In this study, we evaluated the pleasantness or unpleasantness experienced by human beings depending on the intensity of sound; using the nasal skin temperature that was determined using thermograms obtained from an infrared thermograph. Many studies have been carried out on the influence of sound intensity on human beings. However, the effect of sound has not been evaluated on the basis of facial skin temperature. We evaluated the experienced with variations in changes in the pleasure or displeasure noise; this was evaluated on the basis of facial skin temperature, electroencephalogram, and heart rate variability. The experimental results showed that the effect of variations in the sound intensity on the changes in the pleasure or displeasure experienced by human beings can be quantitatively evaluated on the basis of facial skin temperature.
In this paper, we discuss the characteristics of input current vector control of a matrix converter with a generator as the input. The line impedance is higher than the impedance of the power grid, and the resonance between the synchronous reactance of the generator and the input capacitance results in instability behavior operation of the matrix converter. Input current stability control was proposed by the authors as a solution to this problem. However, the efficiency of the generator decreased when conventional control was employed at a light load. By using the proposed method, we can achieve a stable input current by employing proportional-integral-derivative (PID) control and optimize the input power factor according to the pole position of the generator. The validity of the proposed control strategy was confirmed by performing experiments. The proposed control achieves stable operations at an RL load, and a THD of 2.8% is obtained for the input current.
In this paper, we propose novel mathematical models of magnetic fluxes φd and φq for permanent magnet synchronous motors. The models can be used to approximate magnetic characteristics using simple fractional equations by taking magnetic saturation and cross-coupling effects into account. They include only eight constants and some of the constants represent the degree of magnetic saturation and cross-coupling. Because the functions used in our models are low-order functions, they can be transformed into inverse functions. Therefore, a motor model in which saturation characteristics are taken into consideration can be constructed using our models, and it can be used to approximate motor torque accurately. In addition, the introduction of a normalization method facilitates a comparison of motor characteristics that is independent of motor power and size. The normalized constants in our models can function as indices that help to evaluate the saturation characteristics.
Diamagnetic graphite (Pyrolytic graphite: PG) plate carries out passive magnetic levitation above high magnetic field without cooling down. By applying this phenomenon, the authors designed a contact-free two dimensional micro positioning model using PG plate and two dimensional (2D) Halbach permanent magnet (PM) array. In this model, the PG plate motion is performed with change in the surrounding magnetic field, which is provided by approaching a small PM piece. And as far as its keeping position, it does not require supplying electrical power. Recently, precise micro motion control of PG plate above 2D Halbach PM array was realized. For nano-scale precise motion control, currently, improving magnetic stiffness of PG plate has performed. This paper presents the result of improvement of magnetic stiffness and more precise motion of PG plate.
A well-known problem encountered while using method for the detection of DC-bus current in order to reconstruct three-phase-currents is the short DC pulse duration. In order to increase the pulse duration, several PWM modifying methods have been proposed. “Half Pulse Shift method (HPS)“ is one of the promising methods that are both robust to detection error caused by current ripple and offer the advantage of low acoustic noise. In general, common-mode noise current affects DC-bus current and causes detection error, therefore, pulse duration increased by using the PWM modifying method is longer than the decay time of the common-mode noise. This decay time is dependent on the electrical environment, especially on the power -supply cable from the inverter to the motor. Although the pulse duration required to avoid common-mode noise can be estimated, this pulse duration is limited by the controllable range of output voltages. In this paper, a new PWM modifying method in order to ease the limit of the pulse duration is proposed. The results of numerical analysis confirmed that by using the proposed method the operation area over which current can detected is broadened. From the experimental results, it is confirmed that the proposed method guarantees stable operation and robustness for noisy environments.
This paper describes a simplified sensorless vector control based on the average DC bus current for PMSM. This method can be used to design a drive control system at a relatively low cost because the microcontroller does not require a precise timer and the calculation load is slight. In the proposed method, one of the two possible current estimation processes is chosen according to the operation mode. First, the controller estimates d-axis current and identifies the back-EMF parameter in the synchronous operation mode at low speeds. The error in the back-EMF identification affects the efficiency of the proposed system, so it needs to be zero. Second, the controller estimates q-axis current in vector control mode. The identified parameter and q-axis current define voltage reference to realize high efficiency drive. The obtained experimental results confirm the effectiveness of the proposed method.
