Earticle

A Control of the vibrations induced from the earthquake can be accomplished for the multiple story buildings using various optimal control methods. Linear Quadratic(LQ) control method may be feasible provided all state variables of the system can be measured, which is not always possible and practical. However, it has attractive features of infinite gain margin and phase margin greater than 60 degrees. The gain margin and phase margin indicate how robustly stable the closed loop system behaves with uncertainties such as system noise and modeling errors. State feedback control system can be implemented with the only measurable states if constructed in Linear Quadratic Gaussian(LQG) algorithm. It requires an observer to estimate the state variables based on the measured one, but loses the entire gain margin due to the Kalman filter adapted in the algorithm. The H-infinity control may overcome the shortcomings of the LQG with emphasized robustness features against the uncertainties, but it usually ends up with very complicated control system to implement. LQG with loop transfer recovery (LQG/LTR) method is applied in this study to retain the moderate level of stability robustness while keeping the observer alive. The results showed that the LQG/LTR control reduced the relative displacement in the base isolated floor as effectively as the LQG control with moderate level of the gain margin recovered.

본 연구에서는 자동차 엔진에 적용되는 고무마운트의 성능을 극대화하여 시동초기 진동특성를 개선하기 위해 능동형 하이브리드 마운트를 제안하고 진동절연 성능을 실험적으로 고찰하고자 한다. 제안된 하이브리드 마운트는 수동 형 고무요소와 능동형 압전작동기로 구성되었으며, 동적 특성과 제어력의 실험적 고찰을 통해 하이브리드 마운트가 제 작되었다. 수직방향의 진동을 고려하여 관성질량을 갖는 압전-고무 하이브리드 마운트의 동적 지배방정식을 수학적으 로 모델링하였으며 상태 공간 방정식으로 표현하였다. 본 연구에서는 진동을 절연하기 위해 강건한 슬라이딩 모드 제어 기가 구성되어 진동제어 실험에 적용되었다. 마지막으로 넓은 주파수 영역에서 진동제어 성능을 실험적으로 고찰하였으 며 주파수 영역에서의 전달율과 시간영역에서 진동절연 성능을 평가하였다.

A hybrid mount featuring rubber element and piezoelectric actuator is devised to reduce vibration when starting a vehicle engine. As a first step, a passive mount adopting rubber element is manufactured and its dynamic characteristics are experimentally evaluated. After evaluating dynamic characteristics of the manufactured inertial piezoelectric actuator, the proposed hybrid mount is then established by integrating the piezoelectric actuator with the rubber element for performance improvement at non-resonant high frequencies. A mathematical model of the established active vibration control system is formulated and expressed in the state space form. Subsequently, sliding mode controller (SMC) is designed to attenuate the vibration transmitted from the base excitation. Finally, control performances of the proposed hybrid mount are evaluated such as transmissibility in frequency domain and time responses.

In the present study, the inertial electromagnetic actuator (IEA) and the FxLMS (filtered-x least mean square) method were applied to study vibration control using the active mount. IEA was designed and manufactured for the experiment, and FxLMS algorithm was developed to evaluate control performance and mount dynamic characteristics. For the vibration control experiment, active mounts were installed at the top and bottom, and the lower active mount controls the force transmitted to the structure by the excitation signal from the upper active mount. The experiment was performed by simultaneously exciting three frequencies in three axes. From the experimental results, it was confirmed that the force measured at the lower active mount when the actuator is off is greatly reduced when the actuator is on, and that vibration reduction in the vertical z-axis is more effective than vibration reduction in the x-y plane.

The effectiveness of vibration control using Linear Quadratic Gaussian(LQG) method applied in the base isolated building is investigated. The robust stability of the closed loop system measured by phase and gain margin is also studied to verify its demerit. Since the base isolated building exhibits the largest relative displacements in the base isolator, the control target is to reduce them by aid of the LGQ method. The closed loop control system consists of an actuator located in the base isolated floor and an observer. The observer used to estimate all the states, floor displacements in this case, based on the measured state is found to be the most effective when located in the base isolated floor. The results indicated that the LGQ hybrid control method using only one measured displacement suppressed effectively the relative displacement in the base isolated floor compared to the responses from Linear Quadratic(LQ) control method where all the states should be measured. This LQG control system, however, loses all the system stability margin and robustness due to the Kalman filter adapted in its algorithm.

