• Journal of Electrical Engineering and information Science
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• v.3 no.2
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• pp.174-183
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• 1998

A simple and robust digital current control technique for a permanent magnet (PM) synchronous motor under the parameter variations is presented. Among the various current control schemes for an inverter-fed PM synchronous motor drive, the predictive control is known to give a superior performance. This scheme, however, requires the full knowledge of machine parameters and operating conditions, and cannot give a satisfactory response under the parameter mismatch. To overcome such a limitation, the disturbances caused by the parameter variations will be estimated by using a disturbance observer theory and used for the computation of the reference voltages by a feedforward control. Thus, the steady-state control performance can be significantly improved with a relatively simple control algorithm, while retaining the good characteristics of the predictive control. The proposed control scheme is implemented on a PM synchronous motor using the software of DSP TMS320C30 and the effectiveness is verified through the comparative simulations and experiments.

• Journal of Power Electronics
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• v.11 no.5
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• pp.713-718
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• 2011

This paper presents an online voltage disturbance estimator to achieve precise torque control of IPMSMs over a high speed operating region. The proposed design has a type of state-filter based on a Luenburger-style closed loop stator current vector observer. Utilizing the frequency response plot (FRF) approach, the estimation accuracy and the parameter sensitivities are analyzed. Accurate torque control and improved efficiency are provided with the decoupling of the effect of the parameter variations. The feasibility of the presented idea is verified by laboratory experiments.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.6
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• pp.426-433
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• 2016

This paper investigates the effects of operating conditions of an air classifier mill (ACM) on the particle sizes of PVC and rice hull. Based on the Box-Behnken matrix, the pulverization experiments were performed considering three operating factors: the air flow rate, the classifier speed and the mill speed. The response surface methodology was applied to identify the effects of the operating factors on the particle size. Results show that the particle sizes are governed by the linear variations of the operating factors. As less air is supplied and the mill rotates more slowly, the powder of both PVC and rice hull becomes finer. Furthermore, the classifier speed has a significant effect on the PVC powder but almost no effect on the rice hull powder. Thus, it is found that strong interactions exist between the material characteristics of a particle and the operating conditions of the ACM.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.476-479
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• 1997

A Knowledge of friction force in pneumatic cylinders makes it possible to improve cylinder description during simulation and to asses performance under changing operating conditions more accurately. Such knowledge is particularly useful, for example, when modeling continuous pneumatic positioning systems or predicting the operating conditions under which stick slip may occur, as well as in establishing preventive maintenance procedures for pneumatic cylinders. Friction force depends on a number of factors, including operating pressure, seal running speed on the cylinder barrel and rod, barrel material and surface roughness, seal dimensions and profile, seal material, lubrication conditions, cylinder distortion during assembly, and the operating temperature of cylinder components. This paper shows a system for measuring the friction force caused by a seal used in pneumatic cylinders. Results of experimental tests show that seal friction forces for grease lubricated service are clearly dependent on speed and pressure and are les sensitivity to other parameter. i.e., barrel material and roughness, seal material, and profile.

• Tribology and Lubricants
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• v.10 no.4
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• pp.33-42
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• 1994

An influence of inlet pressure on the performance of sector-shaped pad thrust bearings is investigated theoretically. The optimum conditions of film thickness or the optimum positions of pivot are found through the evaluation of load capacity for all available conditions of film thickness, under the operating conditions which the thermal and pad deformation effects can be neglected. The bearing performance including the inlet pressure effects is obtained for a wide operating ranges that inertia parameter(Re$^{*}$) is up to unity, and for the various cases of pad extent angle (number of pad) and the three cases of the angle between pads. The results show that the inlet pressure has a large influence on the performance of sector-shaped pad thrust bearings. In the design of sector-shaped pad bearings, due to the inlet pressure, the optimum number of pad is varied with the operating speed and the angle between pads, and the optimum position of pivot is located toward the leading edge along with the operating speed increases.

• Journal of Power Electronics
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• v.13 no.4
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• pp.729-736
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• 2013

Knowledge of a power semiconductor's operating temperature is important in circuit design and converter control. Designing appropriate circuitry that does not affect regular circuit operation during virtual junction temperature measurement at actual operating conditions is a demanding task for engineers. The proposed method enables virtual junction temperature estimation with a dedicated modified gate driver circuit based on real-time measurement of a semiconductor's quasi-threshold voltage. A simulation was conducted before the circuit was designed to verify the concept and to determine the basic properties and potential drawbacks of the proposed method.

• Journal of Power Electronics
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• v.17 no.2
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• pp.398-410
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• 2017

This work presents the design of a dual extended Kalman filter (EKF) as a state/parameter estimator suitable for adaptive state-of-charge (SoC) estimation of an automotive lithium-iron-phosphate ($LiFePO_4$) cell. The design of both estimators is based on an experimentally identified, lumped-parameter equivalent battery electrical circuit model. In the proposed estimation scheme, the parameter estimator has been used to adapt the SoC EKF-based estimator, which may be sensitive to nonlinear map errors of battery parameters. A suitable weighting scheme has also been proposed to achieve a smooth transition between the parameter estimator-based adaptation and internal model within the SoC estimator. The effectiveness of the proposed SoC and parameter estimators, as well as the combined dual estimator, has been verified through computer simulations on the developed battery model subject to New European Driving Cycle (NEDC) related operating regimes.

• Journal of the Korean Institute of Gas
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• v.7 no.4 s.21
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• pp.20-23
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• 2003

The analysis of reliabilities of process facilities often uses models based on the Weibull distribution. The parameters in these models are functions of operating conditions, and determined by experiments. Using these values, we calculate the reliability, mean time to failure, and standard deviation. The conventional method assumes that the operating condition is constant, and thus treats the model parameters as constants. In this paper, a reliability function is proposed which is applicable when the scale parameter is a function of time, and an analysis method based on this is also presented. A case study on a cooling fan resulted in a big difference from the conventional method to which the average operating conditions were applied. The proposed method is also applicable to other process facilities, and expected to effectively take into account the effects of changes in the operating conditions on the reliabilities of the facilities.

• Journal of the Korean Data and Information Science Society
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• v.20 no.5
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• pp.829-835
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• 2009

Parameter design is an approach to reducing performance variation of quality characteristic value in products and processes. Taguchi has used the signal-to-noise ratio to achieve the appropriate set of operating conditions where variability around target is low in the Taguchi parameter design. However, there are difficulties in practical application, such as complexity and nonlinear relationships among quality characteristics and control factors (design factors), and interactions occurred among control factors. Neural networks have a learning capability and model free characteristics. There characteristics support neural networks as a competitive tool in processing multivariable input-output implementation. In this paper we propose a substantially simpler optimization procedure for parameter design using neural network. An example is illustrated to compare the difference between the Taguchi method and neural network method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.472-483
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• 1997

An experimental facility consisting of two $3{\times}4.4{\times}3.8m$ rooms identical in construction is built. Each room has a control system and storage tank supplying hot water to the radiant floor heating system. The facility enables simultaneous comparision of two different control stratigies each implemented in a separate room. The operating performance of three kinds of flow control scheme is tested and compared in this study : (i) conventional on-off control based on feedback from room air temperature (ii) TPSC(two parameter switching control) (iii) TPOC(two parameter on-off control). Results show that TPSC and TPOC using room air and surface temperature sequentially as feedback signal to control hot water supply is the better temperature regulation scheme than conventional control based on feedback from only room air temperature. They are good candidates for the room with radiant floor heating system under continuous and intermittent heating mode.