Tomoo Fujii

DC-Brushless Servo System Without Rotor Position And Speed Sensor

A variable speed drive system is studied which consists of the inverter-fed permanent magnet field synchronous motor without a rotor position sensor and a rotating speed sensor. A method is explained, which determines the rotor position angles at a standstill or at rotating conditions and the speed at several conditions by measuring the instantaneous values of phase voltages and currents. The experimental results obtained by a prototype drive system without a rotor position and a speed sensor are compared with the those obtained by an ordinary DC brushless servo system with a rotor position sensor and a tachogenerator.

Effect of electrical energy on the electropermeabilization of yeast cells

Abstract A suspension of yeast cells (Saccharomyces cerevisiae) in NaCl solution was exposed to high voltage pulses under defined conditions. The results on perforation through the membrane and the cell wall structure (electropermeabilization) and the resealing process are presented. Capacitor discharges were applied to yeast cells in their logarithmic growth phase. A dye was added at a predetermined time after the electric pulse. Dyed and total (dyed plus undyed) yeast cells were counted microscopically and the rate was calculated. Dyed cells were assumed to have pores. For simplicity, the time constant of the electric circuit was adjusted so that it was almost the same for each capacitance by changing the conductivity of the yeast suspension. The capacitances used in the experiments were 1, 2, 4 and 8 μF yielding different initial field strengths. It was calculated that, under similar perforation and resealing conditions, almost the same energy was applied to the yeast suspension. Our conclusion is that the electrical energy is closely concerned with the electropermeabilization and resealing of the membrane and cell wall.

Effect of alternating magnetic field on the growth of the primary root of corn

Corn seeds each with a primary root were exposed to alternating magnetic fields. Locations of the root before and after exposure were accurately measured, and the growth during the exposure was calculated. These values were compared with those of the control group. Results indicate that the relatively low frequencies used in the experiments hastened the growth of the primary root while relatively high frequencies slowed root development. >

Re-examination of electropermeabilization on yeast cells: dependence on growth phase and ion concentration

Abstract By applying an electric pulse to yeast cell suspensions, we re-examined the dependence of electropermeabilization on the growth phase of the cells and the ion concentration. It was found that the growth phase and the ion concentration play a major role in determining the electropermeabilization yield.

Improved variable speed sensorless servo system by disturbance observer

An improved variable-speed sensorless servo system consisting of an inverter-fed permanent magnet field synchronous motor without any shaft-mounted sensors and with a disturbance torque observer is discussed. The sensorless servo system shows a tendency to become unstable by disturbance torques to the motor. A disturbance torque observer based on a digital signal processor was developed, and the motor current was compensated by the observed torque. Experimental results obtained by the prototype drive system with the disturbance torque observer are compared with those obtained by a sensorless servo system without the observer. These results predict the sufficient performance of the variable speed drive.<<ETX>>