Flexible Beam Structure Research Articles

Wiener Filter를 이용한 보 구조물 위 장비의 능동 진동 절연 성능 해석

Wiener Filter를 이용한 보 구조물 위 장비의 능동 진동 절연 성능 해석

Analysis for active isolation of the equipment on flexible beam structure

This paper dealt with the active isolation of vibration. Many home appliance and vehicles in operation generate the vibration for several reasons. Due to the vibration propagated to the structure, it has a negative influence of the structure such as breakage and decreased reliability. As basic study on vibration isolation, the analytical model is as follows. The analytical model consists of the equipment as source of vibration and the flexible beam to be controlled. The equipment is assumed by rigid body and excited by a concentrated force as disturbance. And the equipment and the beam are connected to spring located at both ends the equipment. The actuators are located slightly away from spring. To minimize the vibration propagated to the beam structure through the equipment, the controller was designed by using the multi-channel Wiener filter after calculating the transfer path through the theoretical formula. The disturbance was given as harmonic components. The propagated vibration to the beam caused by the disturbance was controlled using a designed controller. Finally, the numerical results for the displacement obtained at each point of the beam structure with and without control were carried out and compared.

Coupling dynamics of super large space structures in the presence of environmental disturbances

Considering the effects of the gravity gradient, the solar radiation pressure (SRP) and the thermal radiation, the coupling dynamical model is established for a super large flexible beam structure, which moves in the orbital plane around the earth. The effects of environmental disturbances on the orbital motion, the attitude motion and the structural vibration are analyzed simultaneously. Influences of the initial attitude angle, the structure size and other system parameters have been investigated for the coupling dynamics. The results show that the envelop shapes of the vibration responses are dependent on the attitude motion, and the perturbation of orbital motion increases with the growth of the initial attitude angle. When the structural fundamental frequency is close to the attitude frequency with the increase of the structure size, the average orbit altitude would decrease slightly. The main frequency component of the attitude motion decreases and the frequency component related to the structural vibration encounters and grows up. The resonance then leads to system instability. Moreover, the magnitude of the attitude motion can also be influenced by the slightly intense structural vibration, which might be excited by the momentum exchange devices of the attitude control system. In addition, in the presence of the SRP, the orbital radius is perturbed obviously and the eccentricity of orbital motion is generally changed. The effects of the thermal radiation and the gravity gradient are in the same order of magnitude on the structural vibration in the low orbit while the former one turns to be dominant in geostationary orbit.

Control modal numérico de una estructura viga flexible

Control modal numérico de una estructura viga flexible

A new self-tuning fuzzy controller for vibration of a flexible structure subjected to multi-frequency excitations

This work proposes a new self-tuning fuzzy controller for vibration control of a flexible structure subjected to both single-frequency and multi-frequency excitations. A piezoelectric stack actuator is used to generate control force to attenuate vibrations in the resonant and non-resonant frequency ranges. As a first step, modal frequencies and modal shapes of the flexible beam structure are obtained via the finite element method, and these are verified through comparison with the measured values. Second, in order to attenuate multi-frequency vibration of the beam, a new fuzzy controller with self-tuning factors is proposed. This controller is independent of the structure model and very adaptive to variable excitations. Then, vibration control performances of the self-tuning fuzzy controller are experimentally investigated under two different excitation conditions: single-frequency and multi-frequency excitations. It is shown that vibration control capability of the proposed controller outperforms convent...

Modelling and analysis of vehicle-structure-road coupled interaction considering structural flexibility, vehicle parameters and road roughness

To determine the dynamic forces acting on vehicle components a vehicle-structure-road interaction is considered. Coupled interaction was modelled using a flexible bridge-like thin beam structure with four and six Degree of freedom (DOF) half car models. In addition to the flexible structure, the road conditions were added to the model as random and non-random surface irregularities. A coupled equation of motion of the whole system was derived using Lagrange equations, and converted to a first-order state-space equation and then solved using the fourth-order Runge-Kutta method. Besides the dynamic forces, the effects of the vehicle speed, bridge flexibility, tire stiffness, random or non-random road irregularities on the passenger comfort are widely investigated. The results obtained were compared by several early VBI (Vehicle-bridge-interaction) studies in the literature and proved accurate with a 5 % difference.

