• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.209-216
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• 2007

In this paper, we embodied posture-stabilization and dynamic gait in a walking robot. 10 RC servo motors are used to operate joints. And the joints have enough moving ranges suitable in any walking pattern. Each joint trajectory is generated by cubic spline interpolation method and the stability of the trajectory is verified by using Zero Moment Point from the robot modeling. To avoid complex structure and expression, Zero Moment Point of the biped robot used angular acceleration is suggested. To measure the stability of the biped robot, Tilt sensor and gyro sensor are used. Finally, Personal Computer is used computer monitoring and data processing. Most of computation, such as 10 RC servo motor control, joint trajectory generating, ZMP compensation, sense measuring, etc, was used Digital Signal Processor.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.260-270
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• 1994

With the prevalent use of robot, the interests in moving speed of robot have been increasing for the purpose of upgrading performance of production. But the faster robot manipulator moves, the worse working accuracies are. And mechanical vibration is more and more serious with the increment of the moving speed of robot. So, the study on the cause and control method of robot vibration is one of the points of issue in robotics. This paper focuses on the vibration of 3 DOF parallel link drive mechanism robot. We assume that links of robot manipulator are `rigid' and joints are `flexible elements'. Governing equations of robot system including controller, servo amplifier, D.C servo motor, transmission with elasticity, and manipulator dynamics are derived. On the basis of modelling, we define `controller stiffness' by the proportional gain of controller and `stiffness of transmission'. Numerical and experimental research is performed to study vibration phenomena of robot induced from the variation of these two defined stiffnesses, and its results are shown.

• Journal of Korean Physical Therapy Science
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• v.9 no.1
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• pp.81-88
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• 2002

This paper presents a design and a control of a New Reciprocating Gait Orthosis and dynamic walking simulation for this system. The New Reciprocating Gait Orthosis is distinguished from other one by which has a very light-weight and a new RGO type with servo motors. The gait of a New Reciprocating Gait Orthosis depends on the constrains of mechanical kinematics and initial posture. The stability of dynamic walking is investigated by ZMP(Zero Moment Point) of the New Reciprocating Gait Orthosis. It is designed according to a human wear type and is able to accomodate itself to human environments. The joints of each leg are adopted with a good kinematic characteristics. To test of the analysis of joint kinematic properties, we did the strain stress analysis of dynamic PLS and the study of FEM with a dynamic PLS. It will be expect that the spinal card injury patients are able to train effectively with a Reciprocating Gait Orthosis. The New Reciprocating Gait Orthosis was able to keep smooth walling by the orthotic servo motors and hybrid system, make a sequence of flexion and extension of the joint during the walking. Also, the New Reciprocating Gait Orthosis turned out to be a satisfactory orthosis for walling training, for the spinal cord injury patient.

• Transactions of Materials Processing
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• v.28 no.1
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• pp.15-20
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• 2019

The superplastic forming/diffusion bonding process has been developed to fabricate a core frame structure with joint nodes out of tubes, for the development of a titanium high performance bicycle. The hydroforming process has been applied for bulging of a tube in the superplastic condition before, and during the diffusion bonding process. In this experiment, a commercial Ti-3Al-2.5V tube was selected as raw material for the study. The forming experiment has been performed using a servo-hydraulic press with a capacity of 200 ton. Next, nitrogen gas was used to acquire necessary pressure for the bulging and bonding of the tubes to fabricate the joint nodes. The pertinent processing temperature was $870^{\circ}C$ for the superplastic hydroforming/diffusion bonding (SHF/DB) process, using the Ti-3Al-2.5V tube. The bonding quality and the progress of bulging and diffusion bonding have been observed by the investigation of the joining interfaces at the cross section of the joint structure. The control of the nitrogen pressure throughout the SHF/DB process, was an important factor to avoid any significant defects in the joint structure. The whole progress stage of the diffusion bonding could be observed at a joint interface. A core structure with 5 joint nodes to manufacture a titanium bicycle could be obtained in a SHF/DB process.

