This paper focuses on the high-precision contour-tracking control of an Ethernet-based networked motion control system (ENMCS) with short time-varying delays and repetitive tasks. The delays and the aperiodic exogenous disturbance are the main factors that deteriorate the tracking performance. An integrated control approach is devised, which consists of three parts: a disturbance observer for rejecting the delay and disturbance, an iterative learning controller for achieving perfect individual-axes tracking, and a cross-coupled controller for further improving the contour-tracking performance. In addition, a fuzzy regulator is proposed in the iteration domain to adjust the contour-controller gains so as to smooth iteration processes of individual axes. Comparative simulations and experiments are carried out to verify the feasibility and effectiveness of the approach.
This paper proposes a novel starting method for single-phase induction motors. Induction motors are unable to obtain sufficient starting torque with only a single-phase source. Therefore, the proposed method increases the starting torque by controlling the auxiliary-winding current with a triode for alternating current (TRIAC) and a very small microcontroller. The auxiliary winding is connected to the main windings via the TRIAC and a small capacitor. The intermittent TRIAC connections provide a pulse current series, i.e., half-cycle waveforms of the resonant current. The fundamental component of this current is sufficiently large and leads the main winding current; hence, a better two-phase current is realized. Thus, the proposed control achieves a large starting torque by utilizing only a small capacitor; it does not use any electrolytic capacitors. The effectiveness of the control is verified by theoretical and experimental methods. The proposed method obtained almost twice the starting torque of the conventional method, using the same capacitor.
This paper proposes a new inverter control method to reduce the input current harmonics and switching frequency of electrolytic capacitorless inverters for interior permanent magnet synchronous motor (IPMSM) drives. In an electrolytic capacitorless inverter system, the input current oscillates due to a resonance between the grid inductance and DC-link capacitor. Due to the oscillation in the input current caused by the LC resonance, the regulations for input current harmonics are sometimes not satisfied. The proposed method, which adopts a model predictive direct current control (MPDCC) method, reduces the switching frequency and satisfies the input current harmonics regulations IEC61000-3-2. MPDCC predicts the motor and input currents and evaluates them using a cost function to select a voltage vector. The cost function reduces the number of switching times and results in a current response that follows the current reference. The prediction model for input current is constructed using the state equations of the input LC resonance circuit and IPMSM. The effectiveness of the proposed method is confirmed experimentally. Further, the experimental results confirm that the proposed method satisfies the input current harmonics regulation IEC61000-3-2.
This paper proposes a method for improving the output voltage waveform of dual-inverter fed open-end winding induction motors in the low-speed region. The system consists of two isolated DC power supplies, an open-end winding induction motor, and two voltage source inverters, which are connected to the opposite terminals of the open-end winding with unequal DC-link voltages. The motor losses, which are caused by the harmonics of the voltage applied to the winding, increase when the inverter outputs a pulse-width modulated voltage at a low modulation index. The aim of this paper is to reduce the motor loss at low motor speeds by improving the winding voltage waveform. In the proposed control method, the use of the output voltage difference from the inverters constituting the dual-inverter lowers the peak voltage. In order to obtain the proposed waveform, a method for the space-vector pulse-width modulation of the dual-inverter is presented. Furthermore, this paper presents the commutation sequence of the PWM pattern considering the dead-time and switching device characteristics, especially the turn-off delay time. The proposed method is verified experimentally by driving a dual-inverter fed open-end winding induction motor. The experimental results confirm that the harmonic component of the output voltage, which is related to the switching frequency (5kHz), is reduced from 18.9V to 4.4V by using the proposed method at a motor speed of 300rpm and load torque of 1.43Nm.
This paper presents a modeling and tension controller design approach for web handling systems. In these systems, the web handling technology is a key component in the high-precision manufacturing of web products such as thin films and papers. However, periodic disturbances in the synchronization with the rotational frequencies of the roller deteriorate the tension control performance during web transportation. In this study, the web transportation system is modeled considering the motor control systems and web dynamics including viscoelasticity. Based on the constructed model, resonant filters are designed and used as an additional feedback compensator to shape the sensitivity characteristics for the disturbances. By using the compensator, the sensitivity gain of the tension control system can be reduced at specific frequencies, including the rotational frequencies of the rollers. The effectiveness of the designed tension controller is evaluated by conducting experiments using a prototype of the basic roll-to-roll web handling system.
