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Jonghoon Park

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23 papers

1 author row

ICRA Conference 2009 Conference Paper

State estimation with delayed measurements considering uncertainty of time delay

Minyong Choi
Jinwoo Choi 0004
Jonghoon Park
Wan Kyun Chung

State estimation problem with time delayed measurements is addressed. In dynamic system with noise, after taking measurements, it often requires some time until that is available in a filter. A filter not considering this time delay cannot be used since a current measurement is related with a past state. These delayed measurements problem is solved with augmented state Kalman filter, and uncertainty of the delayed time is also resolved based on the probability distribution of the delay. The proposed method is analyzed by a simple example, and its consistency is verified.

ICRA Conference 2007 Conference Paper

General ZMP Preview Control for Bipedal Walking

Jonghoon Park
Youngil Youm

An online pattern generator for bipedal walking control is designed based on the notion of ZMP preview control using the full dynamics model. The method is called the general ZMP preview control. Conventional implementation by Kajita is based on an approximated table-cart model, which neglects the actual system dynamics. This leads to erroneous ZMP tracking for real robots, even if the system tracks the generated COM pattern exactly. Numerical simulations are provided to show the advantage and character of the method

ICRA Conference 2005 Conference Paper

Control of Ground Interaction at the Zero-Moment Point for Dynamic Control of Humanoid Robots

Jonghoon Park
Youngil Youm
Wan Kyun Chung

In order for stable control of humanoid robots, ground contact forces should be properly controlled for compensating the dynamic disturbances caused by unactuated body movement. The stability in the sense of the zero-moment point (ZMP), guaranteeing secure contacts during control, is a necessary condition for stable motion control. Therefore, we propose a method to control the ground interaction at the ZMP, or ZMP interaction in short, by modifying the system reference acceleration. We also show that simultaneous control of the ZMP interaction and the body movements is not allowed in general. Simulation result is provided to corroborate the theoretical result.

IROS Conference 2005 Conference Paper

Second-order contact kinematics for regular contacts

Jonghoon Park
Wan Kyun Chung
Youngil Youm

Second-order contact kinematics for regular contacts, such as surface-surface, curve-curve, curve-surface, and vertex-surface, are formulated in a unified framework, extending Montana's (1988) first-order contact kinematics for surface-surface contact only. Given two rigid bodies in contact with each other, the contact kinematics is the mathematical expression of the relative motion between them and the five dimensional contact coordinate vector. Second-order contact kinematics describes the second-order derivative of the contact coordinate vector in terms of the derivative of the relative twist. The result can be directly applied to geometric integration of contact dynamics.

IROS Conference 2004 Conference Paper

Geometric numerical integration algorithms for articulated multi-body systems

Jonghoon Park
Wan Kyun Chung
Youngil Youm

Numerical integration methods based on Lie group theoretic geometrical approaches are extended to articulated multi-body systems with rigid body displacements belonging to the special Euclidean group SE (3) as a part of generalized coordinate. Two Lie group integrators, Crouch-Grossman method and Munthe-Kaas method, are formulated for the equation of motion for articulated multi-body systems. The proposed methods provide singularity-free integration, unlike the Euler-angle method, while the integration always evolves on the underlying manifold structure, unlike the quarternion method. Numerical simulation result validates the methods by checking energy and momentum conservation at even integrated system state.

IROS Conference 2002 Conference Paper

Active-external enveloping grasps: dynamical-balance based motion analysis

Jonghoon Park
Wan Kyun Chung
Makoto Kaneko

Enveloping grasp systems not in static equilibrium result in dynamical motion. In this article, we develop a method based on dynamical-balance to solve motion analysis problem for an active-external grasp, that is to determine contact forces and accelerations consistent with the dynamics and friction law for a given torque-wrench pair. Since the method is analytic in nature, it may give the chance for better efficiency and more direct insight than a relevant linear complementarity formulation, although the solutions are the same. The method is verified using two examples: one is a simple grasp system with one frictional contact, and the other is a relatively general one with all frictionless contacts.

