• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.12
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• pp.3883-3891
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• 1996

Performance and productivity of robot manipulator can be improved by increasing its working speed and extending its link length. But heavy weght of the commercial robot links, considered as "rigid body", limits its mazimum working speed and the weght of the links can be reduced for high speed operation. But this light-weight link or long link for special use cannot be consideredas "rigid" structure and vibration of the link due to its flexibility causes errors in end-effector position and orientation. Thus the elastic behaviro of the flexible link should be taken care of for increasing work speed and getting smaller error of end-effector position. In this paper, the fuzzy control theory is selected to design the controller which controlos the joint positions of the robot manipulator and suppress the vibration of flexible link. In the forst place, for the 1 DOF flexible link system, the fuzzy control theory is implemented. The contdroller for the 1 DOF flexible link system is designed. Experimental research is carried out to examine the controllability and the validity of the fuzzy control theory based controller. Next, using the extended desing schemes for the case of the 1 DOF flexible link system and usign the experimental phenomena of the 3 DOF flexible link system, the fuzzy controller for the 3 DOF flexible link system is desinged and experimented.ed and experimented.

• Journal of Advanced Navigation Technology
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• v.20 no.6
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• pp.528-538
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• 2016

In this paper, an extend kalman filter based relative navigation algorithm is proposed for Link-K based relative navigation. Link-K is a tactical data link system for joint operation capability upgrade of ROK forces. Link-K is inter-operable with Link-16 and transmit and received information of operations and target. In Link-K communication channel, PPLI message including transmitter position and TOA measurement can be used for relative navigation. Therefore Link-K based relative navigation system can be operated. In this paper, software based simulations were carried out for operational feasibility test and performance verification as error factors of proposed Link-K based relative navigation system.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.31-46
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• 2009

An Unscented Kalman Filter (UKF) for estimation of the attitude and rate of a spacecraft using only magnetometer vector measurement is developed. The attitude dynamics used in the estimation is the nonlinear Euler's rotational equation which is augmented with the quaternion kinematics to construct a process model. The filter is designed for small satellite in low Earth orbit, so the disturbance torques include gravity-gradient torque, magnetic disturbance torque, and aerodynamic drag torque. The magnetometer measurements are simulated based on time-varying position of the spacecraft. The filter has been tested not only in the standby mode but also in the detumbling mode. Two types of actuators have been modeled and applied in the simulation. The PD controller is used for the two types of actuators (reaction wheels and thrusters) to detumble the spacecraft. The estimation error converged to within 5 deg for attitude and 0.1 deg/s for rate respectively when the two types of actuators were used. A joint state parameter estimation has been tested and the effect of the process noise covariance on the parameter estimation has been indicated. Also, Monte-Carlo simulations have been performed to test the capability of the filter to converge with the initial conditions sampled from a uniform distribution. Finally, the UKF performance has been compared to that of the EKF and it demonstrates that UKF slightly outperforms EKF. The developed algorithm can be applied to any type of small satellites that are actuated by magnetic torquers, reaction wheels or thrusters with a capability of magnetometer vector measurements for attitude and rate estimation.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.1
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• pp.73-80
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• 2000

The stewart platform manipulator proposed by stewart is the parallel manipulator which is composed of several independent actuators connecting the upper plate with the base plate and capable of executing a six degree of freedom motion. The manipulator has a structure of a closed loop form, and provides better load-to-weight ratio and ratio and rigidity than a serial manipulator with an open loop form. Moreover, the manipulator has high positional accuracy because position errors of actuators are not additive. Because of these advantages, this manipulator is widely used in many engineering applications such as a driving simulator, a tool of machining center, a force/torque sensor and so on. When this Stewart platform manipulator is controlled in joint space, it is difficult to design a controller using an analytic method due to nonhnearity and unknown parameters of actuators. Therefore, a PID controller is often used because of easiness in applications. To find the PID control gain, a trial-and-error method is generally used. This method is time-consuming, and does not guarantee a optimal gain. Thus, this paper proposes a GA-PID controller which selects an optimal PID control gain using genetic algorithms. And this proposed controller is evaluated experimentally and shows acceptable performance.

• Journal of Korean Society of Forest Science
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• v.111 no.2
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• pp.287-301
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• 2022

This study aims to propose a crane-tip control method to intuitively control the end-effector vertically or horizontally for improving the crane work efficiency and to confirm the control performance. To verify the control performance based on experimental variables, a laboratory-scale crane was manufactured using an electric cylinder. Through a forward and reverse kinematics analysis, the crane was configured to output the position coordinates of the current crane-tip and the joint angle at each target point. Furthermore, a method of generating waypoints was used, and a dead band using lateral boundary offset (LBO) was set. Appropriate parameters were selected using bang-bang control, which confirmed that the number of waypoints and LBO radius were associated with positioning error, and the cylinder speed was related to the lead time. With increased number of waypoints and decreased LBO radius, the positioning error and the lead time also decreased as the cylinder speed decreased. Using the proportional control, when the cylinder velocity was changed at every control cycle, the lead time was greatly reduced; however, the actual control pattern was controlled by repeating over and undershoot in a large range. Therefore, proportional control was performed by additionally applying velocity gain that can relatively change the speed of each cylinder. Since the control performed with in a range of 10 mm, it was verified th at th e crane-tip control can be ach ieved with only th e proportional control to which the velocity gain was applied in a control cycle of 20 ms.