• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.5
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• pp.488-497
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• 1984

In the assembling process by industrial robots, many difficulties stem from the fact that the assembly operation is impossible or the parts to be assembled can be damaged by reaction forces due to even little misalignment in part mating. In this paper a flexible and sensible robot wrist is developed to make possible the precision insertion operation. The flexibility of the developed wrist were evaluated both analytically and experimentally in actual insertion process. The results show that without the use of feedback control the wrist is capable of doing insertion operations with a small clearance at a low inserting force. For smaller clearance the assembly process was devised involving insertion force feedback and a control algorithm for this active accommodation was developed. The simulation results show that if the active feedback control is used the insertion action can be performed with much less force, as compared with a passive accommodation method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.218-224
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• 2007

Although piezoelectric materials such as PZT have been widely used as actuators in the field of active vibration suppression, the use of bare PZT as an actuator may cause some drawbacks such as critical breaks in the installation process, short circuits in the host material and low fatigue performance. The LIPCA-C2 (lightweight piezocomposite actuator) was developed to alleviate these problems. We implemented the LIPCA as an actuator to suppress the vibration of an aluminum cantilever beam with a tip mass. In our test, we used positive position feedback control algorithm. The filter frequency for this type of feedback should be tuned to the natural frequency of the target mode. The first three experimental natural frequencies of the aluminum cantilever beam agree well with the results of finite element analysis. The effectiveness of using the LIPCA as an actuator in active vibration suppression was investigated with respect to the time and frequency domains, and the experimental results show that LIPCAs with PPF control can significantly reduce the amplitude of forced vibrations and the settling time of free vibrations. For a case study, the forced vibration control of several beams with different thicknesses were performed.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.1
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• pp.17-22
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• 2002

Endoscopes for industrial and medical fields are expected to have multi degree-of-freedom (DOF) motions. A multi-DOF ultrasonic motor we developed consists of a spherical rotor and a bar-shaped stator, and the rotor rotates around three perpendicular axes using three natural vibration modes of the stator. In this study, a multi-DOF unilateral master-slave system for active endoscope using the multi-DOF ultrasonic motor is developed. The configurations of master and slave arms for active endoscope are similar, so that an operator can easily handle the master-slave system. First, driving characteristics of the multi-DOF ultrasonic motor are measured in order to design the slave arm and its controller. Next, the master arm and the slave arm are designed. Then, the unilateral feedback controller for the master-slave system is developed. Finally, the motion control tests of rotor are conducted. As a result, the possibility of the endoscope is confirmed.

• Structural Engineering and Mechanics
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• v.42 no.2
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• pp.211-228
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• 2012

Present study deals with the development of finite element based solution methodology to investigate active control of dynamic response of delaminated composite shells with piezoelectric sensors and actuators. The formulation is based on first order shear deformation theory and an eight-noded isoparametric element is used. A coupled piezoelectric-mechanical formulation is used in the development of the constitutive equations. For modeling the delamination, multipoint constraint algorithm is incorporated in the finite element code. A simple negative feedback control algorithm coupling the direct and converse piezoelectric effects is used to actively control the dynamic response of delaminated composite shells in a closed loop employing Newmark's time integration scheme. The validity of the numerical model is demonstrated by comparing the present results with those available in the literature. A number of parametric studies such as the locations of sensor/actuator patches, delamination size and its location, radius of curvature to width ratio, shell types and loading conditions are carried out to understand their effect on the transient response of piezoceramic delaminated composite shells.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.83-91
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• 2004

This paper illustrates the feasibility and the effectiveness of the disturbance feedforward compensation control proposed in the previous paper. The compensator is designed experimentally by means of the Multiple Filtered-x Least Mean Square algorithm. A 2-DOF active magnetic bearing system subject to base motion is built and the compensation control is applied. The experimental results demonstrate that the compensation control reduces the air-gap responses within 10$%$ of those by the feedback control alone without increasing the control inputs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.678-683
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• 1998

Combustion instability by thermoacoustic feedback incite strong low frequency noise and vibration which damage the system and provoke the environmental problems. Therefore, it is necessary to control the thermoacoustic oscillation. In the way of controlling the instability, active control method using adaptive algorithm is applied. In this study, active noise control method using anti-sound technique is selected, whose principle is cancelling the noise with the addition of opposite phase sound. At first, simulation is performed to confirm the stability of controller, and after that control of combustion instability is carried out to get cancellation of 20-30dB SPL.

• Structural Engineering and Mechanics
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• v.1 no.1
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• pp.119-135
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• 1993

The paper presents a generalized optimal active control algorithm for earthquake-resistant structures. The study included the weighting matrix configuration, stability, and time-delays for achieving control effectiveness and optimum solution. The sensitivity of various time-delays in the optimal solution is investigated for which the stability regions are determined. A simplified method for reducing the influence of time-delay on dynamic response is proposed. Numerical examples illustrate that the proposed optimal control algorithm is advantageous over others currently in vogue. Its feedback control law is independent of the time increment, and its weighting matrix can be flexibly selected and adjusted at any time during the operation of the control system. The examples also show that the weighting matrix based on pole placement approach is superior to other weighting matrix configurations for its self-adjustable control effectiveness. Using the time-delay correction method can significantly reduce the influence of time-delays on both structural response and required control force.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1005-1008
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• 2001

This paper presents average current-mode control AC/DC ZVT(Zero Voltage Transition) Boost Converter. This boost converter perceives feed forward signal of input and feedback signal of output for average current-mode control proposed converter employs active-clamp method for ZVT. This converter gives the good PFC(Power Factor Correction), low line current hormonic distortions and tight output voltage regulations. This converter also has a high efficiency by active-clamp method. The principle of operation, feature, and design considerations are illustrated and verified through the experiment with a 150W, 120kHz prototype converter.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1530-1533
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• 2005

In this paper, we design a Linear Quadratic Gaussian controller for the active suspension. We can improve the inherent suspension problem, trade-off between the ride quality and the suspension travel by selecting appropriate weights in the LQ-objective function. Because any definite rules for selecting weights do not exist, we use an optimization-algorithm, Evolution Strategy (ES) to find the proper control gains for selected frequencies, which have major effects on the vibrations of the vehicle's state variables. The frequencies and proper control gains are used for the neural network data. During a vehicle running, the trained on-line neural network is activated and provides the proper gains for non-trained frequencies. For the full-state feedback control, Kalman filter observes the full states and Fourier transform is used to detect the frequency of the road.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.447-450
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• 2003

This paper concerns on application of active magnetic bearing(AMB) system to levitate the elevation axis of an electro-optical sight mounted on moving vehicles. In such a system. it is desirable to retain the elevation axis within the predetermined air-gap while the vehicle is moving. A disturbance compensation control is proposed to reduce the base motion response. In the consideration of the uncertainty of the system model, a filtered-x least-mean-square(FXLMS) algorithm is used to estimate adaptively the frequency response function of the feedforward control which cancels disturbance responses. The frequency response function is fitted to an optimal feedforward control. Experimental results demonstrate that the proposed control reduces the air-gap deviation to 27.7% that by feedback control alone.