• Smart Structures and Systems
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• v.14 no.3
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• pp.327-345
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• 2014

This paper presents a composite control strategy for the active suppression of vibration due to the unknown disturbances, such as external excitation, harmonic effects and control spillover, as well as high-frequency accelerometer measurement noise in the all-clamped stiffened plate. The proposed composite control action based on the modal approach, consists of two contributions including feedback part and feedforward part. The feedback part is the well-known PID controller, which is widely used to increase the structure damping and improve its dynamic performance close to the resonance frequencies. In order to get better performance for vibration suppression, the weight matrixes is optimized by chaos sequence. Then an improved disturbance observer (IDOB) as the feedforward compensation part is developed to enhance the vibration suppression performance of PID under various disturbances and uncertainties. The proposed IDOB can simultaneously estimate the various disturbances dynamically as well as measurement noise acting on the system and suppress them by feedforward compensation design. A rigorous analysis is also given to show why the IDOB can effectively suppress the unknown disturbances and measurement noise. In order to verify the proposed composite control algorithm (IDOB-PID), the dSPACE real-time simulation platform is used and an experimental platform for the all-clamped stiffened plate active vibration control system is set up. The experimental results demonstrate the effectiveness, practicality and strong anti-disturbances ability of the proposed control strategy.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.5
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• pp.630-639
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• 1999

To achieve fast loading and unloading of containers from a container ship, quick suppression of the remaining sway motion of the container at the end of each trolley stroke is crucial. Due to the pendulum motion of the container and disturbances like sind, residual sway always exists at the end of trolley movement. In this paper, the sway-control problem of a container crane is investigated. A two-stage control is proposed. The first stage is a time optimal controlfor the purpose of fast trolley traveling. The second stage is a nonlinear control for the quick suppression of residual sway, which starts right after the first stage while lowering the container. The nonlinear control is investigated in the perspective of controlling an underatuated mechanical system, which combines partial feedback linearization to account for the known nonlinearities as much as possible, and variable structure control to account for the unmodeled dynamics and disturbances. Simulation and experimental results are provided.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.839-848
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• 2012

In this paper, we propose a robust control scheme of AC servo motors to suppress disturbance torques effectively. The proposed controller consists of both a model based feed-forward controller and a stabilizing feedback controller. The feed-forward controller is designed such that the output of the nominal plant tracks perfectly the reference velocity command with desired dynamic characteristics. The feedback controller stabilizes the overall closed loop system. Furthermore, the feedback controller contains a free function that can be chosen arbitrarily. The free function can be designed so as to achieve both suppression of disturbances and robustness to model uncertainties. In order to illuminate the superior performance of the proposed control scheme to the conventional ones, we present some simulation results.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1872-1875
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• 1998

In the industrial motor drive system, a shaft torsional vibration is often generated when a motor and a load are connected with a flexible shaft. This paper treats the vibration suppression control of such a system. Recently, there are new methods which estimate unknown state variables by using a reduced order observer and feedback these state variables by using a pole placement design method. But there is a trade-off between the fast command following property and the attenuation of disturbances and vibrations in these design methods. In this paper, the vibration suppression control of a two-mass system using a reference model is proposed. Because of using a reference model, the proposed control satisfy the fast command following property and the attenuation of disturbances and vibrations. Control parameter can be changed to maintain high system performance in control using a reference model. Experimental results show the validity of the proposed state feedback control using a reference model, and this controller is compared with the state feedback controller.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.5
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• pp.357-362
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• 2002

The underlying principle of fault detection via unknown input observer is to make the state estimation error independent of disturbances(or unknown inputs). In this paper, we present a systematic method that can exactly assign the eigenstructure with disturbance suppression and fault isolation capability. A desired eigenstructure for both fault isolation and disturbance suppression is obtained by an optimization method. For the dual purposes, terms for fault isolation and far disturbance suppression are included in the employed objective function for the optimization. The proposed scheme is applied to a simple example to confirm the usefulness of the method.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.2
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• pp.145-149
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• 2015

This paper introduces a sway suppression control for container cranes with unknown payloads and sway rates. With no priori knowledge concerning the magnitude of payload mass and sway rate, the proposed control maintains superior sway suppressing and trolley positioning against external disturbances. The proposed scheme combines a second order sliding mode control and an adaptive control to cope with unknown payloads. A second order sliding mode control without feedback of the sway rate is first designed, which is based on a class of feedback linearization methods for stabilization of the under-actuated sway dynamics of the container. Under applicable restrictions of the magnitude of payload inertia and sway rate, a linear regression model is obtained, and an adaptive control with a payload estimator is then designed, which is based on Lyapunov stability methods for the fast attenuation of trolley oscillations in the vicinity of the target position. The asymptotic stability of the overall closed-loop system is assured irrespective of variations of rope length. Simulation are shown in the existence of initial sway and external wind disturbances.

• Journal of National Security and Military Science
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• s.1
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• pp.311-343
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• 2003

In this paper, we propose a generalized disturbance torque suppression control scheme of servo motors for missile fin actuators. Our controller consists of both a model based feed-forward controller and a stabilizing feedback controller. The feed-forward controller is designed such that the output of nominal plant tracks perfectly the reference position command with a desired dynamic characteristics. The feedback controller stabilizes the overall closed loop system. Furthermore, the feedback controller contains a free function that can be chosen arbitrary. The free function can be designed so as to achieve both the suppression of disturbances and the robustness to model uncertainties. In order to illuminate the superior performance of our control scheme to the conventional ones, we present some simulation results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1417-1427
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• 2000

A flow stabilizer, which is made of a honeycomb and three different mesh screens, is located downstream of a butterfly-type valve, for the reduction of flow disturbances behind the valve. Mean flow and turbulence measurements as well as flow visualizations are conducted in the downstream region of the deepens the non-uniformity of the streamwise velocity component and turbulence. The mesh screens considerably reduce the turbulence and enhance the uniformity of mean velocities. The combination of the honeycomb and the three mesh screens results in an efficient reduction in the flow disturbances. In addition, the flow stabilizer proves to have a good performance in the suppression of turbulence at a short distance.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.1
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• pp.82-89
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• 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.

• International Journal of Control, Automation, and Systems
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• v.5 no.3
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• pp.223-233
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• 2007

Crane payloads frequently swing with large amplitude motion that degrades safety and throughput. Open-loop methods have addressed this problem, but are not effective for disturbances. Closed-loop methods have also been used, but generally require the speed of the driving motors to be precisely controlled. This paper develops a feedback control method for controlling motors to cancel the measured payload oscillations by intelligently timing the ensuing on and off motor commands. The effectiveness of the oscillation suppression scheme is experimentally verified on an industrial bridge crane.