Chul-Goo Kang

Closed-form force sensing of a 6-axis force transducer based on the Stewart platform

The 6-axis force transducers based on the Stewart platform require the solution of forward kinematics of the Stewart platform in order to obtain force and torque acting on the upper plate from given six leg forces. However, the solution of forward kinematics is not known in a closed form. In this paper, a closed-form solution of the forward kinematics is derived by means of linearization of the inverse kinematics equations, and the derived solution is applied to the calculation of force and torque acting on the transducer. In order to investigate the validity of the proposed method, a prototype of the transducer based on the Stewart platform is developed and force analysis is conducted. Moreover, the gravity compensation algorithm is proposed to reduce the weight effects of the transducer.

Analysis of the braking system of the Korean High-Speed Train using real-time simulations

The braking system of a high-speed train has a crucial role for the safety of human mass transportation. However, it is hard to acquire design parameters of the braking system in the development stage of a new high-speed train. In this paper, we build a Hardware-In-the-Loop (HIL) system for the braking system of the Korean High-Speed Train (KHST) that is supposed to reach 350 km/h, and analyze the characteristics of the braking system of KHST (composed of 7 cars) via real-time simulations. In the HIL system that is built using a DSP board of dSPACE, the dynamics of the 7 car bodies and several bogies and characteristics of connecting devices between cars are considered individually. Simulation results show that the designed braking system of KHST is valid and satisfies design specifications.

Performance Measure of Residual Vibration Control

The robustness of residual vibration control, such as input shaping, has conventionally been evaluated from the ratio of residual vibration amplitude with input shaping to that without input shaping at the time of the final impulse. However, in that robustness evaluation, vibration-suppressing speed due to each residual vibration control has not been considered, which is also an important aspect of residual vibration control. In this paper, a performance measure including robustness to modeling errors and the effect of vibration-suppressing speed is defined, and the validity of the performance measure is demonstrated by simulations and experimental works.

Design of a Percussive Massage Robot Tapping Human Backs

A percussive massage robot for senior health care is under development at our Intelligent Control and Robotics Laboratory. This paper presents a conceptual design of the massage robot, forward and inverse kinematic analysis, and Jacobian derivation of the robot manipulator that has 4 degree of freedom motion. Furthermore, the shape and magnitude of impact force for percussive massage tapping human backs are obtained through experimental study using a load cell, which give the basics of dynamic analysis and force control of the robot manipulator.

Analysis of a Nonlinear Web-Tension Control System of a High- Speed Gravure Printing Machine

Large printing demand of our modern society requests development of high-speed printing machines. A reasonable model for Web tension plays an important role for the development of a high-speed printing machine. In this paper, we derive a nonlinear Web-tension model of a high-speed gravure printing machine considering span length to be time-varying instead of considering it to be fixed. Time-varying property of the Web span length is due to turret motions of unwinding and rewinding units as well as dancer motions. Furthermore, we analyze Web-tension control performance at transient and steady-state operations. The validity of the Web-tension model and control system has been shown via simulation study

Conceptual design for robotic arm wrestling

Senior welfare problems become more and more serious in modern civilized societies. It is important to assist the senior to keep their physical and mental health in order to lessen social welfare cost and to improve the quality of life of them. This paper presents the conceptual design of a robotic arm wrestling system that is an intelligent exercise machine to help the senior physically and mentally. This robotic machine is intended to perform arm wrestling games with seniors on a table. The robotic machine will determine randomly the winner (robot or human) and the scenario. The proposed scenario generates game process that the arm-wrestler cannot predict in advance and arm wrestlers will influences it.

MIMO Tension Modelling and Control for Roll-to-roll Converting Machines

Roll-to-roll converting machines have significant interactions in tensions and speeds among web spans. A reasonable MIMO model for web tension plays an important role for high-performance converting machines. In this paper, we derive a nonlinear MIMO web-tension model of a high-speed gravure printing machine considering span length to be time-varying instead of considering it to be fixed. Then a feedback control system is constructed and web-tension control performance is analyzed at transient and steady-state condition via simulation studies using Simulink software.

Hardware-in-the-Loop Simulation for a Wheel Slide Protection System of a Railway Train

Abstract A wheel slide protection (WSP) system of a railway train has the role of reducing excessive wheel slide from brake applications in situations where wheel/rail adhesion is temporarily impaired. The mechanism of the WSP is complex and is related to highly nonlinear dynamics of the train. Hardware-in-the-loop simulation (HILS) for the WSP system can test various dangerous braking conditions which are not possible in actual train tests, and help to find appropriate parameters of the WSP system. This paper presents a HILS unit for the WSP system, which is composed of an actual WSP unit, two actual dump valves, a dSPACE module, and a personal computer with Linux operating system. The dSPACE module simulates railway train dynamics in real-time, which includes dynamic models of wheelsets, bogies, a carbody, and a mechanical brake, and also a dynamic model for creep force generation in wheel/rail contacts. The validity of the HILS system for WSP control is demonstrated by ways of off-line simulation studies and experimental tests using the HILS unit for the Korean tilting train, Hanvit 200.

Stability analysis for design parameters of a roll-to-roll printing machine

The stability of multi-input and multi-output web-tension systems is an important factor that is required for the roll-to-roll printing machines to operate properly and to obtain reasonable printing performance. This paper presents a stability analysis of a multi-input and multi-output web-tension system of a high-speed gravure printing machine considering span-length variations due to dancer rollers. Span-length variations due to dancer motions are considered for the modeling of plant dynamics in two ways; one is to include the effect of span-length variations without considering dancer roller inertias and viscous frictions, and the other is to include the effect of span-length variations with considering dancer roller inertias and viscous frictions. Stability of the linearized system of the proposed model is analyzed using eigenvalues of the system matrix. The validity of the analysis is demonstrated by simulation study.

A motion control system developed for research and education purposes

Research and education on motion control requires an easy-to-use and economic experimental apparatus, but present commercial products are expensive, complex in mechanism and hard to use them in general. In this paper, we present an interesting motion control apparatus for research and education which is easy-to-use and economic. For user flexibility, we use an open-source free operation system Linux and a free real-time kernel RTAI. The developed motion control system is reliable in mechanism, and fast enough to implement 100 microsecond sampling time for real-time control. The developed motion control system has been demonstrated by testing PD (proportional-plus-derivative) control and ZV (zero vibration) input shaping experimentally.