• Title/Summary/Keyword: active feedforward

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Improvement in the Control Performance of Instruments used for Minimally Invasive Surgery (최소침습술을 위한 의료용 인스트루먼트의 동작 성능 향상)

  • Park, Hyeonjun;Won, Jongseok;Park, Jaeheung
    • Journal of Institute of Control, Robotics and Systems
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    • v.19 no.12
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    • pp.1160-1166
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    • 2013
  • This paper presents feedforward controllers to improve the control performance of the motion and grasping force of a surgical instrument used in an MIS (Minimally Invasive Surgery) robot. The surgical instrument has a long distance between the drive motors and its active joints. Therefore, the gripper on the instrument is controlled by a cable drive mechanism, which generates a coupled motion between the wrist joint and the grip direction. In order to solve the problem, this paper analyzes the pulley composition of the surgical instrument and proposes feedforward controllers to eliminate the coupled motion. Furthermore, feedforward controllers to regulate the grasping force are proposed to deal with another coupling problem between the grasping force of the instrument and the motion of the instrument joints. The experimental results demonstrate the improved control performance of the motion and grasping force of the instrument.

The Study of Kinematic Analysis and Control by Optimum Design of Redundantly Actuated Parallel Robot (여유구동형 병렬 로봇의 최적설계를 통한 기구학적 분석 및 제어에 관한 연구)

  • Kim, Byeong-Soo;Lee, Jeh-Won;Kim, Young-Suk;Kim, Jin-Dae;Lee, Hyuk-Jin
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.4
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    • pp.426-432
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    • 2012
  • In this study, kinematic analysis of forward kinematic, inverse kinematic and jacobian for 6-bar parallel robot was analyzed. In order to analyze the maximum workspace of 6-bar parallel robot, maximum revolution range of active joint was calculated. Also, to analyze forward dynamics and inverse dynamics of 6-bar parallel robot, recurdyn and simmechanics was utilized. Using a PI controller and Feedforward controller make an experiment with square motion of end_effector. The reference value of active joint and trace of end_effector were compared with actual experimental value.

Electromagnetic Actuator for Active Vibration Control of Precise System (초정밀 시스템의 능동 진동제어용 전자기 액츄에이터)

  • Lee, Joo-Hoon;Jeon, Jeong-Woo;Hwang, Don-Ha;Kang, Dong-Sik;Choi, Young-Kiu
    • Proceedings of the KIEE Conference
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    • 2005.10b
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    • pp.228-230
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    • 2005
  • In this paper, we address an active vibration control system, which suppresses the vibration engaged by magnetically levitated stage. The stage system consists of a levitating platen with four permanent magnetic linear synchronous motors in parallel. Each motor generates vertical force for suspension against gravity and propulsion force horizontally as well. This stage can generate six degrees of freedom motion via the vertical and horizontal forces. In the stage system, which represents the settling-time critical system, the motion of the platen vibrates mechanically. We designed an active vibration control system for suppressing vibration due to the stage moving. The command feedforward with inertial feedback algorithm is used for solving stage system's critical problems. The components of the active vibration control system are accelerometers for detecting stage tables's vibrations, a digital controller with high precise signal converters. and electromagnetic actuators.

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A Study on Implementation and Performance Evaluation of Error Amplifier for the Feedforward Linear Power Amplifier (Feedforward 선형 전력증폭기를 위한 에러증폭기의 구현 및 성능평가에 관한 연구)

  • Jeon, Joong-Sung;Cho, Hee-Jea;Kim, Seon-Keun;Kim, Ki-Moon
    • Journal of Navigation and Port Research
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    • v.27 no.2
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    • pp.209-215
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    • 2003
  • In this paper. We tested and fabricated the error amplifier for the 15 Watt linear power amplifier for the IMT-2000 baseband station. The error amplifier was comprised of subtractor for detecting intermodulation distortion, variable attenuator for control amplitude, variable phase shifter for control phase, low power amplifier and high power amplifier. This component was designed on the RO4350 substrate and integrated the aluminum case with active biasing circuit. For suppression of spurious, the through capacitance was used. The characteristics of error amplifier measured up to 45 dB gain, $\pm$0.66 dB gain flatness and -15 dB input return loss. Results of application to the 15 Watt feedforward Linear Power Amplifier, the error amplifier improved with 27 dB cancellation from 34 dBc to 61 dBc IM$_3$.

