• Journal of Institute of Control, Robotics and Systems
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• v.16 no.9
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• pp.883-890
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• 2010

This paper proposes tip position control system which uses a visual marker to determine the tip position of a robot manipulator. The main idea of this paper is to introduce visual marker for the tracking control of a robot manipulator. Existing researches utilize stationary markers to get pattern information from them. Unlike existing researches, we introduce visual markers to get the coordinates of them in addition to their pattern information. Markers need not be stationary and the extracted coordinate of markers are used as a reference trajectory for the tracking control of a robot manipulator. To build the proposed control scheme, we first obtain intrinsic parameters through camera calibration and evaluate their validity. Secondly, we present a procedure to obtain the relative coordinate of a visual marker with respect to a camera. Thirdly, we derive the equation for the kinematics of the SCORBOTER 4pc manipulator which we use for control of manipulator. Also, we provide a flow diagram of entire visual marker tracking system. The feasibility of the proposed scheme will be demonstrated through real experiments.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.531-536
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• 2003

In this paper, a redesigned guidance and control system for a lunar lander is presented. In past studies, the authors developed a trajectory and attitude control system which achieves the vertical soft landing on the lunar surface. It is confirmed that the system has a good tracking ability to a predefined profile and good robustness against a thruster failure mode where a partial failure of clustered engines was assumed. However, under the previous control laws, the landing point tends to be shifted, in response to the system parameter values, from a target point. Also, an unbalanced moment due to a thruster failure mode was not considered in the simulation. Therefore, in this study, the downrange control is added to the system to enable the vehicle to land at a pre-assigned target point accurately. Furthermore, inhibiting the effect of the unbalanced moment is attempted thorough redesigning the attitude control system. A numerical simulation was performed to confirm the ability of the proposed system with regard to the above problems. Moreover, in the past simulations, a low initial altitude was assumed as an initial condition: in this study, however, the performance of the proposed system is examined over the whole trajectory from an initial altitude of 10 [km] to the lunar surface.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.2
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• pp.140-147
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• 2008

This paper describes a Neural Network based PD control scheme for motion control of pneumatic servo cylinder. Pneumatic systems have inherent nonlinearities such as compressibility of air and nonlinear frictions present in cylinder. The conventional linear controller is limited in some applications where the affection of nonlinear factor is dominant. A self-excited oscillation method is applied to derive the dynamic design parameters of linear model. Based on the parameters thus identified, a PD feedback compensator is designed first and then a neural network is incorporated. The experiments of a trajectory tracking control using the proposed control scheme are performed and a significant reduction in tracking error is achieved by comparing with those of a PD control.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.4
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• pp.350-358
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• 2009

This paper describes a result of the guidance and control for re-entry vehicle during TAEM phase. TAEM phase (Terminal Aerial Energy Management phase) has many conditions, such as density, velocity, and so on. Under these conditions, we have optimized trajectory and other states for guidance in TAEM phase. The optimized states consist of 7 variables, down-range, cross range, altitude, velocity, flight path angle, vehicle's azimuth and flight range. We obtained the optimized reference trajectory by DIDO tool, and used feedback linearization with neural network for control re-entry vehicle. By back propagation algorithm, vehicle dynamics is approximated to real one. New command can be decided using the approximated dynamics, delayed command input and plant output, NARMA-L2. The result by this control law shows a good performance of tracking onto the reference trajectory.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.103-113
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• 2018

In this paper, an improved integral variable structure regulation controller is designed by using a special integral sliding surface and a disturbance observer for the improved regulation control of highly nonlinear rigid robot manipulators with prescribed output performance. The sliding surface having the integral state with a special initial condition is employed in this paper to exactly predetermine the ideal sliding trajectory from a given initial condition to the desired reference without any reaching phase. And a continuous sliding mode input using the disturbance observer is also introduced in order to effectively follow the predetermined sliding trajectory within the prescribed accuracy without large computation burden. The performance of the prescribed tracking accuracy to the predetermined sliding trajectory is clearly investigated in detail through the two theorems, together with the closed loop stability. The design of the proposed regulation controller is separated into the performance design and robustness design in each independent link. The usefulness of the algorithm has been demonstrated through simulation studies on the regulation control of a two-link robot under parameter uncertainties and payload variations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.4 s.175
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• pp.1007-1015
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• 2000

