• Title/Summary/Keyword: Iterative Learning Control

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Orthogonalization principle for hybrid control of robot arms under geometric constraint

  • Arimoto, Suguru
    • 제어로봇시스템학회:학술대회논문집
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    • 1992.10b
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    • pp.1-6
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    • 1992
  • A principle of "orthogonalization" is proposed as an extended notion of hybrid (force and position) control for robot manipulators under geometric endpoint constraints. The principle realizes the hybrid control in a strict sense by letting position and velocity feedback signals be orthogonal in joint space to the contact force vector whose components are exerted at corresponding joints. This orthogonalization is executed via a projection matrix computed in real-time from a gradient of the equation of the surface in joint coordinates and hence both projected position and velocity feedback signals become perpendicular to the force vector that is normal to the surface at the contact point in joint space. To show the important role of the principle in control of robot manipulators, three basic problems are analyzed, the first is a hybrid trajectory tracking problem by means of a "modified hybrid computed torque method", the second is a model-based adaptive control problem for robot manipulators under geometric endpoint constraints, and the third is an iterative learning control problem. It is shown that the passivity of residual error dynamics of robots follows from the orthogonalization principle and it plays a crucial role in convergence properties of both positional and force error signals.force error signals.

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A Second-Order Iterative Learning Algorithm with Feedback Applicable to Nonlinear Systems (비선형 시스템에 적용가능한 피드백 사용형 2차 반복 학습제어 알고리즘)

  • 허경무;우광준
    • Journal of Institute of Control, Robotics and Systems
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    • v.4 no.5
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    • pp.608-615
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    • 1998
  • In this paper a second-order iterative learning control algorithm with feedback is proposed for the trajectory-tracking control of nonlinear dynamic systems with unidentified parameters. In contrast to other known methods, the proposed teaming control scheme utilize more than one past error history contained in the trajectories generated at prior iterations, and a feedback term is added in the learning control scheme for the enhancement of convergence speed and robustness to disturbances or system parameter variations. The convergence proof of the proposed algorithm is given in detail, and the sufficient condition for the convergence of the algorithm is provided. We also discuss the convergence performance of the algorithm when the initial condition at the beginning of each iteration differs from the previous value of the initial condition. The effectiveness of the proposed algorithm is shown by computer simulation result. It is shown that, by adding a feedback term in teaming control algorithm, convergence speed, robustness to disturbances and robustness to unmatched initial conditions can be improved.

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Model-based iterative learning control with quadratic criterion for linear batch processes (선형 회분식 공정을 위한 이차 성능 지수에 의한 모델 기반 반복 학습 제어)

  • Lee, Kwang-Soon;Kim, Won-Cheol;Lee, Jay-H
    • Journal of Institute of Control, Robotics and Systems
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    • v.2 no.3
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    • pp.148-157
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    • 1996
  • Availability of input trajectories corresponding to desired output trajectories is often important in designing control systems for batch and other transient processes. In this paper, we propose a predictive control-type model-based iterative learning algorithm which is applicable to finding the nominal input trajectories of a linear time-invariant batch process. Unlike the other existing learning control algorithms, the proposed algorithm can be applied to nonsquare systems and has an ability to adjust noise sensitivity as well as convergence rate. A simple model identification technique with which performance of the proposed learning algorithm can be significantly enhanced is also proposed. Performance of the proposed learning algorithm is demonstrated through numerical simulations.

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Design and implementation of a high precision

  • Ahn, Hyun-Sik;Oh, Sang-Rok;Choy, Ick;Kim, Kwang-Bea;Ko, Myoung-Sam
    • 제어로봇시스템학회:학술대회논문집
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    • 1990.10b
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    • pp.1415-1419
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    • 1990
  • A novel type of a play-back servo system with high precision is designed using an iterative learning control method by employing the model algorithmic control concept together with an inverse model. A sufficient condition is also provided for the convergency. It is shown by simulation that the proposed control algorithm yields a good performance even in the presence of a periodic load disturbance and proved by experiments using microprocessor-based play-back servo system.

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Precision of Iterative Learning Control for the Multiple Dynamic Subsystems (복합구조물의 선형반복학습제어 정밀도 연구)

  • Lee, Soo-Cheol
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.3
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    • pp.131-142
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    • 2001
  • 다양한 산업체에서 반복적인 특정업무를 수행하는 경우가 흔히 발생한다. 반복되는 오차의 경험치를 근거로 주어진 작업을 추진하는 과정에서 이들 업무의 정밀도제고를 추구함으로써 갖는 성능개선은 사업장의 품질관리와 직결된다. 학습제어의 본래 적용동기는 생산조립라인에 투입되어 반복적인 일을 수행하는 산업로봇의 정밀도 제고이다. 본 논문에서 분산이산시형시스템에서 출발하였으며, 이를 산업용로봇에 적용하기 위하여 수학적으로 모델링한 모의실험을 통하여 알고리즘의 안정성과 반복오차를 줄여가는 과정을 보여 주었다. 입출력정보가 상호간섭 하는 산업용로봇과 같은 복합구조물에서도 모든 시스템(링크)의 정밀도를 만족함을 보여 줌으로써 복합구조물에서 선형반복학습제어의 안정성을 증명하였다.

