ISSN:1122-8385    

DOI:10.1002/stc.4300060101

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

ISSN:1122-8385    

DOI:10.1002/stc.4300060102

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

ISSN:1122-8385    

DOI:10.1002/stc.4300060103

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractThis paper is an extended summary of the dissertation presented by the author for the Ph.D degree in civil engineering at the University of Pavia.The aim of the dissertation is the design and the experimental validation of an active control scheme, the simulation of possible real operating problems (such as sensor failures) and the reliability assessment of the active control system. The goal is to identify and discuss a scenario of possible problems the designer will meet in implementing an active control scheme.The work consists of a preliminary theoretical part, necessary for the implementation of the active control system, an experimental activity on a suitably scaled structural model and a reliability analysis of the adopted active control system.

ISSN:1122-8385    

DOI:10.1002/stc.4300060104

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractThe goal of this dissertation was to develop an active vibration damping system for high‐speed elevator cars to achieve a ride comfort not reached before by passive means. The system developed comprises eight actuators, six accelerometers, eight position sensors, a signal conditioning unit, and power electronics. It is controlled by a real‐time computer utilizing a digital signal processor. A laboratory test rig was designed and constructed to allow testing the active damping system fitted to a full‐scale high‐speed elevato car. The unevennes of the two guide rails, which is the main source of vibrations, is emulated using eight hydraulic cylinders. A multivariable system identification procedure in the frequency domain was developed to obtain a linear time‐invariant system model. A first controller loop utilizes the acceleration outputs to suppress the vibrations. Due to asymmetric load distributions in the cabin, the orientation of the car with respect to the guide rails may change to the extent that for one or more actuators there may not be enough actuation distance. To correct the car orientation, a second controller loop utilizing position outputs is used. However, since the position measurements are taken between the car and the guide rails, nulling the position error signals means forcing the car to follow an average line of the two rail profiles which is the main source of vibrations. To avoid a conflict between the two loops, a frequency domain separation of the bandwidths of the two controllers is achieved. The two multivariable controllers are designed using the H∞robust design method and employing the plant non‐inverting GS/T weighting scheme. The effectiveness of the active system was tested using rail profiles previously measured in a real building and emulated by the hydraulic excitation system. The vibration reduction factor achieved is around 5 as to a passive damping system. Meanwhile, the controller is capable of correcting the car orientation caused by asy

ISSN:1122-8385    

DOI:10.1002/stc.4300060105

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractThe scope of the work has been to study the static and dynamic behaviour of deployable or self‐deployable structures composed by rigid elements interconnected by pin‐jointed ends and intermediate pivots, that can be assembled in order to form movable roofing systems or similar applications. Modelling of the behaviour of self‐deployable systems has been approached both during the deployment and in the fully deployed configuration. In particular, the non‐linear dynamic simulation of the deployment phase is approached as a coupled problem of dynamics and kinematics leading to a non‐linear model of the system. The problem of applying active control techniques to the resulting system is also faced, leading to the solution of the non‐linear control problem for the deployment phase, and to a bounded ‐state approach for the in‐service phase. Numerical developments have been performed in the MAT

ISSN:1122-8385    

DOI:10.1002/stc.4300060106

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractIn active control applications to civil engineering structures, large control forces are required, but the generation of such forces may render the active control implementation impractical.To overcome this drawback, the actuator force can be supplied by the flow of compressed air: it applies a force to the jet supporting structure thanks to the principle of Momentum Preservation (Conservation). The air is stored in a tank and it flows towards a semi‐rigid pipe to the final actuator‐jets, simply realized as nozzles. The flow through each nozzle is controlled by an on‐off electro‐valve, and the system response is monitored by accelerometers.The main achievement is that the resulting control system is indipendent of external energy supply, enough energy having been stored, as compressed air, in a tank. In this way the reliability of the control system is not affected by the availability of external electric power, that in case of earthquake can easily be interrupted.While many studies have been made on pulse‐control methods, only a few have investigated the implementation of such nonlinear control schemes. The focus of this work is on the experimental investigation of some of the numerous practical issues one meets in the development of actuators based on mass‐ejection techniques.A single degree of freedom system, i.e. a simple vertical cantiliver with a lumped mass at the top, is tested on a shaking‐table under different excitation time‐histories, and the efficiency of the controll

ISSN:1122-8385    

DOI:10.1002/stc.4300060107

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractThis paper describes the application of a recurrent dynamic neural network to the problem of adaptive active flutter suppression. A significant feature of the neural controller is its application to an unstable and non‐minimum phase system. The development of the system and its experimental verification are carried out on a wing model with two control surfaces, one on the leading and one at the trailing edge, and two accelerometers. The controller combines a first network for the identification of the variables to be controlled, i.e. the two wing tip accelerations at the leading and trailing edge, with a second network, that commands the deflection required to the control surfaces. It is used for the control task using the output generated by the first network. Adaptivity is obtained by maintaining an on‐line training on both of the neural networks. Extensive preliminary numerical simulations have permitted the authors to define the values of the design parameters aimed at the achievement of an optimal compromise between computational requirements and system performances. The results of the application to the real wing model have shown the effectiveness of such a controller in adapting to different operational conditions, extending flutter free envelope of the wing model up to a speed 30% higher than the uncontrolled flutter on

ISSN:1122-8385    

DOI:10.1002/stc.4300060108

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

ISSN:1122-8385    

DOI:10.1002/stc.4300060109

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY

摘要:

AbstractA linear theory of electroelastic plates capable of thickness changes is presented. It is shown that, for transversely isotropic plates, the general boundary‐value problem decouples into a membrane problem and a flexure problem; in each subproblem, piezoelectric and electrostrictive effects are in order, with peculiar forms. An example is studied, where thickness changes in membrane regime are induced either by mechanical loads or by electric load

ISSN:1122-8385    

DOI:10.1002/stc.4300060110

出版商:John Wiley&Sons, Ltd    

年代:1999

数据来源: WILEY