• Advances in robotics research
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• v.2 no.2
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• pp.113-127
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• 2018

Robotics and automation are rapidly growing in the industries replacing human labor. The idea of robots replacing humans is positively influencing the business thereby increasing its scope of research. This paper discusses the development of an experimental platform controlled by a robotic arm through Robot Operating System (ROS). ROS is an open source platform over an existing operating system providing various types of robots with advanced capabilities from an operating system to low-level control. We aim in this work to control a 7-DOF manipulator arm (Robai Cyton Gamma 300) equipped with an external vision camera system through ROS and demonstrate the task of balancing a ball on a plate-type end effector. In order to perform feedback control of the balancing task, the ball is designed to be tracked using a camera (Sony PlayStation Eye) through a tracking algorithm written in C++ using OpenCV libraries. The joint actuators of the robot are servo motors (Dynamixel) and these motors are directly controlled through a low-level control algorithm. To simplify the control, the system is modeled such that the plate has two-axis linearized motion. The developed system along with the proposed approaches could be used for more complicated tasks requiring more number of joint control as well as for a testbed for students to learn ROS with control theories in robotics.

• Proceedings of the Korea Multimedia Society Conference
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• 1998.04a
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• pp.262-267
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• 1998

A hierarchical motion control system for animation of 3D human character is implemented using the motion database in realtime. The proposed motion control system consists of coordination controller for gait timing and balancing of walking motion, joint servo controller for realistic limb movement, and motion database for goal-directed character animation which makes time-consuming animation relatively easy task. As one example among the various applications of the proposed motion control system. We present a simple virtual reality system in which the motion control system plays a central role in generating realistic motion of virtual human character.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.4
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• pp.85-102
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• 1990

Up to now, most robot control systems are very naive. They consist of a number of independent position-servo loops to control each joint angle separately. Those control systems have constant predefined gains and do not cover the complex dynamic interactions between manipulator joints. As a result, the manipulator is severely limited in range of application, speed of operation and variation of payload. This study proposed a new method to design a robot manipulator controller capable of tracking the reference trajectories of joint angles in a reasonable accuracy to cope with actual situations of varying payload, uncertain parameters. The adaptive model following control method has been used to improve existing robot manipulator controllers. The proposed controller is operated by adjusting its gains based on the response of the manipulator in such a way that the manipulator closely matches the reference model trajectories defined by the designer. The stability of adaptive controller is based on the Second Method of Lyapunov. The coupling among joints and the nonlinearity in the dynamic equation are explicitly considered. The designed manipulator controller shows good tracking performance under various load varia- tion and parameter uncertainties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.2
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• pp.414-430
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• 1996

In this paper, a new kinematic structure of a parallel manipulator with six Cartesian degrees of freedom is proposed. It consists of a platform which is connected to a fixed base by means of 3-PPSP(parameters P, S denote the prismatic, spherical joints) subchains. Each subchain has a link which is concected to a passive prismatic joint at the one end and a passive spherical joint at the other. The spherical joint is then attached to perpendicularly arranged prismatic actuators which are fixed at the base. The spherical joint is then attached to perpendicularly arranged prismatic actuators which are fixed at the base. This arrangement provides a basis to control all six Cartesian degrees of motion of the platform in space. Due to its efficient architecture, the colsed-form solutions of the inverse and forward kinematics can be obtained. As a consequence, this new kinematic structure can be servo controlled using simple inverse kinematics becaese forward kinematics allows for measuring the platform's position and orientation in Cartesian space. Furthermore, the proposed structure provides an effective functional workspace. Series of simulations are performed to verify the results of the kinematics analyses.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.466-471
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• 2003

The characteristics of a rock joint which influence the stability of rock mass structures, such as the cut slopes and the tunnels, are largely controlled by the conditions of the rock joint as well as its boundary conditions. Boundary conditions can be represented by assuming that the deformability(or stiffness) of the rock mass surrounding the joints is modelled by a spring with stiffness. A new direct shear apparatus is developed in this study, which adapts a servo control system using PID algorithm. This apparatus can be used to investigate the various aspects of shear characteristics of the rock joints at conditions of constant normal stress and constant normal stiffness and so on. It is possible that the behavior under the constant normal stiffness condition can be predicted by the normalized graphic method with results obtained from the tests in the constant normal stress condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.3
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• pp.260-269
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• 1988

Conventional torque and position control scheme is developed to control a robot manipulator using the knowing mass of links of load. This paper presents a torque and position control method which performs under unknown mass of links or load. This method takes full advantage of known parameters and servo error in joint coordinate space. We illutrate the theory with some simulations and show that the results is effective.