High-speed and high-precision weighing is required in industrial and medical fields. Recently, medical services have improved rapidly and the demand for medicines have increased. Because improper medication can lead to life-threatening symptoms, precise filling and weighing all medicines are vital processes. On the other hand, there are requirements from suppliers to increase production volume. For this problem, Reduction the time by applying vibration-suppression control for a weighing cell is presented. The weighing cell exhibits oscillating responses as it has vibration mechanism inside. This vibration increases the weighing time and then reflected-wave rejection is introduced to suppress the vibration. Because reflected-wave rejection is a phase-stabilizing method, the controller attains a robustness against modeling errors. As a result, the weighing cell did not vibrate regardless of existence of a load. In addition, lift-up operations of vial bottles with water by the weighing cell were also conducted. The water surface did not fluctuate and immediately settled. Reflected-wave rejection certainly contributes to reducing the time for weighing.
High-frequency train operation with a moving-block signaling system has begun to be introduced mainly in urban rail transit. Under high-frequency operation, however, subsequent trains can repeatedly be forced to slow down according to deceleration pattern generated by the signaling system to avoid collision with preceding trains, which increases the energy consumption of subsequent trains. In this paper, train trajectory optimization with dynamic programming is applied to evaluate the effect of considering preceding trains' trajectory on subsequent trains' energy reduction in a line with moving-block signaling system. The result shows that the method reduces the increase in energy consumption compared to the preceding train 1/3 times more than when not considering the position of the preceding train.
This paper proposes a novel feedback control loop based on damping control in a V/f control for stabilizing interior permanent magnet synchronous motors (IPMSMs) with a long electrical time constant. A problem with the conventional damping control is that the ignored roots move to the unstable region due to the conventional damping gain K1. In addition, the ignored roots are prone to become unstable because of its long electrical time constant. Therefore, a novel method is proposed to solve this instability problem. In this paper, first, a boundary condition of the stable region is derived based on the state equation. Then, a novel current feedback loop is added to the output voltage command. The experimental results show that the motor becomes unstable with the conventional damping control under a rated speed of 0.9p.u. and a rated torque of 0.7p.u. Under general operating conditions, the motor is stabilized by employing a novel feedback control loop.
A three-phase wireless power transfer (WPT) system, which has six primary coils and six secondary coils is proposed in this paper. The three-phase WPT system reduces the radiation noise by canceling the noise using pairs of coils placed opposite to each other. However, a magnetic interference among the multiple coils decreases the transmission efficiency due to a circulating current among the primary coils, and the secondary coils in WPT systems with multiple coils. The proposed three-phase WPT system cancels out the effect due to the interference among the six coils on each side. First, the WPT system with the 12 coils is proposed. Then, a canceling condition of the magnetic interference among the coils is mathematically introduced from the voltage equation on the coils. Finally, the proposed WPT system is experimentally demonstrated with the 3-kW prototype. The experimental result shows that the radiation noise at the fundamental frequency is suppressed from 12.2dBµA to 2.1dBµA.
The controller area network (CAN) is one of the serial bus systems used in various applications, such as automobiles, airplanes, and industrial robots. This study focuses on analysis of electromagnetic interference (EMI) caused by a buck converter installed close to a CAN bus, and highlights the problems in a conventional EMI evaluation, followed by the development of an experimental EMI mitigation method. The verification experiments show that the periodic switching noise of a buck converter causes data-transmission failure in CAN. Finally, this study proposes a novel control method for a buck converter, which can mitigate EMI in CAN.
