• Title/Summary/Keyword: Initial Trajectory

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Walking Pattern Analysis for Reducing Trajectory Tracking Error in a Biped Robot (이족보행로봇의 궤적 추종 오차 감소를 위한 걸음새 분석)

  • 노경곤;공정식;김진걸
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.10
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    • pp.890-897
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    • 2002
  • This paper deals with the reduction of trajectory tracking error by changing the initial postures of a biped robot. Gait of a biped robot depends on the constraints of mechanical kinematics and the initial states including the posture. Also the dynamic walking stability in a biped robot system is analyzed by zero moment point(ZMP) among the stabilization indices. Path trajectory, in which knee joint is bent forward like human's cases, is applied to most cases considered with above conditions. A new initial posture, which is similar to bird's gait, is proposed to decrease trajectory tracking error and it is verified through real experimental results.

Pitch Command Generation Method for Consistent Initial Trajectory of Thrust-Vector-Controlled Vehicle (추력벡터제어 비행체의 일관된 탄도 성형을 위한 피치각명령 산출 방법)

  • Lee, Yong-In;Choe, Dong-Gyun;Hwang, Tae-Won
    • Journal of the Korea Institute of Military Science and Technology
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    • v.16 no.6
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    • pp.739-744
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    • 2013
  • In this paper, we propose a method of generating pitch commands for consistent initial trajectories irrelevant to flight conditions in the initial boosting phase of a thrust-vector-controlled vehicle. After shape assumption of the pitch command profile, parameters of the profile are determined in real time in order for the summit height of the trajectory to be a desired value by deriving the summit height considering thrust performance, gravity, and other flight conditions. Computer simulation results demonstrate good performance of the proposed method.

Real-time Implementation and Comparative Study on Trajectory Planning Methods for Robot Manipulators (로보트 매니퓰레이터에 대한 궤적 계획 방법들의 실시간 구현 및 상호 비교 연구)

  • Cho, Jeong-Ho;Suh, Il-Hong;Li, Joon-Hong;Yang, Hai-Won;Im, Dal-Ho
    • Proceedings of the KIEE Conference
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    • 1989.11a
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    • pp.462-466
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    • 1989
  • This paper describes the methods of spline low-order polynomial trajectory planning using only a few limited look-ahead knots on the desired trajectory for the real-time computing. Specifically presented are the mixed joint trajectory planning methods which apply linear or LSPB method to initial and finial segments, overlapped cubic spline method to the other segments, where the displacements for initial and finial segments are chosen to be relatively smaller than the displacements for the other, equidistant segments. Experimental and simulation results of these methods show smooth motions and improved path tracking performances compared with any other interpolated joint trajectory planning methods.

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Application of Iterative Learning Control to 2-Mass Resonant System with Initial Position Error (위치 오차를 갖는 2관성 공진계에 대한 반복학습 제어의 적용에 관한 연구)

  • Lee, Hak-Seong
    • Proceedings of the KIEE Conference
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    • 2003.11b
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    • pp.307-310
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    • 2003
  • In this paper, an iterative learning control method is applied to suppress the vibration of a 2-mass system which has a flexible coupling between a load an a motor. More specifically, conditions for the load speed without vibration are derived based on the steady-state condition. And the desired motor position trajectory is synthesized based on the relation between the load and motor speed. Finally, a PD-type learning iterative control law is applied for the desired motor position trajectory. Since the learning law applied for the desired trajectory guarantees the perfect tracking performance, the resulting load speed shows no vibration. In order to handle the initial position error, the PD-type learning law is changed to PID-type and a weight function is added to suppress the residual vibration caused by the initial error. The simulation results show the effectiveness of the proposed learning method.

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Convolution-based Desired Trajectory Generation Method Considering System Specifications (시스템 사양을 고려한 컨볼루션 기반 목표궤적 생성 방법)

  • Lee, Geon;Choi, Young-Jin;Kim, Jin-Hyun
    • Journal of Institute of Control, Robotics and Systems
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    • v.16 no.10
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    • pp.997-1005
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    • 2010
  • Most motion control systems consist of a desired trajectory generator, a motion controller such as a conventional PID controller, and a plant to be controlled. The desired trajectory generator as well as the motion controller is very important to achieve a good tracking performance. Especially, if the desired trajectory is generated actively utilizing the maximum velocity, acceleration, jerk and snap as given system specifications, the tracking performance would be better. For this, we make use of the properties of convolution operator in order to generate a smooth (S-curve) trajectory satisfying the system specifications. Also, the proposed trajectory generation method is extended to more general cases with arbitrary initial and terminal conditions. In addition, the suggested trajectory generator can be easily realized for real-time implementation. Finally, the effectiveness of the suggested method is shown through numerical simulations.