Active Control of Vibrational Intensity in a Compound Vibratory System (복합진동계의 진동 인텐시티 능동 제어)

  • Kim, Gi-Man
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.6
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    • pp.109-118
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    • 2002
  • The vibrational intensity and the dynamic response of a compound vibratory system had been controlled actively by means of a feedforward control method. A compound vibratory system consists of a flexible beam and two discrete systems - a vibrating source and a dynamic absorber. By considering the interactive motions between discrete systems and a flexible beam, the equations of motion for a compound vibratory system were derived using a method of variation of parameters. To define the optimal conditions of a controller the cost function, which denotes a time averaged power flow, was evaluated numerically. The possibility of reductions of both of vibrational intensity and dynamic response at a control point located at a distance from a source were fecund to depend on the positions of a source, a control point and a controller. Especially the presence of a dynamic absorber gives the more reduction on the dynamic response but the less on the vibrational intensity than those without a dynamic absorber.

Active Control of Reaction Forces for Flexible Structures (유연 구조물의 능동 반력 제어기 설계)

  • 김주형
    • Journal of KSNVE
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    • v.11 no.1
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    • pp.68-75
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    • 2001
  • A method for actively controlling dynamic reaction forces in flexible structures subject to persistent excitations is presented. Since reaction forces are not directly measured in flexible structures, reaction forces are estimated by using the Kalman filter. The estimated reaction force is used as an error signal in the adaptive feedforward disturbance cancellation controller. In order to compensate the static effect of the truncated modes in the reaction forces, the residual flexibility matrix is used with the Kalman filter. The paper presents the formulation of the reaction forces in conjunction with the Kalman filter estimator and the adaptive feedforward controller. The results show that the dynamic reaction forces at its supports in a flexible beam test rir are well suppressed.

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Analysis of Perturbation Effect for Satellites (인공위성의 섭동력 영향분석)

  • 박수홍
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.229-232
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    • 1997
  • In this paper, the case study of reducing rotational errors is done for a grinding spindle with an active magnetic bearing system. The rotational errors acting on the magnetic bearing spindle are due to mass unbalance of rotor, runout, grinding excitation and unmodeled nonlinear dynamics of electromagnets. For the most case, the electrical runout of sensor target is big even in well-finished surface; this runout can cause a rotation error amplified by feedback control system. The adaptive feedforward method based on LMS algorithm is discussed to compensate this kind of runout effects, and investigated its effectiveness by numerical simulation and experimental analysis. The rotor orbit size in both bearings is reduced about to 5 pin due to lX rejection by feedforward control up to 50,000 rpm.

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Analysis and Design of Diaphragm-type Air Braking System for Train (철도차량의 막판식 공기제동시스템의 해석 및 설계)

  • 노진환;김재도
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.605-608
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    • 1997
  • In this paper, the case study of reducing rotational errors is done for a grinding spindle with an active magnetic bearing system. The rotational errors acting on the magnetic bearing spindle are due to mass unbalance of rotor, runout, grinding excitation and ed nonlinear dynamics of electromagnets. For the most case, the electrical runout of sensor target is big even in well-finished surface; this runout can cause a rotation error amplified by feedback control system. The adaptive feedforward method based on LMS algorithm is discussed to compensate this kind of runout effects, and investigated its effectiveness by numerical simulation and experimental analysis. The rotor orbit size in both bearings is reduced about to 5 pin due to lX rejection by feedforward control up to 50,000 rpm.

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On-line Frequency Estimation Based on Cascade Adaptive Notch Filter and Application to Active Noise Control

  • Kim, Sunmin;Park, Youngjin
    • 제어로봇시스템학회:학술대회논문집
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    • 1998.10a
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    • pp.81-84
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    • 1998
  • For ANC systems applied to aircrafts or passenger ships, engines from which reference signals are usually measured are located so far from seats where main part of controllers are placed. It can make feedforward ANC scheme difficult to implement or very costly. Feedback ANC algorithms which do not require reference signals and use error signals alone to update the filter, are usually sensitive to measurement noise ' and impulse noise. In this paper, reference signal needed for the feedforward control is not measured directly but generated with the estimated frequencies. Cascade adaptive notch filter (ANF), which has the low computational burden, is used to implement ANC system in real time. Several ANFs of order 2 are connected in series to estimate multiple sinusoids. Computer simulations and experiments in the laboratory for verifying efficacy of the proposed algorithm are carried out.

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Active Vibration Control Using Piezostack Based Mount (압전작동기 마운트를 이용한 능동진동제어)

  • Nguyen, Vien-Quoc;Choi, Sang-Min;Paeng, Yong-Seok;Han, Young-Min;Choi, Seung-Bok;Moon, Seok-Jun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.63-68
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    • 2007
  • This paper presents vibration control performance of an active hybrid mount featuring piezostack actuators. The proposed hybrid mount is devised by adopting piezostack as an active actuator and rubber as a passive element. After experimentally identifying actuating force characteristics of the piezostack and dynamic characteristics of the rubber, the hybrid mount was designed and manufactured. Subsequently, a vibration control system with a specific mass loading is constructed, and its governing equations of motion are derived. In order to actively attenuate vibration transmitted from the base, a feedforward controller is formulated and experimentally realized. Vibration control responses are then evaluated in time and frequency domains.

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