캡슐내시경의 조직샘플 채취기능 연구

공경철(Kyoungchul Kong),차진훈(Jinhoon Cha),전도영(Doyoung Jeon),조동일(Dong-il Dan Cho) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

Recently the technology of capsule endoscopy has been developed dramatically and many researchers are making efforts to combine surgical function into the capsule endoscope. In this paper, the micro biopsy device which is a part of the capsule endoscope is proposed. The proposed device consists of a trigger with paraffin block, rotational tissue-cutting razor with a torsion spring, and controller. They are designed to operate sequentially so that the tissue sampling, sealing, and fixing are achieved in one operation. It becomes possible for the capsule endoscope to get sample tissue inside the small intestine which can not be reached by a conventional biopsy device. Experiments were performed with the small intestine of a cow and rabbit. In conclusion, the tissue samples of 1.0㎜ long were extracted successfully by the proposed biopsy device of the capsule endoscope.

와이어 구동방식 외골격 보조기의 제어 연구

공경철(Kyoungchul Kong),전도영(Doyoung Jeon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

Recently the active power assistive equipments have been widely developed to help the human body motion. But for the elderly people and the patients, some limits exist due to the weight and volume of the equipments. In this paper, a tendon-driven exoskeletal power assistive suit and a caster walker are considered to solve these problems. Since the caster walker carries the burdens such as actuators and controllers, the weight and volume of the exoskeletal assistive suit are minimized. The required joint torques are estimated from a human body model and subjected to the torque feedback algorithm. Experiments were performed with a normal person and the performance is compared by the magnitude of the EMG. With the proposed equipment, the required muscle power for sitting up and down has reduced up to 40%.

와이어 구동방식의 새로운 외골격 보조기 설계 연구

공경철(Kyoungchul Kong),전도영(Doyoung Jeon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

This paper proposes a tendon-driven exoskeletal power assistive device to reduce the problem of the existing exoskeletal power assistive equipment. In addition, this paper suggests a caster walker, which can be moved by pushing, in order to carry heavy peripheral devices and maintain stable balance of the user at the same time. A muscle fiber expansion signal is used to control this proposed tendon-driven exoskeletal assistive device in order to compensate for the delay time of a motor and perform an easy assistance by sensing the user's action in advance. The muscle fiber expansion signal has the characteristics that the signal is ahead of the action and in proportion to joint torque.

복합가공기용 리니어 모터 시스템의 제어 연구

공경철(Kyoungchul Kong),전도영(Doyoung Jeon) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월

Though the technology on the ultra-precise machining has been developed intensively, the high speed and high precision for large machining range is still very hard to achieve. The linear motor system for the universal machining center is proper for high speed and high precision, but it has drawback of sensitivity to disturbance. In this research, two degrees of freedom controller based on the zero phase error tracking controller (ZPETC) and disturbance observer are proposed to improve the tracking performance and dynamic stiffness of linear motor system. The proposed controller is verified in simulations and experiments on a nano-positioner system, and the experimental result shows that the tracking performance improved. In addition, the PID optimization method is proposed for the commercialized controller such as the PMAC based system. The tracking as well as impedance is included in the cost function of optimization.

가변 전압기와 역기전력 차동방식을 이용한 센서리스 BLDC 전동기 드라이버 설계

이명석,공경철,Lee, Myoungseok,Kong, Kyoungchul 제어로봇시스템학회 2015 제어·로봇·시스템학회 논문지 Vol.21 No.10

A sensorless motor control scheme with conventional back-Electro Motive Force (EMF) sensing based on zero crossing point (ZCP) detection has been widely used in various applications. However, there are several problems with the conventional method for effectively driving sensorless brushless motors. For example, a phase mismatch of 30 degrees occurs between the ZCP and commutation time. Additionally, most of the motor speed/current controls are achieved based on a pulse width modulation (PWM) method, which generates significant noise that distracts the back-EMF sensing. Due to the PWM switching, the ZCP is not deterministic, and thus the efficiency of the motor is reduced because the phase transition points become uncertain. Moreover, the motor driving performance is degraded at a low speed range due to the effect of PWM noise. To solve these problems, an improved back-EMF detection method based on a differential line method is proposed in this paper. In addition, the proposed sensorless BLDC driver addresses the problems by using a variable voltage driver generated from a buck converter. The variable voltage driver does not generate the PWM switching noise. Consequently, the proposed sensorless motor driver improves 1) the signal-to-noise ratio of back-EMF, 2) the operation range of a BLDC motor, and 3) the torque characteristics. The proposed sensorless motor driver is verified through simulations and experiments.

