• 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.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.159-161
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• 2003

Electrode movement signal has been widely used in resistance spot welding system This study is to compare accelerometer signal with gap sensor signal in servo gun system. This study propose that accelerometer output signal is a useful technique of quality monitoring in resistance welding processes.

• 대한의용생체공학회:의공학회지
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• 제20권3호
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• pp.315-321
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• 1999

본 논문에서는 근전도의 신호만으로 동적 운동시 근육에 발생하는 근력 예측을 위한 수학적 모델의 개발에 목표를 두고 있다. 이를 위하여 인체의 관절 운동중에 발생하는 근력과 근전도의 상관관계를 규명하는 것이 필요하기 때문에 동역학적 관절모델로서 수근관절을 포함한 주관절이 고려되었으며, 기구학 및 동역학 해석을 위하여 2개의 자유도를 갖는 Flexible Goniometer 로 관절의 각변위, 각속도, 가가속도등의 데이터를 실시간 측정하였다. 근전도 측정을 위해서는 비교적 신호가 뚜렷한 이두박근이 선정되었으며, 운동시 발생하는 이두박근의 근전도 신호는 표면전극을 이용한 다태널 Noraxon EMG 장치로 측정하였다. 결과로서, 근력과 근전도의 측정 시간에 따른 적분값의 비교는 1차 함수의 형태로 비례하는 상관관계로 표현됨을 알 수 있었으며, 동적인 운동시 발생하는 근수축을 동심 수축 구간( Concentric Contraction Period)과 편심 수축 구간(Eccentric Contraction Period)으로 양분하여 분석하였을 때도 근력과 근전도의 측정 시간에 따른 적분값의 비교는 1차 함수의 형태로 비례함을 알 수 있었다. 이 상관관계식을 이용하여 근전도 신호 측정을 통하여 관절에 작용하는 근육의 근력 예측이 가능함을 알 수 있었으며, 각기 다른 신체 부위의 관절에도 적용할 수 있는 가능성을 보여주고 있다.

• 센서학회지
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• 제28권3호
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• pp.198-204
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• 2019

In this study, we propose a wearable force sensor using 3D printed mold and liquid metal. Liquid metal, such as Galinstan, is one of the promising functional materials in stretchable electronics known for its intrinsic mechanical and electronic properties. The proposed soft force sensor measures the external force by the resistance change caused by the cross-sectional area change. Fused deposition modeling-based 3D printing is a simple and cost-effective fabrication of resilient elastomers using liquid metal. Using a 3D printed microchannel mold, 3D multichannel Galinstan microchannels were fabricated with a serpentine structure for signal stability because it is important to maintain the sensitivity of the sensor even in various mechanical deformations. We performed various electro-mechanical tests for performance characterization and verified the signal stability while stretching and bending. The proposed sensor exhibited good signal stability under 100% longitudinal strain, and the resistance change ranged within 5% of the initial value. We attached the proposed sensor on the finger joint and evaluated the signal change during various finger movements and the application of external forces.

• 한국산업정보학회논문지
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• 제21권4호
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• pp.43-53
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• 2016

본 논문에서는 선반가공에서 모터전류 신호를 이용하여 공구 파손을 감지하는 연구를 수행하였다. 본 연구에서는 먼저, 다양한 환경 변화에 대한 모터 전류 신호의 특성을 명확하게 파악하기 위해 신뢰성을 갖고 있는 절삭력과 모터전류 사이의 상관관계를 분석하였으며, 이를 기준으로 하여 공구파손시의 모터 전류 신호에 대해 분석하였다. 다양한 가공 실험을 통하여 절삭조건 변화에 따른 절삭력 신호와 주축 모터전류 신호의 정적 성분에 대한 상관관계를 분석하였다. 그 결과 절삭력과 모터전류 사이에 비례관계가 존재한다는 것을 알 수 있었으며, 이를 통해 모터 전류 신호만으로도 공구 파손을 감지 할 수 있을 것으로 판단하였다. 한편, 다양한 공구 파손 실험을 통해 절삭력과 모터전류 신호 사이에도 높은 상관관계가 존재함을 확인하였다. 이러한 공구파손 신호와 일반적인 선반가공의 가공신호를 분류하기 위해 본 논문에서는 새로운 방식의 감지 방법을 제시하였다. 제시한 분류 방법에 대해 여러 차례에 걸친 검증을 통해 공구파손 감지를 위한 모터 전류신호의 감지 신뢰성을 평가하였다.

