• Transactions of the Korean Society of Automotive Engineers
• /
• v.11 no.4
• /
• pp.165-172
• /
• 2003

This study aims to find frequency weighting curves for the evaluation of drivers' discomfort by vertical and rotational steering wheel vibration. Equal sensation curves, inverse of frequency weighting curves, were determined for the two kinds of vibrations respectively by using the sinusoidal signals with reference amplitudes from 0.2 to 0.4 m/s2 in the frequency range from 5 to 100 ㎐. Twelve subjects joined at the tests, and median values of the twelve judgments were used to determine the equal sensation curves. An experiment was followed to compare the relative sensation magnitude between the two kinds of equal sensation curves, which showed discomfort by the rotational vibration was 1.5 times of that by the vertical vibration at 50 ㎐.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.11
• /
• pp.1757-1763
• /
• 2010

Flywheel energy storage system (FESS) is defined as a high speed rotating flywheel system that can save surplus electric power. The FESS is proposed as an efficient energy storage system because it can accumulate a large amount of energy when it is operated at a high rotating speed and no mechanical problems are encountered. The FESS consists of a shaft, flywheel, motor/generator, bearings, and case. It is difficult to simulate rotor dynamics using common structure simulation programs because these programs are based on the 3D model and complex input rotating conditions. Therefore, in this paper, a program for the FESS based on the 2D FEM was developed. The 2D FEM can model easier than 3D, and it can present the multi-layer rotor with different material each other. Stiffness changing of the shaft caused by shrink fitting of the hub can be inputted to get clear solving results. The results obtained using the program were compared with those obtained using the common programs to determine any errors.

• Superconductivity and Cryogenics
• /
• v.8 no.2
• /
• pp.15-19
• /
• 2006

• Journal of Aerospace System Engineering
• /
• v.13 no.2
• /
• pp.26-33
• /
• 2019

Control moment gyro (CMG) employed as satellite actuators, generates a large torque through the steering of its gimbals. Although each gimbal holds a high-speed rotating wheel, the wheel imbalances induces disturbance and degrades the satellite control quality. Therefore, the disturbances ought to be detected and identified as a precaution against actuator faults. Among the method used in detecting disturbances is the state observers. In this paper, we apply a continuous second order sliding mode observer to detect single disturbances/faults in CMGs. Verification of the algorithm is also done on the hardware satellite simulator where four CMGs are installed.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.6
• /
• pp.58-65
• /
• 1999

The spinning machine has been developed for a bus and truck wheel disc which is manufactured by spinning process method. This machine has the mechanical structure with bed, 2-column, cross head, 2-vertical slide, 2-horizontal slide with forming roller, clamp slide and main spindle similar to large size vertical lathe. Main spindle attached the mandrel is rotated about 500rpm drived by 280kW power DC motor, and a rotating black material pressed on the mandrel with the clamp slide is spinformed by 2-forming rollers which are attached inner end of the 2-horizontal slides. The 2-vertical and 2-horizontal slides are actuated by the hydraulic cylinder which is controlled by the servo valve individially, and these servo valves are controlled by control signal of the CNC controller which is computed with position signal feedbacked from the encoder sensor. The developed machine can manufacture wheel disc of various section profile without mandrel change because section profile is easily modified using program editing in the CNC controller processor. The wheel disc manufactured by spinning process method has many advantages that the endurance is increased by 2 times and the weight is decreased by 30% compared with a conventional disc.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2011.01a
• /
• pp.279-280
• /
• 2011

2바퀴이상의 로봇은 중심점을 기준으로 안정화가 이루어진다. 그러나 2바퀴이하의 로봇으로 수직 자세를 유지하기 위해서는 로봇자체를 기울여 중심점을 이동하므로 수평을 유지할 수 있다. 그러나 이러한 중심점의 이동은 속도나 방향성분이 같이 출력되므로 정확한 센서의 계산이 요구되고 정밀한 제어를 필요로 한다. 또한 많은 구조물로 인해 장애물 인식 및 자율주행 알고리즘 등이 필요하며 장시간 정보획득과 무인기 연동을 위한 빠른 움직임을 가져야한다. 위의 2조건을 만족하기 위한 구성으로 최근들어 두 바퀴를 가지는 모바일 역진자 로봇에 대한 연구가 활발히 이루어지고 있다. 이는 서비스 및 주행 로봇의 알고리즘이 휴머노이드에서 모바일 역진자 로봇으로 변화되었기 때문이다. 모바일 역진자 로봇은 휴머노이드에 비하여 사용되는 모터의 수가 적고 균형을 잡으려면 관절마다 값비싼 고성능 모터가 필요하며 이를 가동하려면 전력도 많이 소모되며 대용량 배터리를 장착할 수밖에 없게 된다. 반면 바퀴로 움직이는 로봇은 전력이 적게 들고 이동도 쉽다. 따라서 본 연구에서는 IMU를 이용한 간단하면서도 정확한 센서의 연산 방법과 이를 이용한 자세제어 방법을 연구한다.

• Journal of Aerospace System Engineering
• /
• v.2 no.4
• /
• pp.25-30
• /
• 2008

In general, we utilize momentum wheel to control spacecraft. It needs vacuum test to analyze the effect of space environments. The conventional vacuum connector which is composed of steel has problems for test with built in momentum wheel because of weight, thermal expansion, etc. We suggest possibility to manufacture the vacuum connector using aluminum mount, epoxy and industrial D-Sub considering cost, weight. We verify the performance through vacuum test.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.23 no.11 s.170
• /
• pp.2033-2039
• /
• 1999

One of the main causes of severe wear or crack initiation in wheel and rail is the contact stress due to wheel-rail contact. In this paper, the shape design based on more reasonable contact stress analysis rather than a general Hertzian contact theory is investigated in order to reduce the contact stress. The optimal design is performed using the simple 2-D finite element model and its results are verified by 3-D finite element analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.11 no.2
• /
• pp.137-143
• /
• 2012

This study analyzes flywheel through the analyses of stress, fatigue and vibration. Maximum equivalent stress is 15.271MPa at the mid round shape and maximum deformation is 0.02264mm at the outer teeth. Among the cases of nonuniform fatigue loads, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of -$10^4$MPa and the amplitude stress of 1000 to 2900MPa, the possibility of maximum damage becomes 30%. This stress state can be 20 times greater than the damage possibility of 'SAE bracket history' or 'SAE transmission'. The range of natural frequencies becomes 200 to 820Hz and the values of these deformations are not more than 10mm. The structural result of this study can be effectively utilized with the design of flywheel by investigating prevention and durability against its damage.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.4 no.2
• /
• pp.7-20
• /
• 2007

TCU is a shift controller far automatic transmission of which major functions are to determine the shift point and manage the shifting process based on the various input signals. As the recent digital control technologies advance, it plays a key-role to improve a transmission performance and its algorithm becomes more complicated. This paper describes the development of transmission simulator fur wheel loader that enables a TCU for normal stand-alone operation by the real-time emulation of TCU interface signals. It can be utilized for the analysis of shift control algorithm implemented in a commercial TCU as well as for the development of brand new TCU.