• Journal of Institute of Control, Robotics and Systems
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• v.6 no.6
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• pp.471-477
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• 2000

The position control accuracy of a robot arm is significantly deteriorated when a long arm robot is operated at a high speed. In this case, the robot arm must be modeled as a flexible structure, not a rigid one, and its control system should be designed with its elastic modes taken into account. In this paper, the tip position control scheme of a one-link flexible manipulator using 2-DOF controller with sliding mode is presented. The robot consists of a flexible arm manufactured with a thin aluminium plate, an AC servo motor with a harmonic drive for speed reduction, an optical encoder and a CCD camera as a vision sensor for on-line measuring the tip deflection of the flexible m. Simulation and experimental results of the flexible manipulator with a proposed controller are provided to show the effectiveness of the controller.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.740-745
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• 2005

This study is intended to build a controller of redundant manipulators with the simultaneous abilities of trajectory tracking and obstacle avoidance without any preparations of path planning to achieve full automation even for one production of one kind, while keeping the avoidance ability high and keeping its shape away from object to reduce the possibility that the manipulator crashes to the object. To evaluate the avoidance ability of the intermediate link, we proposed a scalar value of Avoidance Manipulability Shape Index(AMSI), which is independent of the obstacle's shape. On the other hand, the danger to crash to the obstacle is depending on the shape of the obstacle, which could be evaluated by the potential field set around the obstacle. This paper proposes control method of the manipulator's shape based on the AMSI to simultaneously avoid obstacles and keep the avoidance ability high with potential.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.2
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• pp.220-227
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• 1999

The position control accuracy of a robot arm is significantly deteriorated when a long slender arm robot is operated at a high speed. In this case, the robot arm needs to be modeled as a flexible structure, not a rigid one, and its control system needs to be designed with its elastic modes taken into account. In this paper, the vibration control scheme of a one-link flexible manipulator using adaptive input shaper in conjunction with PID controller is presented. The robot consists of a flexible arm manufactured with a thin aluminium plate, an AC servo motor with a harmonic drive for speed reduction, an optical encoder and an accelerometer. On-line identification of the vibration mode is done using the pruned decimation-in-time FFT algorithm to estimate the parameter of the input shaper. Experimental results of the flexible manipulator with a PID controller and input shaper are provided to show the effectiveness of the advocated controllers.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.811-814
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• 1997

In this paper, the torque optimization of a kinematically redundant manipulator for minimizing the torque demands is discussed. The minimum torque solution based on a local optimization has been known to encounter the instability problem and then the global torque optimization was suggested as one of the alternatives. Herein, by adopting the infinity-norm rather than the 2-norm for the magnitude of torques, we are to propose a new cost function more advantageous to the avoidance of torque limits. By the way, a solution to the global torque optimization formulated with the new cost function can not be obtained by the previous methods due to their difficulties such as inability to treat discontinuous cost functions and various constraints on the joint variables. Thus, to overcome those deficiencies, we are developing a new approach using the dynamic programming. The effectiveness of the proposed method is shown through simulation examples for a 3-link planar redundant manipulator.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.117-122
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• 1994

In this paper, we discuss the modeling of flexible manipulators. In the modeling of flexible manipulators, there are two approaches: one is based on the distributed-parameter modeling and the other on the lumped-parameter modeling. The former has been applied to control and analysis of simple manipulator requiring precision, while the latter has been applied to multi-link spatial manipulator, because of the model's simplicity. We have already proposed the lumped-parameter modeling method for simple manipulator, and investigate that model of how much degree of precision we can get. The experiments and simulations are performed, comparing these results, the approximate performance of our modeling method is discussed.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.174-179
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• 1999

A binary parallel robot manipulator uses actuators which have only two stable states and is structure is variable geometry truss. As a result, it has a finite number of states and fault tolerant mechanism because of kinematic redundancy. This kind of robot manipulator has the following advantages compared to a traditional one. Feedback control is not required, task repeatability can be very high, and finite state actuators are generally inexpensive. Because the number of states of a binary robot manipulator grows exponentially with the number of actuators, it is very difficult to solve an inverse kinematic problem. The goal of this paper is to develop an efficient algorithm to solve an inverse kinematic problem when the number of actuators are too much or the target position is located outside of workspace. The backbone curve is generated optimally by considering the curvature of the robot manipulator configuration and length of link. Then, the robot manipulator is fitted along the backbone curve with some criteria.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.353-356
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• 1997

Hydraulically driven manipulators are superior to electrically driven ones in the power density and electrical insulation. But an electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and this parameter fluctuations are greater than those of electrically driven manipulator. So this is relatively difficult to realize not only stable contact work but also accurate force control for the autonomous field task such as the maintenance task of high voltage active electric line or the automatic excavation task by hydraulic excavator. In this report, we propose robust force control algorithm, which can be applied to there real field task such as the construction field, nuclear plant and so on. Proposed force controller has the same structure as that of disturbance observe for position control. The difference between force and position disturbance observer is that the input and output of disturbance observer are forces in the case force disturbance observer and the plant varies much compared to the case of position control. In the design of force disturbance observer, generalized plant is derived and the stabilized filter is designed by H infinity control theory to ensure the robuts t stability even though the stiffness of environment changes from sponge to steel, and the contact surface also changes from flat to round shape. Experimental results show that highly robust force tracking by a 6-link electro-hydraulic manipulator could be achieved under various environment conditions.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.3
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• pp.189-199
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• 2004

A bridge transported servo manipulator (BTSM) system for the advanced spent fuel conditioning process (ACP) has been developed to overcome the limitation of access, which is a drawback of mechanical master-slave manipulators (MSM) for the equipment maintenance. The servo manipulator is composed of a slave manipulator attached to the telescoping tubesets equipped with the overhead bridge installed at a hot cell and a master manipulator installed at an out-of-hot cell. Each manipulator has 7 degrees-of-freedom (DOF): a body rotation, an upper-arm tilt, a lower-arm tilt, a lower-arm rotation, a wrist pan & tilt, and a grasp motion. A wire-driven mechanism for a lower-arm rotation, a wrist pan and tilt, and a grasp motion of the manipulator has been adopted to increase the handling capacity compared to the manipulator weight and decrease the friction. The main disadvantage of the wire-driven mechanism is that if one link is in motion, other links can be affected. In this paper, the transmission characteristics among the wire-driven links have been formulated to overcome this drawback. The unexpected behaviors are confirmed by analyses of transmission characteristics as well as experiments. Also, the experimental results show that the unexpected behaviors are greatly decreased by the proposed compensation equations.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.468-471
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• 1995

In this paper, we propose a new strategy for a space robot to control its attitude. A space robot is an example of a class of non-holonomic systems, a system of which cannot be stabilized into its equilibria with continuous static state feedbacks even in the case that the system is, in some sense, controllable. Thus, we cannot design stabilizing controllers for space robots using conventional control theories. The strategy presented here transforms the non-holonomic system into a time-state control form, and allows us to make the state of the original system any desired one. In the stabilization, any conventional control theory can be applied. For simplicity, a space robot with a two-link manipulator is considered, and a simulated motion of the controlled system is shown.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.144-150
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• 2000

In this paper, we introduce a modified six-degrees-of-freedom parallel-link manipulator, which will be applied to the human vibration experiments. We analyze the inverse kinematics and workspace of this manipulator and comprehend the characteristics of kinematics analyzed. Additionally, solutions of forward kinematics are obtained through the iterative Newton-Raphson method known as one of the most used numerical analysis. Finally, dynamic equation of the manipulator is derived in closed form through the Newton-Euler approach, which will be used for the development of control software.