Shota Kondo

Position and velocity sensorless control of IPMSM using full-order observer based on extended electromotive force with a new observer design method

The reduced order observer (disturbance observer) based on the the extended electromotive force(eemf) model, which can be applied to the position and velocity sensorless control for all synchronous motors included IPMSMs(Interior Permanent Magnet Synchronous Motors), had been proposed by authors. However, the design of a full-order eemf observer is difficult, because the error equations of the observers become ones of the fourth order. Therefore, this paper proposes a design method of the full-order eemf observer whose objective is the robust position estimation against the velocity estimation error, using H∞ control theory. Moreover, a new design method of the more robust full-order eemf observer is proposed by restudying the error system of the observer, and the simulation and experimental results of the position and velocity sensorless control of IPMSM under the maximum torque per ampere(MTPA) show that a new design method of the full-order eemf observer is very useful.

Position and velocity sensorless control for synchronous reluctance motor at low speeds and under loaded conditions using high-frequency extended EMF observer and heterodyne detection

Recently, synchronous reluctance motors (SynRMs) have attracted study because of their favorable properties, including limited thermal expansion of the shaft due to low heat generation by the rotor, the ability to drive at high velocity, a low degree of torque ripple and an absence of demagnetization problems. Sensorless control of SynRMs is now desired, and several methods have been proposed. These methods, however, have difficulties at low speed when the voltage signal necessary to estimate rotor position is very small. This paper proposes a new rotor position estimation method using both a high-frequency extended e.m.f.(EEMF) disturbance observer and a heterodyne detection. In this paper, it is shown, experimentally, that it is possible to control the SynRMs at low speeds and under loaded conditions without the position and velocity sensor using the new proposed method.

Analysis of the GTPase motif of FlhF in the control of the number and location of polar flagella in Vibrio alginolyticus

Vibrio alginolyticus normally has a single polar flagellum whose number and placement are regulated positively by FlhF. FlhF is a GTPase and homolog of a signal recognition particle (SRP) protein called Ffh and SRP receptor FtsY. FlhF is located at the cell pole and directs formation of the flagellum. To study the mechanism of FlhF localization, we introduced random mutations into flhF by means of hydroxylamine and isolated mutants that could not generate the flagellum at the cell pole. The novel mutations were only mapped to the GTPase motif of FlhF. The mutant FlhF proteins showed reduced polar localization as compared to the wild type and still could associate with the membrane. These results support the assumption that the GTPase motif of FlhF plays a critical role in the polar localization of this protein during formation of the flagellum.

Position sensorless control of SynRM at low speeds by estimating high-frequency extended EMF using disturbance observer

Synchronous reluctance motors (SynRMs) have attracted attention as the motor which complement IMs and IPMSMs, etc., because SynRMs have no winding and magnet in the rotor. Position sensorless control at low speeds of SynRMs is now desired, and several methods have been proposed. This paper proposes a new position sensorless control method of SynRMs at low speeds by estimating a high-frequency extended e.m.f.(EEMF) caused by injecting a high-frequency current, by a disturbance observer on the stator frame. In this method, the frequency of the injecting high-frequency current is set to 200 Hz which is quite lower than a mechanical resonance frequency of the motor, to consider reduction in noise of the motor. The superimposed signal of thus low frequency influences the current control system driving the motor. Therefore, this paper proposes a new method for eliminating the superimposed signal by subtracting a reference value of the high-frequency current from the current fed back to the current controller. Finally, it is experimentally shown that the position sensorless control is capable, at low speeds and under load conditions, using the proposed method.

A design method of full-order flux observer for realization of both MTPA control and position sensorless control of IPMSM

A flux model, which is capable of both MTPA (Maximum Torque Per Ampere) control and position sensorless control of IPMSMs (Interior Permanent Magnet Synchronous Motors), has been proposed. This paper proposes that the flux is estimated using the full-order observer. And a design method for the full-order observer is also proposed. The design method of the full-order observer that robust flux estimation become possible against the velocity estimation error, by solving γ-positive real problem and H∞ control problem. In this paper, the experimental result of the position sensorless control of IPMSMs shows that a proposed design method of the full-order observer is very useful.

Biochemical analysis of GTPase FlhF which controls the number and position of flagellar formation in marine Vibrio

FlhF controls the number and position of the polar flagellar formation of Vibrio species. FlhF, is a paralog of FtsY, a GTPase acting in the Sec membrane transport system of bacteria, and localizes at the cell pole. Mutations in the conserved GTPase motif of FlhF lost polar localization capability and flagellar formation. Vibrio FlhF has not, until now, been purified as soluble protein. Here, we report that addition of MgCl2 and GTP or GDP at the step of cell lysis greatly improved the solubility of FlhF, allowing us to purify it in homogeneity. Purified FlhF showed GTPase activity only in the presence of FlhG. Of twelve FlhF GTPase motif mutants showing reduced function, eleven were recovered as precipitate after the cell disruption. The E440K substitution could be purified and showed no GTPase activity even in the presence of FlhG. Interestingly an FlhF substitution in the putative catalytic residue for GTP hydrolysis, R334A, allowed normal flagellar formation although GTPase activity of FlhF was completely abolished. Furthermore, size exclusion chromatography of purified FlhF revealed that it forms dimers in the presence of GTP but exists as monomer in the presence of GDP. We speculate that the GTP binding allows FlhF to dimerize and localize at the pole where it initiates flagellar formation, and the GDP-bound form diffuses as monomer.

Position sensorless control of synchronous reluctance motors at very low speeds region using high-frequency current control system

Synchronous reluctance motors (SynRMs) have attracted studies, because SynRMs have no magnets in the rotors. The position sensorless control at low speeds of SynRMs is now desired, and several methods have been proposed. In this paper, by using the high-frequency current control system, a new position sensorless control method of SynRMs at low speeds by superimposing high-frequency current whose amplitude is small constant value has been proposed. The experiments show that the proposed method is very useful even if the very low speeds region.

A study of design method of full-order observer based on extended electromotive force for position sensorless control of IPMSMs

Several position sensorless control methods of IPMSMs(Interior Permanent Magnet Synchronous Motors) using the observers have been proposed. In case of the full-order observers, these designs are difficult, because the order of the error equations of the observers becomes four. In this paper, for the position sensorless control of IPMSMs, a design method of the full-order observer based on the extended electromotive force (EEMF) is proposed. The experimental result shows that this design method of full-order observer is very useful.

Study of influence of inductance variation of position sensorless control of SynRM at low speeds by estimating high-frequency extended EMF caused by superimposed current

Synchronous reluctance motors (SynRMs) have attracted attention, because SynRMs have no magnets in the rotor. Position sensorless control at low speeds of SynRMs is now desired, and several methods have been proposed. The new position sensorless control method of SynRMs at low speeds by estimating a high-frequency extended e.m.f.(EEMF) caused by superimposed high-frequency current has been proposed by authors. The feature is that the amplitude of the superimposed high-frequency current is controlled to a small constant value. In this paper, the influence of inductance variation, which is large in the SynRMs, of the proposed position sensorless control method is investigated. And, in the proposed method, it is experimentally shown that the influence of the position estimation caused by the inductance variation is very small and the position sensorless control method is useful.