ICRA Conference 2002 Conference Paper

Characterization of Instability of Dynamic Control for Kinematically Redundant Manipulators

Jonghoon Park
Wan Kyun Chung
Youngil Youm

In redundant manipulator research community, the phenomenon called torque instability has not yet been completely characterized using unanimous agreement on its mechanism. This article shows that the behavior is indeed caused by incomplete compensation of null dynamics related with self-motion. This instability can be avoided by proper control with compensation of nonlinear null dynamics, and we propose a method to stabilize conventional redundancy resolution schemes extended to dynamic controls.

ICRA Conference 2002 Conference Paper

Determining Contact Force Distribution for Enveloping Grasps: Subspace Structure and Dynamical Balance

Jonghoon Park

This paper addresses one of standard problems in enveloping grasp analysis, the so-called contact force distribution. First, a subspace structure is analyzed using projection matrices into four subspaces of contact force space. Motivated by an example demonstrating that a careless definition of contact force subspaces leads to completely invalid result, we propose a proper set of projection matrices using a special weighted pseudo-inverse. Next, an example of statical ambiguity is provided in obtaining contact force distribution, which implies that contact forces can not be determined in light of statical viewpoint. To resolve such ambiguity, we propose the notion of dynamical balance. By presenting a tool for identification of dynamically balanced motions and forces, we can have a complete characterization of the force distribution for a general enveloping grasp system.

IROS Conference 2001 Conference Paper

Analysis of frictional forces in indeterminate enveloping grasps

Jonghoon Park
Kensuke Harada
Makoto Kaneko

The problem due to the statically indeterminate contact forces arising in indeterminate frictional enveloping grasps is addressed. First, we show that the statical model for the contact forces is incomplete in the sense that the mathematical frictional forces may have an infeasible component. To resolve this infeasibility, we directly derive the enveloping grasp infeasibility condition on the frictional forces based on the coordinate transformation developed for frictional enveloping grasps. Then the indeterminate grasp can be analyzed in cooperation with the enveloping grasp feasibility inequality, as shown in a numerical example.

ICRA Conference 2001 Conference Paper

Enveloping Grasp Feasibility Inequality

Jonghoon Park
Kensuke Harada
Makoto Kaneko

The enveloping grasp feasibility inequality is formulated in this article using a coordinate transformation based on the concept of frictional degrees-of-freedom. Various analysis and synthesis problems pertinent to enveloping grasp of whole-limb systems can be handled within the same mathematical framework, even under the situation where statically indeterminate contact forces exists. Simulations are also shown to explain the basic idea.

ICRA Conference 2001 Conference Paper

Multiple Tasks Kinematics Using Weighted Pseudo-Inverse for Kinematically Redundant Manipulators

Jonghoon Park
Youngjin Choi
Wan Kyun Chung
Youngil Youm

This paper proposes a method to accommodate multiple tasks for redundancy utilization, which is based on a specific weighted pseudo-inverse. The proposed method also has task priority imposition property same as those conventional task priority based methods. In order to deal with general situations of task specification, the so-called semi-definitely weighted pseudo-inverse is devised.

ICRA Conference 2001 Conference Paper

Transition to nonlinear H-inf optimal control from inverse optimal solution for Euler-Lagrange system

Jonghoon Park
Wan Kyun Chung

One of recent achievements in the field of nonlinear /spl Hscr//sub /spl infin// optimal control theories for Euler-Lagrange systems is the analytic solution to the Hamilton-Jacobi-Isaacs (HJI) equation associated to the so-called nonlinear /spl Hscr//sub /spl infin// inverse-optimal control. In this paper, we address the problem of nonlinear /spl Hscr//sub /spl infin// optimal control design for an Euler-Lagrange system, rather than the inverse-optimal problem. By introducing a technique of control weight loosening and state weight strengthening, we show that the associated HJI inequality, not the equation, for nonlinear /spl Hscr//sub /spl infin// optimal control can be solved also analytically using the inverse-optimal solution.

