Recently, interest in energy savings in railway systems has been increasing because of its environment-friendly aspects, e.g., CO2 emissions. In this paper, the authors propose a scheduling and control system for Automatic Train Operation (ATO) that saves energy. Current research in ATO concentrates on the optimization of speed profiles to save energy. The differences in this system from previous work are substantiative experiments on the track and a design that explicitly considers the following energy-saving operations. First, coasting is installed in speed profiles and maximum speed is decreased by jerk regulation. Second, power-limiting braking is used in the braking section and regenerative energy is increased. To achieve this braking efficiency, notch operations are updated. Finally, second-order scheduling is achieved by high speed control using ATO. For the experiments on the track, the efficiency of a linear-motor train was measured in a pre-experiment and used to perform accurate numerical calculations. In conclusion, the numerical study shows an energy efficiency increase by 7.3% and the plan for further experiments is determined.
A plant with unstable zeros is known as difficult to control because of initial undershoot of step response and unstable poles of its inversion system. There are two reasons why a plant has unstable zeros in a discrete time domain: 1) non collocation of actuators and sensors and 2) discretization by zero-order hold. Problem 2) has been solved using the perfect tracking control (PTC) method based on multirate feedforward control proposed by our research group. However, the conventional PTC method cannot achieve the perfect tracking for a plant with continuous-time unstable zeros because of the divergence of the desired state trajectories. This paper proposes a preactuation perfect tracking control (PPTC) method to solve problem 1) through the state trajectory generation based on a time axis reversal. The validity of the proposed method is demonstrated through simulations in comparison with three single-rate feedforward control methods.
A method is proposed for designing a feedforward profile for a discrete closed loop system that considers the robustness of the system. The feedforward is obtained from a sinusoidal series and a ramp function to prevent the effect of the plant uncertainty caused by mechanical resonances in a high frequency range. We express plant input and output using the finite series expression of z-i. We select the coefficients of z-i by considering overshoot and undershoot specifications. We apply the proposed feedforward to a HDD (hard disk drive) benchmark.
When an accident or a natural disaster occurs in railways, it becomes impossible for trains to operate through the accidental area. Thus, in order to avoid further inconvenience of passengers, it is required to continue operating trains in other areas of the railway. This means we partially cancel trains and turn trains back to the neighboring stations in the accidental area. Although many papers about the rescheduling algorithm are published, none of them deal with partial cancellation and turning back of trains. In this paper, we propose a rescheduling algorithm that enables partial cancellation and turning back of trains. Our algorithm assumes a basic timetable while the duration of the accident is given, and it outputs a rescheduling plan in which the sum of the total delays and the penalties for cancellation is minimized based on mixed integer liner programming formulation.
Vector control of induction motor is widely used in industrial applications. Many methods have already been proposed in this field. There are many restrictions involved in using mechanical sensor; moreover, the extra expense and allocation problems make using such sensor difficult in some cases. Stability analysis of a speed sensorless vector control system based on the feedback of the estimated torque-producing current is performed.
In this paper, a novel differential equation for an adaptive rotor flux observer, taking core loss into account, is introduced. Next, small signal stability analysis is carried out on the speed sensorless vector control system of an induction motor and stability analysis method is proposed.
A design for an inverter circuit configuration of integrated half-bridge modules with focus on the circulating resonant current is clarified in this paper. Although this configuration has the advantages of a small DC-side stray inductance, an analysis of the equivalent circuit suggests that the DC-link capacitor current increases depending on the relationship between the resonant and switching frequencies. This leads to an increase in the capacitor volume. The capacitor current was experimentally investigated under PWM operation at switching frequencies up to 100kHz using SiC-MOSFETs. The experimental results demonstrate that the resonant current is remarkable when the resonant frequency was close to either the fundamental or the third harmonics of the switching frequency. Using the proposed design considering the quality factor and the resonant frequency, the increase in the capacitor current based on the resonant phenomenon can be avoided.
