• Journal of Institute of Control, Robotics and Systems
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• v.21 no.12
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• pp.1193-1200
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• 2015

An effective swing trajectory of legged robots is different from the swing trajectories of humans or animals because of different dynamic characteristics. Therefore, it is important to find optimal parameters through experiments. This paper proposes a real-time nonlinear programming (RTNLP) method for optimization of the swing trajectory of the legged robot. For parameterization of the trajectory, the swing trajectory is approximated to parabolic and cubic spline curves. The robotic leg is position-controlled by a high-gain controller, and a cost function is selected such that the sum of the motor inputs and tracking errors at each joint is minimized. A simplified dynamic model is used to simulate the dynamics of a robotic leg. The purpose of the simulation is to find the feasibility of the optimization problem before an actual experiment occurs. Finally, an experiment is carried out on a real robotic leg with two degrees of freedom. For both the simulation and the experiment, the design variables converge to a feasible point, reducing the cost value.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.612-620
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• 2006

This paper proposes an optimal trajectory generation method for biped robots for walking up-and-down stairs using a Real-Coded Genetic Algorithm (RCGA). The RCGA is most effective in minimizing the total consumption energy of a multi-dof biped robot. Each joint angle trajectory is defined as a 4-th order polynomial of which the coefficients are chromosomes or design variables to approximate the walking gait. Constraints are divided into equalities and inequalities. First, equality constraints consist of initial conditions and repeatability conditions with respect to each joint angle and angular velocity at the start and end of a stride period. Next, inequality constraints include collision prevention conditions of a swing leg, singular prevention conditions, and stability conditions. The effectiveness of the proposed optimal trajectory is shown in computer simulations with a 6-dof biped robot model that consists of seven links in the sagittal plane. The optimal trajectory is more efficient than that generated by the Modified Gravity-Compensated Inverted Pendulum Mode (MGCIPM). And various trajectories generated by the proposed GA method are analyzed from the viewpoint of the consumption energy: walking on even ground, ascending stairs, and descending stairs.

• Journal of Korea Spatial Information System Society
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• v.10 no.1
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• pp.29-40
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• 2008

With the spread of mobile devices and advances in communication techknowledges, the needs of application which uses the movement patterns of moving objects in history trajectory data of moving objects gets Increasing. Especially, to design public transportation route or road network of the new city, we can use the similar patterns in the trajectories of moving objects that move on the spatial network such as road and railway. In this paper, we propose a spatio-temporal similar trajectory search algorithm for moving objects on road network. For this, we define a spatio-temporal similarity measure based on the real road network distance and propose a grid-based index structure for similar trajectory search. Finally, we analyze the performance of the proposed similar trajectory search algorithm in order to show its efficiency.

• Journal of Navigation and Port Research
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• v.42 no.2
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• pp.87-96
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• 2018

A trajectory control system plays an important role in controlling motions of marine vehicle when a series of way points or a path is given. In this paper, a sliding mode control (SMC)-based trajectory tracking controller for marine vehicles is presented. A small-sized unmanned ship is considered as a control object. Both speed and heading angle of a ship should be controlled for tracking control. The common point of related researches was to separate ship's speed and heading angle in control methods. In this research, a new control law from a general sliding mode theory that can be applied to MIMO (multi input multi output) system is derived and both speed and heading angle of a ship can be controlled simultaneously. The propulsion force and rudder force are also applied in modeling stage to achieve accurate simulation. Disturbance induced by wind is also tackled in the dynamics considering robustness of the proposed control scheme. In the simulation, we employed a way-point method to generate ship's trajectory and applied the proposed control scheme to ship's trajectory tracking control. Our results confirmed that the tracking error was converged to zero, thus demonstrating the effectiveness of the proposed method.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.6
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• pp.936-941
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• 1987

This paper prexents an adaptive control scheme which adjusts any deviations of the manipulator from a desired trajectory. The scheme combines a new adaptive control and the conventional nominal control which drives the manipulator to the neighborhood of the trajectory. The proposed adaptive control is developed based on the lineatized perturbation equations in the vicinity of the trajectory and the Lyapunov design method, which makes the perturbations exponentially decay and has less computational requirements than the existing ones.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.369-373
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• 1992

Force control of a planar two-link structurally flexible robotic manipulator is considered in this study. The dynamic model is obtained by using the extended Hamilton's principle and the Galerkin criterion. A method is pressented toobtain the linearized equations of motion in Cartesian space for use in designing the control system. The approachto solving the control problem is to use feedforward and feedback control torques. The feedforward torques maneuver the flexible manipulatro along a nominal trajectory and the feedback torques minimize any deviations from the nominal trajectory. The linear quadratic Gaussian/loop transfer recovery (LQG/LTR) design methodology is explotied to design a robust feedback control system that can handle modeling errors and sensor noise, and operates on Cartesian space trajectory errors. The Lqg/LTR compenstaor together with a feedforward ollp is used to control the flexible manipulator. Simulated results are presented for a numerical example.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.479-486
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• 1998

In this paper, the design and the implementation of a robust adaptive controller for trajectory tracking of robot manipulator is presented. The proposed control scheme ensures that tracking errors are converged to some boundaries in the presence of a state-dependent input disturbances as well as the ideal case without any prior knowledge of the robot manipulator parameters. The 3 DOF robot manipulator including actuator dynamics is used for the implementation of the proposed control scheme. The experimental results show that the proposed control scheme is valid for trajectory tracking of the robot manipulator.

• Transactions of The Korea Fluid Power Systems Society
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• v.4 no.2
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• pp.1-6
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• 2007

During the last few decades, excavation automation has been investigated to protect the operator from the hazardous working environment and to relieve the cost of the skilled operator. Therefore, a number of modelling and controller design methods of the hydraulic excavator are proposed in many literatures to realize the excavation automation. In this article, a geometric approach far the multi-body system modeling is adopted to develop the excavator mechanism model that contains 4 kinematic loops and 12 links. Considering a simple soil mechanism model with a number of uncertain soil parameters, an adaptive trajectory tracking control strategy based on the developed excavator model is proposed. The improved performance of the designed controller over the simple PID controller is validated via the simulation study.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.1
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• pp.118-128
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• 2006

This paper deals with auto-landing guidance system design applicable to Smart UAV(Unmanned Aerial Vehicle). The proposed guidance law generates horizontal position, velocity and altitude commands in the longitudinal channel and heading angle command in the lateral channel to track a predetermined trajectory for automatic landing. The longitudinal guidance commands are derived from an approximated dynamic equations in vertical plane. These longitudinal guidance commands are appropriately distributed to each control input as the flight mode of Smart UAV is changed. The concept of VOR(VHF Omni-directional Range) guidance system is applied to generate the required heading angle commands to eliminate the lateral deviation from the desired trajectory. The performance of the proposed guidance system for Smart UAV is evaluated using the nonlinear simulation. Simulation results show that the proposed guidance system for auto- landing provides good tracking performance along the predetermined landing trajectory.

• International Journal of Control, Automation, and Systems
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• v.2 no.3
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• pp.289-297
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• 2004

This paper deals with the design and control of passive multiple trailer systems for practical applications. Due to the cost and complexity of the trailer mechanism, passive systems are preferred to active systems in this research. The design and control objective is to minimize the trajectory tracking errors occurring in passive multiple trailers. Three sorts of passive trailer systems, off-hooked, direct-hooked, and three-point, are discussed in this paper. Trajectory tracking performance and stability issues under constant curvature reference trajectories are investigated for these three types. As well, various simulations and experiments have been performed for each type. It is shown that the proposed off-hooked trailer system produces a tracking performance that is superior to the others.