The vibration control of a flexible rotor supported on cavitated short squeeze film dampers is investigated. According to Pan's theory, the shape of cavitation in fluid film bearings depends on the level of oil supply pressure, as a result, both the direct and the cross coupled damping coefficients of a cavitated short squeeze film damper are varied widely. In this paper, controling the level of oil supply pressure by fuzzy theory, a significant reduction in journal eccentricity ratio, rotor amplitude and force transmissiblilty of a flexible rotor system is achieved.

In this study, an active vibration control experiment was conducted on a display manufacturing system weighing approximately 15 tons. Three pneumatic shakers were installed underneath the equipment to excite the entire structure at three different frequencies. On the top side of the equipment, four inertial-type electromagnetic actuators capable of generating forces in the x, y, and z directions were mounted, enabling 12 degrees of freedom to be controlled. At locations near the actuators, four tri-axial accelerometers were installed to obtain 12 error signals. Vibrations at three distinct frequencies induced by the pneumatic shakers were measured at these 12 locations using the accelerometers. Active vibration control was performed by driving the inertial actuators using a narrow-band Fx-LMS algorithm to reduce the measured error signals. As a result of the control, the vertical vibration at 24 Hz was successfully reduced by 10.95 dB.

The purpose of this paper is to investigate the vibration phenomenon occurring in the structure such as a ship with the hemispherical substructure and operating at fixed frequency, and to suggest the active vibration control method using the Fx-LMS algorithm to reduce vibration amplification. In order to study the possibility of reducing vibration in the hemispherical structure, the active vibration control model was developed and a vibration control experimental device for the hemispherical structure was constructed. The narrowband Fx-LMS algorithm was developed to enable precise real-time control at a specific frequency, and the secondary path for dynamic control was modeled with two coefficients per frequency. The experimental device is equipped with three exciters, six 3-axis actuators, and six 3-axis error sensors, which can acquire 18 error sensor signals. Real-time secondary path tracking was possible with the secondary path consisting of two coefficients and the control algorithm, and effective vibration control performance was confirmed through this. And the experimental results of active vibration control of the exciter for three frequencies showed that the exciter vibration was reduced by a minimum of 63.7% and a maximum of 97.7%, which shows the possibility of reducing the vibration of the structure in real time using the proposed method.

Recently, a study on reducing the weight of the robot arm, which enables a high-speed operation and enables reducing the energy consumption has been actively carried out. A lightweight robot arm is hard to control because it behaves like a flexible body rather than a rigid body. This paper proposes a controller which combines a PID controller and a fuzzy logic controller for control the position and vibration of the flexible robot arm. In order to show the effectiveness of the proposed controller, MSC.ADAMS computational model which incorporates the finite element flexible robot arm model is developed, and is used for performing simulations. Simulations are carried out with two reference inputs, and three end masses. Simulation results show that the proposed controller controls the position and vibration of the flexible robot arm adaptively without being affected by the reference input and the end mass.

In this study, a control algorithm was developed to suppress the free vibration amplitude of a cantilever beam with time-varying dynamic characteristics. In other words, since it is assumed that the natural frequency and mode shape of the vibrating structure are not fixed, the system model of the vibrating structure was not used in the control algorithm. A single electromagnet was chosen as the actuator, so the attractive force was applied to only one fixed location in the structure. Through experiments, the proposed control algorithm is proven to effectively suppress the amplitude of vibration even when the dynamic characteristics of the cantilever beam change. Contrary to the usual active vibration control method, the proposed algorithm is just simple and intuitive without complicated mathematics in the modeling and control process. However, the proposed control method is very effective to suppress the vibration even when the dynamic characteristics of the target structure is not exactly known, as is often the case in industries or laboratories.

To improve vibration reduction in the railway vehicle, the semi-active suspension system using MR damper was developed and the vibration performance of the passive suspension system and a semi-active MR suspension system was compared. For the experiment, the MR damper and suspension system were designed and manufactured. Tensile and compression tests were performed on the MR damper while varying the input current. The damping force of the MR damper was measured and analyzed using the Bingham model. The railway vehicle was modeled with 9 degrees of freedom, and the sky hook control algorithm was simulated using the MR damper, using the Bingham model. This verified the effectiveness of the sky hook controller. Furthermore, to compare the vibration performance of the railway vehicle, the driving test was conducted with the MR damper and the passive damper. The lateral acceleration vibration reduction performance of the suspension system with MR dampers and passive dampers was verified, and it was confirmed that the vibration reduction performance of the vehicle with the semi-active suspension system using MR damper was approximately 50% better than that of the vehicle with the passive damper.