Active Vibration Control of a Flexible Beam Structure Using Chaotic Fractal Search Algorithm

The performance of lightweight and flexible systems such as beam, plate and shell structures are vulnerable to excessive vibration level. Thus, many vibration control techniques have been developed in the past two decades in order to overcome this problem. In this paper, the development of active vibration control to suppress the unwanted vibration from a flexible beam structure is presented. The objective of this work was to evaluate the performance of chaos-enhanced Stochastic Fractal Search (CFS) optimization algorithm in modeling and vibration control of flexible beam system. Parametric modeling of the system was developed using auto-regressive exogenous (ARX) model structure based on the input-output data from previous experimental finding. The first two resonance frequencies of flexible beam structure was found at 3.418 Hz and 21 Hz. The accuracy of generated flexible beam model was validated using correlation and system stability tests. A PID controller incorporated with CFS optimization algorithm was employed to attenuate the unwanted vibration from the flexible beam system. Based on the proposed method, about 83.95% of the initial vibration disturbance successfully been suppressed with the mean-squared error value of 1.5178 x 10-4 been achieved. In conclusion, the simulation study indicates that the CFS algorithm possess capability to extract an adequate and stable model of the flexible beam structure, hence a better performance of control strategy can be achieved.

Implementation of swarm algorithm in modeling a flexible beam structure

The application of System Identification techniques for modeling a flexible beam structure are presented in this paper. The flexible beam has been widely applied in various fields engineering and industrial. However, the flexible structure is easily influenced by unwanted vibration which may lead to fatigue, performance reduction and structure damage. Thus, the unwanted vibration must be controlled and reduced. In order to have a good controller performance for vibration suppression, an appropriate model of flexible beam is required. Hence, to obtain a model of the flexible beam structure, Particle Swarm Optimization (PSO) and Artificial Bee Colony (ABC) are implemented in this study as System Identification techniques. The implementation of PSO and ABC requires experimental data input and output retrieved from data acquisition from a well-developed experimental test rig via MATLAB Simulink platform. Results obtained are displayed in graphical plots and numerical values. The predicted model is validated via mean square error (MSE) and correlation tests. To represent the dynamic model of the flexible beam structure, model with minimum MSE value and correlation test within 95 % confidence interval is selected as the best fit model. The result shows that PSO algorithm produces better performance compared to ABC algorithm with a 3rd order predicted model that has lowest MSE value and correlation tests within 95 % confidence interval for the beam system.

순응형 파지와 정밀한 집기가 가능한 유연한 그리퍼의 강도 및 강성 분석

In this paper, we introduce a flexible gripper that we have engineered to precisely pinch in parallel and compliantly grasp objects. As found in most conventional industrial grippers, the parallel pinching property is essential for precise manipulation. On the other hand, the grippers with a flexible structure are more adept at grasping objects with arbitrary shapes and softness. To achieve these disparate properties, we introduce a flexible gripper mechanism composed of multiple flexible beam structures. Utilizing these beam structures, the proposed gripper is able to grasp arbitrarily shaped objects. Additionally, a unique combination of flexible beams enables the gripper to pinch objects using the parallel fingertips for enhanced precision. A detailed description of the proposed mechanism is provided, and an analysis of the strength and stiffness of the fingertip and finger body is presented. The Results section compares the theoretical and experimental analyses and verifies the properties and performance of the proposed gripper.

Time-Delayed Vibration Control of a Rotating Flexible Manipulator Based on Model Output Prediction Feedback

AbstractThis paper is concerned with vibration control of a single-link flexible beam structure. The proposed beam is controlled by a servo motor through a harmonic gear reducer. After obtaining the models by system identification, a time-delayed optimal controller based on model output prediction and optimal control theory was designed to compensate the unknown time delay in the controlled system. Then, experiments on the proposed control scheme were conducted in a set-point vibration control process. The experimental results demonstrate that the performance of vibration suppression can be improved substantially when applying the proposed method in the presence of time delay compensation, as compared to the traditional proportional and derivative (PD) controller. The accuracy of models was validated according to experimental results, and the factors that influence the output prediction accuracy are analyzed in this paper.

