Eunsoo Jung

A Nine-Phase Permanent-Magnet Motor Drive System for an Ultrahigh-Speed Elevator

This paper presents a nine-phase permanent-magnet synchronous motor (PMSM) drive system based on multiple three-phase voltage source inverters. The nine-phase PMSM was developed as a traction motor for an ultrahigh-speed elevator. The mathematical model of the motor was simplified through symmetry of the system. Using the simplified model, the drive system can be controlled by the well-known d-q control theory. The feasibility and validity of the drive system were experimentally demonstrated at the worlds tallest elevator test tower. Moreover, an additional experiment was performed to ensure the fault-tolerance capability of the system.

Gemigliptin improves renal function and attenuates podocyte injury in mice with diabetic nephropathy

Podocytes participate in the formation and regulation of the glomerular filtration barrier. Loss of podocytes occurs during the early stages of diabetic nephropathy and impairs glomerular filtration. Dipeptidyl peptidase-4 (DPP-4) inhibitors are widely used as anti-diabetic agents in clinical practice. In this study, we showed that gemigliptin, a novel DPP-4 inhibitor, reduced podocyte apoptosis in type 2 diabetic db/db mice without reducing hyperglycemia. Gemigliptin (100mg/kg/day) was administered orally for 12 weeks in db/db mice. Blood glucose levels and albuminuria were measured. The renal cortex was collected for histological examination, and molecular assays were used to detect 8-hydroxydeoxyguanosine, advanced oxidation protein products (AOPP), the receptor for advanced glycation end products (RAGE), and integrin-linked kinase (ILK). Type 2 diabetic db/db mice exhibited albuminuria, renal histopathological changes, and podocyte loss. Administration of gemigliptin to db/db mice suppressed albuminuria, enzyme activity and expression of DPP-4, and podocyte apoptosis. The effect of gemigliptin on diabetes-induced podocyte loss was associated with the suppression of oxidative damage, AOPP accumulation, RAGE expression, and ILK expression. These results indicate the possible benefits of using gemigliptin in diabetes patients to treat renal impairment without affecting glycemic control.

Application of a Disturbance Observer for a Relative Position Control System

This paper presents an application of a disturbance observer for a relative position control system. In this system, since the prefixed motion profile is not defined ex ante, the acceleration state which is generated based on the profile is also not available. Therefore, feedforward acceleration controls cannot be used, and the position control performance is restricted solely by the bandwidth of the position controller. To enhance the control performance, disturbance observers can be utilized actively. The proposed method considers the position reference just as the result of a disturbance. Therefore, the relative position control can be performed by a disturbance observer as well as a position controller. As a result, the position control performance of the proposed method has been enhanced by up to 30% compared with that of the conventional method. The feasibility of the proposed method has been verified by experimental results using a high-precision linear motion control system as well as by analysis based on Bode plots.

Implementation of Grid-connected Single-phase Inverter Based on FPGA

Exploiting the capability of an FPGA, a digital current controller of a single-phase inverter for grid interface is designed and implemented. A Proportional and Resonant (PR) controller realized in a parallel structure in the FPGA is used to reduce the harmonic current to ac grid. The harmonic compensators based on the PR controller are implemented up to the 19th order. The size of the LCL filter has been extremely reduced because the switching frequency is increased to 100 kHz. The validity of the FPGA based grid-connected single-phase inverter has been evaluated by experimental results.

Pharmacological profiles of gemigliptin (LC15-0444), a novel dipeptidyl peptidase-4 inhibitor, in vitro and in vivo

Gemigliptin, a novel dipeptidyl peptidase (DPP)-4 inhibitor, is approved for use as a monotherapy or in combination therapy to treat hyperglycemia in patients with type 2 diabetes mellitus. In this study, we investigated the pharmacological profiles of gemigliptin in vitro and in vivo and compared them to those of the other DPP-4 inhibitors. Gemigliptin was a reversible and competitive inhibitor with a Ki value of 7.25±0.67nM. Similar potency was shown in plasma from humans, rats, dogs, and monkeys. The kinetics of DPP-4 inhibition by gemigliptin was characterized by a fast association and a slow dissociation rate compared to sitagliptin (fast on and fast off rate) or vildagliptin (slow on and slow off rate). In addition, gemigliptin showed at least >23,000-fold selectivity for DPP-4 over various proteases and peptidases, including DPP-8, DPP-9, and fibroblast activation protein (FAP)-α. In the rat, dog, and monkey, gemigliptin showed more potent DPP-4 inhibitory activity in vivo compared with sitagliptin. In mice and dogs, gemigliptin prevented the degradation of active glucagon-like peptide-1 by DPP-4 inhibition, which improved glucose tolerance by increasing insulin secretion and reducing glucagon secretion during an oral glucose tolerance test. The long-term anti-hyperglycemic effect of gemigliptin was evaluated in diet-induced obese mice and high-fat diet/streptozotocin-induced diabetic mice. Gemigliptin dose-dependently decreased hemoglobin A1c (HbA1c) levels and ameliorated β-cell damage. In conclusion, gemigliptin is a potent, long-acting, and highly selective DPP-4 inhibitor and can be a safe and effective drug for the long-term treatment of type 2 diabetes.