ICRA Conference 2000 Conference Paper

Unified Motion Specification and Control of Kinematically Redundant Manipulators

Jonghoon Park
Wan Kyun Chung
Youngil Youm

The kinematically decoupled joint space decomposition (KD-JSD) is proposed as a systematic method for synthesis of dynamic control of kinematically redundant manipulators. The method leads to a proper control for direct specification and control of the self-motion of kinematically redundant manipulators, as well as the task motion. To cover various possibilities in specifying desired self-motion behaviors the conventional gradient projection method and task priority based method are reformulated within the framework of the KD-JSD. The validity of the proposed control method is shown experimentally adopting a three degrees-of-freedom direct-drive planar redundant manipulator.

IROS Conference 1999 Conference Paper

On dynamical decoupling of kinematically redundant manipulators

Jonghoon Park
Wan Kyun Chung
Youngil Youm

The kinematically decoupled joint space decomposition is proposed as a general coordinate transformation between the joint space and the task space of kinematically redundant manipulators. The method can describe the kinematic, force, and dynamic redundancy in a unified way using a minimal number of systematic motion variables. Based on the method, a set of equivalent dynamical models of redundant manipulators is constructed and its characteristics are studied focusing on the dynamical decoupling between the task and the null motion dynamics.

ICRA Conference 1999 Conference Paper

Performance of Linear Decentralized H-Infinity Optimal Control for Industrial Robotic Manipulators

Jonghoon Park
Wan Kyun Chung
Youngil Youm

Industrial manipulators are under various limitations against high quality motion control, for example friction and dynamic uncertainties, and simple control structure. A robust linear PID motion controller, called the reference error feedback, is proposed, which solves the nonlinear L/sub 2/-gain attenuation control problem. Making use of the fact that the single parameter L/sub 2/-gain /spl gamma/ controls the performance and robustness, we propose a simple and stable method of tuning the controller called the "square law". The analytical results are verified through experiments of six degrees of freedom industrial manipulator.

ICRA Conference 1998 Conference Paper

Analytic Nonlinear Hinfty Optimal Control for Robotic Manipulators

Jonghoon Park
Wan Kyun Chung
Youngil Youm

Recent successes in nonlinear H/sub /spl infin// control design has been applied to control of robot manipulator systems. It is known that the existence of H/sub /spl infin// optimal control reduces to solvability of the Hamilton-Jacobi-Isaacs partial differential equation, which is very difficult to solve. In this article, a robust control in the sense of L/sub 2/-gain attenuation from an external disturbance and one due to model uncertainties is designed for a class of Euler-Lagrange system based on a class of analytic solution to the associated Hamilton-Jacobi-Isaacs equation.

IROS Conference 1998 Conference Paper

𝒽 ∞ robust motion control of kinematically redundant manipulators

Jonghoon Park
Wan Kyun Chung
Youngil Youm
Moonsang Kim

A robust motion control with special focus on kinematically redundant manipulators is proposed based on the kinematically decoupled (KD) joint space decomposition and the analytic nonlinear /spl Hscr//sub /spl infin// control. Within the /spl Hscr//sub /spl infin// control design, robustness can be achieved by formulating the disturbance input to include model uncertainties and external disturbances as well. The proposed /spl Hscr//sub /spl infin// control is based on the analytic solution of the related Hamilton-Jacobi-Isaccs equation, and does not require any further assumptions except the Euler-Lagrange properties. Two components of motion, task and null motion, of a redundant manipulator are robustly controlled by the proposed KD reference motion compensation (RMC) reference error feedback (REF) control.