This paper proposes an adaptive trajectory generation strategy of using on-line ZMP information and an impedance control method for biped robots. Since robots experience various disturbances during their locomotion, their walking mechanism should have the robustness against those disturbances, which requires an on-line adaptation capability. In this context, an on-line trajectory planner is proposed to compensate the required moment for recovering stability. The ZMP equation and sensed ZMP information are used in this trajectory generation strategy. In order to control a biped robot to be able to walk stably, its controller should guarantee stable footing at the moment of feet contacts with the ground as well as maintaining good trajectory tracking performance. Otherwise, the stability of robot will be significantly compromised. To reduce the magnitude of an impact and guarantee a stable footing when a foot contacts with the ground, this paper. proposes to increase the damping of the leg drastically and to modify the reference trajectory of the leg. In the proposed control scheme, the constrained leg is controlled by impedance control using the impedance model with respect to the base link. Computer simulations performed with a 3-dof environment model that consists of combination of a nonlinear and linear compliant contact model show that the proposed controller performs well and that it has robustness against unknown uneven surface. Moreover, the biped robot with the proposed trajectory generator can walk even when it is pushed with a certain amount of external force.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.105-111
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• 2006

This paper describes a Neural Network based PID control scheme for pneumatic NC axes. Pneumatic systems have inherent nonlinearities such as compressibility of air and nonlinear frictions present in cylinder. The conventional PID controller is limited in some applications where the affection of nonlinear factor is dominant. A self-excited oscillation method is applied to derive the dynamic design parameters of linear model. The gains of PID controller are determined using a self tuning scheme. The experiments of a trajectory tracking control using the proposed control scheme are performed and a significant reduction in tracking error is achieved by comparing with those of a PID control.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.12
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• pp.1132-1138
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• 2012

The MPC (Model Predictive Control) is one of the techniques that can be used to control an unmanned vehicle. It predicts the future vehicle trajectory using the dynamic characteristic of the vehicle and generate the control value to track the reference path. If some obstacles are detected on the reference paths, the MPC can generate control value to avoid the obstacles imposing the inequality constraints on the MPC cost function. In this paper, we propose an obstacle modeling algorithm for MPC with inequality constraints for obstacle avoidance and a method to set selective constraint on the MPC for stable obstacle avoidance. Simulations with the field test data show successful obstacle avoidance and way point tracking performance.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.179-181
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• 2007

This paper presents the desired position control of the mobile inverted pendulum system(MIP). The MIP is required to track the circular trajectory in the xy plane through the kinematic Jacobian relationship between the xy plane and the joint space. The reference compensation technique of the radial basis function(RBF) network is used as a neural network control method. The back-propagation teaming algorithm of the RBF network is derived and embedded on a DSP board. Experimental studies of tracking the circular trajectory are conducted.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.969-980
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• 2018

This paper aims to design of the neutrosophic fuzzy-PID controller and it has been compared with the conventional fuzzy-PID controller for position tracking control in terms of robustness. In the neutrosophic fuzzy-PID controller, error (e) and change of error (ce) were assessed separately on two fuzzy inference systems (FISs). In this study, the designed method is different from the conventional fuzzy logic controller design, membership degrees of antecedent variables were determined by using the T(true), I(indeterminacy), and F(false) membership functions. These membership functions are grouped on the universe of discourse with the neutrosophic set approach. These methods were tested on three-dimensional (3-D) position-tracking control application of a spherical robot manipulator in the MATLAB Simulink. In all tests, reference trajectory was defined for movements of all axes of the robot manipulator. According to the results of the study, when the moment of inertia of the rotor is changed, less overshoot ratio and less oscillation are obtained in the neutrosophic fuzzy-PID controller. Thus, our suggested method is seen to be more robust than the fuzzy-PID controllers.