Synchronized On-line Trajectory Generation Method for Mechanical System with Multiple Degrees-of-Freedom (다자유도 기계 시스템의 모션 제어를 위한 동기된 온라인 궤적 생성 방법)

  • Won, Daehee;Shin, Eunchol
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.9
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    • pp.1385-1391
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    • 2017
  • This work presents a synchronized on-line trajectory generation algorithm for mechanical system with multiple degrees-of-freedom. Proposed algorithm is designed to generate time-optimized trajectories and synchronized trajectories under the constraints such as maximum speed, acceleration, deceleration, non-zero initial velocity, etc. Also, because of small computation time, therefore this can be applied in real-time and it is easier to change the trajectory when an event occurs. We verified the feasibility through various trajectory generation.

Robust Trajectory Tracking Control of a Mobile Robot Based on Weighted Integral PDC and T-S Fuzzy Disturbance Observer (하중 적분 PDC와 T-S 퍼지 외란 관측기를 이용한 이동 로봇의 강인 궤도 추적 제어)

  • Baek, Du-san;Yoon, Tae-sung
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.21 no.2
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    • pp.265-276
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    • 2017
  • In this paper, a robust and more accurate trajectory tracking control method for a mobile robot is proposed using WIPDC(Weighted Integral Parallel Distributed Compensation) and T-S Fuzzy disturbance observer. WIPDC reduces the steady state error by adding weighted integral term to PDC. And, T-S Fuzzy disturbance observer makes it possible to estimate and cancel disturbances for a T-S fuzzy model system. As a result, the trajectory tracking controller based on T-S Fuzzy disturbance observer shows robust tracking performance. When the initial postures of a mobile robot and the reference trajectory are different, the initial control inputs to the mobile robot become too large to apply them practically. In this study, also, the problem is solved by designing an initial approach path using a path planning method which employs $B\acute{e}zier$ curve with acceleration limits. Performances of the proposed method are proved from the simulation results.

A Study on the Gait Analysis for Initial Posture of a Biped Robot (이족 보행 로봇의 초기 자세에 따른 걸음새 해석에 관한 연구)

  • Noh, Kyung-Kon;Kim, Jin-Geol
    • Proceedings of the KIEE Conference
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    • 2001.11c
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    • pp.301-303
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    • 2001
  • This paper deals with the biped robot gait on changing the initial postures. Gait of a biped robot depends on the constraints of mechanical kinematics and initial posture. Also biped robot's dynamic walking stability is investigated by ZMP(Zero Moment Point). The path trajectory. with the knee joint bent like a human, is generated and applied with the above considerations. To decrease trajectory tracking error, in this paper, a new initial posture similar to bird's case is proposed and realized with the real robot.

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Trajectory Optimization for a Supersonic Air-Breathing Missile System Using Pseudo-Spectral Method

  • Park, Jung-Woo;Tahk, Min-Jea;Sung, Hong-Gye
    • International Journal of Aeronautical and Space Sciences
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    • v.10 no.1
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    • pp.112-121
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    • 2009
  • This paper deals with supersonic air-breathing missile system. A supersonic air-breathing missile system has very complicated and incoherent thrust characteristics with respect to outer and inner environment during operation. For this reason, the missile system has many maneuver constraints and is allowed to operate within narrow flight envelope. In this paper, trajectory optimization of the missile is accomplished. The trajectory optimization problem is formulated as a discrete parameter optimization problem. For this formulation, Legendre Pseudo-Spectral method is introduced. This method is based on calculating the state and control variables on Legendre-Gauss-Lobatto (LGL) points. This approach helps to find approximated derivative and integration quantities simply. It is shown that, for this trajectory optimization, trend analysis is performed from thrust characteristics on various conditions so that the trajectory optimization is accomplished with fine initial guess with these results.

Anomalous Propagation Characteristics of an Airy Beam in Nonlocal Nonlinear Medium

  • Wu, Yun-Long;Ye, Qin;Shao, Li
    • Current Optics and Photonics
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    • v.5 no.2
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    • pp.191-197
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    • 2021
  • The anomalous propagation characteristics of a single Airy beam in nonlocal nonlinear medium are investigated by utilizing the split-step Fourier-transform method. We show that besides the normal straight propagation trajectory, the breathing solitons formed by the interaction between Airy beam and nonlocal nonlinear medium can propagate along the sinusoidal trajectory, and the anomalous trajectory can be modulated arbitrarily by altering the initial amplitude and the nonlocal nonlinear coefficient. In addition, the initial amplitude and the nonlocal nonlinear coefficient can have inverse impacts on the formation and transformation of the equilibrium state of spatial solitons, when the two parameters are larger than certain values. Therefore, the reversible transformation of the evolution dynamics of two soliton states can be realized by adjusting those two parameters properly. Finally, it is shown that the propagation properties of the solitons formed by the interaction between Airy beam and nonlocal nonlinear medium can be controlled arbitrarily, by adjusting the distribution factor and nonlocal coefficient.