In this paper, a new reactor with a wire guide for a small-size toroidal core that can be used in the high frequency range is proposed. Theoretically, the reactor size can be reduced in proportion to the switching frequency. However, practically, as the switching frequency is increased, reactors are affected by the parasitic capacitance existing between the windings and between the winding and the core, and the inductance characteristic of the reactors is deteriorated. Therefore, there is a limit to increasing the switching frequency. This paper proposes two types of wire guides, namely a two-layer winding guide and a three-layer winding guide, to reduce the parasitic capacitance. Moreover, the impedance characteristics of the reactors using the proposed wire guides are evaluated. The wire guides are manufactured using a 3D printer and attached to the center hole of the toroidal core. With the proposed guides, the parasitic capacitance decreases by 0.73 times and 0.66 times compared with the conventional reactor. The linear regions of the impedance, which can be regarded as a pure inductance, are enlarged. In addition, the materials of the wire guide are also evaluated. It is shown that the ultraviolet curing resin guide is superior to the thermoplastic resin guide.
Fast-response with high-precision positioning for industrial robots is an indispensable requirement in a wide range of applications. Nonetheless, resonant vibrations due to flexibilities in mechanical structures generally deteriorate their motion performance. A practical approach to achieve fast and precise positioning is to use a two-degree-of-freedom (2-DoF) control system with feedback and feedforward compensators. Conventionally, a cascade feedback control system is constructed based on P-PI control, where the position and velocity controllers are respectively implemented using a proportion (P) and a proportion-integrator (PI). The paper proposes robust vibration suppression using H∞ control as an alternative design for the feedback compensators in the 2-DoF cascade closed-loop control framework of a flexible robot arm. Acceleration feedback is also applied to improve the control performance. The effectiveness of the proposed design has been verified by conducting experiments using a prototype.
Uninterruptible power supplies (UPSs) are fundamental components of the power systems of important infrastructure facilities. However, in UPSs, the output voltage must be precisely controlled under load variations. For large-scale UPSs, the power rating of the inverter is several hundred kVA or more and its switching frequency must be under several kHz. The carrier interval is thus large, deteriorating its robustness to load disturbances. Hence, this paper proposes a deadbeat control with disturbance compensation using a 1-MHz multisampling method for three-phase pulse-width modulated inverter systems. Using an FPGA based hardware controller, 1-MHz sampling is realized within the carrier interval of the pulse-width modulated pulse. Simulation and experiments show that the robustness to load variation is better than that of the conventional deadbeat control method.
A power packet dispatching system for a robot hand operation is proposed in this paper. The power packet dispatching system is a power distribution system in which DC voltage is delivered with an information tag in the same power line. To include the information in the packet, the switching speed of the switching device should be over the megahertz range. A SiC or GaN device is an attractive solution to realize a power packet system. The operation of a robot hand using the power packet dispatching system is designed and evaluated in this study. Wi-Fi feedback control is introduced to provide feedback of the pressure sensor information of each finger. The design concept to interface the power and information simultaneously is described and the proposed method is evaluated.
An isolated three-phase AC-DC converter is proposed in this paper for integrating energy storage elements such as batteries to the utility grid. The proposed topology uses a matrix based AC-AC converter for three-phase to single-phase conversion, facilitates the use of high-frequency transformers for galvanic isolation, and provides the necessary turns ratio for matching the required voltages on both sides, and uses a full-bridge controlled rectifier section for AC-DC conversion. A Space Vector Modulation (SVM) based switching technique is implemented for the matrix-based converter to obtain superior input power quality and improved power conversion efficiency, and Sinusoidal Pulse Width Modulation (SPWM) is used for the full bridge controlled rectifier. A T-shaped LCL input filter is developed to provide low-pass filtering effect. Also, the filter realizes an inductance dominance, which provides current source characteristics hence, only a capacitive output filter is used. The simulation was carried out using Powersim (PSIM) simulation software. The variation of voltage gain for SVM and SPWM modulation indices is also presented. The converter is able to generate a charging voltage as well as three-phase sinusoidal voltage with a THD of 3%. A closed-loop control is developed for the matrix type AC-AC converter part. The control is capable of performing bidirectional operation of the system. The proposed converter topology and switching scheme are experimentally verified.
