• 한국정밀공학회지
• /
• 제28권2호
• /
• pp.168-175
• /
• 2011

Contouring accuracy of CNC machine tools is very important for high-speed and high-precision machining. In particular, large contour error may occur during corner tracking. In order to reduce the corner contouring error, acceleration and deceleration control or tool-path planning methods have been suggested. However, they do not directly control the corner contouring error. In the meantime, network servo systems are widely used because of their easiness of building and cost effectiveness. Communication latency between the master controller and servo drives, however, may deteriorate contouring accuracy especially during corner tracking. This paper proposes a control strategy that can accurately calculate and directly control the corner contouring error. A prediction control is combined with the above control to cope with communication latency. The proposed control method is evaluated through computer simulation and experiments. The results show its validity and usefulness.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.1162-1165
• /
• 2003

Contouring errors are important especially for high speed and precision machining. Since the contouring errors of a machine tool affect the error of a machined part directly, it is necessary to find the contouring errors by some relevant tests. In this study, contouring errors are obtained by performing circular tests with a grid plate. Various error sources are diagnosed by a least square method.

• 한국정밀공학회지
• /
• 제20권11호
• /
• pp.166-170
• /
• 2003

Contouring errors are important especially for high speed and precision machining. In this study, contouring errors along contours having inflection points are studied. When a table of a machine tool moves along a circular path, acceleration acts toward the center of the circle. Thus, at inflection points, acceleration as well as inertia force changes its direction abruptly. The effect of inertia force on the contouring error is investigated in this study. It is found that the contouring error at an inflection point is proportional to the acceleration. This result can be useful in determining contouring errors along general paths.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1996년도 춘계학술대회 논문집
• /
• pp.466-471
• /
• 1996

This work is concerned with the development of digital contouring controller formulti-axial servosystems. Digital optimal contouring controller is proposed to coordinate each of the controllers of multiple feed drives and specifically improve the controuring performance. The optimal control formulation includes the contour error explicity in the performance index to be minimized. The contouring control is exercised for straight line and circular contours. Substantial improvement in contouring perfomance is obtained for a range of contouring conditions. Both steady state and transient error measures have been considered. The simulation study presented has estiblished the potential of the proposed controller to improve contourning perfomance.

• 한국공작기계학회논문집
• /
• 제15권6호
• /
• pp.105-113
• /
• 2006

This work is concerned with the development of digital contouring controller for multi-axial servosystems. Digital optimal contouring controller is proposed to coordinate each of the controllers of multiple feed drives and specifically improve the contouring performance. The optimal control formation includes the contour error explicitly in the performance index to be minimized. The contouring control is exercised for straight line and circular contours. Substantial improvement in contouring performance is obtained for a range of contouring conditions. Both steady state and transient error measures have been considered. The simulation study presented has established the potential of the proposed controller to improve contouring performance.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.1003-1006
• /
• 2002

In machining free-form curves with a machine tool equipped with parallel device, improving contouring accuracy is very important. In this paper, we present contouring control algorithm far parallel machine tool. The relation between the error in Joint space and the error in catesian space is evaluated, and we estimate contouring error vector which efficiently determines the variable gains for the cross coupled control. To show the validity of the algorithm, the contouring control is simulated for free form contour trajectory in cubic parallel machine tool model.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
• /
• pp.186-188
• /
• 1995

In this paper, Cross-Coupled Controller proposed for multi axes servo system. Tracking error and contouring error exist when a machine tool moves along the trajectory in multi exes system. The proposed scheme enhances the contouring performance by reducing contour error. Feedforward compensator reduces the effects of a nonlinear disturbance such as friction or dead zone. The proposed control scheme reduces the contour error which occured when the tool tracks the reference trajectory. Simulation results show that this scheme improves the contouring performance along the reference trajectory in XY-table.

• 한국공작기계학회논문집
• /
• 제14권6호
• /
• pp.1-7
• /
• 2005

This paper deals with the position control for a feed drive system in CNC milling machine. The study shows that reduction in tacking error does not necessarily increase contouring accuracy, and proposes that a proper control scheme is able to exhibit the optimal tracking and contouring accuracy. The proposed scheme is to fix the parameter of the contouring control, and to find the optimal value of the parameter of the tracking control, which is automatically tuned. The effectiveness of the proposed scheme is confirmed through simulations.

• 한국지능시스템학회논문지
• /
• 제7권5호
• /
• pp.1-7
• /
• 1997

CNC공작기계의 두 서보축을 대상으로 가공 정밀도를 향상시키기 위한 신경망 윤과제어 알고리즘을 제안한다. 이 연구에서는 두 축 상호간에 미치는 영향을 신경망의 학습 능력을 이용하여 보상하고자 한다. 윤곽제어를 위해서는 매 샘플링 주기마다 윤곽오차를 계산하여하나, 윤곽오차는 직선경로를 이동하는 경우 쉽게 계산가능하나 원호, 인볼루트곡선등 비선형 경로를 가공하는 경우에는 정확하게 계산하기 힘들다. 먼저 이 논문에서는 임의의 비선형 곡선경로에 대하여도 윤곽오차를 정확히 구해낼 수 있는 새로운 윤곽오차 모델링 방법을 제안다. 또한 이러한 윤곽오차에 대한 항을 포함하는 성능지수를 정의하고, 신경망 윤곽제어를 위한 온라인 학습법칙을 유도한다. 이러한 신경망윤곽제어기의 사용으로 시스템이 비선형 특성을 가지거나 외부 환경이 변화하는 경우에도 좋은 윤곽제어 성능을 유지할 수 있다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.271-274
• /
• 2001

The present paper deals with the development of digital contouring controller for multiaxial servosystem. Instead of coordinating the commands to the individual feed drives and implementing closed position loop control for each axis, this work is achieved by the evaluation of a optimal cross-couple compensator aimed specifically at improving contouring accuracy in multi-axial feed drives. The optimal control formulation explicitly includes the contour error in the performance index to be minimized. The contouring control is simulated for straight line. The results show that the proposed controller reduces contouring errors considerably, as compared to the conventional uncoupled control for biaxial systems.