This paper examines the cogging torque in permanent magnet (PM) motors resulting from the asymmetrical properties of the rotor and stator such as the variation in magnet properties and slot opening widths of the stator. A PM motor with 10 poles and 12 slots is selected for verification, because the motor with a pole/slot ratio of 5/6 is sensitive to the variation of the rotor and stator. We propose an estimation method of cogging torque using the torque vector, which corresponds to the torque produced on the each magnet or stator core. The validity of this method is confirmed by comparison with the results obtained using FEM. The calculation method of cogging torque probability distribution using the proposed estimation method of cogging torque is also shown.
In a non-contact power supply system for railway vehicles, eddy current and hysteresis losses caused by leakage flux pose a problem for power transmission efficiency because the transmission coil is installed near a rail. To solve this problem, we proposed a figure-of-eight coil shape capable of decreasing the leakage flux. However, the coupling factor of the figure-of-eight coil is smaller than that of a rectangular coil when the coil width is the same and the influence of the rail is neglected. In this study, the magnetic coupling characteristics and loss the in rail with the respect to the width of the figure-of-eight and rectangular coils were evaluated by analysis and experiment. The results contribute to design methods for the coil shape and width of non-contact power supply systems for railway vehicles.
Wireless power transfer (WPT) has been a popular research topic in recent years. The allowed frequencies for WPT are limited by the industrial, scientific, and medical (ISM) radio bands and the laws of the respective countries. Different applications of wireless power transfer require different frequency bands. A single transmitter coil that can adapt to multiple frequency bands is needed to reduce the number of transmitter coils. In this paper, a transmitter coil design for two frequencies using a high order resonant frequency of an open end coil and a short end coil are proposed. Two types of multi-band coils, an open end coil and a short end coil are discussed. In the case of the open end type, for fundamental study, the second resonant frequency is set at 13.56MHz (ISM band) by adjusting the coil shape. It is confirmed that only the second resonant frequency can be set by adjusting the coil shape parameters and can be used for WPT by experiment. In the case of the short end type, the first resonant frequency is set at 85kHz (for Electric Vehicles) by using capacitor. The second resonant frequency is set at 6.78MHz (ISM band) by adjusting the coil shape. It is confirmed that the second resonant frequency can be set by adjusting the coil shape parameters and can be used for WPT by experiment. Finally, it is confirmed that a short end coil with a capacitor is superior to an open end coil because two resonant frequencies can be set independently.
To achieve higher power and high-efficiency drive for various motors, a new structure of Simple Variable Magnetic Flux Motor (SVMFM) is proposed. SVMFM can control the field magnetic flux automatically by itself according to the torque without any actuator. To confirm the effect on power and efficiency, a prototype motor was experimentally manufactured and evaluated. It is found that the prototype motor could excel in terms of power and efficiency compared with the existing SPM motor.
In applications involving high-speed drive or short-range movement, the effective performance of linear motors is assessed by evaluating transient states. However, there are fewer reported cases of performance evaluation methods for transient states, as compared to those for steady states. This study investigates a transient characteristic evaluation method for linear motors. We propose a method to quantify energy during acceleration and deceleration using the integral of input and output waveforms. The performance at the transient state is calculated by using control simulation and the FEM analysis. The evaluation results of the proposed method are reported. The validity of this method is verified through comparison between experimental and simulation results of energy loss.
In Japan, commercial grid for ordinary residential houses consists of a single-phase three-wire system. In general, unbalanced load power is supplied by the commercial grid. Recently, there have been an increasing number of houses equipped with the emergency power units in preparation for possible power outages. However, because most of the conventional power inverters in these units cannot supply unbalanced power, home appliances must be reconnected to dedicated outlets when they are used in the grid-disconnected operation. To solve such an inconvenient situation, we propose a method that enables the uninterruptible power supply between the grid-connected and grid-disconnected operations for single-phase three-wire systems. This control method is mounted on the power inverters and is called the virtual synchronous generator (VSG) control. The method is developed expanding the previous method for a single-phase two-wire system.