Modal-based mixed vibration control for uncertain piezoelectric flexible structures

H-infinity norm relates to the maximum in the frequency response function and H-infinity control method focuses on the case that the vibration is excited at the fundamental frequency, while 2-norm relates to the output energy of systems with the input of pulses or white noises and 2-norm control method weighs the overall vibration performance of systems. The trade-off between the performance in frequency-domain and that in time-domain may be achieved by integrating two indices in the mixed vibration control method. Based on the linear fractional state space representation in the modal space for a piezoelectric flexible structure with uncertain modal parameters and un-modeled residual high-frequency modes, a mixed dynamic output feedback control design method is proposed to suppress the structural vibration. Using the linear matrix inequality (LMI) technique, the initial populations are generated by the designing of robust control laws with different H-infinity performance indices before the robust 2-norm performance index of the closed-loop system is included in the fitness function of optimization. A flexible beam structure with a piezoelectric sensor and a piezoelectric actuator are used as the subject for numerical studies. Compared with the velocity feedback control method, the numerical simulation results show the effectiveness of the proposed method.

Model based vibration control of smart flexible structure using piezoelectric transducers

This paper focuses on development and implementation of optimal control algorithms for vibration control of flexible beam structures with embedded piezoelectric actuators. Piezoelectric transducers have become the leading active elements in smart structures based on their characteristics and reliability. Piezo laminated beam with collocated pairs of piezoelectric sensors and actuators is modelled using the methodology of system identification. The obtained model has been implemented in the model based optimal control algorithms. Linear quadratic regulator and model predictive control are developed and tested using LabVIEW and NI cRIO platform. The MPC algorithm shows better performance due to the constraint handling and requires more powerfull real-time and FPGA controller target.

Motion planning for a piezo‐actuated structure modeling a wingsail

AbstractThis contribution presents the modeling and the motion planning of a flexible interconnected beam structure representing a wingsail. The structure is equipped with spatially distributed embedded actuators. The solution of the motion planning provides a feedforward control law to realize a desired spatial‐temporal out‐of‐plane deflection trajectory. For this, a systematic flatness‐based methodology is proposed, that allows for an efficient numerical solution exploiting, e.g., finite element approximations. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Adaptive LQR-Control Design and Friction Compensation for Flexible High-Speed Rack Feeders

Rack feeders for the automated operation of high bay rackings are of high practical importance. They are characterized by a horizontally movable carriage supporting a tall and flexible vertical beam structure, on which a cage containing the payload can be positioned in vertical direction. To shorten the transport times by using trajectories with increased maximum acceleration and jerk values, accompanying control measures can be introduced counteracting or avoiding undesired vibrations of the flexible structure. In this contribution, both the control-oriented modeling for an experimental setup of such a flexible rack feeder and the model-based design of a gain-scheduled feedforward and feedback control structure are presented. Whereas, a kinematical model is sufficient for the vertical axis, the horizontal motion of the rack feeder is modeled as a planar elastic multibody system with the cage position as scheduling parameter. For the mathematical description of the bending deflections, a one-dimensional Ritz ansatz is introduced. The tracking control design is performed separately for both the horizontal and the vertical axes using decentralized state-space representations. Remaining model uncertainties are estimated by a disturbance observer. The resulting tracking accuracy of the proposed control concept is shown by measurement results from the experimental setup. Furthermore, these results are compared to those obtained with an alternative control concept from previous work.

Hardware-in-the-loop optimization of an active vibration controller in a flexible beam structure using evolutionary algorithms

In this study, active vibration control of a cantilevered flexible beam structure equipped with bonded piezoelectric sensor/actuators is investigated. The linear quadratic regulator technique together with an observer is adopted to design the controller as well as to provide the full-state feedback. Two different approaches are subsequently used for simultaneously integrated optimization of the controller and observer parameters. In the first approach, a linear experimental model of the system is obtained using identification techniques, and the optimization is then performed based on a computer simulation of the system. However, in the second approach, a hardware-in-the-loop optimization scheme is proposed and applied to automatically tune the parameters. In both cases, a hybrid metaheuristic algorithm called tabu continuous ant colony system is utilized to find the optimal controller and observer. The integrated performance is experimentally evaluated to demonstrate effectiveness of the proposed hardware-in-the-loop optimization method. Finally, a comparison is made between the frequency response of the current controller with a pole placement controller from the literature in order to assess the improvement achieved through hardware-in-the-loop optimization.