ICRA Conference 1996 Conference Paper

Control input reconstruction using redundancy under torque limit

Jonghoon Park
Wan Kyun Chung
Youngil Youm
Moonsang Kim
Mankeun Kim

Various physical limitations which intrinsically exist in the manipulator control system, for example kinematic limits and torque limit, cause some undesirable effects. Specifically, when one or more actuators are saturated in torque the expected control performance can not be achieved. The effect of torque limit, especially for redundant manipulators, is studied in this article, and a local and analytic method to reconstruct the control input using the redundancy is proposed based on the kinematically decoupled modeling of redundant manipulators. It results in exact compensation of the task motion dynamic error at the cost of the least null motion dynamic error. Numerical simulations help to verify the advantages of the proposed scheme.

ICRA Conference 1996 Conference Paper

Design of compliant motion controllers for kinematically redundant manipulators

Jonghoon Park
WanKyun Chang
Youngil Youm

Design of a compliant motion controller using a redundant manipulator is addressed in this article. Specifically, a hybrid controller and an impedance controller are extended to general redundant manipulators based on the kinematically and geometrically decoupled joint space decomposition. Geometrically decoupled task space decomposition provides a systematic ways of geometric modeling of general constraints. Both controllers have the advantage that the closed-loop dynamics of the manipulator are decomposed into position-controlled, force-controlled, and null motion-controlled subspaces, and each are linearized, reshaped to desired dynamics, and decoupled from the others. A simple numerical simulations prove the applicability of the proposed algorithms.

IROS Conference 1996 Conference Paper

Reconstruction of inverse kinematic solution subject to joint kinematic limits using kinematic redundancy

Jonghoon Park
Wan Kyun Chung
Youngil Youm
Moonsang Kim

Various physical limitations which intrinsically exist in the manipulator inverse kinematic system, for example joint travel and velocity limits, cause some undesirable effects. Specifically, when one or more joints are limited the desired task velocity can not be anticipated. The effect of joint kinematic limits, especially for redundant manipulators, is studied in this article, and an analytic method to reconstruct the inverse kinematic solution using the redundancy is proposed based on the kinematically decoupled modeling of redundant manipulators. It results in no error in the task motion at the cost of the least error in the null motion. Numerical simulations help to verify the advantages of the proposed scheme.

ICRA Conference 1996 Conference Paper

Weighted decomposition of kinematics and dynamics of kinematically redundant manipulators

Jonghoon Park
Wan Kyun Chung
Youngil Youm

The kinematics and dynamics of kinematically redundant manipulators are to be decomposed in consistent way with the joint space decomposition induced by the weighted pseudo-inverse operation. The weighted kinematically decoupled joint space decomposition results to a family of decomposed kinematics and dynamics, parametrized by the symmetric positive-definite weight matrix, in the task motion and weighted null motion space. The inertially-decoupled weighted decomposition is shown to be only possible with the inertia as the weight. Also, the feedback motion controller which is consistent with a specific joint space decomposition is developed. The controller realizes the decoupled and linearized reference acceleration tracking controller in the task motion and weighted null motion space.

IROS Conference 1995 Conference Paper

Specification and control of motion for kinematically redundant manipulators

Jonghoon Park
Wan Kyun Chung
Youngil Youm

Useful specification and stable control of motions for redundant manipulators are two important application aspects. In this article, the dynamic controller which can stabilize the output motion and the null motion is proposed, which has also a unified null motion specification algorithm in it. It is distinctive in that it renders the closed loop system dynamics linear and decoupled in the null space as well as the output space. All the work in this article are based on the kinematically decomposed modeling.

ICRA Conference 1994 Conference Paper

Behaviors of Extended Jacobian Method for Kinematic Resolutions of Redundancy

Jonghoon Park
Wan Kyun Chung
Youngil Youm

The characteristic of an inverse kinematic solution for redundant manipulators using EJM is exploited with the sufficient condition for EJM. A new analytic perspective other than the well-known algebraic and less-known geometric one on algorithmic singularity of EJM is proposed, on the basis of optimization process. The characteristic of a solution with EJM is shown to be able to change only by crossing the algorithmic singularity thereof. A 3-DOF planar redundant robot is analyzed when EJM is applied with the manipulability as an example. >