Dual Observers for the Disturbance Rejection of a Motion Control System

The conventional motion control system simply consists of a PID position controller and a disturbance observer. The estimated speed from the observer has been used to control the speed as a feedback and the estimated disturbance force, which is a byproduct of the observer, has been used to reject the disturbance. However, in this case the disturbance rejection performance should be traded off with speed estimation performance. This paper explains this trade-off using Bode analysis and presents a dual observer system for the motion control application. The proposed method uses two observers, where one is dedicated to the speed estimation and the other to disturbance compensation. The disturbance rejection performance is enhanced by the custom tuned disturbance observer in the proposed method. The feasibility of the proposed method has been verified by the experimental results using a high precision linear motion control system as well as by the analysis based on Bode plot.

Nine-phase Permanent Magnet motor drive system for ultra high-speed elevator

In this paper, a 9-phase Permanent Magnet (PM) synchronous motor drive system based on multiple 3-phase conventional drive systems has been proposed. A 9-phase motor has been developed as a traction motor for a world record ultra high speed elevator. The simplified mathematical model, which can be incorporated with 3-phase current controller, has been derived. The feasibility and the validity of the proposed drive system have been demonstrated by experimental results of the scaled version of a prototype 9-phase motor.

FPGA-based motion controller with a high bandwidth current regulator

In this paper, a motion controller based on a Field Programmable Gate Array (FPGA) with a high performance current regulator is presented. This system contains a processor and a high bandwidth current regulator as a peripheral, and all of these are implemented on a single-chip FPGA. The execution time of the current regulator is less than 200 ns at 100 MHz clock frequency. Thanks to this fast execution, the inevitable digital delay, which is 1.5 times the sampling period in a PWM inverter has been reduced to a half of the sampling period. As the result, the control bandwidth of the current regulator has been extended up to about 3 kHz at 10 kHz PWM switching frequency. By exploiting the performance of the current regulator, the speed regulation bandwidth also enhanced up to 700 Hz. The experimental results are presented to demonstrate the validity of the proposed system and the performance of the regulator.

Gemigliptin, a novel dipeptidyl peptidase-4 inhibitor, exhibits potent anti-glycation properties in vitro and in vivo

This study evaluated the inhibitory effects of gemigliptin, a highly selective dipeptidyl peptidase-4 inhibitor, on the formation of advanced glycation end products (AGEs) and AGE cross-links with proteins in in vitro as well as in type 2 diabetic db/db mice. In in vitro assay, gemigliptin dose-dependently inhibited methylglyoxal-modified AGE-bovine serum albumin (BSA) formation (IC50=11.69 mM). AGE-collagen cross-linking assays showed that gemigliptin had a potent inhibitory effect (IC50=1.39 mM) on AGE-BSA cross-links to rat tail tendon collagen, and its activity was stronger than aminoguanidine (IC50=26.4 mM). In addition, gemigliptin directly trapped methylglyoxal in a concentration-dependent manner in vitro. To determine whether gemigliptin inhibits the in vivo glycation processes, gemigliptin (100 mg/kg/day) was orally administered into type 2 diabetic db/db mice for 12 weeks. Elevated serum levels of AGEs in db/db mice were suppressed by the administration of gemigliptin. These inhibitory effects of gemigliptin on the glycation process in both in vitro and in vivo suggest its therapeutic potential for ameliorating AGE-related diabetic complications.

Control of a Synchronous Motor With an Inverter Integrated Rotor

In this paper, a synchronous motor with an inverter integrated rotor (SMIIR) is introduced, and its control scheme is proposed. This presents a new breed of synchronous motor in that it integrates an inverter inside the rotor. The basic operational principle and control strategies are discussed. Given these new strategies, the SMIIR can be considered as a synchronous motor which changes its field according to the harmonic voltage of the stator inverter. The feasibility of the proposed structure of the drive system and its operation principle are evaluated through experimental results.