efficient drives into reality, associated current command determination is indispensable. This paper proposes three new efficient current command determination methods such as torque error feedback method, modified bootstrap method, and Newton-Raphson direct method. Each method can solve a set of five-variable nonlinear simultaneous equations that govern the torque and minimum loss constraints, which are newly formulated in this paper. The effectiveness of the methods is validated by numerical experiments.