• Title/Summary/Keyword: Torque limit

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Evaluation of stability of interface between CCM (Co-Cr-Mo) UCLA abutment and external hex implant

  • Yoon, Ki-Joon;Park, Young-Bum;Choi, Hyunmin;Cho, Youngsung;Lee, Jae-Hoon;Lee, Keun-Woo
    • The Journal of Advanced Prosthodontics
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    • v.8 no.6
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    • pp.465-471
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    • 2016
  • PURPOSE. The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS. Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of $1.0{\times}10^6$cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS. Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION. Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.

Design and Analysis of Surface-Mounted PM Motor of Compressor for Electric Vehicles Applications according to Slot/Pole Combinations (전기자동차 압축기용 표면부착형 영구자석 전동기의 극/슬롯수 조합에 따른 특성해석 및 설계)

  • Choi, Jang-Young;Park, Hyung-Il;Jang, Seok-Myeong;Lee, Sung-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.10
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    • pp.1846-1857
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    • 2011
  • This paper deals with design and analysis of surface-mounted PM (SPM) motor for compressor of air-conditioning system for electric vehicle applications according to slot/pole combination. First, required torque-speed curve characteristics are determined from operating conditions of the compressor. Restricted conditions such as motor size limit and current density are also determined. And then, under same rated and restricted conditions, twelve models which have different slot/pole combinations each other are designed for various pole arc/pitch ratio using simple equations and 2-d finite element (FE) analyses. Designed models are analyzed and compared in terms of back-emf THD, cogging torque, torque ripple, power losses, efficiency, etc. On the basis of analysis results, it is found that the motor with a 6-pole PM rotor and a 27-slot stator has most outstanding performances in electromagnetic aspects. Finally, through the mechanical modal analysis and demagnetization analysis, it is concluded that the determined motor is most suitable for the compressor of air-conditioning system for electric vehicles.

Optimal Starting Torque Control of Wound Rotor Induction Motor by Microprocessor (개용분 PFN-PMW의 유전특성에 관한 연구)

  • Park, Min-Ho;Jung, So-Woong
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.33 no.8
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    • pp.316-324
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    • 1984
  • In the wound rotor induction motor, the external resistor is usually added to the rotor circuit in order to limit the starting current. In this scheme, whilst the starting current is limited, the available torque is remarkably reduced. In this paper, to improve the starting characteristics the stator current can be maintained constant by adjusting the external resistor. To change the external resistor, teh chopper and the resistor is connected in parallel, and the chopper duty cycle is adjusted by microprocessor. The duty cycle is calculated according to the actual speed of motor by microprocessor look-up table map. In this suggested scheme, the starting characteristics are remarkably improved without over-current. The starting time of this system is reduced by 20-48 Percent compared with fixed extemal resistance system in the same load.

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Optimal Redundant Actuation of Parallel Manipulators with High Operational Stiffness (고강성 병렬형 로봇의 최적 여유 구동)

  • Kim, Sung-Bok
    • Journal of Institute of Control, Robotics and Systems
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    • v.6 no.2
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    • pp.181-189
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    • 2000
  • This paper presents the optimal redundant actuation of parallel manipulators for complicated robotic applications such as cutting grinding drilling and digging that require a high degree of operational stiffness as well as the balance between force applicability and dexterity. First by taking into account the distribution(number and location) of active joints the statics and the operational stiffness of a redundant parallel manipulator are formulated and the effects of actuation redundancy are analyzed, Second for given task requirements including joint torque limit task force maximum allowable disturbance and maximum allowable deflection the task execution conditions of a redundant parallel manipulator are derived and the efficient testing formulas are provided. Third to achieve high operational stiffness while maintaining moderate dexterity the redundant actuation of a parallel manipulator is optimized which determines the optimal distribution of active joints and the optimal internal joint torque, Finally the simulation results for the optimal redundant actuation of a planar parallel manipulator are given.

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Hybrid Optimization Strategy using Response Surface Methodology and Genetic Algorithm for reducing Cogging Torque of SPM

  • Kim, Min-Jae;Lim, Jae-Won;Seo, Jang-Ho;Jung, Hyun-Kyo
    • Journal of Electrical Engineering and Technology
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    • v.6 no.2
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    • pp.202-207
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    • 2011
  • Numerous methodologies have been developed in an effort to reduce cogging torque. However, most of these methodologies have side effects that limit their applications. One approach is the optimization methodology that determines an optimized design variable within confined conditions. The response surface methodology (RSM) and the genetic algorithm (GA) are powerful instruments for such optimizations and are matters of common interest. However, they have some weaknesses. Generally, the RSM cannot accurately describe an object function, whereas the GA is time consuming. The current paper describes a novel GA and RSM hybrid algorithm that overcomes these limitations. The validity of the proposed algorithm was verified by three test functions. Its application was performed on a surface-mounted permanent magnet.

