This paper describes a rotor speed estimation technique of an induction motor, which utilizes slot harmonics on the d-axis caused by permeance variation across the air gap. The frequency of the slot harmonics is a multiple of the actual rotor speed, and is proportional to the number of rotor slots. In order to extract the slot harmonics, a novel adaptive band-pass filter incorporating coordinate transformation is proposed, which is effective to estimate the rotor speed from 400 to 2000r/min. This rotor speed estimation is applied to a field-oriented controller as well as a speed controller. In addition, performance improvement is carried out by compensating a motor parameter mismatch. Feasibility of the proposed technique is confirmed through several tests, using a prototype experimental setup.
This paper proposes variable-speed wind generation system using the boost converter. The proposed system has three speed control modes for the wind velocity. The control mode of low wind velocity regulates the armature current of the generator with the boost converter to control the speed of wind turbine. The control mode of middle wind velocity regulates the DC link voltage with the vector controlled inverter to control the speed of wind turbine. The control mode of high wind velocity regulates the pitch angle of the wind turbine with the pitch angle control system to control the speed of wind turbine. The hybrid of three control modes extends the variable-speed range. The proposed system simplifies the maintenance and improves the reliability and reduces the cost in compare with the variable-speed wind generation system using PWM converter. This paper describes the control strategy and modeling for simulation using Matlab Simulink of the proposed system. Also this paper describes the control strategy and modeling of variable-speed wind generation system using PWM converter. The steady state and transient responses for wind velocity changes are simulated using the Matlab Simulink. This paper verifies the fundamental performance of the system using boost converter by discussing the simulation results of the both systems.
Novel modulation which consists of conventional space vector modulation (SVM) based on a virtual AC/DC/AC conversion and carrier signal modulation for matrix converters is proposed. In this proposed modulation, duties for the switching pattern decided by conventional SVM are changed into those for each switch of matrix converter. The new duties for each output phase are compared with the triangle carrier. By using proposed modulation, switchings between the input phase voltage with minimum value and the voltage with maximum value are eliminated. In this paper, the conventional SVM and proposed modulation are explained. Next, for both conventional and proposed modulations waveforms of input current, output voltage and output current and their frequency spectra are calculated by PSIM simulation program. Simulation results show the proposed modulation can reduce harmonics of output voltage waveforms.
This paper proposes a large-scale matrix converter system which connects two main circuits in parallel and in which the carriers operating each main circuit have a phase difference of 180 degrees. A matrix converter needs an LC filter, not only because it acts as a conventional filter which reduces high frequency ripples caused by the converter switching, but also because the capacitor of the LC filter acts as a virtual voltage source. Therefore, this filter must be connected at the input side. The proposed system uses a miniaturized LC filter because the harmonics of the current flowing into the LC filter contain only the even number harmonics of the carrier and the cut-off frequency of the LC filter can be raised. For example, when the cut-off frequency is doubled, the inductor or the capacitor of the LC filter can be reduced to 1/4. The principle of raising the filter current's frequency is verified theoretically using simulations. Furthermore, in the proposed system, the distortion of the output voltages become less than with a conventional single matrix converter, and the common mode voltage and the common mode current, which cause electromagnetic interference (EMI), can also be decreased.
This paper proposes a method for quantitative estimation of conducted emission from an inverter system, which helps the optimal design of EMI filters. The basic concept of the proposed method is the usage of a circuit simulator with detailed modeling of the components of the inverter system, i.e. passive devices, switching devices, and measurement instruments. The proposed method provides the conducted emission of the inverter in the form prescribed in CISPR 22, that is, the simulation results can be compared to the experiments directly. It is revealed that the simulation result agrees very well with the experiment with the error of ±6dB ranging from 150kHz to 5MHz. A great benefit from the proposed method is that the mode separation, differential and common, of the conducted emission becomes possible. Discussions and analyses are set forth in this paper with making full use of this benefit, which greatly makes the design of the EMI filter efficient.
