• 제어로봇시스템학회논문지
• /
• 제12권10호
• /
• pp.1012-1017
• /
• 2006

By breaking the symmetry of the velocity profile in the S-curve, we developed a fast starting and smooth ending motion profile, named asymmetric S-curve(AS-curve). The problem for generating motion profile is formulated, and the algorithm for the AS-curve is derived and the flow chart of the AS-curve is illustrated. By various simulations, the derived algorithm is tested and shows the validity. This AS-curve can be applied to the high precision machines where fast and vibrationless motion is required in the near future.

• 제어로봇시스템학회논문지
• /
• 제20권11호
• /
• pp.1125-1130
• /
• 2014

In this paper, we discuss the relation between the motion profile and pre-filter. As previously reported in various literatures [1-3], a tuned motion profile can effectively reduce residual vibration by placing inherent zeros of the motion profile at the vibratory pole of systems similar to the role of the input shaping technique. From the results, we factorize the motion profile into a basis function and an input shaper. In contrast to the previously reported impulse-sequence-based input shapers, the input shaper extracted from the motion profile has unique characteristics. Thanks to the characteristics of the input shaper extracted from the motion profile, it has advantages to reduce the vibrations caused by not only the modeled vibratory mode but also unmodeled dynamics which exist in higher frequency ranges.

• Smart Structures and Systems
• /
• 제23권2호
• /
• pp.141-153
• /
• 2019

This research deals with wave propagation of the functionally graded (FG) nano-beams based on the nonlocal elasticity theory considering surface and flexoelectric effects. The FG nano-beam is resting in Winkler-Pasternak foundation. It is assumed that the material properties of the nano-beam changes continuously along the thickness direction according to simple power-law form. In order to include coupling of strain gradients and electrical polarizations in governing equations of motion, the nonlocal non-classical nano-beam model containg flexoelectric effect is used. Also, the effects of surface elasticity, dielectricity and piezoelectricity as well as bulk flexoelectricity are all taken into consideration. The governing equations of motion are derived using Hamilton principle based on first shear deformation beam theory (FSDBT) and also considering residual surface stresses. The analytical method is used to calculate phase velocity of wave propagation in FG nano-beam as well as cut-off frequency. After verification with validated reference, comprehensive numerical results are presented to investigate the influence of important parameters such as flexoelectric coefficients of the surface, bulk and residual surface stresses, Winkler and shear coefficients of foundation, power gradient index of FG material, and geometric dimensions on the wave propagation characteristics of FG nano-beam. The numerical results indicate that considering surface effects/flexoelectric property caused phase velocity increases/decreases in low wave number range, respectively. The influences of aforementioned parameters on the occurrence cut-off frequency point are very small.

• 소음진동
• /
• 제6권5호
• /
• pp.567-574
• /
• 1996

This paper concerns an articulated space robot with flexible links. The equations of its motion are derived by means of the Lagrangian mechanics. Assuming that magnitude of elastic motions are relatively small, the perturbation approach is taken to separate the original equations of motion into linear and nonlinear equations. Th effect the desired payload motion, open loop control inputs are first determined based on the nonlinear equations. One the other hand, in order to reduce the positional errors during the maneuver, vibration suppression is actively done with a feedforward control for disturbance cancellation to some extent. Additionally, for performance robustness against residual disturbance, an LQ control modified to have a prescribed degree of stability is applied based on the linear equations. Measurement equations are formulated to be used for the maximum likelihood estimator to reconstruct states from the original robot equations of motion. Finally, numerical simulations show effectiveness of the proposed control design scheme.

• 제어로봇시스템학회논문지
• /
• 제9권1호
• /
• pp.82-89
• /
• 2003

A robust motion control method is proposed fur the point-to-point position control of a XY positioning system which consists of a base cart, elastic ben and moving mass. The horizontal motion controller consists of the feedforward controller to suppress the single mode vibration of the elastic beam and the feedback controller to get the high-accuracy positioning performance of the base cart. Input preshaping vibration suppression method based on system modeling with analytic frequency equation is proposed and integrated into the robust internal-loop compensator(RIC) to increase the robustness of the whole closed-loop system The vertical motion controller is proposed based on the dual RIC structure. Through experiments, it is shown that the proposed method can stabilize the system and suppress the vibration in the presence of uncertainties and disturbances.

