When controlling a robot arm that includes flexible structures such as space manipulators, there occur problems such as vibration during operation and errors between commands and responses. As a result, it is difficult for operators to accurately move the manipulator, and hence precise work cannot be realised. Therefore, a control method is required to solve these problems. In this paper, a method is proposed to suppress the vibration of the flexible robot arm and enable high precision control by changing the apparent stiffness of the flexible structure based on the nominal stiffness design of the load side observer. Also, input shaping is considered to realise robust control. Simulation and experimental results of the position control of two mass resonant systems showed that the flexible structure induces vibration and that errors occur in the response. By adopting the proposed method, the above-mentioned problems are solved, and the effectiveness of the method is shown.
We developed a combined battery system using a “capacity-type” battery and a “power-type” battery for low-cost electric vehicles, which can prolong the battery life. In order to estimate the effect of the proposed combined battery system, an accurate degradation model of lithium ion batteries is needed. It is known that the main degradation factor of lithium ion batteries is the side reaction, which is the reason for the solid electrolyte interface. Usually, this degradation process of lithium ion batteries follows a square root of time law. However, in the case of some lithium ion batteries, this rule cannot be applied due to the fact that they degrade suddenly. We developed a degradation model for lithium ion batteries considering this sudden degradation, including the dissipation phenomena of the conduction path due to electrolyte dry-out. We simulated the life-extension effect of the combined battery system by using the developed degradation model and found that the “capacity-type” battery lifetime in the case of the combined battery system can be 1.65 times longer than that of the original “capacity-type only” battery system.
DC link voltage variable systems with DC/DC converter are used in hybrid electric vehicles for improving the power of the system by boosting the DC link voltage. Voltage feedback control using only proportional compensator has been proposed as a control method for the DC/DC converter. The control system can be easily designed, but there is a possibility that a steady-state error occurs in the DC link voltage. In this paper, a proportional integral compensator is proposed to eliminate the steady-state error of the DC link voltage in DC link voltage feedback controllers. In addition, when designing the gain of the compensator, the frequency band of the disturbance is considered. The proposed method is verified through experiments on the downsizing model.
To improve noise and vibration of Electric Power Steering (EPS) system, we focus on the reduction of the sixth-order radial force of an EPS motor by regulating its harmonic current. Because an EPS system is operated in a wide speed range, a reduction method is required to work even for dynamic motor speed. In this paper, we introduce our method and report its test result to show the reduction of sixth-order radial vibration of an EPS motor.
This paper proposes a position-sensorless control technique for switched reluctance generators. The proposed system applies voltage pulses to the two unexcited windings and observes the winding currents. The timing signals for commutating the inverter are obtained by comparing these currents. Almost no predetermined parameters are required for this system. In the experiments, the control method achieved appropriate generation operations under a transient condition in which the DC-link voltage was varied from 70V to 130V.
The theory for three types of power conversion is established. In a controlled rectifier circuit, the input poly-phase AC sources are switched and connected to the load one by one; thus, AC-DC conversion is established. This mechanism is referred to as power conversion by change of sources. On the other hand, in a DC-DC step-up chopper circuit, there is an interval when the input source supplies energy to a reactor and this reactor energy possessing its own direction is defined as electromagnetic momentum. After a switching action, in the next interval, the circuit begins to enclose the load and forms a current loop circulating through the source, reactor and load. Then, the electromagnetic momentum will force the current to flow into the load which is at a higher voltage than the source. The switch action will be repeated on and off, and the current loop will be changed accordingly; then, power conversion will be established and this mechanism is named as power conversion by change of loops. In addition, by using a four-quadrant switching device to change the source polarity, DC-AC conversion can be achieved, and this mechanism is defined as combined power conversion. Extensive discussions on the technical terms have also been undertaken, such as classification naming for the diode and the thyristor.
In the dynamic wireless power transfer (WPT) for electric vehicles, the series/series (S/S) compensated WPT circuit via magnetic resonance coupling is adopted to achieve high-efficiency and high-power transmission. However, when the magnetic field coupling between the primary side and secondary side coils is low, the primary side resonance capacitor can cause a breakdown. Therefore, the embedded equipment must be repaired. This paper proposes a method to adopt a capacitor-less coil that can self-resonate at 85kHz without external resonance capacitors on the primary side. This can result in reduced cost of the WPT system. A previous study stated that high-power transmission is impossible owing to high resistance; however, it was found that not only the skin and proximity effects but the dielectric increases the resistance. By considering these factors, the resistance was reduced, and the measurement results showed that the evaluated load power was 3kW class at 90% of transmission efficiency.
This paper proposes an energy storage system for the improvement of the amount of power generation in a photovoltaic generation system. The proposed system can be easily incorporated with an existing system because it must be connected to the input terminal of the power conditioning system. The proposed charging and discharging control method does not disturb the MPPT control of the PCS and maximum power point operation of the PV panel. The basic operation of the proposed control method is verified by experimental results. In addition, it is confirmed by experimental results using solar radiation data that the generated power amount improved by 14.2% owing to the continuous operation of the PCS. These results show that the proposed energy storage system can improve the power generation of an existing solar power generation system.
A 50-kW class three-phase photovoltaics (PV) inverter typically applies a transformerless circuit configuration due to its high efficiency and small volume/size. On the other hand, the conventional PV inverter may suffer from deterioration of solar panels due to a dc leakage current flowing through the stray capacitance of the solar panels. To solve this problem, this paper presents a transformerless three-phase PV inverter consisting of multiple bidirectional choppers, which prevents the dc leakage current by maintaining a negative PV array voltage with respect to the ground potential to a dc voltage that is zero or higher. In addition, the size/volume of an ac filter can be reduced by applying the so-called phase-shifted PWM to the inverter. In this paper, the operating principles and control method of the inverter are discussed and the validity of the control method is verified by performing computer simulation using the “PSCAD/EMTDC” software package and conducting experiments using a 150-V downscaled model.
Various studies have been conducted on photovoltaic (PV) power generation systems that focus either on a generation control circuit (GCC) to prevent power reduction due to a partial shade or on an active power decoupling method (APD) to reduce the power pulsation with twice the utility frequency. However, to the best of the authors' knowledge, only few studies have examined the PV power generation systems in which both the GCC and the APD functions are installed. In this paper, a novel PV power generation system equipped with both the GCC and the APD functions is proposed, and its fundamental operation is verified.
This letter shows that a coupled-inductor suppresses the output voltage ripple in the Cockcroft-Walton (CW) circuit. The coupled-inductor plays two roles: boost of the output voltage by resonance with the parasitic capacitance in the CW circuit and suppression of the output voltage ripple. First, the amplitude and phase of the output voltage ripple in the CW circuit are theoretically derived. Then, a design procedure for the coupled-inductor is shown. The experimental results demonstrate the effectiveness of the proposed method.
This letter proposes a single-phase full-bridge inverter with a capacitor embedded in a bus bar. In order to reduce the switching ripple flowing in the electrolytic capacitor, the proposed structure embeds a barium titanate (BaTiO3) ceramic capacitor in the bus bar. The experimental results verified the operation of the inverter circuit, rated 300V, 4.1A with a switching frequency of 100kHz.
We mainly study the modeling and design optimization of electric machinery based on computational electromagnetics. Recent years, we focus on topology optimization, application of deep leaning for design and fast computations using model order reduction and homogenization.