• 제어로봇시스템학회:학술대회논문집
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• 1992.10b
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• pp.1-6
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• 1992

A principle of "orthogonalization" is proposed as an extended notion of hybrid (force and position) control for robot manipulators under geometric endpoint constraints. The principle realizes the hybrid control in a strict sense by letting position and velocity feedback signals be orthogonal in joint space to the contact force vector whose components are exerted at corresponding joints. This orthogonalization is executed via a projection matrix computed in real-time from a gradient of the equation of the surface in joint coordinates and hence both projected position and velocity feedback signals become perpendicular to the force vector that is normal to the surface at the contact point in joint space. To show the important role of the principle in control of robot manipulators, three basic problems are analyzed, the first is a hybrid trajectory tracking problem by means of a "modified hybrid computed torque method", the second is a model-based adaptive control problem for robot manipulators under geometric endpoint constraints, and the third is an iterative learning control problem. It is shown that the passivity of residual error dynamics of robots follows from the orthogonalization principle and it plays a crucial role in convergence properties of both positional and force error signals.force error signals.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.51.1-51
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• 2001

Teleoperation is a rapidly progressing field promising to have significant application in space, mining, medical, and other areas. Unfortunately, significant communication delays are expected in teleoperation. With this problem, the two major issues in teleoperation are stability robustness and transparency performance. Recent work in bilateral teleoperation in the two-channel showed that for any two-channel control architecture, stability robustness is enhanced if the feedforward control parameters are lowered. In this paper, we analyze the stability and performance robustness of the three channels control architectures using the passivity-based Llewellyn´s absolute stability criterion as wall as the minimum values and Z-width´s of the operator and environment transmitted impedances. And the stability and the performance robustness of two and three channels control architectures are quantitatively compared.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.337-341
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• 2003

This paper provides a design method for a dynamic output feedback controller which stabilizes a class of linear time invariant systems. We suppose all the states of the given system is not measurable and only the outputs are used to stabilize the system. The systems considered cannot be stabilized by a static output feedback only. In the scheme we first assume that the given system can be stabilized by a state feedback composed of its output, velocity of the output and its higher order derivative terms. Instead of using the derivatives of the output, however, a dynamic system is constructed systematically which replaces the role of the derivative terms. Then, a high-gain output feedback stabilizes the composite system together with the newly constructed system. The performance of the proposed control law is illustrated in the comparative simulation studies of a numerical example with an observer-based control law.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.333-335
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• 2006

This paper presents a force-reflecting teleoperation scheme with time delay. In reciprocal systems, to improve the stability and performance of the tleleoperation system, the network provides a wide bandwidth, no congestion. However, as use of Internet increases, congestion situation of network increased and transmission time and packet loss increased accordingly. This can make system unstable at remote control. In this paper, we present a passive control scheme for a force reflecting bilateral teleoperation system via the Internet and we investigated how a varying time delay affects the stability of a teleoperation system. A new approach based on a passive control scheme was designed for the system. The simulation results and the tracking performance of the implemented system are presented in this paper.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.85-87
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• 2009

This paper presents a new PID controller for a DC/DC boost converter model that has a parasitic inductor resistance. In order to maintain the robust output regulation property under load variations the proposed controller is designed by using an additional state variable developed via a parallel-damped passivity-based control approach. Simulation results using Matlab/Simulink SimPowerSystems compare the performances of the proposed controller with a conventional PI controller for reference step changes and load uncertainties.

• Journal of Mechanical Science and Technology
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• v.18 no.7
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• pp.1131-1139
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• 2004

A new impedance controller is proposed for bilateral teleoperation under a time delay. The proposed controller does not need to measure or estimate the time delay in the communication channel using the force loop-back. In designing a stable impedance controller, absolute stability is used as a stability analysis tool, which results in a less conservative controller than the passivity concept. Moreover, in order to remove the conservatism associated with the assumption of infinite port impedances, the boundaries of human and environment impedance are set to finite values. Based on this, this paper proposes a parameter design procedure for stable impedance controllers. The validity of the proposed control scheme is demonstrated by experiments with a 1-dof master/slave system.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.588-591
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• 1998

In this paper, we present a robust adaptive backstepping output feedback controller for nonlinear systems perturbed by unmodelled dynamics and disturbances. Especially, backstepping technique with modular approach is used to separately design controller and identifier. The design of identifier is based on the observer-based scheme which possesses a strict passivity property of observer error system. We will use Switching-${\sigma}$ modification at the update law and the modified control law to attenuate the effects of undodelled dynamics and disturbances for nonlinear systems.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.63-64
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• 2007

In this paper, an adaptive passivity based excitation and governor control scheme is proposed to enhance the transient stability of a single machine infinite bus power system with parametric uncertainties. We employ a state model where the frequency, the difference between active and mechanical power, and the difference between the squared terminal voltage and its reference are regarded as state variables. Using this state model, the proposed controller is obtained in two steps; firstly, a simple direct adaptive passivation controller is designed for the power system with parametric uncertainties; then a linear PI controller is applied to guarantee the stability of the closed loop system.