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Development of Piano Playing Robot (피아노 연주 로봇의 개발)

  • Park, Kwang-Hyun;Jung, Seong-Hoon;Pelczar, Christopher;Hoang, Thai V.;Bien, Zeung-Nam
    • Proceedings of the KIEE Conference
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    • 2007.04a
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    • pp.334-336
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    • 2007
  • This paper presents a beat gesture recognition method to synchronize the tempo of a robot playing a piano with the desired tempo of the user. To detect an unstructured beat gesture expressed by any part of a body, we apply an optical flow method, and obtain the trajectories of the center of gravity and normalized central moments of moving objects in images. The period of a beat gesture is estimated from the results of the fast Fourier transform. In addition, we also apply a motion control method by which robotic fingers are trained to follow a set of trajectories, Since the ability to track the trajectories influences the sound a piano generates, we adopt an iterative learning control method to reduce the tracking error.

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A Design Method of Discrete Time Learning Control System (이산시간 학습제어 시스템의 설계법)

  • 최순철
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.13 no.5
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    • pp.422-428
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    • 1988
  • An iterative learning control system is a control system which makes system outputs follow desired outputs by iterating its trials over a finite time interval. In a discrete time system, we proposed one method in which present control inputs can be obtained by a linear combination of the input sequence and time-shifted error sequence at previous trial. In contrast with a continous time learning control system which needs differential opreration of an error signal, the time shift operation of the error sequence is simpler in a computer control system and its effectiveness is shown by a simulation.

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Implementation of an Intelligent Learning Controller for Gait Control of Biped Walking Robot (이족보행로봇의 걸음새 제어를 위한 지능형 학습 제어기의 구현)

  • Lim, Dong-Cheol;Kuc, Tae-Yong
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.59 no.1
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    • pp.29-34
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    • 2010
  • This paper presents an intelligent learning controller for repetitive walking motion of biped walking robot. The proposed learning controller consists of an iterative learning controller and a direct learning controller. In the iterative learning controller, the PID feedback controller takes part in stabilizing the learning control system while the feedforward learning controller plays a role in compensating for the nonlinearity of uncertain biped walking robot. In the direct learning controller, the desired learning input for new joint trajectories with different time scales from the learned ones is generated directly based on the previous learned input profiles obtained from the iterative learning process. The effectiveness and tracking performance of the proposed learning controller to biped robotic motion is shown by mathematical analysis and computer simulation with 12 DOF biped walking robot.

Thrust and Propellant Mixture Ratio Control of Open Type Liquid Propellant Rocket Engine (개방형 액체추진제로켓엔진의 추력 및 혼합비 제어)

  • Jung, Young-Suk;Lee, Jung-Ho;Oh, Seung-Hyub
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.1143-1148
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    • 2007
  • LRE(Liquid propellant Rocket Engine) is one of the important parts to control the motion of rocket. For operation of rocket in error boundary of the set-up trajectory, it is necessarily to control the thrust of LRE according to the required thrust profile and control the mixture ratio of propellants fed into combustor for the constant mixture ratio. It is not easy to control thrust and mixture ratio of propellants since there are co-interferences among the components of LRE. In this study, the dynamic model of LRE was constructed and the dynamic characteristics were analyzed with control system as PID control and PID+Q-ILC(Iterative Learning Control with Quadratic Criterion) control. From the analysis, it could be observed that PID+Q-ILC control logic is more useful than standard PID control system for control of LRE.

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Implementation of a Direct Learning Control Law for the Trajectory Tracking Control of a Robot (로봇의 궤적추종제어를 위한 직접학습 제어법칙의 구현)

  • Kim, Jin-Hyoung;Ahn, Hyun-Sik;Kim, Do-Hyun
    • Proceedings of the KIEE Conference
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    • 2000.11d
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    • pp.694-696
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    • 2000
  • In this paper, the Direct Learning Control is applied to robot's trajectory tracking control to solve the problem that lies in the existing Iterative Learning Control(ILC) and the tracking Performance is analyzed and the better approach is searched using computer simulation and experiments. It is assumed that the Direct Learning Control(DLC) is saved onto memory basically after obtaining control input Profiles for several Periodic output trajectories using the ILC. In case the new output trajectory has special relations with the previous output trajectories, there is an advantage that the desired control input profile can be obtained without iterative executions only using the DLC. The robot's tracking control system is comprised of DSP chip. A/D converter, D/A converter and high-speed pulse counter included in the control board and the performance is examined by carrying out the tracking control for the given output trajectory.

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