• 대한기계학회논문집
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• 제17권8호
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• pp.1951-1962
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• 1993

The creation process of a typical machined surface is treated here as a dynamic system. An investigation is carried out to establish a relationship between the characteristics of cutting force fluctuations that cause vibration response of the tool-workpiece system and the formation of surface in face cutting by sintered carbide cutting tool. Cutting force is measured and analyzed in frequency domain. The power spectral densities of cutting force give a useful information in surface generation and it can be used to find out the control factor of surface roughness. The terms, PSD ratio & Normalized spindle frequency PSD, are defined and when the value of power in spindle frequency is absolutely little but relatively large, it is obtained high accuracy surface roughness. The aim of this research is to find surface profile by measured and analyzed cutting force signals. The simulation of surface generation gives the comprechension of its mechanism and help to predict and control the surface quality. In this study, it is suggested what informations about surface generation can be acquired from the cuttuing force signal and an way of generating a better surface.

• 대한기계학회논문집A
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• 제30권4호
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• pp.364-372
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• 2006

In this paper, we present a finger tip tactile sensor which can detect contact normal force as well as slip. The sensor is made up of two different materials, such as polyvinylidene fluoride (PVDF) known as piezoelectric polymer, and pressure variable resistor ink. In order to detect slip on the surface of the object, two PVDF strips are arranged along the normal direction in the robot finger tip and the thumb tip. The surface electrode of the PVDF strip is fabricated using silk-screening technique with silver paste. Also a thin flexible force sensor is fabricated in the form of a matrix using pressure variable resistor ink in order to sense the static force. The developed tactile sensor is physically flexible and it can be deformed three-dimensionally to any shape so that it can be placed on anywhere on the curved surface. In addition, a tactile sensing system is developed, which includes miniaturized charge amplifier to amplify the small signal from the sensor, and the fast signal processing unit. The sensor system is evaluated experimentally and its effectiveness is validated.

• 대한기계학회논문집A
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• 제31권11호
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• pp.1069-1076
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• 2007

This paper presents the road simulator control technology for reproducing the road input signal to implement the real road data. The simulator consists of the hydraulic pump, servo valve, hydraulic actuator and its control equipment. The QFT(Quantitative Feedback Theory) is utilized to control the simulator effectively. The control system illustrates a tracking performance of the closed-loop controller with low order transfer function G(s) and pre-filter F(s) for a parametric uncertain model. A force controller is designed to communicate the control signal between simulator and digital controller. Tracking specification is satisfied with upper and lower bound tolerances on the steep response of the system to the reference signal. The efficacy of the QFT force controller is verified through the numerical simulation, in which combined dynamics and actuation of the hydraulic servo system are tested. The simulation results show that the proposed control technique works well under uncertain hydraulic plant system. The conventional software (Labview) is used to make up for the real controller in the real-time basis, and the experimental works show that the proposed algorithm works well for a single road simulator.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 D
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• pp.1846-1847
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• 2006

In this study, we developed the real-time controller for control loading system (CLS) of aircraft simulator. The CLS is given the forces as inputs: the exerted force by a pilot, which is determined according to the position of the control stick, and the calculated force by the host computer. And then CLS makes the pilot feel the back loading force by supplying the motor drive with the actuator signal. The developed real-time controller for CLS is organized into the five parts which are the position sensing part including a encoder, the A/D converter part for the analog load cell signal, the communication interface part to communicate with the host, the D/A converter for the actuator signal, and the CPU DSP2812 to carry out a control algorithm. We constructed the test control loading system and carried out the experiment with the developed real-time controller. The experimental results showed that the real-time controller generates the back loading forces similar to the desired back loading force graph.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1808-1813
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• 2005

In this paper, we present the finger tip tactile sensor which can detect contact normal force as well as slip. The developed sensor is made of two different materials, such as polyvinylidene fluoride(PVDF) that is known as piezoelectric polymer and pressure variable resistor ink. In order to detect slip to surface of object, a PVDF strip is arranged along the normal direction in the robot finger tip and the thumb tip. The surface electrode of the PVDF strip is fabricated using silk-screening technique with silver paste. Also a thin flexible force sensor is fabricated in the form of a matrix using pressure variable resistor ink in order to sense the static force. The developed tactile sensor is physically flexible and it can be deformed three-dimensionally to any shape so that it can be placed on anywhere on the curved surface. In addition, we developed a tactile sensing system by miniaturizing the charge amplifier, in order to amplify the small signal from the sensor, and the fast signal processing unit. The sensor system is evaluated experimentally and its effectiveness is validated.