This paper is concerned with the real-time automatic tuning of the positive position feedback controller for smartstructures by the genetic algorithms. The genetic algorithms have proven its effectiveness in searchin...
详细信息
This paper is concerned with the real-time automatic tuning of the positive position feedback controller for smartstructures by the genetic algorithms. The genetic algorithms have proven its effectiveness in searching optimal design parameters without falling into local minimums thus rendering globally optimal solutions. The advantage of the positive position feedback controller is that if it is tuned properly it can enhance the damping value of a target mode without affecting other modes. In this paper, we develop a real-time algorithm for determining a tuning frequency of the PPF controller based on the genetic algorithm. Hence, the traditional positive position feedback controller can be used in adaptive fashion in real time. To this end, the digital PPF control law is downloaded to the DSP chip and a main program, which runs genetic algorithms in real time, updates the parameter of the controller in real time. The real-time tuning of the PPF controller is applied to cases of initial disturbance and persistent harmonic disturbance. In both cases, the real-time tuning is achieved successfully. Hence, vibrations are suppressed satisfactorily. The experimental results also show that the PPF controller tuned by GA gives better performance than the manually tuned PPF controller for accommodating harmonic disturbances did.
In this paper the design of an optimal controller using discretely placed collocated sensor/actuator pairs to control the vibration of a plate structure is presented. Three-dimensional finite elements are used to mode...
详细信息
In this paper the design of an optimal controller using discretely placed collocated sensor/actuator pairs to control the vibration of a plate structure is presented. Three-dimensional finite elements are used to model the smart structure containing discrete piezoelectric sensors and actuators by the use of a combination of solid, transition, and shell elements. Since several discrete piezoelectric patches are spatially distributed in the structure to effectively observe and control the vibration of a structure, the system model is thus utilized to design multi-input-multi-output (MIMO) controller. The output feedback controller is then employed to emulate the optimal controller by solving the Riccati equations from modal space model. An optimal controller design for the vibration suppression of a clamped plate is presented for the steady state excitation case. The reduction in the sound pressure level inside an enclosure radiated from this optimally controlled vibrating plate is also estimated.
The strain-temperature hysteresis for shape memory alloy (SMA) actuators has been shown to undergo large changes according to the applied load. This paper provides an adaptive hysteresis model capable of accounting fo...
详细信息
The strain-temperature hysteresis for shape memory alloy (SMA) actuators has been shown to undergo large changes according to the applied load. This paper provides an adaptive hysteresis model capable of accounting for a time-varying hysteresis, specifically SMA hysteresis under a varying applied stress. Previous research has established excellent performance, in both numerical and laboratory experiments, of the adaptive hysteresis model for actuators with fixed hysteresis. In this paper, the performance of the adaptive model when there are significant changes in the hysteresis characteristics is examined in laboratory tracking experiments.
Dynamic behaviors of a 1-story and 4-story steel structures subject to multi-dimensional ground motion excitations were experimentally investigated by using a shaking table. Linear and nonlinear structural responses w...
详细信息
Dynamic behaviors of a 1-story and 4-story steel structures subject to multi-dimensional ground motion excitations were experimentally investigated by using a shaking table. Linear and nonlinear structural responses were obtained as observation data for the identification. Dynamics characteristics of the model structures were identified using the adaptive H∞ filter, which was developed for identifying structural systems with non-stationary dynamic characteristics by adding the function of memory fading (forgetting factor) for past observation data to the H∞ filter. Identification results show that the H∞ filtering technique are very efficient for identifying linear and nonlinear structural systems. Especially, the nonlinear behavior of the model can be traced effectively.
New class of automobiles has structural skins that are quite different from their current designs. Particularly, new families of composite skins are developed with new injection molding processes. These skins while su...
详细信息
New class of automobiles has structural skins that are quite different from their current designs. Particularly, new families of composite skins are developed with new injection molding processes. These skins while support the concept of lighter vehicles of the future, are also susceptible to damage up on impact. It is important that their design should be based on a better understanding on the type of impact loads and the resulting strains and damage. It is possible that these skins can be integrally designed with active materials to counter damages. This paper presents a preliminary analysis of a new class of automotive skins, using piezoceramic as a smart material. The main objective is to consider the complex system with, the skin to be modeled as a layered plate structure involving a lightweight material with foam and active materials imbedded on them. To begin with a cantilever beam structure is subjected to a load through piezoceramic and the resulting strain at the active material site is predicted accounting for the material properties, piezoceramic thickness, adhesive thickness including the effect of adhesives. A finite element analysis is carried out to compare experimental work. Further work in this direction would provide an analytical tool that will provide the basis for algorithms to predict and counter impacts in the future class of automobiles.