이 논문은 시스템 식별 기법을 이용하여 외팔보 진동제어 시스템의 수학적 모델을 구한 후 PID 제어기를 장착하여 효과적인 진동제어 결과를 제시하였다. 압전세라믹(piezo-ceramic)은 작동기로서 가장 기본적인 유연 구 조물의 형태인 외팔보의 진동을 억제하는데 사용되었으며 레이저 센서가 보의 굽힘 변위를 측정하는데 사용되었 다. 압전 세라믹의 입력 전압으로부터 레이저 감지기의 출력 전압까지의 전달함수를 계단입력에 대한 응답 실험데 이터에 시스템 식별 기법을 적용하여 구하였다. PID제어기는 산업현장에서 널리 사용되고 있으나, 적절한 이득 값 을 결정하는 것은 간단하지 않아, 본 연구에서는 Ziegler-Nichols 기법을 통해 PID 제어기를 튜닝하여 압전 세라 믹을 작동기로 사용하는 외팔보 시스템의 진동 제어에 적용하였고 시뮬레이션과 실험적 결과를 통하여 시스템식 별 기법을 통해 구한 수학적 모델의 유용성과 설계된 제어기의 효과적인 진동 제어 성능을 확인하였다.

In this paper first we obtained a mathematical model for a cantilever beam vibration control system with a piezoceramic actuator using system identification techniques and then implemented a PID controller for active vibration control. A piezoceramic is used as an actuator to control the vibration of a cantilever beam which has been used in many real structures, and a laser sensor is used to measure tip displacement of the cantilever beam in transverse motion. A transfer function from piezoceramic’s input voltage to laser sensor’s output voltage is obtained using system identification techniques utilizing experimental data from step response of the open-loop cantilever beam control system. The PID controller is tuned by Ziegler-Nichols technique and implemented to the beam control system. The result exhibits good performance in terms of vibration reduction, which validates the identification of the system and tuning of the PID controller.

This paper presents investigations into the development of a Proportional-Integral Sliding Mode Control (PI-SMC) for trajectory tracking and vibration control of a flexible single link manipulator. The motor at the single rotating joint is the control actuator. Two SMC control laws are reviewed. The classical discontinuous control based on the signum function and a modified control law where the servomotor output voltage depends on the instantaneous values of the states. The selection of the discontinuity gain is reviewed for exact model (certain case) as well as when the parameter variations are present (uncertain case). To prove the reaching condition, we use the Lyapunov stability criteria. It is proven that this design is equivalent to a full state feedback with its steady state motion constrained to the sliding hyper-surfaces. Simulation results of the response of the flexible manipulator with both controllers are presented. The performances of the control schemes are examined for input tracking capability, level of vibration reduction and time response specifications. A comparative assessment of both control techniques shows the effectiveness of the second control law and its invariance to so-called matched uncertainty.

Multi Degree of Freedom Joints (MDJ) are typically thought to be used for industrial purposes however they are beginning to gain the attention of the medical field. A current application pertains to using the precision and stability of a robot arm with MDJ to assist in minimally invasive surgery. In this research, adaptive sliding mode controls are presented as robust controls for multi degree of freedom joints. The objective of the study is to design controls for actuators without the knowledge of boundary of uncertainties/disturbances by using an adaptive sliding mode control while elucidating the robustness of the adaptive sliding mode control. A sliding mode control provides for ultimate accuracy in the presence of the bounded disturbance/uncertainties, although the sliding mode control also causes chattering. Chattering is undesirable for use with robot medical tools, since it might causes damage to them with a subsequent loss of accuracy and oscillation on end-effectors tools. Such chatter is caused by overestimation of the controller gain. An adaptive sliding mode is proposed as a solution to the problems created by chattering.

