• Journal of Mechanical Science and Technology
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• v.15 no.4
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• pp.433-440
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• 2001

A new design of the sliding mode control is proposed for the uncertain linear time-varying second order system. The proposed control drives system states to the target point in the minimum time with specified ranges of parametric uncertainties and disturbances. One of the advantages of the proposed control scheme is that the control inputs do not go beyond saturation limits of the actuators. The other advantage is that the minimum arrival time and the acceleration of the second order actuators system can be estimated with given parametric bounds and can be expressed in the closed from; conversely, the designer can select actuators based on the condition of the minimum arrival time to the target point. The superior performance of the proposed control scheme to other sliding mode controllers is validated by computer simulations.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.7
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• pp.599-604
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• 2013

Path planning of mobile robots has a purpose to design an optimal path from an initial position to a target point. Minimum driving time, minimum driving distance and minimum driving error might be considered in choosing the optimal path and are correlated to each other. In this paper, an efficient driving trajectory is planned in a real situation where a mobile robot follows a moving object. Position and distance of the moving object are obtained using a web camera, and the rotation angular and linear velocities are estimated using Kalman filters to predict the trajectory of the moving object. Finally, the mobile robot follows the moving object using a single curvature trajectory by estimating the trajectory of the moving object. Using the estimation by Kalman filters and the single curvature in the trajectory planning, the total tracking distance and time saved amounts to about 7%. The effectiveness of the proposed algorithm has been verified through real tracking experiments.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.826-829
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• 1995

In this paper, the problem of minimum-time trajectory planning of a robot manipulator with an arbitrary path is dealt. As for a straight path, the trajectory planning can be done without difficulty since the path is easily parameterized by its length. However, this is not the case for a non-straight path. In this paper, by noting that the others' joint angles and velocities are determined if one joint's angle and velocity are known, we reduce the problem of trajectory planning on a non-straight path to one in the 2-dimensional space of one joint's angle and velocity. Then, by applying the dynamic programming, we achieve the minimum-time trajectory planning. A simulation is done for verifying this.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.263-266
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• 1996

A method to determine an optimal temperature trajectory that guarantees polymer products having controlled molecular weight distribution and desired values of molecular weight is presented. The coordinate transformation method and the optimal control theory are applied to a batch PMMA polymerization system to calculate the optimal temperature trajectory. Coordinate transformation method converts the original fixed-end-point, free-end-time problem to a free-end-point, fixed-end-time problem. The idea is that by making the reactor temperature track the optimal temperature trajectory one may be able to produce polymer products having the prespecified physical property in a minimum time. The on-line control experiments with the PID control algorithm have been conducted to establish the validity of the scheme proposed in this study. The experimental results show that prespecified polymer product could be obtained with tracking the calculated optimal temperature trajectory.

• Journal of Mechanical Science and Technology
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• v.20 no.11
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• pp.1834-1847
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• 2006

A robust minimum-time control (RMTC) strategy is addressed and it is extended to the dual-stage servo design. Rather than conventional switching type sub-optimal controls, it is a reference following control approach where the predetermined minimum-time trajectory (MTT) is tracked by the perturbation compensator based feedback controller. First, the minimum-time trajectory for a mass-damper system is derived. Then, the perturbation compensator to achieve robust tracking performance in spite of model uncertainty and external disturbance is suggested. The RMTC is also applied to the dual-stage positioner which consists of coarse actuator and fine one. To best utilize the actuation redundancy of the dual-stage mechanism, a null-motion controller to actively regulate the relative motion between the two stages is formulated. The performance of RMTC is validated through simulation and experiment.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.162-167
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• 2003

In this paper, a novel feasible real-time system was researched for a differential driven wheeled autonomous mobile robot so that the mobile robot can move in a smooth, safe and elegant way. Least Square Minimum Path Planning was well used for the system to generate a smooth executable path for the mobile robot, and the point-to-point tracking algorithm was presented as well as its application in arbitrary path tracking. In order to make sure the robot can run elegantly and safely, trapezoidal speed was integrated into the point-to-point path tracking algorithm. The application to guest following for the autonomous mobile robot shows its wide application of the algorithm. The novel design was successfully proved to be feasible by our experiments on our mobile robot Interactive Robot Usher (IRU) in National University of Singapore.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.101-106
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• 2003

In the area of tracking control, it is important to design not only the controllers but also the trajectories to which a system has to follow. $5^{th}$ order polynomial is often used with constraints of initial and final states. Smooth ending with possible minimum time is important for many systems because of vibration or jerky motions. Examples are increased with development of technology in smaller, more accurate systems. On the base of a polynomial like trajectory generation method from a paper in ACC2002 and RIC(Robust Internal-loop Compensator) control scheme of Robotics and Bio-mechanics lab. of POSTECH, generalized and expanded polynomial like trajectory generation method is showed.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1587-1592
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• 2004

In the area of tracking control, it is important to design not only the controllers but also the trajectories to which a system has to follow. Position in the form of the $5^{th}$ order polynomial is often used with constraints of initial and final states. Smooth ending with possible minimum time is important for many systems to be away from vibrations or jerky motions. A simple polynomial-like trajectory generation method based on zero final state constraints is suggested and named ZSPOT. The effects of suggested method are shown through experiments in which a system follows an easy and computationally light reference trajectory.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.2
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• pp.61-71
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• 2005

The study reported deals with investigating the feasibility of control strategy for a serial rigid link manipulator that applies impulsive torques at the joints. The strategy is illustrated for a planar three rigid link manipulator. An impulse-based concept which uses successive torque impulses on rigid link as the controller for motion correction was introduced. This control strategy was tested over the entire trajectory to demonstrate that the tracking error could be reduced effectively. The best condition for minimizing the tracking error with the least impulse input at each joint is investigated by considering one design and one operating parameter. The first was the damping in the system, and the second was the sampling time during operation. The results show that this approach can provide useful guidance for the design and control of robot manipulators that require minimum impulse feedback for accurate tracking.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.301-305
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• 2001

Conventionally, robot control algorithms are divided into two stages, namely, path or trajectory planning and path tracking(or path control). This division has been adopted mainly as a means of alleviating difficulties in dealing with complex, complex, coupled manipulator dynamics. The minimum-time manipulator control problem is solved for the case when the path is specified and the actuator torque limitations are known. In path planning, DP is applied to applied to find the shortest path form initial position to final position with the assumptions that there is no obstacle and that each path is straight line. In path control, the phase plane technique is applied to the minimum-time control with the assumptions that the bound on each actuator torque is a function of joint position and velocity or constant. This algorithm can be used for any manipulator that has rigid link, known dynamics equations of motion, and joint angles that can be determined at a given position on the path.