전동기 시스템의 미지외란 및 전류 관측기 설계

이명석,정경모,공경철,Lee, Myoungseok,Jung, Kyungmo,Kong, Kyoungchul 제어로봇시스템학회 2015 제어·로봇·시스템학회 논문지 Vol.21 No.7

DOB (Disturbance Observer) is an useful control method for estimating the disturbance applied to dynamic systems. Disturbance observer can be used to implement a robust control system to generate a control input for rejecting the disturbance, and it can be also used to estimate the disturbance to obtain information. The system that uses disturbance estimation is investigated for high performance control such as automatic door systems, walking robot and electric power steering system in vehicles. In this paper, a novel disturbance observer which is called disturbance and current observer for estimating load torque in the motor system is proposed. The difference between the DOB for disturbance rejection and DCOB is mathematically verified. Current and angular velocity are required for estimating the load torque of the motor in DOB. However, the DCOB can estimate load torque and current without current sensor. DCOB is designed based on modeling of the motor system. Appropriate Q-filter is selected and the applicability of DCOB is verified by simulation. The estimated disturbance and current of the electric motor can be verified without current sensor, as experiments of the actual motor system.

시변 상보필터와 보행상태 추정을 이용한 경골의 기울어짐 각도추정

송석기,우한승,공경철,Song, Seok-ki,Woo, Hanseung,Kong, Kyoungchul 제어로봇시스템학회 2015 제어·로봇·시스템학회 논문지 Vol.21 No.10

Recent studies on ankle-foot prostheses used for transtibial amputees have focused on the adaptation of the ankle angle of the prosthesis according to ground conditions. For adaptation to various ground conditions (e.g., incline, decline, and step conditions), ankle-foot prostheses should first recognize the ground conditions as well as the current human motion pattern. For this purpose, the ground reaction forces and orientation angle of the tibia provide fundamental information. The measurement of the orientation angle, however, creates a challenge in practice. Although various sensors, such as accelerometers and gyroscopes, can be utilized to measure the orientation angles of the prosthesis, none of these sensors can be solely used due to their intrinsic drawbacks. In this paper, a time-varying complementary filtering (TVCF) method is proposed to incorporate the measurements from an accelerometer and a gyroscope to obtain a precise orientation angle. The cut-off frequency of TVCF is adaptively determined according to the human gait phase detected by a fuzzy logic algorithm. The performance of the proposed method is verified through experiments.

고효율 BLDC 전동기를 위한 진상각 보상 드라이버 설계

이명석(Myougseok Lee),공경철(Kyoungchul Kong) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

Due to the inductance of the three-phase brushless direct-current (BLDC) motor windings, the magnetic flux of a rotor and that of a stator are not generated at the same time, which causes a phase delay in energizing phases. Subsequently, the efficiency of the BLDC motor at a high speed tends to be decreased remarkably. In this paper, a phase advance angle compensation (PAAC) driver with an incremental encoder is proposed for improving efficiency of a BLDC motor. The PAAC driver is designed by a customized circuit and an incremental encoder in order to control real-time according to angular velocity of the motor. The proposed motor driver system is verified by experimental results in terms of efficiency of the motor at the high speed range.

정밀 정찰을 목적으로 하는 4족 보행 로봇을 위한 머리모듈 진동저감 메커니즘 설계 연구

서영식(Yeongsik Seo),공경철(Kyoungchul Kong) 제어로봇시스템학회 2017 제어·로봇·시스템학회 논문지 Vol.23 No.12

Quadruped robots have been developed for various purposes including surveillance, transportation and the other service applications. However, the locomotion of a quadruped robot unavoidably accompanies translational and rotational vibrations at the robot body with multiple and varying frequency components. The vertical vibrations particularly deteriorate the surveillance accuracy of a quadruped robot. Therefore, this paper proposes a vibration suppression system of a quadruped robot for the purpose of precise surveillance. Based on the vibration analysis of a quadruped robot, called Cheetaroid-I Carrier, the proposed vibration suppression system is designed with a two-link manipulator in a bi-articular structure. The mechanical parameters of the proposed system, i.e., the frame lengths and the gravity spring constants, are optimally designed considering the vibration characteristics of the actual robot system. In the proposed system, a sky-hook controller is utilized to reject the vibration of an end-effector. The vibration suppression performance of the propose system is verified in both the time domain and the frequency domain.

직렬탄성구동기를 이용한 장하지 보조기의 임피던스 보상방법

나병훈(Byeonghun Na),공경철(Kyoungchul Kong) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

Recently, walking assistance systems are receiving a great attention according to the increase of elderly population. To effectively assist human motions, such systems are required to generate precise and large assistive torques. Moreover, the assistive systems should be light and compact for the comfort and safety issues. In this paper we designed lower extremity assistive device with compact rotary series elastic actuators(cRSEAs) that are designed considering those factors. A worm gear is utilized to amplify the motor torque in the limited space. Also, to generate joint torque as desired, a torsional spring is installed between the motor and the human joint. The device generates large assistive torques by using worm gear, but the large friction introduced by the warm gear makes the controller design challenging. In this paper, a feedback control algorithm is utilized to compensate for such undesired friction. The proposed method is verified by experiments.