In order to reduce the fluctuation in the power grid due to the power generated by renewable energy sources, a grid connected hybrid energy storage system, which combines lithium-ion batteries and ultra-capacitors is used. In this paper, a new high-efficiency charge/discharge control method for power division as well as stored energy balance is proposed. The battery bank, ultra-capacitor bank, and power converters are individually analyzed. The control method is based on the high efficiency voltage range (HEVR), which is a new method of determining the highest efficiency work-point of the energy storage systems. A 1kW scaled prototype is used to assess the performance of the proposed system. The experimental results show that the proposed system achieves a higher total efficiency than the conventional method, while being able to control the energy balance of the storage devices.
It is important to consider the environment for realizing stable contact motion, such as direct teaching for polishing motion including contact with environment. To realize stable contact motion without bouncing, the velocity and acceleration should be brought to zero after contact with the environment. This study focuses on the torque-velocity duality and a two-spring system is constructed using motor-side velocity control for a two-inertia system with environmental considerations. An equivalent resonance ratio control (ERRC) is proposed to suppress the vibrations in a two-spring system. This method achieves the same scheme as the resonance ratio control applied in position control. A force impulse control is applied based on the ERRC for stable contact motion without bouncing. Stable contact motion is realized in all numerical simulations and experiments.
Currently, multilevel inverters (MIs) are very popular in many industrial and renewable energy applications. Fast and accurate fault diagnosis is very important for improving their reliability. The present study proposes a fault diagnosis method based on the probabilistic principle component analysis (PPCA) and support vector machine (SVM) to control switches in single phase five-level voltage controlled cascaded H-Bridge MI (CHMI). The output voltage signals under different fault conditions of the CHMI are taken as fault features by using the phase-shift pulse width modulation technique. PPCA is used to optimize the data and reduce the dimension of the fault features. Finally, SVM classifier is used to diagnose the different fault modes. An experimental setup of CHMI is designed to validate the proposed fault diagnosis method. The simulation and experimental results show that by using PPCA-SVM, the accuracy of the fault location can be improved, and the time require for the fault diagnosis in CHMI can be reduced.
This work discusses the feasibility of series/parallel switching circuits with power MOSFETs to minimize the reduction in the output power of photovoltaic power systems due to the partial shading problems by connecting shaded panels and adjacent panels in parallel. The following observations were made on the basis of the experimental results: 1) When at least one of the photovoltaic panels is shaded, 50% of the reduction ratio of the solar radiation intensity becomes the lower limit of the threshold value for the series/parallel switching control. 2) The effect of the series/parallel switching control can be expected to be higher when more than two of the photovoltaic panels are shaded. However, the sum of the solar radiation intensities applied to the panels in the parallel circuit should be less than 150% of the maximum intensity of the photovoltaic power system. 3) The shaded panel, which should be connected to the adjacent panel in parallel, can be detected using bypass current measurements rather than direct measurements of the solar radiation intensity. The authors developed a prototype of a switching circuit module and performed the operation tests by using three photovoltaic panels. The results showed that the switching circuit module successfully detects the partial shading conditions and switches from the series operation mode to the parallel operation mode.
Hybrid circuit breakers are key components for high voltage DC transmission as they are the only way to avoid a complete shutdown of a DC grid in case of faults. In this paper, we focus on the design of a new hybrid circuit breaker with improved current injection, which allows fast and reliable arc extinction in the mechanical switch that conducts the line current under normal operation conditions. After presenting the turn-off procedure, the design of the switching modules and the optimization of the pulse circuit are shown. Additionally, a reliable control is presented, which adapts the pulse current to the line current and ensures successful current interruption.
This paper proposes a method to design the control system of a traction inverter for the purpose of an increase in regenerative brake power. In a DC-electrified railway system, it is possible to transmit more regenerative brake power to an accelerating train by maintaining a higher DC input voltage of the regenerating train. On the other hand, regenerative brake control of a traction motor according to the DC input voltage of a traction inverter is generally applied. With regard to the proportional gain of this control system, the higher gain contributes to an increase in the DC input voltage in regeneration. However, there is a possibility that the control system can become unstable by applying higher gain. Considering the trade-off between the energy saving effect and the stability, this paper proposes a method to design the maximum gain that keeps the traction circuit stable. At first, a linearized model for the proposed method which includes the model of the traction system, its control system and DC feeder circuit is introduced. Further, this paper reveals that the proposed method keeps the control system stable by using real scaled experiments.
In order to increasing the efficiency of axial gap motors, a motor was designed to achieve an efficiency of 98% based on the IE 5-11kW motor (motor efficiency of 96%). Based on the design, we created a prototype with ceramic housings, thinned coil conductors, and nanocrystalline materials for the stator core as real items to reduce losses. We verified its effect by evaluating the motor characteristics. As a result, it was confirmed that the prototype can achieve a motor efficiency of 98.3% at 3,000min-1 and 11kW rated driving. Moreover, in the temperature rise test, it was demonstrated that class B type (130°C) could be achieved.