The paper presents a methodology for evaluating the effective stiffness of unidirectional composite materials with shape memory alloy (SMA) fibers in the presence of matrix cracks. The solution is obtained for the cas...
详细信息
The paper presents a methodology for evaluating the effective stiffness of unidirectional composite materials with shape memory alloy (SMA) fibers in the presence of matrix cracks. The solution is obtained for the case where SMA fibers in the intact composite are in the austenitic phase. However, elevated stresses in the sections of SMA fibers adjacent to the crack planes cause the martensitic transformation affecting the stiffness of the material. The solution has to account for thermal residual stresses in SMA and `ordinary' fibers and in the matrix. The order of magnitude of these stresses is calculated in the paper for two representative composite systems. As follows from the numerical examples, thermal residual stresses in the SMA fibers increase proportionally to their volume fraction but remain relatively small. However, thermal stresses in the matrix may reach rather high values reducing the strength of the matrix by a significant factor.
In this work the control of vibration in an elastic plate, by piezoelectric transducers, is considered. The model of the plate is that presented in [2]. An approximation of the optimal controller by a derivative parti...
详细信息
In this work the control of vibration in an elastic plate, by piezoelectric transducers, is considered. The model of the plate is that presented in [2]. An approximation of the optimal controller by a derivative partial operator is given. It is based on a development in series of the Riccati operator with respect to the reverse of the stiffness. Its implementation in term of distributed analog electronic circuits, is developed. Numerical simulations, obtained by the coupling of Finite Elements code and a circuit simulator, Alecsis, are presented. To improve the preceding result an iterative algorithm of approximation of the optimal controller, being able to be implemented by an electronic circuit, is developed. The algorithm is inspired by the approach of [4].
In this work, refined finite element models based on higher order displacement fields have been developed to study the mechanical and electrical behavior of laminated composite plate structures with embedded and/or su...
详细信息
In this work, refined finite element models based on higher order displacement fields have been developed to study the mechanical and electrical behavior of laminated composite plate structures with embedded and/or surface bonded piezoelectric actuators and sensors. Sensitivity analysis and optimization techniques are also applied in order to maximize the piezoelectric actuator efficiency, improve the structural performance and/or minimize the weight of the structure. To show the performance of the proposed models several illustrative and simple examples are presented.
Wavelets provide a new tool in vibration, identification and control. By their properties wavelets transform are stronger than FEM and FFT. We dispose to several wavelets family as Haar, Daubechies, Morlet, Mallat, et...
详细信息
Wavelets provide a new tool in vibration, identification and control. By their properties wavelets transform are stronger than FEM and FFT. We dispose to several wavelets family as Haar, Daubechies, Morlet, Mallat, etc. and use the filter banks for vibration analysis. This paper deals with the problem of controlling the bending oscillations of a thin walled cantilever beam with arbitrary cross section. The control is achieved via the action of a bending moment applied at a tip of structure. A possibility to generate the control bending moment at the wing tip is via the implementation into the structure of piezoactuators. The velocity feedback control allows the possibility to generate damping through the feedback gain coefficient. Feedback law where the bending moment at a tip is proportional to the velocity is included into matrix wavelet implementation. Numerical examples for PDE are computed and compared with other examples for particular cases included in earlier paper of Librescu, Na. The paper uses the Haar wavelet transform to algebrize PDE leading to a powerful and general method to study the nonlinear problems with more flexibility and localization of peak resonance in comparison with other procedures.
The systems theory approach to the feedback stabilization of finite-amplitude disturbances in plane Poiseuille flow results in high-order system models to accurately represent the disturbance dynamics. From a practica...
详细信息
The systems theory approach to the feedback stabilization of finite-amplitude disturbances in plane Poiseuille flow results in high-order system models to accurately represent the disturbance dynamics. From a practical standpoint, a controller developed for a specific flow control task will often have to be implemented in real-time. The need for the synthesis of rigorous control theory and experimental methods has been noted by several researchers over the years. A key step to this synthesis is the development of low dimensional descriptions of flow dynamics for control synthesis. This paper examines the use of the optimal projection method for reduced-order controller synthesis for flow disturbance model systems with relatively high order (greater than 40).
暂无评论