A space vector modulation (SVM) technique of a dual-inverter system for an open-end winding motor drive is described in this paper, where one inverter has a battery power source and the other has an only capacitor across the dc bus. The SVM must be achieved to operate the motor with field-oriented control and simultaneously to control the capacitor voltage at a constant value by using redundant switching states of the dual-inverter system. The control of the capacitor voltage is carried out by selecting a charging or a discharging mode in each redundant switching state, taking the instantaneous motor power factor into account. In addition, it is also required to reduce the error voltage pulses, which are generated in output multilevel voltage waveforms during the dead time. The compensation method of the existing dead-time scheme and the improved SVM sequence to reduce the error voltage vectors are proposed in this paper. The proposed methods are examined through several experimental tests and are confirmed to generate superior output voltage waveforms from the viewpoint of the measured total harmonic distortion and dv/dt.
SUMMARYMost robots moving autonomously are equipped with batteries as an energy source. Since the energy stored in the batteries is proportional to their volume, the operating time is drastically reduced as the robot is miniaturized. To resolve this problem, it is necessary to supply energy externally. Considering the checking of pipes in electric power generating stations as the target, a microrobot has been developed that autonomously moves inside the pipe with energy supplied by microwaves. A previous report [1] noted the problems that the energy could not be supplied when the robot is rotated and that the power supply method was not suitable for the sensor circuit, since the driving waveform of the actuator was produced by amplitude modulation of the microwaves. In the present paper, a method is proposed to allow the supplying of energy with circular polarization by means of four rectennas. Autonomous reversing motion is successfully achieved by installing a driver control circuit and an infrared sensor on the robot. The microrobot proposed in this paper moves at 10 mm/s, using a power of 200 mW supplied in a pipe with a diameter of 15 mm.
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