• 동력기계공학회지
• /
• 제8권3호
• /
• pp.58-66
• /
• 2004

The sway motion control problem of a container hanging on the trolly is considered in the paper. In the container crane control problem, suppressing the residual swing motion of the container at the end of acceleration, deceleration or the case of that the unexpected disturbance input exists is main issue. For this problem, in general, many trolley motion control strategies are introduced and applied. In this paper, we introduce and synthesize a swing motion control system in which a small auxiliary mass is installed on the spreader made by ourselves. In this control system, the actuator reacting against the auxiliary mass applies inertial control forces to the container to reduce the swing motion in the desired manner. Especially, we apply the $H_{\infty}$ based gain-scheduling control technique the anti-sway control system design problem of the controlled plant. In this control system, the controller dynamics are adjusted in real-time according to time-varying plant parameters. And the simulation result shows that the proposed control strategy is shown to be useful to the case of time-varying system and, robust to disturbances like winds and initial sway motion.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.631-636
• /
• 2004

The sway motion control problem of a container hanging on the trolly is considered in the paper. In the container crane control problem, suppressing the residual swing motion of the container at the end of acceleration, deceleration or the case of that the unexpected disturbance input exists is main issue. For this problem, in general, many trolley motion control strategies are introduced and applied. In this paper, we introduce and synthesize a swing motion control system in which a small auxiliary mass is installed on the spreader made by ourselves. In this control system, the actuator reacting against the auxiliary mass applies inertial control forces to the container to reduce the swing motion in the desired manner. Especially, we apply the $H_{\infty}$ based gain-scheduling control technique the anti-sway control system design problem of the controlled plant. In this control system, the controller dynamics are adjusted in real-time according to time-varying plant parameters. And the experiment result shows that the proposed control strategy is shown to be useful to the case of time-varying system and, robust to disturbances like winds and initial sway motion.

• 한국정보과학회논문지:소프트웨어및응용
• /
• 제31권11호
• /
• pp.1474-1482
• /
• 2004

본 논문에서는 적응적 가중치 함수를 이용하여 블록 단위의 모션 벡터를 필터링하는 방법을 제안한다. 제안하는 방법에서는 먼저 인접한 영상을 받아 들여 가변적 크기의 블록 정합 방법을 이용하여 모션 벡터를 추출한다. 그리고 추출된 모션 벡터를 강건 예측에 적용하여 아웃라이어(outlier)를 제거함으로써 강건 예측에서 사용하는 동작 모델에 근접한 모션 벡터만을 추출한다. 제안된 적응적 강건 예측은 연속적인 시그모이드 가중치 함수를 사용하여 정상 자료와 아웃라이어의 소속 정도를 보다 효과적으로 표현한다. 또한, 최소화 기법의 반복 단계에서 잔여에러가 감소함에 따라 점진적으로 시그모이드 가중치 함수를 조율함으로써 정상 자료와 아웃라이어를 보다 유연하게 분리한다. 실험에서는 카메라의 동작이 포함된 비디오 데이타를 입력 받아 성능을 비교 분석함으로써 제안한 방법의 우수함을 보인다.

• 한국정밀공학회지
• /
• 제24권11호
• /
• pp.91-100
• /
• 2007

Many manufacturing devices must execute motions as quickly as possible to achieve profitable high-volume production. Most of them have devices having flexibility and a time delay of one sampling is added to the plants when they are controlled by fast discrete controllers, which brings about non-minimum phase zeros. This paper develops a control strategy that combines feedforward and feedback control with command shaping for such devices. First, the feedback controller is designed to increase damping and eliminate steady-state error. Next, the feedforward controller is designed to speed up the transient response. Finally, an appropriate reference profile is generated using command-shaping techniques to ensure fast point-to-point motions with minimum residual vibration. The particular focus of the paper is to understand the interactions between these individual control components. The resulting control strategy is demonstrated on a model of a high-speed semiconductor manufacturing machine.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
• /
• pp.189-191
• /
• 2005

In the scalable extension of H.264/AVC, the codec is based on a layered approach to enable spatial scalability. In each layer, the basic concepts of motion compensated prediction and intra prediction are employed as in standard H.264/AVC. Additionally inter-layer prediction algorithm between successive spatial layers is applied to remove redundancy. In the inter-layer prediction, as the prediction we can use the signal that is the upsampled signal of the lower resolution layer. In this case, coding efficiency can be variable as the kinds of interpolation filter. In this paper, we investigate the approach to select the interpolation filter for residual signal in order to optimal prediction.