A multi-level power converter with series-connected solid-state transformer (SST) units for a power conditioning system for photovoltaic (PV) generation was developed. Each SST unit has an LLC converter driven by SiC-MOSFETs and a high-frequency transformer. By applying the developed converter, the system can be optimized and made lighter than a conventional system using a commercial transformer. A method for controlling the LLC converter so as to maintain its high efficiency over a wide voltage range of a PV panel is proposed. According to the results of an experimental evaluation of a prototype SST unit, the efficiency of the LLC converter is 98% or more even when the input voltage from the PV panel changes.
This paper presents an analytical model and a design criteria for additional windings to reduce electromagnetic field (EMF) generated from inductive power transfer (IPT) systems. In particular, the canceling windings are connected to the main windings with common-mode connection, differential-mode connection, or short-circuited connection. Parameter variation, which may degrade the system efficiency, occurs in the IPT system owing to the unwanted coupling between the main windings and the canceling windings. Therefore, the theoretical analysis of the IPT system considering the canceling windings is conducted to evaluate the effects of the EMF shielding methods on system parameter variation. The calculation results of the system parameters agree with the measurement results in the prototype of the four-winding IPT coils, the error is lower than 5%. The simulation results with a 1-kW prototype IPT system indicate that the magnetic flux density at the distance of 50cm from the bottom of the receiving coils decreases by at most 41% with the differential-mode connection.
The increasing requirement for high-power-density converters has resulted in the need for accurate analysis of the power loss of inductive components. Some inductors are operated at high frequency and current. However, the maximum AC ripple current measurement range of B-H analyzer, which is a high precision measurement device, is ±6A. In this paper, a low-cost measurement method using the shunt resistor as a high current sensor is proposed. To abbreviate the measurement deviation caused by the parasitic inductance of shunt resistor, the Runge-Kutta calculation method is applied to determine the inductor current. Furthermore, a shunt resistor connection configuration is proposed to reduce the influence of parasitic inductance. To demonstrate the feasibility of this method, an inductor is measured under 160A (RMS) current, 10kHz switching frequency, and 50% duty cycle square-wave-voltage as an example.
With regard to the auxiliary power systems used in public transport such as hybrid bus, trolleybus, light rail trams, and subways, riding the weight and volume of the power equipment need to be reduced in order to accommodate more passengers or provide a more comfortable space. A converter with a higher capacity density, smaller volume, and lower weight was developed to improve the vehicle layout design and transport capability. With advantages such as faster switching frequency, lower power losses, and higher working temperature, silicon carbide metal-oxide-semiconductor field-effect transistor (SiC MOSFET) devices can be used to promote the operation of auxiliary power converters. In most of the metro trains in China, such as Beijing, Shanghai, and Guangzhou, the power supply line is at a level of DC 1500V. However, 3300V SiC devices are rarely available in the market, series SiC MOSFETs are mostly available at levels of 600V to 1200V. In this research, a cascaded full-bridge topology with input-series output-parallel (ISOP) connected converter adapting 1700V/300A SiC MOSFET is proposed. An improved input voltage sharing control method is applied to improve the system rapidity and stability of the ISOP converter. The working characteristics, device losses, and system efficiency of a phase-shifted full-bridge (PSFB) converter with ISOP topology based on 1700V/300A SiC MOSFET are studied. Aiming at the application to auxiliary power systems, the other two types of converter topologies are also analyzed. The 1700V/300A (silicon-based insulated gate bipolar transistor) Si IGBT PSFB converter with ISOP topology and the 3300V/400A Si IGBT single unit PSFB converter are investigated of the control, weight, losses, efficiency, cost, and structure complexity. Simulation and experiment show the application of SiC devices exerting a positive effect on the volume reducing, weight decreasing and efficiency increasing.
Dual Active Bridge (DAB) converters are an interesting solution for the battery interfaces of storage systems used in traction applications. Due to the environmental conditions and space limitations, the design of the transformer and cooling system is crucial for achieving a high power density. Therefore, in this paper, a detailed design of a transformer with an integrated liquid cooling structure and high isolation voltage is presented. Analytic models for the design are presented and verified through FEM simulations and measurements on a prototype system.
