Elevator group control systems decide which car gets allocated to a new hall call in some elevators, when a passenger in the elevator hall pushes the hall call button. The primary purpose of the group control system is to maximize the transport efficiency and reduce the waiting time of passengers. Recently, there has been increasing interest in energy-saving performance. Considerable efforts have been made toward reducing the number of available cars and limiting the use of lights and air conditioners in cars for saving energy; however, this leads to a decrease in the transport efficiency and comfort for passengers. This paper presents an elevator group control method for reducing total running distance. This method is used to calculate the cost from the estimated running distance of a car when the car to be allocated to a new hall call is decided. The weight coefficient of the cost varies dynamically depending on the traffic. Simulation results show that the average waiting time in the conventional method and that in the present method are not significantly different. The improvements in the total running distance and power consumption are also demonstrated.
There are many studies on underactuated systems that control input number is less than output one. That system leads cost reduction and space-saving. Previously, an observer was used widely to control an underactuated system; moreover, time delay occurs because of a low-pass filter. Generally, we use a low-pass filter to obtain the derivative. Recently, Levant suggested a sliding mode differentiator that can estimate the derivative of a input signal, and its time delay is low. Therefore, a new construction of a observer using sliding mode differentiator is proposed, and we investigate how to design the gain of the differentiator. The proposed method was evaluated via a crane experiment. Furthermore, the result showed that the proposed method is effective for controlling an underactuated system.
In this paper, the theoretical error evaluation of a coupling coefficient is discussed to establish the design method for a novel magnetic-resonance-coupling-based distance sensor using a relay antenna. In the proposed system, the target position is estimated by measuring the coupling coefficient between the transmitter part and the target antenna. The contributions of this paper are as follows. First, a new configuration of a novel magnetic-resonance-coupling-based distance sensor using a relay antenna is proposed. Second, the error rate of the estimated coupling coefficient is formulated on the basis of the equivalent circuit model. Finally, the theoretical formula of the error rate of the estimated coupling coefficient is validated through experiments.
In recent years, renewable energy has been used to generate electric power. The design of a small electric generator is a complicated procedure for non-specialists. This paper presents the design procedure of a small electric generator by CAD and analysis software. The proposed procedure applied the recommended standard dimensions of parts to eliminate difficult analysis and design. The proposed method and procedure was confirmed by the trial production of an electric generator. The results of electric generation capacity using free software are equivalent to those obtained using paid software. The design time was decreased by using standard dimensions of components. The combination of standard dimensions and design procedure is sophisticated for novice designers and students. The proposed design procedure of a small electric generator by CAD and analysis software was found to be reliable and significant. Therefore, this method and procedure can be utilized for academic purpose by students and beginners.
This paper proposes a receiver circuit topology of a non-contact battery charger for an Electric vehicle (EV), which has a carefully designed series capacitor added to the parallel resonant circuit of the receiver. The simulation and experimental results are presented to show that the circuit can improve the power factor as well as efficiency, and as a result, enlarge the gap between the transmitter and the receiver coils.
This paper presents a theoretical analysis and control of a three-phase modular multilevel cascade converter based on double-star chopper-cells (MMCC-DSCC). The analysis and control are characterized by applying the so-called “αβ0” and “dq0” coordinate transformations to the converter. Existing analysis and control methods were unable to use any coordinate transformation because the three-phase converter was considered as three sets of single-phase converters that were analyzed and controlled independently. As a result, it was difficult to avoid mutual interferences among the three-phase ac currents, circulating currents inside the converter, and dc current. Power-flow analysis using the two coordinate transformations succeeds in decoupling these currents, as well as in deriving lucid relationships between the power flow and the circulating currents. Moreover, the power-flow analysis makes it possible to design a decoupled digital controller for balancing and regulating the dc mean voltages of all the floating dc capacitors. The validity of the design is confirmed by computer simulation using a software package of PSCAD/EMTDC.
Self-servo track writing (SSTW) in hard disk drives (HDDs) is a process of writing a subsequent track from the previously written track. One of the issues with SSTW is how to minimize the propagation of writing errors from previous tracks. This paper presents a control method for reducing error propagation in the SSTW process. The proposed method determines the error compensation signal according to the repeatable run-out, which is calculated from the previous writing error. The effectiveness of the proposed method is confirmed by numerical simulations of the benchmark problem for HDDs.
A modular multilevel cascade inverter based on double-star chopper-cells (MMCI-DSCC) is expected to be used as one of the next-generation medium-voltage PWM inverters suitable to motor drives for energy savings. This three-phase inverter comprises six modular arms, each of which consists of a cascaded stack of multiple bidirectional chopper-cells. It suffers from ac-voltage fluctuation in the dc-capacitor voltage of each chopper-cell at low speed. The frequency of this fluctuation is equal to the stator-current frequency. This paper attempts to suppress the fluctuation by injecting a common-mode voltage of 45Hz and circulating currents among the three legs. Experimental results obtained from a 400-V, 15-kW downscaled system verify that stable operation is achieved at an ultra-low speed of 17min-1 with a load torque of τL = 40%, as well as “three-phase” dc-current feeding operation. Moreover, the motor can start up from a standstill without producing any overvoltage or overcurrent.
This paper proposes a high-speed switching method of MOSFETs applied to a high-frequency half-bridge inverter. The turn-off time of the MOSFETs can be shortened by employing a set of auxiliary switches in parallel with a load; this reduces switching loss of the MOSFETs. It was confirmed through experimental tests that the total efficiency of the inverter was improved by the proposed method, particularly in a low-load range.
A rotor position sensorless control system of a permanent magnet synchronous motor has been used widely for practical use in home electronics as well as in the industry. Recently, higher performance sensorless control has been required to expand its applicability in various fields. Accurate estimation of the rotor position at a standstill or an initial rotor position is important to achieve sensorless control over the entire speed range. This paper proposes a new method of the rotor position estimation of an interior permanent magnet synchronous motor based on a model reference adaptive system (MRAS) at a standstill. The proposed method estimates the rotor position by injecting a high-frequency pulse voltage. Several experimental results are presented to show the performance of the method.