• Journal of the Korean Society for Precision Engineering
• /
• v.2 no.1
• /
• pp.72-81
• /
• 1985

This paper deals with the Z-8000 microprocessor based optimal controller problem of large rotating system. Control algorithm consists of Global Mode and Fine Mode. In Global Mode, motor is driven with maximum torque, while, in Fine Mode, the speed of response and overshoot improved by multi-gains. Friction term of the plant was measured in the 1-st test, jerking effect by the nonlinearity of friction was compensated in the 2-nd test and the 3-rd test was carried out to finalize the control system model. Test results show that the speed of response and overshoot are highly improved.

• 한국HCI학회:학술대회논문집
• /
• 2006.02a
• /
• pp.753-759
• /
• 2006

햅틱인터페이스 기술을 이용하면 가상물체의 형태를 만져보고 느껴볼 수 있다. 물체마다 다른 수학적 마찰력 모델을 적용하여 실감있는 마찰력 표현도 가능하다. 그러나 각 물체에 해당하는 마찰력 모델을 선정하는 것과 적절한 마찰계수 등을 반복적 실험을 통하여 알아내는 것은 쉽지 않다. 실제 물체의 마찰력이 알려진 마찰력 모델과 다르다면 수학적 모델로 표현할 수 없는 경우도 있다. 본 논문에서는 신경회로망 학습을 이용하여 마찰력 모델의 선택이나 마찰계수 등을 정하는 과정 없이 실제 물체의 마찰력을 표현하는 방법을 제시하고 있다. 상용 햅틱인터페이스 장치인 PHANToM 2 대를 이용하여 마찰력 획득 시스템을 구성하고 고무판, 종이 등의 물체 표면에서의 속도와 물체에 작용하는 힘을 획득하여 가공한 데이터를 입력 및 출력으로 갖는 신경회로망을 통해 학습시킨 후 OpenGL로 구현한 가상물체에 적용하여 보았다. Force/Torque 센서를 사용하지 못한 일부 문제가 있었으나 예상보다 사실적인 마찰력을 표현할 수 있었다.

• Proceedings of the KIPE Conference
• /
• 2016.07a
• /
• pp.253-254
• /
• 2016

This paper proposes a novel starting method of a high speed induction motor with air bearings for turbo blowers. The friction of air bearings varies according to rotating speed, operating temperature and usage time. Specially, friction torque at initial starting state under low bearing temperature usually results in starting failures of the conventional V/F control method. Therefore, this paper proposes a new starting method, which consists of an initial I/F control mode and smooth transition method to V/F control mode to overcome the starting failure. The experimental results are shown to verify the analysis and the usefulness of the proposed method.

• Transactions of Materials Processing
• /
• v.3 no.1
• /
• pp.63-83
• /
• 1994

In this paper, the slab method have been applied to investigate the strip casting process in which hot coil is produced from molten steel directly. In the twin roll strip casting process, molten steel supplied by the nozzle cools and solidifies due to the heat extraction effect of the rolls and hot rolling of the solidified shell takes place simultaneously. The analysis of hot rolling has been carried out by using the existing results of solidification analysis for the twin roll strip casting process. The current slab method provides basic design data such as roll separation force, rolling torque, rolling power as well as end dam separation force which are required to design strip caster. The effect of friction on the basic process parameters are investigated also. It is shown that the use of appropriate friction coefficient is important and that the characteristics of hot rolling in the twin-roll strip casting process is quite different from the conventional hot rolling processes.

• Korea-Australia Rheology Journal
• /
• v.13 no.2
• /
• pp.89-95
• /
• 2001

Effects of particulate size and frictional characteristics were examined on the melting behavior of PP(polypropylene) in a twin screw extruder. Powder and pellet types of PP were used and each component was blended with PE(polyethylene) wax and clay, respectively. It was observed that small size particulates, 1.e. powder systems exhibit accelerated melting behavior; and it was also found that the abrasive auditive acts as an effective agent for fast melting of PP powder. Retardation of melting due to the reduced friction was observed in both types of PP, contrary to the result found in a batch mixer. The tendency observed in variation of torque and exit temperature was explained in terms of frictional effect and length of compacted region formed during evolution of melting.

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.4
• /
• pp.329-337
• /
• 2015

In this paper, a simulation based estimation method of energy consumption of the spindle and feed drives for the NC machine tool during the cutting process is proposed. To predict energy consumption of the feed drive system, position, velocity, acceleration and jerk of the table are analyzed based on NC data and then the power and energy are calculated considering friction force and mass of the stages. Energy consumption of the spindle is estimated based on models from acceleration motion of rotating parts, friction torque and power loss of motors. Moreover, simulation models of cutting power and energy for the material removal along the NC tool paths are proposed.

• KSTLE International Journal
• /
• v.4 no.2
• /
• pp.43-46
• /
• 2003

Water-lubricated frictional characteristics of a stainless steel ball bearings are not well known compared to the oil-lubricated frictional characteristics. Furthermore a study on friction at a high temperature is rare because the bearing maintenance strategy for water-lubricated or chemicals-lubricated bearings of equipment is generally based on the replacement of the failed bearings-and parts. Ball bearings and ball screw are installed in the power transmission for the newly developing integral reactor and these are lubricated with chemically-controlled pure water at a high temperature and a high pressure. Bearings and power transmitting mechanical elements for an atomic reactor requires high reliability and high performance during the estimated lifetime, and it should be verified. In this paper, experimental research results of the frictional characteristics for water-lubricated ball bearings are presented as a preliminary investigation.

• 제어로봇시스템학회:학술대회논문집
• /
• 1994.10a
• /
• pp.553-557
• /
• 1994

We propose a design method that uses H$_{\infty}$ optimization method to suppress oscillation of a shaft between motor and load for high precision (0.001 % of reference input) position controls. PI speed control loop was introduced as a minor loop. Standard problem is used for the modeling of the system and Glover-Doyle's algorithm is used for the optimization in the H$_{\infty}$ space. Friction is considered to be an important factor that makes it difficult for the system to reach steady state in short time. In this paper, we propose a hybrid controller that includes PI speed feedback loop, which is expected to have a role to reject torque disturbance like friction.n.n.

• 제어로봇시스템학회:학술대회논문집
• /
• 1990.10a
• /
• pp.269-274
• /
• 1990

Usually, robot manipulators in production lines are operated with reperting work trajectories. This paper presents the repeated adaptive learning algorithm for robot manipulates for the case of a trajectory. This algorithm uses the nonlinear dynamic model including the repeated friction compensating term, The advantage of the scheme is that It allows friction compensation which may be otherwise difficult for differently constructed models. A secondary advantage of the sheme is that it can also adapt to torque calculation in order to reduce the computational load of the control computer. To show the efficiency of the proposed controller, a computer simulation is performed for the planar robot manipulator with a 2 degree of freedom.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1994.10a
• /
• pp.249-253
• /
• 1994

In machine tools, frictional force exists between the table and the bed, and in ballscrews. In this paper, feed motor current is used to measure the motor torque and frictional force. A hall sensor is used to measure the feed motor current. Some frictional pheonomina in feed drice systems, such as, the relationship between feedrate and frictional force, lubrication conditions and frictional force, and feed direction and frictional force, are obtained. Generally, the friction behavior is in good agreement with Stribeck's curve. However, the data shows significant scatter when feedrate is high.