• 한국정밀공학회지
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• 제16권3호통권96호
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• pp.38-46
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• 1999

Spindle motor current is used to estimate the cutting force indirectly and control the feed rate for the cutting force regulation. The proposed algorithm is implemented to a DSP board based hardware for the industrial application. The software to make POP terminal communicate with the DSP board and POP server is coded under Windows 95 environment. Experiments under varying cutting conditions show that the DSP board recognizes the information of installed cutting tool and cutting conditions delivered from the POP server to use them for the proper control of the feed rate. The cutting force is regulated well during machining of tapered or stepped workpiece and circular shaped workpiece as well.

• 대한기계학회논문집
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• 제18권1호
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• pp.113-120
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• 1994

The dynamic characteristics of turning processes are complex, non-linear and time-varying. Consequently, the conventional techniques based on crisp mathematical model may not guarantee cutting force regulation. This paper presents a fuzzy controller which can regulate cutting force in turning process under varying cutting conditions. The fuzzy control rules are extablished from operator experience and expert knowledge about the process dynamics. Regulation which increases productivity and tool life is achieved by adjusting feedrate according to the variation of cutting conditions. The performance of the proposed controller is evaluated by cutting experiments in the converted conventional lathe. The results of experiments show that the proposed fuzzy controller has a good cutting force regulation capability in spite of the variation of cutting conditions.

• 한국정밀공학회지
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• 제13권2호
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• pp.133-145
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• 1996

This paper presents an indirect cutting force measuring system, which uses the current signals from the AC servo drive units of the horizontal machining center, with its applications to the adaptive regulation of the cutting forces in various milling processes and to the on-line monitoring of tool breakage. A typical model for the feed-drive control system of a horizontal machining center is developed to analyze cutting force measurement from the drive motor. The pulsating milling forces can be measured indirectly within the bandwidth of the current feedback control loop of the feed-drive system. It is shown that the indirectly measured cutting force signals can be used in the adaptive controller for cutting force regulation. The whole scheme has been embedded in the commercial machining center and a series of cutting experiments on the face cutting processes are performed. The adaptive controller reveals reliable cutting force regulating capability against the various cutting conditions. It is also shown that the tool breakage in milling can be detected within one spindle revolution by adaptively filtering the current signals. The effect of the cutter run-out has been considered for the reliable on-line detection of tool breakage.

• 대한기계학회논문집A
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• 제25권8호
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• pp.1173-1182
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• 2001

Recent noticeable advances of CNC machine tools have considerably improved productivity and precision in manufacturing processes. However, in the respect of productivity some defects still remain because selection of machining conditions entirely depends on the experiences of programmers. Usually, machining conditions such as feed rate and spindle speed have been selected conservatively by considering the worst cases, and it has brought the loss of machining efficiency. Thus, the improvement of cutting force controller has been done to regulate cutting force constantly and to maximize feedrate simultaneously in case that machining conditions change variously. In this study, sliding mode control with boundary layer is applied to milling process for cutting force regulation and in a commercial CNC machining center data transfer between PC and PMC (programmable machine controller) of CNC machine is done using a standard interface method. And in the cutting force measurement, an indirect cutting force measuring system using current signal of AC servo is adopted in order not to use high-priced equipment like tool dynamometer. The purpose of this study is to maximize the productivity in milling process, thus its results can be applied to cases such as rough cutting process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.219-224
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• 2002

There are two important variables in machining process control, which are feed and cutting speed. In this work, a two degree-of-freedom controller is designed and implemented to achieve on-line cutting force control based on the modelling of cutting process dynamics which are established through step response test. Two schemes are proposed and implemented. The first is feed control under the constant spindle speed and spindle speed control under the constant fled speed. The second is a simultaneous control of feed and spindle speed. Those are confirmed to work properly. Especially the latter shows a faster response and we'll be evaluated to pare away workpiece by simultaneous control of position and cutting farce sooner or later.

• 한국정밀공학회지
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• 제10권4호
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• pp.73-80
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• 1993

There and two important variables in machining process control, which are feed and cutting speed. It is possible to improve the machining accuracy and the productivity by maintaining the optimal feed and cutting speed. In this work, a controller is designed to achieve on-line cutting force control based on the modeling of cutting process dynamics established through step response test. Two schemes are proposed and implemented. The first is feed control under the constant spindle speed and the second is spindle speed control under the constant feed. Finally, both are proved to work properly through simulation and experimentation.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.188-191
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• 2001

Generally, main factors of tool damage are cutting speed, feed rate and depth of cut. The increase of those factors can cause tool breakage or worsen product quality such as machining accuracy deterioration. Those three factors are concerned with cutting force. Cutting force reaches at its maximum value when cutter blade cuts away the object directly, and it is the time when tool damages are at high probability. In this study, we detect the maximum cutting force affecting tool damage and control the maximum cutting force based on the measured peak force.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.605-609
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• 1996

Continuous sliding mode control is applied to turning process for cutting force regulation. The highest feedrate compatible with the allowable cutting force is applied in rough cutting process such that maximum productivity is ensured and tool breakage is avoided. The programmed feedrate is overridden after the control algorithm is carried out. However, most CNC lathe manufacturers offer limited number of data bits far feedrate override, thus resulting in nonlinear behavior of the machine tools. Such nonlinearity brings “quantized” effect, and the optimal faedrate is rounded off before being fed into the CNC system. To compensate for this problem, continuous sliding mode control is applied. Conventional switching control law at a sliding surface is replaced by a smooth control interpolation in a selected boundary layer to avoid the excitation of high-frequency dynamics. Simulation results are presented in comparison with those obtained by applying adaptive control.

• 대한기계학회논문집
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• 제10권3호
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• pp.376-382
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• 1986

본 연구에서는 절삭과정의 정적특성에 관한 식과 그에 포함된 계수를 실험을 통하여 결정함으로써 절삭과정을 모델링하고, 절삭시에 검출되는 주절삭력에 따라 이 송속도를 제어하며 절삭과정의 변동에 관계없이 시스템의 안정을 보장하는 제어 프로 그램 및 제어장치를 개발하여 선삭작업에 응용하여 보고자 한다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.141-146
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• 2002

Real-time monitoring and control of the cutting force is essential for unmanned cutting process. Although the cutting force can be measured directly using tool dynamometers, their implementation is not feasible in industry due to high cost. Alternative approach is the cutting force estimation based on spindle drive models, but it requires the knowledge of their characteristics with the spindle speed variation. This paper investigates the power-factor and frictional characteristics of three-phase induction motors and determines its characteristics below and above the base speed, respectively. In order to realize the proposed cutting force monitoring system, a stand-alone DSP board was utilized. Its monitoring and control performance is evaluated in a CNC lathe.