• International Journal of Control, Automation, and Systems
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• v.4 no.2
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• pp.227-235
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• 2006

For a sophisticated humanoid that explores and learns its environment and interacts with humans, anthropomorphic physical behavior is much desired. The human vision system orients each eye with three-degree-of-freedom (3-DOF) in the directions of horizontal, vertical and torsional axes. Thus, in order to accurately replicate human vision system, it is imperative to have a simulator with 3-DOF end-effector. We present a 3-DOF anthropomorphic oculomotor system that reproduces realistic human eye movements for human-sized humanoid applications. The parallel link architecture of the oculomotor system is sized and designed to match the performance capabilities of the human vision. In this paper, a biologically-inspired mechanical design and the structural kinematics of the prototype are described in detail. The motility of the prototype in each axis of rotation was replicated through computer simulation, while performance tests comparable to human eye movements were recorded.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.1-4
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• 1995

We propose a new design method for a generalized predictive control (GPC) system based on the parametrization of two-degree-of freedom control systems. The objective is to design the GPC system which guarantees the stability of the control system for a perturbed plant. The design procedure of our proposed method consists of three steps. First, we design a basic controller for a nominal plant using the LQG method and parametrize a whole control system. Next, we identify the deviation between the perturbed plant and the nominal one using a closed-loop identification method and design a free parameter of parametrization to stabilize the closed-loop system. Finally, we design a feedforward controller so as to incorporate GPC technique into our controller structure. A numerical example is presented to show the effectiveness of our proposed method.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.130-136
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• 2013

This paper presents the magnetic equivalent circuit analysis of a double-excited, two-degree-of-freedom (DOF) motor. The double-excited, 2-DOF motor is a laminated structure, making it easy to manufacture and giving it simple operating principles. We explain the structure of the 2-DOF motor and analyze the static characteristics using a magnetic equivalent circuit (MEC) to reduce analysis time. The feasibility of MEC analysis was confirmed by experimental results of the tilting, panning motion. We also confirmed the occurrence of holding torque in every motion.

• Earthquakes and Structures
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• v.13 no.3
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• pp.231-239
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• 2017

Fundamental period is one of the most critical parameters affecting the seismic design of buildings. In this paper, a very simple approach is presented for estimating the fundamental period of multiple-degree-of-freedom (MDOF) structures. The basic idea behind this approach is to replace the complicated MDOF system with an equivalent single-degree-of-freedom (SDOF) system. To realize this equivalence, a procedure for replacing a two-degree-of-freedom (2-DOF) system with an SDOF system, known as a two-to-single (TTS) procedure, is developed first; then, using the TTS procedure successively, an MDOF system is replaced with an equivalent SDOF system. The proposed approach is expressed in terms of mass, stiffness, and number of stories, without mode shape or any other parameters; thus, it is a very simple method. The accuracy of the proposed method is investigated by estimating the fundamental periods of many MDOF models; it is found that the results obtained by the proposed method agree very well with those obtained by eigenvalue analysis.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.193-199
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• 1988

The forced vibrations of nondissipative nonlinear two-degree-of-freedom system, subjected to periodic forcing functions, are investigated by use of the method of slowly changing phase and amplitude. The first order differential equations are derived for nonrationally solutions and the coupled nonlinear algebraic equations for stationary solutions. Through investigating the response curves of the system, which are obtained numerically by using Newton-Raphson method, it is found that the resonances can occur at more than the number of degree-of-freedom of the system depending on the relation between the nonlinear spring parameters, which has no counterpart in linear systems.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.341-345
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• 1996

Many mechanical and electrocal systems use the number of motors to make multi degree of freedom motion. One method to reduce the number of motors is suggested by using the 3 D.O.F. motor. The 3 D.O.F. motor has advantages such as downsize, weight reduction, and simplification of the existing 3 D.O.F. systems. In this study, a mathematical model for the 3 D.O.F. motor is suggested and the dynamic equation is derived to analyze the 3 D.O.F. motion. Generallinear control methods are very hard to get the good performance because of the nonlinear terms of each degree of each degree of freedom. To control the motion properly, the nonlinear terms are decoupled using a feedback control law. Nonlinear feedback control law which can arrage the poles arbitrarily is derived. The effects of the gains are examined through computer simulations.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.230-233
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• 1999

This paper is concerned with the design method of a de-centralized linear control system and its application to vibration control of multi degree of freedom structures. The method is based on the partial model matching on frequency domain by minimizing the relative model error functions between the diagonal elements of the open loop transfer function matrix of the control system and these of the reference model. The method is examined and evaluated by both simulation and experiment of a multi degree of freedom structure(MDFS).

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.1-8
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• 1997

In order to reject the steady-state tracking error, it is common to introduce integral compensators in servosystems for constant reference signals. However, if the mathematical model of the plant is exact and no disturbance input exists, the integral compensation is not necessary. From this point of view, a two-degree-of-freedom(2DOF) servosystem has been proposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. The present paper considers robust stability of this 2DOF servosystem incorporating an observer to the structured and unstructured uncertainties of the controlled plant. A robust stability condition is obtained using Riccati inequality, which is written in a linear matrix inequality (LMI) and independent of the gain of the integral compensator. This result impies that if the plant uncertainty is in the allowable set defined by the LMI condition, a high-gain integral compensation can be carried preserving robust stability to accelerate the tracking response.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.605-610
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• 1994

Optimal design of fault-tolerant, spatial type maniplators is treated in this paper. Design objective is to guarantte three degree-of-freedom translational motions in the task space, upon failure of one arbitrary joint of 4 degree-of -freedom manipulators. Realizing the nonfault-tolerant characteristics of current, wrist-type industrial manipulators, several 4 degree-of-freedom redundant structures with one joint redundancy are suggested as the fault-tolerant spatial -type manipulators. Fault-tolerant charactersitics are investigated basedon the analysis of the self-motion and the null-space elements, of a redundant manipulator. Finally, in order to maximize the fault-tolerant capability,optimal design is performed for a spatial-type manipulator with respect to the global isotropic index, and the performance enhancement of the optimized case is shown by simulation.

• 제어로봇시스템학회:학술대회논문집
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• 1998.10a
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• pp.1-7
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• 1998

Robots utilized in the field of welfare or agriculture should be light in weight and flexible in structure. A pneumatic actuator has properties such that it is more powerful compared with a motor of same weight, and that it is flexible, clean and unexplosive. In this paper we propose a new structure of the pneumatic actuator with two-degree-of-freedom. By using proposed pneumatic actuators, we can easily construct multi-degree-of-freedom pneumatic manipulators. Here we constructed a fourteen-degree-of-freedom pneumatic dual manipulator. The performance of the dual manipulators is confirmed through experiments for ball-handling with impedance control. In the experiments several control schemes, including the decentralized control and the simple adaptive control (SAC), were used. The results show that a flexibility of the pneumatic actuator is appropriate to accomplish the coordinative motion of the right and left arms of the robot.