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ABSTRACT: 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.
Robotics and Automation, 2009. ICRA '09. IEEE International Conference on; 06/2009
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2007 IEEE International Conference on Robotics and Automation, ICRA 2007, 10-14 April 2007, Roma, Italy; 01/2007
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ABSTRACT: Numerical integration methods based on the Lie group theoretic geometrical approach are applied to articulated multibody systems with rigid body displacements, belonging to the special Euclidean group SE(3), as a part of generalized coordinates. Three Lie group integrators, the Crouch-Grossman method, commutator-free method, and Munthe-Kaas method, are formulated for the equations of motion of articulated multibody systems. The proposed methods provide singularity-free integration, unlike the Euler-angle method, while approximated solutions always evolve on the underlying manifold structure, unlike the quaternion method. In implementing the methods, the exact closed-form expression of the differential of the exponential map and its inverse on SE(3) are formulated in order to save computations for its approximation up to finite terms. Numerical simulation results validate and compare the methods by checking energy and momentum conservation at every integrated system state.
IEEE Transactions on Robotics 11/2005; · 2.54 Impact Factor
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ABSTRACT: Based on the linear complementarity formulation of a unilaterally inextensible wire model, the behavior of motion and stability of wire-suspended dynamical systems is addressed in this paper. The concept of tension properness is developed to determine kinematical motion property, particularly the instantaneous degrees-of-freedom. Further, motion determinacy in spite of tension indeterminacy is proven. The notion of tension closure is described to help analyze the stability behavior of wire-suspended dynamical systems. By analyzing the maximal closure-domain of relative tension closure, one can assess the stability behavior of wire-suspended systems qualitatively as well as somewhat quantitatively. Some numerical examples and simulations will clarify and corroborate the theoretical results of this paper.
IEEE Transactions on Robotics 07/2005; · 2.54 Impact Factor
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Proceedings of the 2005 IEEE International Conference on Robotics and Automation, ICRA 2005, April 18-22, 2005, Barcelona, Spain; 01/2005
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Advanced Robotics. 01/2004; 18:637-653.
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ABSTRACT: 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
Robotics and Automation, 2002. Proceedings. ICRA '02. IEEE International Conference on; 02/2002
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Jonghoon Park
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ABSTRACT: 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
Robotics and Automation, 2002. Proceedings. ICRA '02. IEEE International Conference on; 02/2002
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ABSTRACT: One of recent achievements in the field of nonlinear H <sub>∞</sub> optimal control theories for Euler-Lagrange systems is the analytic solution to the Hamilton-Jacobi-Isaacs (HJI) equation associated to the so-called nonlinear H <sub>∞</sub> inverse-optimal control. In this paper, we address the problem of nonlinear H <sub>∞</sub> 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 H <sub>∞</sub> optimal control can be solved also analytically using the inverse-optimal solution.
Robotics and Automation, 2001. Proceedings 2001 ICRA. IEEE International Conference on; 02/2001
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ABSTRACT: 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.
Robotics and Automation, 2001. Proceedings 2001 ICRA. IEEE International Conference on; 02/2001
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ABSTRACT: 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
Intelligent Robots and Systems, 2001. Proceedings. 2001 IEEE/RSJ International Conference on; 02/2001
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ABSTRACT: The success in nonlinear H<sub>∞</sub> control design is
applied to the control of Euler-Lagrange systems. It is known that the
existence of H<sub>∞</sub> optimal control depends on solvability
of the so-called Hamilton-Jacobi-Isaacs H<sub>∞</sub> partial
differential equation. In the article, the associated HJI equation for
nonlinear H<sub>∞</sub> inverse-optimal control problem for a
Euler-Lagrangian system is solved analytically. The resulting control is
referred to as the reference error feedback, which takes conventional
PID controller form. Consequently, robust motion control can be designed
for robot manipulators using L<sub>2</sub>-gain attenuation from
exogenous disturbance and parametric error
IEEE Transactions on Robotics and Automation 01/2001;
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Proceedings of the 2001 IEEE International Conference on Robotics and Automation, ICRA 2001, May 21-26, 2001, Seoul, Korea; 01/2001
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ABSTRACT: 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
Robotics and Automation, 2000. Proceedings. ICRA '00. IEEE International Conference on; 02/2000
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IEEE Transactions on Robotics. 01/2000; 16:847-854.
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ABSTRACT: 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</sub>-gain attenuation control problem. Making use of
the fact that the single parameter L<sub>2</sub>-gain γ 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
Robotics and Automation, 1999. Proceedings. 1999 IEEE International Conference on; 02/1999
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01/1999
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ABSTRACT: 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 ℋ<sub>∞</sub> control. Within the ℋ<sub>∞</sub> control design, robustness can be achieved by formulating the disturbance input to include model uncertainties and external disturbances as well. The proposed ℋ<sub>∞</sub> 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
Intelligent Robots and Systems, 1998. Proceedings., 1998 IEEE/RSJ International Conference on; 11/1998
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ABSTRACT: Recent successes in nonlinear H<sub>∞</sub> control design
has been applied to control of robot manipulator systems. It is known
that the existence of H<sub>∞</sub> 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</sub>-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
Robotics and Automation, 1998. Proceedings. 1998 IEEE International Conference on; 06/1998
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01/1998
