IEEJ Journal of Industry Applications Vol. 6(2017) No. 3

This study investigates compensation methods for harmonic components to realize PMSM position sensorless control in inverter overmodulation drive. While applying PMSMs as traction motor motors in an EV or HEV, operating PMSM in inverter overmodulation drive is an effective method to widen high-speed drive region of PMSM and achieve fast torque response when voltage saturates because it enable to utilize 27% higher fundamental voltage as compared to linear drive. In addition, position sensorless control is regarded as an important technique for adding a fail-safe function and downsizing of the drive system. However, the harmonic components which are inevitably generated in inverter overmodulation drive have negative effects on closed current control and position estimation systems.

The key to realize position sensorless control in inverter overmodulation drive is an appropriate compensation for the harmonic components in the input voltage and input current of a the position estimator. There are several methods to achieve this, and differences in position estimation performance possibly exist among these methods.

In this study, the compensation methods for harmonic components in overmodulation drive are compared, and a suitable compensation method for sensorless control is investigated through an experiment.

This study proposes advanced torque control of permanent magnet synchronous motors (PMSMs) using a finite element analysis (FEA) based motor model with a real-time simulator. This model can simulate the behavior of an actual motor including nonlinear characteristics such as spatial harmonics and magnet saturations. Therefore, model-based control with an FEA based motor model is advantageous for motor control. This study aims to achieve advanced motor control and drive techniques. In this study, high performance torque control techniques for PMSMs are proposed. The proposed torque control is developed based on direct torque control with torque prediction. This method can achieve fast response and smooth torque production. Its effectiveness is verified through simulations and experiments.

Generally, standard direct torque control (DTC) does not require fine current responses from the current controller because the torque and flux of a DTC-based drive are controlled by a closed-loop system without current loops. It is often difficult for the standard DTC to achieve the desired current regulation and fine harmonic current disturbance suppression performancew. In order to overcome these problems, this paper proposes a new stationary reference frame position sensorless control system based on stator flux linkage estimation, and a new sinusoidal current tracking controller. In this paper, the current control performance of IPMSMs using the proposed sinusoidal current tracking controller is evaluated through numerical simulation and experiments. Finally, using the proposed sinusoidal current tracking controller, the effectiveness of the proposed stationary reference frame position sensorless control system with the stator flux control method is confirmed through experimental results.

This paper presents the design of an infinite-order disturbance observer (IFDOB) to suppress disturbances including a periodic disturbance. An IFDOB includes the dynamics of a periodic disturbance to suppress it. However, a conventional IFDOB finds it difficult to suppress disturbances in the low-frequency domain. In contrast, a disturbance observer (DOB) can suppress disturbances in the low-frequency domain, however, it has difficulty suppressing a periodic disturbance. Therefore, this paper proposes a designed IFDOB that can suppress both a periodic disturbance and low-frequency disturbances. The proposed method is constructed by designing parameter γ of an IFDOB considering sensitivity and complementary sensitivity functions. Simulations were conducted, and the validity of the proposed method in a practical system was confirmed by experiments using a multi-axis manipulator.

Unobservable oscillations of the controlled variable of sampled-data positioning control systems may degrade the performance and reliability of mechatronic products. For example, a control input in the sampled-data control system can easily excite transient vibrations of mechanical resonances around the sampling frequency. However, these vibrations are difficult to measure in the sampled-data control system. The degree to which these oscillations are unobservable or observable depends on the sampling frequency, oscillation frequency, and the initial phase of the oscillations. This paper shows the relationship between the sampling frequency, oscillation frequency, and the initial phase of the oscillations. As a result, two indexes of an unobservable position are proposed with maximum and root-mean-square amplitudes to estimate the effects of the unobservable oscillations of mechanical resonances in positioning control systems. These indexes show that the sampling frequency and number of samples of measurement data for estimating the unobservable magnitude of oscillations are important parameters that designers must choose carefully. To demonstrate the use of the proposed indexes, unobservable magnitudes of oscillations are analyzed for a head-positioning control system in a hard disk drive.

An insulated signal transmission system using a near-field resonant coupler was developed for providing driving signal transmission to control power switching devices. The resonant coupling in the near-field can reduce the unwanted leakage that prevents conventional wireless systems from being deployed inside the metal housing of the switching devices. The focus was on the parasitic capacitance of the resonant coupler because the capacitance needs to be reduced for suppression of the noise current caused by the switching devices. An equivalent circuit model of the resonant coupler was introduced to simulate the capacitance, and validated by showing agreement between the calculated value of 0.76pF and the measured value of 0.80pF. An insulated communication module configured with the resonant couplers and two transceivers on the PCB was fabricated. The module demonstrated the switching operation of 3.3kV-1200A insulated-gate bipolar transistors (IGBTs) without disturbances between the high-power switching IGBTs and RF transceivers.

In this study, we studied Lamb wave resonator driver circuit with inductive compensation of the internal capacitance to improve the frequency limit by the transition frequency f_T which is one of the important parameters of active components for deciding amplification and oscillation. Comparing with an SAW resonator, the Lamb-wave oscillator can provide highly stable frequency-temperature characteristics and smaller frequency deviation at the normal temperature. The inductive cancellation scheme of the internal capacitor of the CMOS inverter realizes oscillation over f_T.

Determining the torque distribution ratio for electric bicycles with independently driven front and rear wheels is important. Both wheels should be driven properly to ensure the safety of riders, and the slip ratio, which indicates the slip state, should be the same for both wheels. In this paper, a method to determine the torque distribution by making the slip ratios of both wheels equal is proposed. The validity of the proposed method is verified by simulations and experiments.

This paper presents theoretical formulae for circuit parameter design as design guidelines in a step-down rectifier in a power system connected to a 6.6-kV AC power grid, where a modular multilevel converter (MMC) is applied. In particular, this paper focuses on the design of heat sinks, capacitors, and arm inductors. In addition, the worst case for each component design is shown as the first step of the converter design. First, the formula for the ripple current in the electrolytic capacitor is derived in order to evaluate the capacitor lifetime. Second, the formulae for the semiconductor losses are clarified on the basis of the analysis of the arm current. Third, the formula for the ripple current in the arm inductor is derived on the basis of the ripple current model of a chopper circuit. Finally, all formulae are verified by experiments with a miniature model. It is confirmed that theoretical values from formulae agree with the measured values with the errors lower than 12%.

This paper proposes a method to improve the operationality of bilateral teleoperation systems under time varying delay. Operationality is an index of the smoothness of an operation and is a performance index of bilateral teleoperation systems. Deterioration of operationality is salient under time varying delay communication because it causes system vibration. Therefore, this paper presents a novel method to improve the operationality in bilateral teleoperation systems by introducing differential signal based data modulation. The data modulation method transmits the original signal and its derivative via the network to mostly eliminate the effect of varying components in the time delay on the received information. Compared with conventional methods, the proposed method improves the operationality of a system while maintaining its symmetric structure but not increasing the time delay. Two experiments were conducted to show the validity of the proposed method.