Synchronized switch damping (SSD) techniques have recently been developed, as an alternative to active vibration control techniques, to address the problem of structure vibration control. In these techniques, a piezoelectric patch is bonded on the vibrating structure and shunted by a network of electrical elements. During the structure motion, the piezoelectric patch is connected and disconnected from the shunt circuit, according to the displacement extremum, through switching action controlled by a digital signal processing system. Thus the voltage in the piezoelectric patch is enhanced and time shifted in the time domain from the displacement of the vibrating structure. This voltage when shunted through electrical circuit results in increased energy dissipation with enhanced damping effect. This paper proposes to further increase the dissipated energy through a new technique called the synchronized switch damping on negative capacitance and voltage sources (SSDNCV). The idea is to further increase the value of voltage in the piezoelectric patch though the use of negative capacitance and two extra voltage sources in the shunt circuit. First theoretical expressions are derived for SSDNCV method to determine the maximum energy dissipated from the shunt circuit and the corresponding maximum damping. The effectiveness of SSDNCV method, as compared to the previous SSD methods, is then demonstrated in the first resonance mode control of a cantilever beam containing piezoelectric patch. The SSDNCV control reduced the vibration amplitude by 82 % as compared to 63 % and 29 % obtained from SSDNCI and SSDV controls respectively.

This paper summarizes vibration control methods in the process of machining, and the current research progresses, in view of the difference in vibration control technologies and methods, from several aspects such as the eliminating vibration control technology, the isolating vibration control technology, and absorbing vibration control technology, etc .Simultaneously with the continuous improvement of the traditional control method, the organic combination the new material technology and intelligent control methods will also be the future trend of development.

According to this research paper, fuzzy hype plane controller is applied to robust nonlinear controller to reduce the vibration of motor. To control of multi degree of freedom joint, nonlinear controllers are the best candidate. Sliding mode controller is one of the best choices to robust control of this nonlinear system. The sliding mode controller is used to speed up the error convergence when the error is greater than one. To reduce the error terminal sliding mode controller is recommended in this research. Fuzzy hype-plane variable sliding mode controller is adopted to guarantee the error convergence to zero in a finite time when the error is near the zero. The chattering in the conventional sliding model control systems is avoided with the employed continuous controller. To increase the system robustness in presence of uncertainty fuzzy logic controller is recommended. This technique is used to adjust the band of terminals. The simulation results show that the proposed scheme has strong robust against the uncertainties and disturbances, as well as leads to the convergence of the output to the desired value quickly and precisely than employing either sliding mode controller or terminal sliding mode controller alone.

This paper proposes new fuzzy type sliding mode controller for multi-DOF joints to reduce/eliminate motor vibration. The fuzzy (PI+D)2 single-input single-output (SISO) fuzzy system is applied to modify each element of the control in a sliding mode controller. The proposed method is designed based on the Lyapunov method. Mathematical proof for the stability and the convergence of the system is presented. Various operation situations such as the set point control and the trajectory control are simulated. The simulation results demonstrate that the chattering and the steady state errors, which usually occur in the classical sliding mode control, are eliminated and satisfactory trajectory tracking is achieved.

Refer to this research, an integral criterion-based hybrid fuzzy controller is proposed for vibration reduction in sensitive actuators. The first problem of the fuzzy logic controller was stability in certain and uncertain systems. This problem can be reduced in certain system by using hybrid fuzzy control law. However fuzzy hybrid controller based on PID methodology has advantage in certain system, but it has challenge in presence of uncertainty and motor vibration. To solve this challenge direct adaptive methodology applied to hybrid fuzzy controller. This type of adaptive technique is model-reference variable structure control. Regarding to proposed method, chattering eliminate as well improve the stability and robustness. The simulation results exhibit that the proposed method works well in certain system.

Comparing to the big volume, large weight and high power consumption of the conventional samplers which are fixed on the lunar rover, the paper firstly described a novel flexible mini lunar sampling robot. Then the nonlinear dynamics resonance broken system is built to model the contact between the sampling robot and the lunar regolith. It is found to be suitable for drilling when the sampling robot is in the resonance condition. For the nonlinear time-varying system of the dynamic modeling of the sampler in drilling, we presented the method of the frequency neural-fuzzy adaptive control based on the dynamic resonant frequency prediction of the flexible sampling robot using neural networks. Firstly the algorithm predicts the dynamic resonant frequency of the sampling robot by GRNN. Then a neural-fuzzy adaptive control system is established, in which the frequency prediction error, the amplitude and its variable are adopted as the input and the sweep frequency bandwidth as the output, to adjust the frequency bandwidth dynamically. What’s more, the simulation results verify the effectiveness of the control strategy. Finally, the experimental results show that the control algorithm can improve the drilling depth, drilling efficiency and the discarding efficiency by 66.7%, 65.2% and 67.4%, respectively, in stimulant lunar regolith.