We propose an electric energy storage system with batteries by a current source inverter. It is interconnected to the single-phase three-wire distribution system. In order to reduce the dc reactor capacity and change the discharging and the charging operations by signals, a set of DC-DC converters is added between the inverter and the batteries. In this paper, the proposed circuit configuration, the control scheme and the operating method are described, and then the discharging and the charging characteristics are discussed experimentally.
A robust servo system is important for performance improvement of motion control system in several industry applications. Generally, a high speed positioning servo system consists of robust control systems with integrator, such as PI controller. The industrial servo system always has the limitation for the capacity of actuator and power amplifier. An ordinary industrial position servo system often has the saturation of motor current and motor speed. It is difficult for the high speed positioning servo system to keep the robust position control against the saturation of motor current and motor speed. Because, an ordinary position servo system has the complicated control structure with many control loops. Hence, it sometimes has the large overshoot and the oscillated response by the limitation of motor current and motor speed. In order to overcome this problem, this paper proposes a new robust high speed positioning servo system considering the saturation of torque current and motor speed. The experimental results show that the proposed robust high speed positioning servo system the quick and stable position response for the saturation of motor current and motor speed.
Direct AC/AC converters have been investigated for miniaturization, high efficiency and harmonics reduction of mains current. These converters are classified into direct switch AC/AC converter (matrix converter) and PWM rectifier-inverter AC/AC converter in view of each circuit configuration. Firstly, this paper proposes averaged DC link voltage control of direct AC/AC converters, and details of the control method are described. In this method, averaged DC link voltage is derived from two selecting phase-to-phase mains voltages and the duty ratio of these selecting voltages for each modulation period. The averaged DC link voltage is used for the calculation of modulation index at each output phase. Secondly, this paper discusses a compensation method of output voltage error from commutation in case of applying the averaged DC link voltage control. Generally, the output voltage error occurs in direct AC/AC converters from commutation sequence consisting of two or four steps. And the compensation method reduces the error by analyzing commutation pattern created by the averaged DC link voltage control. Finally, experimental results are demonstrated, and it is confirmed that the harmonic distortion of the output current is efficiently reduced with the proposed compensation method.
This paper presents an analysis of steady and transient characteristics of the diode rectifier circuits with commutation capacitors for the three-phase rectangular-waveform distribution system. The commutation capacitors can improve the input total power factor, and reduce the ripple of the output voltage. From the analysis of the diode rectifier circuit, the authors also propose the design method of the input inductances, the commutation capacitors and the output smoothing capacitor. In order to verify the effectiveness of the proposed method, the experimental characteristics of the rectifier circuit have been shown.
In this paper, we propose a novel method for magnetic levitation force generation. In our method, we utilized three AC electromagnets that generate the inductive and AC Ampere forces. One electromagnet is installed above the surface and the other two in the both sides of a thin plate. Phase conditions providing the maximum levitation force are derived from 2-dimentional finite element analysis. In order to confirm the performance of the proposed method, we performed some experiments. The experimental results show that in difference from conventional AC methods, the magnetic levitation force is increased around 5.9 times for the same eddy current inside the aluminum plate. In addition, the relations between excitation frequency, plate thickness and total levitation force are explained in details.
Multilevel inverter circuit generates the stair-like voltage without using transformer and interphase reactor, and it is the circuit which realizes reduction in the harmonics and enlargement of the capacity. In addition, the application of the PWM control improves the waveform, and it reduces the switching component to the conventional half, and the filter capacity is reduced. In this paper, improvement on voltage utilization factor and feed-back control of output voltage are applied to multilevel inverter circuit. For the DC power supply with the intense fluctuation, it is necessary to construct inverter circuit which can supply stabilized AC voltage. One-chip microcomputer with various functions is used for the control equipment of this circuit, and miniaturization and cost reduction of the control equipment are realized. Here, control principle and experimental result of this equipment are mainly reported.
