Jae Yeon Choi

Semi-Automatic Pipeline Inspection Robot Systems

As the need of well-being life becomes popular, one of important issues is clean drinking water. Delivery of clean water from the main water fountain to the end user is very crucial. However, typical pipelines are being contaminated by rust and several chemicals. And thus the water delivered to house is not trustful as the drinking water. Thus, cleaning and inspection of the in-house pipeline becomes important issue. In order for development of in-house pipeline with the diameter of 13mm, it is very hard to use motorized automatic robot that has been employed in most pipeline robot system for large sized pipelines. Thus, this paper introduces a new semi-automotive pipeline inspection robot system for small sized pipelines. It consists of a CCD camera, a steering mechanism, and sensors to locate the robot inside the pipeline. The robot system is carried by an extension cable, which is in advance being penetrated into the pipeline by a compressed air. A lab prototype pipeline was developed to test the feasibility of the developed pipeline inspection robot system and the feasibility of this semi-automatic pipeline inspection method was proven successfully through experimentation

Development of Semi-Automatic Inspection System for Indoor Pipeline

As the need of well-being life becomes popular, one of important issues is clean drinking water. Delivery of clean water from the main water fountain to the end user is very crucial. However, typical pipelines are being contaminated by rust and several chemicals. And thus the water being delivered to house is not trustful as the drinking water. Thus, cleaning and inspection of the in-house pipeline becomes an important issue. However, there does not exist a small-sized motor adequate to the robot for the inspection of the in-house pipeline with diameter of 15 mm. Thus, this paper introduces a new semi-automotive pipeline inspection robot system for small-sized pipelines. It consists of a camera module, a steering mechanism, a gyro sensor, and an encoder to locate the position and orientation of the robot inside the pipeline. The robot system is carried by an extension cable, which is in advance being penetrated into the pipeline by a compressed air. Also the robot system has the map building function. A lab prototype for the semi-automatic pipeline robot was developed to test the feasibility as the pipeline inspection robot system. The feasibility of this semi-automatic pipeline inspection method was proven successfully through experimentation.

Powered upper-limb control using passivity-based nonlinear disturbance observer for unknown payload carrying applications

This paper proposes a passivity-based nonlinear disturbance observer (DOB) design for a powered upper-limb robot control. The proposed DOB allows for the nonlinearities of the robot dynamics, whereas the typical DOB designs cannot. Moreover, by virtue of the passivity property, human operator and environmental interactions can be embedded in the control loop. As a DOB, the proposed approach has a disturbance observation property that makes the actual robot behave like a nominal model selected by the user. Performance analysis proposes a gain tuning rule. In experimental validation, actual powered upper-limb robot is used to perform unknown payload carrying applications.

Variable impact dynamics of a finger mechanism

When a robot system collides with its environment, various impacts occur under the same robot and environmental condition. In order to apprehend this phenomenon, the analysis of impact dynamics is performed using a 3DOF finger mechanism. The external impulse exerted on a wall by a finger mechanism is a function of the robots geometry and dynamic parameters. Here, coefficient of restitution (COR) is an important parameter to calculate the impulse. Generally, COR has been assumed a constant value. However, COR varies according to the colliding condition. In this paper, we derive an analytical model of COR for the 3DOF finger model colliding with a wall, and show that COR varies according to the colliding velocity and its contact area through experiment.

Impact dynamics of a flying soccer ball with consideration of variable characteristic of coefficient of restitution

This paper deals with the impact dynamics of a soccer ball. The trajectory of the ball is decided according to its initial velocity, launch angle, and some aerodynamic effect. Specially, the initial velocity is created by an instant impulse given to the ball. The external impulse exerted on a ball by a kicking robot is a function of the robots geometry and dynamic parameters. Here, the coefficient of restitution (COR) is an important parameter to calculate the impulse applied to the ball when the collision is occurred. Usually, COR has been assumed a constant value. We derive an analytical model of COR for the pendulum model colliding with a soccer ball, and show that COR varies according to the velocity. The drag force is taken into account in the COR model. The velocity-dependent characteristic of COR is applied to simulation of a soccer ball traveling a long distance. It is shown that the velocity-dependent COR considerably affects the traveling distance of the flying ball.

Localization for an unmanned forklift in a refrigerated warehouse

This paper presents a localization algorithm for an unmanned forklift in a refrigerated warehouse. At the begging, an unmanned forklift and its environment are described and its kinematic analysis is conducted. For navigation in such a cold environment, a localization algorithm of a forklift based on particle filters with odometry and two magnetic sensors is presented. Finally, a path planning algorithm based on A-star search is applied to tasks in a refrigerated warehouse. The usefulness of the proposed algorithms is verified through simulations.

A method of optimization based human dynamic simulation for exoskeleton robot design and assessment

In this paper we formulate optimization based mathematical model of human dynamic motion prediction which can be used as an exoskeleton robot design and assessment tool. With this approach, motion is governed by human performance measures which is act as objective functions to be minimized in the formulation. As an exoskeleton robot model, external forces to the skeletal model of human body are applied. Lifting task is adopted and formulated as a numerical example. The human model has 55 degrees of freedom - 49 revolute joints and 6 global translation & rotation joints. An algorithm based on the sequential quadratic programming approach is used to solve the nonlinear optimization problem, and analytical gradients for the optimization process are calculated and provided. The results with joint torques and mechanical energy of human over the motion are recovered and analyzed under various cases. It shows that the effect of exoskeleton robot to the human body and proves the ability of this research as an exoskeleton design and assessment tool.

Impact dynamics of a finger mechanism with application to onset of a cart motion

In impact dynamics, coefficient of restitution (COR) is an important parameter to calculate the impulse. Generally, COR has been assumed a constant value. However, COR varies according to the colliding condition. In order to apprehend this phenomenon, analysis of impact dynamics is conducted using a 3-DOF finger mechanism. The external impulse exerted on a wall or a cart by the mechanism is a function of the robots geometry and dynamic parameters. In this paper, we derive an analytical model of COR with the 3DOF finger model colliding to a wall and a cart, and emphasize that the actual motion just after impact is not the same as what we expected unless the variable COR is considered. The effectiveness of proposed COR model is verified through wall and cart impact experiments using the finger mechanism.

Force sensor-less interaction force control in the de-burring task using dual-arm manipulation

In tightly coupled cooperative manipulation of two arms, an interaction force control is one of the important issues. In this paper, a sensor-less interaction force control in a de-burring task using a dual-arm is introduced. The dual arm manipulation increases the motion dexterity in the de-burring task as compared to the single arm manipulation. A closed form interaction force control algorithm is proposed, which does not require any force sensor. In the motion planning, the 12 Lagrangian coordinates of the system are decomposed into 9 motion degrees and 3 constrained degrees. Then, the whole dual arm can be modeled as a kinematically redundant robot. The primary task is to control the 9 motion degrees and the secondary task is to control the interaction force and the relative motion between the two arms. The concept of virtual joints is employed to represent the constrained degrees, which include the interaction force and the relative motion between the two arms. Through the simulation results, we show that the smooth de-burring task can be accomplished by using the suggested interaction force model without force sensor.