SUMMARYIn this paper, we propose a new mathematical model for synchronous motors and a sensorless control method based on it. To control permanent magnet synchronous motors, knowledge of rotor position and velocity are necessary. Heretofore, expensive sensors have been used to detect rotor position information. Although many sensorless control methods based on the electromotive force (EMF) have been developed for non-salient-pole permanent magnet motors, they cannot be applied for salient-pole motors without approximation because of complications in the mathematical model; this is turn may lead to problems of instability. To solve this problem, we propose an extended electromotive force model for synchronous motors. The proposed model has a simple structure, making position estimation possible without approximation. Experimental results show that the proposed model and method are valid.
Biodegradable
injectable polymer (IP) systems exhibiting temperature-responsive
sol-to-gel transitions between room temperature and body temperature
have the potential for use in biomedical applications. However, gelation
of such IP systems is a reversible process through physical cross-linking,
and the hydrogels thus formed are likely to revert to the sol state
under highly wet conditions after injection. In this study, a biodegradable
IP system exhibiting temperature-responsive irreversible sol-to-gel
transition by covalent bond formation was developed by simple mixing
of polymers. A triblock copolymer of poly(caprolactone-co-glycolic acid) and poly(ethylene glycol) (tri-PCG) and tri-PCG with
attached succinimide ester groups at both termini (tri-PCG-SA-OSu)
were prepared and mixed together with a water-soluble polyamine (typically
poly-l-lysine). The obtained IP formulation was in the sol
state after mixing, but exhibited a rapid sol-to-gel transition within
30 s upon increasing the temperature to 37 °C. Once formed, the
hydrogel did not revert to the sol state, even after cooling to 4
°C, because of the formation of covalent bonds upon transition.
The obtained hydrogel soaked in phosphate buffered saline (PBS) exhibited
a significantly longer duration time of the gel state. This IP system
exhibiting a rapid and irreversible sol-to-gel transition is convenient
for medical professionals and possesses great potential for use in
biomedical devices for clinical applications such as drug delivery
systems and antiadhesive materials.
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