Conservation of the environment has become critical to the automotive industry. Recently, requirements for on-board diagnostic and engine control systems have been strictly enforced. In the present paper, in order to meet the requirements for a low-emissions vehicle, a novel construction method of the air-fuel ratio (A/F) control system is proposed. The construction method of the system is divided into two steps. The first step is to design the A/F control system for the engine based on an open loop design. The second step is to design the A/F control system for the catalyst system. The design method is based on the generalized predictive control in order to satisfy the robustness to open loop control as well as model uncertainty. The effectiveness of the proposed A/F control system is verified through experiments using full-scale products.
This paper discusses a 6.6-kV transformerless motor drive system based on the back-to-back connection of two five-level diode-clamped PWM converters. In addition, this paper designs, constructs and experimentally tests a down-scaled model rated at 200V and 5.5kW. This system consist of the two five-level converters, a common dc-link, and voltage-balancing circuits using two bi-directional buck-boost choppers. Experimental results obtained from the down-scaled model verify the validity of the system design, giving promise of the viability of the 6.6-kV transformerless motor drive system.
Thin-steel-plates are used in the space industry, the auto mobile industry, and so on. In the manufacturing process, generally the thin-steel-plates are conveyed with rollers. However problems, such as cracks, are arisen by contact friction. Then, the non-contact carrier system using the magnetic levitation system is proposed. The feedback control is indispensable to the stable levitation of the system. So, in order to make the continuous line for the conveyance, a lot of electromagnets and gap sensors are needed. It is necessary to solve the problems of the cost of the sensors and the collocation of the sensor with the corresponding magnet. Therefore, to eliminate the problems, the real-time vibration analysis technique using the Finite Element Method (FEM) is suggested. In this paper, we discuss the analysis technique in the one-dimensional model of the thin-steel-plate. First, finite-element expression of the vibrational motion equation of the thin-steel-plate is derived. Second, for the sensorless support control, controllability and observability of the system is secured, and the stability of the system is studied. Finally, sensorless support test is conducted.
A lot of researches about speed sensor-less vector control methods of the IM have been published and applied to practical systems. However, because of various errors caused by dead time, temperature variation of resistance and so on, the speed estimation error is inevitable in the practical applications. The inverter voltage control error is very sensitive to phase current near zero cross. Therefore, the speed estimation becomes unstable when the phase current zero cross and the zero frequency condition occur simultaneously. In order to solve these problems, this paper proposes a novel method to reduce the inverter voltage control error. The phase current references are forbidden to stay near zero, where the voltage control error is very sensitive to the phase current. The phase current non-zero control causes the harmonics which influences the speed estimation. The harmonics is compensated appropriately by a novel method, which cancels the harmonic component in the input signals to the speed estimator. The experimental results with phase current non-zero control showed good performance in low speed range.
In optical-disc drives (ODDs), disturbances can be roughly classified in two groups: external disturbances and defects. The first group requires a higher closed loop bandwidth than the second group. If the closed loop has a high bandwidth the controller may have a good performance against external disturbances but it might follow the defects of the disc surface. In order to make ODDs more robust against surface defects, a new control method for compensating the defects has been developed. The developed control method can estimate the plant state. The feedforward control input, which can transfer the estimated state to zero, is systematically generated by using a final-state control (FSC) method. The simulation results show that the developed control method can significantly improve the robustness against the defects.
A fast-settling control method for the fine actuator system in an optical disc drive has been developed. The fast-settling control is performed by two-degree-of-freedom control, which uses the reference trajectory. The reference trajectory according to the initial state at mode switching between seeking and settling is determined by using a final-state control. Tests with a 16x DVD-ROM drive experimentally confirm that the proposed settling control significantly improves the settling capability.
This paper proposes a new induction heating technology capable of controlling a precise exothermic distribution, which is named as “zone-control induction heating (ZCIH)." The ZCIH system consists of two or more sets of a high-frequency inverter unit and a work coil. The inverter units control the phase angle of the coil current to be in phase with each other. The ZCIH has capability of operation with the mutual inductance, and enables to locate the coils as close as possible. As a result, the ZCIH technology makes it possible to achieve rapid heating performance with extremely precise exothermic distribution. This paper presents experimental results of a 150-kW six-zone ZCIH system for semiconductor heat processing.