PM motor drive systems are widely used for industrial drives. However, PM motors basically produce the torque ripple due to the fluctuation of the magnetic field distribution. Dead time of the inverter, offset of sensors and current measurement errors lead to the torque ripple, too. The torque ripple leads vibration noises. In this paper, we proposed a torque ripple suppression method based on perfect tracking control, in which the torque ripple is measured by a low-bandwidth sensor. Finally, we show the advantages of the proposed method by simulations and experiments with a SPMSM.
In recent times, the decrease in the number of experienced engineers has become a serious problem. One of the solutions for this problem is to develop a training system which robots assist people to acquire the necessary skills. For developing training system, the extraction and quantitative assessment of information on an engineer's motion is required. In particular, force information is important, especially for a contact motion. Thus, quantitative assessment of the force information is necessary. In this study, a “haptic pen” is used to obtain the exerted writing pressures as force information. Next, the most universal motion from among a number of motions of the engineer is selected and the degree of coincidence of the motion with the most universal motion is determined. The concept of “eigen-universality” is introduced to assess motion, which is of the same type and performed by the same person. To quantitatively evaluate the eigen-universality, graph theory and the coefficient of correlation are used. Moreover, using the coefficient of correlation to obtain “universality” helps us to analyze the degree of coincidence between the most general motion and another motion. The validity of the proposed method is confirmed by experiments.
A linearization method is proposed for controlling the start-up operation of a rotating induction motor. The dynamics of this motor are deteriorated when the starting operation is carried out at high frequencies. In this method, the characteristics of the method are analyzed to reveal that the aforementioned problem is caused by the low equivalent gain of the induced voltage during the rotor flux establishment. A method to compensate for the angle of the rotor-flux-induced voltage vector is proposed to overcome this problem. The proposed method is experimentally verified by a test set, and the influence of changes in the rotor resistance is analyzed.
Nonlinear friction, resonant vibration modes, in addition to dead time of a positioning mechanism deteriorate the control performance in the microscopic displacement range. A control scheme composed of two types of control methodology is proposed in this paper in order to obtain high speed and high precision positioning of a ball-screw-driven mechanism: a feedforward compensator, based on coprime factorization of the positioning mechanism with dead time compensator, and a feedback compensator, an auto-tuned PDFLC (Proportional plus Derivative Fuzzy Logic Controller) based on real coded genetic algorithm as an optimization technique, with nonlinear friction compensation by using inverse model-based disturbance observer. Experimental results verified the effectiveness and robustness of the proposed control system against the difference of the nonlinear friction accompanied with the repetitive motion.
This paper describes a method for discriminating of the human forearm motions based on the myoelectric signals using an adaptive fuzzy inference system. In conventional studies, the neural network is often used to estimate motion intention by the myoelectric signals and realizes the high discrimination precision. On the other hand, this study uses the fuzzy inference for a human forearm motion discrimination based on the myoelectric signals. This study designs the membership function and the fuzzy rules using the average value and the standard deviation of the root mean square of the myoelectric potential for every channel of each motion. In addition, the characteristics of the myoelectric potential gradually change as a result of the muscle fatigue. Therefore, the motion discrimination should be performed by taking muscle fatigue into consideration. This study proposes a method to redesign the fuzzy inference system such that dynamic change of the myoelectric potential because of the muscle fatigue will be taken into account. Some experiments carried out using a myoelectric hand simulator show the effectiveness of the proposed motion discrimination method.
A fuel cell/electric double layer capacitor hybrid power source using a multi-port bidirectional DC-DC converter has been developed to reduce load variations for the purpose of extending fuel cell life. The proposed converter operates to maintain the fuel cell current, load voltage and bus voltage at constant values with a digital signal processor. The effect of the proposed converter is evaluated. The charging or discharging current of the EDLC rapidly changes along with step loading, and the voltage and current of the fuel cell are maintained at the constant values. Short-time transient responses show that the fuel cell current ripples 0.35 A at 1 A load change in 6 ms.