Maximum torque control of SynRM drive using ANN (ANN을 이용한 SynRM 드라이브의 최대토크 제어)

  • Ko, Jae-Sub;Park, Ki-Tae;Choi, Jung-Sik;Park, Byung-Sang;Chung, Dong-Hwa
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2007.05a
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    • pp.311-315
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    • 2007
  • In this paper, a new approach for the Synchronous Reluctance Motor control which ensures producing Maximum Torque per Ampere(MTPA) over the entire field weakening region is presented. In addition, This paper presents a speed sensorless control scheme of SynRM using artificial neural network. Also, by adjusting the base speed for the field weakening operation according to the flux level, the current and voltage limit, the smooth and precise transition into the field weakening operation can be achieved The proposed scheme is verified validity through simulation.

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Development of Human-Sized Biped Robot (인체형 이족 보행로봇의 개발)

  • 최형식;박용헌;이호식;김영식
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.15-18
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    • 2000
  • We developed a human-sized BWR(biped walking robot) driven by a new actuator based on the ball screw which has high strength and high gear ratio. The robot overcomes the limit of the driving torque of conventional BWRs. Each leg of the robot is composed of three pitch joints and one roll joint. In all, a 10 degree-of-freedom robot with two balancing joints was developed. The BWR was developed to walk autonomously such that it is actuated by small torque motors and is boarded with DC battery and controllers. In the performance test, the BWR performed nice motions of sitting-up and sitting-down. Through the test, we could find capability of high performance in biped-walking.

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Maximum Torque Operation of Interior Permanent Magnet Synchronous Motor in Flux-Weakening Control

  • Kim, Jan-Mok;Rhew, Hong-Woo;Kwon, Jung-Lock;Sul, Seung-Ki
    • Journal of Electrical Engineering and information Science
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    • v.3 no.1
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    • pp.103-109
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    • 1998
  • A new flux-weakening scheme for an Interior Permanent Magnet Synchronous Motor (IPMSM) is proposed. This control scheme enables the maximum torque operation for the fast acceleration in the constant power region according to the current and voltage limit condition. Especially the dynamic performance of the braking in the flux-weakening region is improved with the compensation of the stator resistance. Also since the onset of the flux weakening operation is adjusted according to the load conditions, the machine parameters, and whether motoring or braking region, the stable and precise transition operation into or out of the flux weakening region can be achieved. The effectiveness of the proposed scheme is verified through experiments with an IPMSM drive system.

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The Control of Flexible Beam using Nonlinear Compensator with Dual-Input Describing Function (쌍입력 기술함수를 갖는 비선형 보상기를 이용한 유연한 빔의 제어)

  • 권세현;이형기;최부귀
    • Journal of Institute of Control, Robotics and Systems
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    • v.4 no.5
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    • pp.644-650
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    • 1998
  • In this paper , a state space model for flexible beam is presented using the assumed-modes approach. The state space equation is derived for a flexible beam in which one end is connected to a motor and is driven by a torque equation and the other end is free. Many of the transfer function proposed thus far use the torque to the flexible beam as the input and the tip deflection of the flexible beam as the output. The Technique for the analysis and synthesis of the dual-input describing function(DIDF) is introduced here and the construction of a non-linear compensator, based on this technique, is proposed. This non-linear compensator, properly connected in the direct path of a closed-loop linear or non-linear control system. The above non-linear network is used to compensate linear and non-linear systems for instability, limit cycles, low speed of response and static accuracy. The effectiveness of the proposed scheme is demonstrated through computer simulation and experimental results.

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Off-line parameter Estimation of Induction Motors for Vector Control in Industrial Field (산업현장에서 벡터제어용 유도전동기의 오프라인 파라미터 추정)

  • 권병기;박가우;신원창;조응상;이진섭;최창호
    • Proceedings of the KIPE Conference
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    • 1998.07a
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    • pp.234-238
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    • 1998
  • Parameter estimation of induction motor for vector control presented in this paper can be easily implemented and applied to inverters in the industrial field, because it needs no additional hardware such as voltage sensor and measuring equipment. At first, the stator resistance including switching loss of inverter is measured by simple voltage-current equation. Next, in pre-magnetization of machine by imposing the d-axis constant field-current, q-axis torque current is forced to the machine until its speed feedback reachs to pre-defined level of speed limit. At this time, we can measure the rotor time-constant by decreasing the distorted output-voltage of inverter. At last, stator inductance, transient inductance, and moment of inertia can be measured by the relationship of output voltage, output torque and speed feedback. The validity and usufulness of this method is verified by experimental results.

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