The 3-dimensional magnetic field in magnetic shield is analyzed by a proposed magnetic field calculation method of equivalent B-H method (a kind of homogenization method) for thin steel plate. When the proposed equivalent B-H method is applied to a full-scale size magnetic shield room (length is 5.8m, width is 3.3m, height is 3.3m), the measured leakage magnetic flux density distribution is in good agreement with the calculated leakage magnetic flux density distribution. The equivalent B-H method has such superior property such as taking into account for magnetic saturation and magnetic anisotropy and no numerical calculation to obtain the equivalent B-H characteristics of equivalent element, because the magnetic characteristics of an equivalent element are introduced from the magnetic characteristics of the ferromagnetic materials by analytical equations in an assumption that the equivalent element continues frequently in 3-dimensional space boundlessly.
New method to estimate electromagnetic screening effect of rigid frame viaducts has been developed. Mutual relationship among the effects of electrical connecting manner of girding bridges; conductivity of the ground; and harmonic frequency was identified theoretically and numerically based on the results of multiple conductor circuit model simulations and field measurements using over 3km length test cables set on a viaduct section of Shinkansen line under construction. Adding, developed modeling method to simplify the equivalent circuit of vast amount of steel bars in the reinforced concrete accelerates the estimation process with enough accuracy. As the result, it became easy to calculate the induced voltage in the cables or in the track circuits with enough accuracy.
Although equipments that support physical therapy have been developed, there are few types of equipment to improve quality of physical therapy. This paper proposes a new concept of robotic biofeedback exercise equipment that displays human muscle force during training. The concept tries to have therapeutic value through grasping of condition for trainee during exercise and giving an incentive to perform training. The equipment is not only for convalescent patients but also for athletes and healthy persons with a physical trouble. The manipulator is designed to support lower limb rehabilitation of knee and hip joints in sagittal plane, where a 3-degrees-of-freedom manipulator is adopted in order to realize low height equipment. Since the manipulator has redundant degree of freedom, collision avoidance is performed by a controller based on acceleration control by disturbance observer. Moreover, simultaneous isokinetic movement for knee and hip joints that has an adjustment capability of maximum speed and time constant is realized in order to perform safe training by isokinetic muscular contraction. Desired motion is realized experimentally by the proposed manipulator.
Because of various errors caused by dead time, temperature variation of resistance and so on, the speed estimation error is inevitable in the speed sensor-less vector control methods of the induction motor. Especially, the speed control loop becomes unstable at near zero frequency. In order to solve these problems, this paper proposes a novel design of an adaptive observer for the speed estimation. Adding a feedback loop of the error between the estimated and reference fluxes, the sensitivity of the current error signals for the speed estimation and the primary resistance identification are improved. The proposed system is analyzed and the appropriate feedback gains are derived. The experimental results showed good performance in low speed range.
This paper investigates and proposes new system structures for vector control of permanent-magnet synchronous motors (PMSMs) with core loss. The proposed vector control systems have the following versatile features. (a) The systems employ the structures allowing control of the stator current through control of the load current. (b) The systems employ unique “stator voltage feedback-use” structures in order to accomplish simply the load current control. (c) The produced torque is directly related to the load current, and the precise torque control can be attained through the load current control. (d) The relation between produced torque and the load current is nonlinear for salient-pole PMSMs similarly to the case of no core loss, and a variety of the load current commands can be selected from viewpoints of minimum loss and/or wide speed range drives. The system structures add no constraints to the selection of the load current commands. (e) In addition to the torque control, the speed control can be allowed, where linearity between output of the speed controller and produced torque is kept. The validity of versatile features is verified through the numerical experiments.
This paper proposes a new compensation method that can efficiently compensate errors appearing in the phase estimate by the high-frequency voltage injection methods for sensorless drives of permanent-magnet synchronous motors. In the proposed method, the phase estimate is supposed to be determined by high-frequency components of stator current in the rotational reference frame aiming to be in phase with the rotor phase.