This paper presents a high power density silicon carbide (SiC)-based inverter, with a two-level voltage-source structure having forced air cooling, which provides a high volumetric power density of 70kW/liter or 50kW/kg in gravimetric terms. In order to achieve a power density greater than that of conventional inverters, the losses must be reduced or the cooling performance must be improved. Small light-weight SiC MOSFET power modules with directly soldered foil fins having good thermal conductivities, are developed in this study. The antiparallel SiC Schottky barrier diodes (SBDs) are removed from the modules to improve the power density. Gate drivers are developed to reduce the switching losses and switching time. A prototype of the proposed high power density inverter, which includes the developed power modules and proposed gate driver, is fabricated. The volume and weight of the prototype inverter are approximately 0.5 liter and 660g, respectively. Experimental results confirm that the prototype inverter can operate continuously with an output power up to 35kW. Therefore, the power density of the prototype inverter is approximately 70kW/liter or 50kW/kg. The efficiency of the prototype inverter is found to be more than 98%. Hence, the measures undertaken in this study have been verified to improve the power density of the inverters. The proposed high power density inverters can be applied in future aircraft and other electric vehicles.
This paper proposes a two-step commutation method for a three-phase-to-single-phase matrix converter. Conventional two-step commutation cannot be applied at all operation regions because a commutation failure still owing to detection error of grid voltages. In our proposed two-step commutation, we modulate only one of two devices in a bidirectional switch and utilize a zero vector to let the switches naturally turn off, in this manner, the commutation failures are avoided completely regardless of the voltage detection error. From experimental results, it is confirmed that the proposed two-step commutation undertakes safe operation to avoid commutation failure. The input current total harmonic distortion at 10kW with the proposed two-step commutation is improved by 38% in comparison with the conventional four-step commutation.
This paper shows how to implement a vision-based control for a Ball on Ball system. The control task is to stabilize a ball on top of another ball in the unstable upper rest position. In order to stabilize the upper ball, the position of the upper ball has to be measured. This is done optionally by using two triangulation sensors or an industrial camera. To stabilize the upper ball in the unstable upper rest position, a PD controller, a linear quadratic regulator, and a flatness-based nonlinear controller are designed. By using these controllers and the designed image processing, which are implemented entirely on a standard industrial programmable logic controller, it is possible to stabilize the upper ball with both measurement types. The disturbance rejection of the system is shown, and the resulting RMS position error when stabilizing the upper ball is 1.8 mrad.
Rotor position and speed in sensorless control based on back-electromotive force (back-EMF) estimation can be estimated from back-EMF estimator and rotor position estimator in an interior permanent magnet synchronous motor (IPMSM). Even if the rotor position and speed are correctly estimated by these estimators in the steady state, the performance of estimators in the transient state may be degraded by the gain design of estimators. This paper describes the design method of estimators and current controller to ensure stable sensorless control of IPMSM not only in the steady state but also in the transient state such as for torque or speed variation. The performance of our proposed method is verified through a simulation and experimental results.
This paper proposes a remote control method for a mobile robot based on the force feedback generated using a collision prediction map. The collision prediction map expresses the relation between the mobile robot and its surrounding environment as the collision prediction time at each translational and angular velocity. The force feedback is generated by using this collision prediction map. In the proposed method, the operator can feel the environmental information as the tactile sensation. This improves the operability of the remote control system. The validity of the proposed method was confirmed from the experimental results.
For the control of permanent magnet synchronous motors, speed control, current control, sensorless control exist, and control gain design is required. In general, the control gain needs to be designed in consideration of stability and responsibility, and various researches have been conducted on this.
In this paper, the influence of the control band of the three types of control on the stability is analyzed by combining the analysis of the pole placement of the closed-loop transfer function and stability judgment considering the axial error which is the difference between the actual position and the estimated position, the relationship between each control band that can secure the results is discussed.