Torque Mode Control of a Bowden Cable-Driven Assistive System

Kyoungchul Kong,Joonbum Bae 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

A cable-driven actuating system is proposed in this paper. The proposed system is attractive for rehabilitation systems because the weight of the actuator is not imposed on the human body. Since the end-effector and the actuators are connected by Bowden cables, the humans are allowed to freely move in a certain range while being assisted. However, it is a challenge to account for the variable friction of the Bowden cable and the inertia and friction of the actuator in the design of control algorithms. In this paper, a hierarchical control strategy is adopted to control the proposed cabledriven actuating system. To determine the reference trajectory of the motor in real-time, a sensor fusion method based on a kinematic Kalman filter with MEMS accelerometers is proposed. By the proposed control methods, the cable-driven actuating system realizes a precise force-mode actuation. The system performance is evaluated by experiments.

Boosted dark matter signals uplifted with self-interaction

Kong, Kyoungchul,Mohlabeng, Gopolang,Park, Jong-Chul North-Holland Pub. Co 2015 Physics letters. Section B Vol.743 No.-

<P><B>Abstract</B></P> <P>We explore detection prospects of a non-standard dark sector in the context of boosted dark matter. We focus on a scenario with two dark matter particles of a large mass difference, where the heavier candidate is secluded and interacts with the standard model particles only at loops, escaping existing direct and indirect detection bounds. Yet its pair annihilation in the galactic center or in the Sun may produce boosted stable particles, which could be detected as visible Cherenkov light in large volume neutrino detectors. In such models with multiple candidates, self-interaction of dark matter particles is naturally utilized in the <I>assisted freeze-out</I> mechanism and is corroborated by various cosmological studies such as <I>N</I>-body simulations of structure formation, observations of dwarf galaxies, and the small scale problem. We show that self-interaction of the secluded (heavier) dark matter greatly enhances the capture rate in the Sun and results in promising signals at current and future experiments. We perform a detailed analysis of the boosted dark matter events for Super-Kamiokande, Hyper-Kamiokande and PINGU, including notable effects such as evaporation due to self-interaction and energy loss in the Sun.</P>

Impedance Compensation of SUBAR for Back-Drivable Force-Mode Actuation

Kyoungchul Kong,Hyosang Moon,Beomsoo Hwang,Doyoung Jeon,Tomizuka, M. IEEE 2009 IEEE TRANSACTIONS ON ROBOTICS Vol.25 No.3

<P>The Sogang University biomedical assistive robot (SUBAR), which is an advanced version of the exoskeleton for patients and the old by Songang (EXPOS) is a wearable robot developed to assist physically impaired people. It provides a person with assistive forces controlled by human intentions. If a standard geared DC motor is applied, however, the control efforts will be used mainly to overcome the resistive forces caused by the friction, the damping, and the inertia in actuators. In this paper, such undesired properties are rejected by applying a flexible transmission. With the proposed method, it is intended that an actuator exhibits zero impedance without friction while generating the desired torques precisely. Since the actuation system of SUBAR has a large model variation due to human-robot interaction, a control algorithm for the flexible transmission is designed based on a robust control method. In this paper, the mechanical design of SUBAR, including the flexible transmission and its associated control algorithm, are presented. They are also verified by experiments.</P>

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%.

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.

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 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.

Design and Analysis of Force-Sensor-Less Power-Assist Control

Sehoon Oh,Kyoungchul Kong,Hori, Yoichi IEEE 2014 IEEE transactions on industrial electronics Vol.61 No.2

<P>Due to the recent trend of the application of robots and other mechatronic devices to human life support, the force control draws more attention than ever. However, to use force sensors in all the required cases makes the system not only expensive but also bulky. Force-sensor-less power-assist control (FSPAC) which uses only encoders to obtain the external force information and provides force control performance can address this problem. Due to its simplicity and wide application, FSPAC is an essential technology to control a motor in a human-friendly way, but the design of FSPAC is different from the conventional feedback controllers so a new design methodology needs to be established. In order to attack this problem, this paper generalizes and analyzes the structure and characteristics of FSPAC. The generalized structure reveals how FSPAC can achieve the assistance, and the transfer function analysis based on the structure addresses the robustness and assistance performance evaluation problems. The robustness of FSPAC is analyzed in terms of the gain margin and robust stability, and the limitation of the power assistance to guarantee the robust stability is derived. Then, the evaluation way of feedback control design in FSPAC is provided. All the discussion in this paper provides the readers with understanding and appropriate design methodology of FSPAC.</P>

Mechanical Parameter Tuning Based on Iterative Learning Mechatronics Approach

Jung, Joonyoung,Kong, Kyoungchul IEEE 2018 IEEE/ASME transactions on mechatronics Vol.23 No.2

<P>In most mechatronics applications, the best control performance cannot be obtained by only shaping a control input signal because, in practice, such control is effective within only the performance range realizable by the actuator and control system. Therefore, to obtain the best control performance, the mechanical parameters should be optimally selected such that the desired control performance can be achieved with minimal control effort. However, it is difficult to accurately predict the control performance without conducting an actual experiment because the control performance is dependent on not only the mechanical design parameters, but also on various practical factors, such as the input and output saturation of the actuator, the heat problem, and sensor limitations. For these reasons, a recursive mechanical parameter tuning process based on control experiments is proposed in this paper. Based on a set of control signals (e.g., a control input and a tracking error), the proposed mechanical parameter tuning method seeks a better mechanical design parameter for improving the control performance (i.e., to reduce the control input power). For verification of the proposed method, the method was applied to case studies including simulations and experiments.</P>

Phenomenology of universal extra dimensions with bulk-masses and brane-localized terms

Flacke, Thomas,Kong, Kyoungchul,Park, Seong Chan Springer-Verlag 2013 Journal of high energy physics Vol.2013 No.5