Study on Vibration Control of a Flexible Cantilever Beam Based on Fuzzy PID

The overall performance of large aerospace vehicles is determined to a great extent by the wings structure of aircrafts. In order to prevent wings vibration due to external interference, schemes of combined fuzzy-PID and fuzzy adapt PID controllers are proposed based on flexible beam structure. The MATLAB simulation model demonstrates that the proposed controllers not only has good dynamic characteristics, but also reduce the vibration effect greatly caused by external disturbance, which lay the foundation for the active vibration control of aircraft wings.

Electromagnetic Synchronized Switch Damping for Vibration Control of Flexible Beams

An electromagnetic synchronized switch damper integrated with the receding horizon optimal control law was developed to enhance the damping characteristics of flexible beam structures subject to dynamic loads. The damper system consists of a magnet attached to an aluminum beam and a coil placed at the bottom of the magnet. Both ends of the coil were connected to the external switching circuit, which includes an electromagnetic transducer, a capacitor, a resistor, and a switcher designed for efficient energy dissipation to reduce structural vibration. Further, a coil-based self-sensing scheme without additional measurement of the displacement and the velocity was successfully applied to the present switching scheme without performance loss. The present results show that the electromagnetic synchronized switching scheme can be successfully employed to improve the electromagnetic damping of the flexible structures, resulting in the robust vibration control regardless of changes to the circuit parameters.

Dynamics of 3D beam elements in a corotational context: A comparative study of established and new formulations

This paper deals with Newmark time stepping methods and finite rotations for nonlinear finite element analysis of flexible beam structures. The corotational method is used to develop expressions of the internal forces and the corresponding tangent stiffness matrices. For the dynamic part, four formulations based on different parameterizations of rotations are compared. The first three are classic formulations taken from the literature with some modifications for two of them. The last one is new and uses three of the four Euler parameters (quaternion) as rotational variables. For all these approaches, theoretical derivations as well as practical implementations are given in detail. The similarities and differences between the formulations are pointed out. Six numerical examples are studied in order to compare these four formulations in terms of numerical accuracy and computational efficiency. Regarding efficiency, the choice of the predictor at each time step and the possibility to simplify the tangent inertia matrix are carefully investigated. The numerical results show that these four formulations have the same numerical accuracy, but that the computational efficiency depends on the choice of the tangent inertia matrix. Besides, the new formulation proposed in this paper turns out to be the fastest one.

Implementation of linear model predictive control using a field-programmable gate array

This study investigates the design of a field-programmable gate array-based custom computer architecture solution for implementing model predictive control (MPC). The solution employs a primal logarithmic-barrier interior-point algorithm in order to handle actuator constraints. The solution also incorporates practical aspects of a control algorithm including state observation and data sampling. The resulting circuit is profiled by application to a disturbance rejection control problem of a 14th-order lightly damped flexible beam structure with actuator constraints. This is achieved at 2 kHz sampling frequency and with 16-sample prediction horizon.

A comparative analysis of some one-dimensional shape memory alloy constitutive models based on experimental tests

Recently, Shape Memory Alloys (SMAs) have been receiving more attention and further study, due to their ability to develop extremely large, recoverable strains and great forces. In this paper, three major models of SMA behavior, used in the literature, for studying the static performance of SMA components attributed to Tanaka, Liang and Rogers, and Brinson, have been analyzed and compared. The major differences and similarities between these models have also been emphasized and presented in this paper, based on the experimental data of the shape memory and superelastic behavior of an SMA wire. It is shown that these models all agree well in their prediction of the superelastic behavior of SMAs at higher temperatures, but the models developed by Tanaka, and Liang and Rogers cannot be used for predicting the shape memory effect behavior of SMAs. It is also shown analytically that the original evolution kinetics, proposed by Brinson, in a specified region, are inadmissible for some thermomechanical loading and initial conditions. Furthermore, corrected evolution kinetics is addressed here in detail, that is; admissible and valid in this region. According to this research, regarding the validation assessment of three major 1-D constitutive models with experimental data, it will be shown that the Brinson model with the corrected evolution kinetics developed by Chung et al. can be applied for the modeling of SMA smart structures, such as flexible SMA beam structures.