• 제어로봇시스템학회논문지
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• 제21권5호
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• pp.471-476
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• 2015

This paper presents a maximum velocity trajectory planning algorithm for differential mobile robots with wheel velocity constraint to cope with physical limits in the joint space for two-wheeled mobile robots (TMR). In previous research, the convolution operator was able to generate a central velocity that deals with the physical constraints of a mobile robot while considering the heading angles along a smooth curve in terms of time-dependent parameter. However, the velocity could not track the predefined path. An algorithm is proposed to compensate an error that occurs between the actual and driven distance by the velocity of the center of a TMR within a sampling time. The velocity commands in Cartesian space are also converted to actuator commands to drive two wheels. In the case that the actuator commands exceed the maximum velocity the trajectory is redeveloped with the compensated center velocity. The new center velocity is obtained according to the curvature of the path to provide a maximum allowable velocity meaning a time-optimal trajectory. The effectiveness of the algorithm is shown through numerical examples.

• 한국정밀공학회지
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• 제16권12호
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• pp.14-23
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• 1999

This paper proposes a method to generate the velocity trajectory which guarantees user specified contour errors at corners for high speed and high precision motion control of CNC machines. The relation among the desired trajectory, system bandwidth and corner contour error are derived. Experiments show that the corner contour error specified by users can be guaranteed with the proposed velocity trajectory.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권3호
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• pp.282-293
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• 2018

This paper attempts to address the motion parameter skip problem associated with three-dimensional trajectory tracking of an underactuated Autonomous Underwater Vehicle (AUV) using backstepping-based control, due to the unsmoothness of tracking trajectory. Through kinematics concepts, a three-dimensional dynamic velocity regulation controller is derived. This controller makes use of the surge and angular velocity errors with bio-inspired models and backstepping techniques. It overcomes the frequently occurring problem of parameter skip at inflection point existing in backstepping tracking control method and increases system robustness. Moreover, the proposed method can effectively avoid the singularity problem in backstepping control of virtual velocity error. The control system is proved to be uniformly ultimately bounded using Lyapunov stability theory. Simulation results illustrate the effectiveness and efficiency of the developed controller, which can realize accurate three-dimensional trajectory tracking for an underactuated AUV with constant external disturbances.

• 제어로봇시스템학회논문지
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• 제19권6호
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• pp.540-546
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• 2013

This paper presents a trajectory planning algorithm for TMR (Two-wheeled Mobile Robots). The trajectory is developed in joint space and considers the physical limits of a TMR. First, we present a process for generating a smooth curve through a Bezier curve. The trajectory for the center of the TMR following the Bezier curve is developed through a convolution operator taking into consideration its physical limits. The trajectory along the Bezier curve is regenerated using time-dependent parameters which correspond to the distance driven by the velocity of the center of the TMR in a sampling time. The velocity commands in the Cartesian space are converted to actuator commands for two wheels. In case that the actuator commands exceed the maximum velocity, the trajectory is redeveloped with compensated center velocity. We also suggest a smooth trajectory planning algorithm in joint space for the two segmented paths. Finally, the effectiveness of the algorithm is shown through numerical examples and application to a simulator.

• 한국군사과학기술학회지
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• 제21권1호
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• pp.1-9
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• 2018

In this paper, we have proposed a prediction method for sabot-trajectory of projectile using high speed camera data analysis. Through analyzing trajectory of sabot with high speed camera data, we can extract its real velocity and acceleration including effects of friction force, pressure of flume, etc. Using these data, we suggest a prediction method for sabot-trajectory of projectile having variable acceleration, especially for minimum and maximum acceleration, by using interpolation method for velocity and acceleration data of sabot. Also we perform the projectile launching tests to achieve the trajectory of sabot in case of minimum and maximum thrust. Simulation results show that they are similar to real tests data, for example velocity, acceleration and the trajectory of sabot.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.977-980
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• 1995

This paper proposes the look ahead algorithm with the trapezoidal velocity trajectory in each G-code block. The algorithm requires the information on the length of next trajectories and the connecting angle between each trajectiories. A method of generating the maximum corner velocity upon the connecting angle within the machining tolerance is developed and applied to the look ahead algorithm. Simulations and experiments witha machining center show the effectiveness of the methodology.

• 대한기계학회논문집A
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• 제38권11호
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• pp.1193-1199
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• 2014

서비스 로봇이 충돌안전성을 확보한 상태에서 고속 주행 임무를 수행하기 위해서는 동적 장애물의 속도를 고려한 궤적 계획이 필요하다. 정적 장애물만을 고려한 상태에서 궤적을 계획하는 경우 장애물과의 상대속도로 인해서 로봇이 장애물과 충돌할 수 있다. 본 연구에서는 동적 장애물의 속도를 고려한 궤적시간조정기법을 제안한다. 제안된 기법을 통해서 기존에 생성된 궤적의 시간을 조정해서 장애물 회피가 가능한지를 평가할 수 있다. 만일 회피가 불가능할 경우 생성된 경로가 아닌 다른 경로를 선택할 수 있다. 모의 시험 결과를 통해서 제안된 기법을 통해서 짧은 시간 내에 장애물 회피를 수행할 수 있음을 보였다.

• 제어로봇시스템학회논문지
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• 제8권6호
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• pp.498-505
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• 2002

Reducing odometer errors caused by kinematic imperfections in wheeled mobile robots is imestigated. Wheel diameters and wheelbase are corrected by using encoders without landmarks. A new velocity trajectory is proposed that compensates for an orientation error due to acceleration- resolution constraints on motor controllers. Based on this velocity trajectory, the wheel velocity of one out of two driven wheels may be changed by the traveled distance of the mobile robot. It is shown that a wheeled mobile robot can't move along a straight line exactly, even if kinematic correction are achieved perfectly, and this phenomenon is attributable to acceleration-resolution constraints on motor controllers. We experiment on a wheeled mobile robot with 2 d.o.f. are used in the experiment to verify the proposed scheme.

• International Journal of Control, Automation, and Systems
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• 제1권1호
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• pp.68-75
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• 2003

This paper presents an effective trajectory planning algorithm for industrial robot manipulators. Given the end-effector trajectory in Cartesian space, together with the relevant constraints and task specifications, the proposed method is capable of planning the optimum end-effector trajectory. The proposed trajectory planning algorithm considers the joint acceleration limit, end-effector velocity limits, and trajectory allowance. A feedforward compensator is also incorporated in the proposed algorithm to counteract the delay in joint dynamics. The algorithm is carefully designed so that it can be directly adopted with the existing industrial manipulators. The proposed algorithm can be easily programmed for various tasks given the specifications and constraints. A three-dimensional test trajectory was planned with the proposed algorithm and tested with the Performer MK3s industrial manipulator. The results verified effective manipulator performance within the constraints.

• 한국정밀공학회지
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• 제11권5호
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• pp.143-152
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• 1994

The velocity trajectory profile of trolley is designed to minimize both swinging while transportation of load and the stop position error at the final stop position. This profile is designed to be automatically programmed by the digital control algorithm when the length of chain and the desired travel distance are given as a priori. Also, to minimize both swinging and the stop position error the anti-swing controller which improves poor damping characteristics of the crane and the stop position controller are employed. The experimentalresults of sequential adaptation of the velocity trajectory profile and these two controllers show that this control scheme has excellent control performance as compared with that of the uncontrolled crane system.